CA2090340C - Method of extracting sennosides a, b and a1 - Google Patents
Method of extracting sennosides a, b and a1Info
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- CA2090340C CA2090340C CA002090340A CA2090340A CA2090340C CA 2090340 C CA2090340 C CA 2090340C CA 002090340 A CA002090340 A CA 002090340A CA 2090340 A CA2090340 A CA 2090340A CA 2090340 C CA2090340 C CA 2090340C
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- C—CHEMISTRY; METALLURGY
- C07—ORGANIC CHEMISTRY
- C07H—SUGARS; DERIVATIVES THEREOF; NUCLEOSIDES; NUCLEOTIDES; NUCLEIC ACIDS
- C07H15/00—Compounds containing hydrocarbon or substituted hydrocarbon radicals directly attached to hetero atoms of saccharide radicals
- C07H15/20—Carbocyclic rings
- C07H15/24—Condensed ring systems having three or more rings
- C07H15/244—Anthraquinone radicals, e.g. sennosides
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- A—HUMAN NECESSITIES
- A61—MEDICAL OR VETERINARY SCIENCE; HYGIENE
- A61P—SPECIFIC THERAPEUTIC ACTIVITY OF CHEMICAL COMPOUNDS OR MEDICINAL PREPARATIONS
- A61P1/00—Drugs for disorders of the alimentary tract or the digestive system
- A61P1/10—Laxatives
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Abstract
The present invention provides a process for obtaining sennosides A, B and Al of the formula:- which are substantially free from sennosides C, D and D1, and from aloe-emodin derivatives, wherein a) a sennoside mixture is reduced to rhein-9-anthrone-8-glucoside and aloe-emodin-9-anthrone-8-glucoside, b) a liquid-liquid partitioning of the compounds obtained is carried out between a polar organic solvent which is only partly miscible with water and an aqueous phase and c) the rhein-9-anthrone-8-glucosides contained after the partitioning in the aqueous phase is again oxidised to the corresponding sennosides and these are recovered.
The present invention also provides sennosides A, B and Al obtainable according to this process and pharmaceuctial compositions containing them.
The present invention also provides sennosides A, B and Al obtainable according to this process and pharmaceuctial compositions containing them.
Description
20903'10 A- -.4 Ihe present invention is concerned with a process .or obtaining sennosides A, ~ and Al .~hich are sl~s~a~ially free from sennosi~es C, D and Dl and rom aloe-emodin components, as ~ell ~s with the sennosides obtainable according to this process and pharmaceutical compositions which contain these sennosides.
The sennosides are laxative-acting substances which occur in the dried drugs of the genus Cassia and Rheum. The senna drug consists of the dried leaves and pods of the senna plant, for example of Indian senna (Cassia angustifolia)~
The laxative-active sennosides are dianthrone glucosides derived from rhein and aloe-emodin, the most important ones being sennosides A, B, Al, C, D
and Dl. They correspond to the general formula:-6 11~5 ~ 0 OH
~-~ ~ ~ COOH
C6 11~5 ~ OH
- In the case of sennosides A, B and Al, R stands for COOH and in the case of sennosides C, D and Dl, R
stands for CH20H. Sennosides A, B and A1 and C, D and D1 are stereoisomers and differ from one another by the configuration on carbon atoms 10 and 10'.
Besides the sennosides, the crude drug also contains aglycones (sennidines), semi-glycosylated sennidines, polymers, decomposition products of the sennosides, aloe-emodin and derivatives thereof etc.
which can bring about undesired side effects, such as ill-feeling, vomiting, flatulence and colic.
Processes for obtaining sennosides from senna drug are described, for example in German Patent No.
1,617,667, French Patent No. M 6,611, Canadian Patent No. 1,203,800 and U.S. Patent No. 4,595,592. Depending upon the drug, the sennosides obtained according to these known processes contain a sennoside mixture with 1.5 to 5% of sennosides C, D and D1. As has already been indicated above, these contain in their molecule a moiety derived from aloe-emodin of the formula:
~
HO O OH
~
It would be desirable if sennosides could be obtained which are substantially free from sennosides C, D and D1.
A substantially complete separation of sennosides C, D and D1 from a sennoside mixture is not known from the present state of the art.
20903~u Therefore, it is an object of the p.ese~t invention to provide a process for obtaining sennosides A, B and Al which are substantiall~ free from u~esi-ed acco~pany-ing materials ~ndespecial~y from sennosides v, D and Dl.
ThUs~ accordin~ to the present inventio,., there is provided a process for obtaining sennosides A, B and Al of t~e formula:-C6H11 5 ~ O OH
lcco~
CCOH
~o 13 C6~11~5 ~ OH
wherein al a sennoside mixture is reduced to rhein-9-anthrone-8 glucoside and aloe-emodin-9-ant~rone-8-glucoside, b) a liquid-liquid partitioning of the compounds obtained is carried out between a polar organic solve~t which is only partly miscible with water and a~ aqueous p~ase and c) t~e rhein-9-anthrone-8-glucoside contained after partitioning in the agueous phase is again oxidised to the corresponding sennosides and these are recove~d.
~0~40 Step a) As starting material for the process according to the present invention, there are, in general, used sennoside mixtures such as are obtained in the extraction of senna drug according to the above-mentioned processes. For example, as starting material, a sennoside mixture can be used which is obtained by the process described in Canadian Patent No. 1,203,800 and U.S. Patent No. 4,595,592.
Thereafter, the senna drug is first extracted with aqueous methanol. The concentrate remaining after complete removal of the methanol contains the sennosides in the form of the potassium salts. This concentrate can be used as starting material for the process according to the present invention.
The concentrate can also be purified by liquid-liquid extraction with alcohols or ketones which are partly soluble in water, for example butan-2-ol, butan-2-one or acetone. The raffinate is acidified to a pH of about 1.5 to 2.0 and the sennosides are brought to crystallisation by seeding. The crude sennoside mixture obtained can also be used as starting material for the process according to the present invention. If desired, the crude sennoside mixture can also be recrystallised.
Alternatively, the concentrate mixed with an alcohol or ketone which is partly soluble in water, especially butan-2-ol, can be used as starting material.
In the case of the extraction of the senna drug, the ratio of drug to extraction solvent is preferably 1:4 to 1:15 and especially 1:4 to 1:10.
20903~0 The extraction is ?referably carried out in the prese~ce of a buf er, for example trisodium citrate, glycine, sodium bicarbonate or sacc~arose According to the process of the present invention, t~ese starti~g materials are completely reduced to the corresponding rhein-9-anthrone-8-glucoside (R = COO~) a~d to the corresponding aloe-emodin-9-anthrone-8-glucoside (R = CE20H) of the ge~eral formula:-C5~1C5 ~ O OH
~ R
~educi~g agents with an appropriate reduction pote~ial ind~de, for example, stannous chloride, sulphur dioxide, alkali metal boron hydrides and preferab~ a~kali metal dithionites, especial~y sodiuE di~hionite.
For carrying out the reduction, the startin~
material can be present i~ aqueous solution or suspension a~d the reducing agent added thereto in o solid form or dissolved in water. Especially in thecase of using senna fruit primary extract according to Canadian Patent No. 1,203,800 and U.S. Patent No.
4,595,592 (aqueous concentrate), it is also possible to work in a two-phase mixture by adding a polar organic solvent which is partly miscible with water, especially butan-2-ol or acetone.
The reduction can be carried out at ambient temperature or at an elevated temperature. The reduction is preferably carried out at 40 to 60~C and especially at 50 to 55~C. Working can be carried out at a weakly acidic to weakly alkaline pH value of the solution or suspension of the starting sennoside solution and preferably at a pH value of from 5 to 10.5. If desired, the reduction can be carried out several times, especially 2 to 10 times.
20~03~0 The 9-a~throne-8-glucoside formed is precipitated out by the addition of an acid, for example of sulphuric acid, up to a p~ value of about 2 to 4.5.
The temperature s~ould thereb~ preferably be ~ot more than 40~C, In t~e case of precipitating out the antbrone glucosides, a~d i~ the case of of the isolation thereof, for example b~ fi~tration, it is preferab~e to work u~der an atmosphere of nitrogen in order to prevent an uncontrolled oxidatio~ of t~ese compounds.
It is importsnt that the reduction proceeds to completion. ~herefore, it IS preferable to use the reducing age~t in large excess, Ditbionites and especially sodium dithionite are, in ge~eral, used in a l to 4 ~old amount bg weight, referred to the content of sennosides i~ the starting material, Furthermore, the reducing age~ is allowed to act for at least 2 ~ours and preferably for at least ~ hours. In general, the reduction takes place for ~ot longer tban lO bours, h post-reduction is preferablg carried out u~der the given conditions.
Before its use in step b), the product obtai~ed is preferably reprecipitated b~ bringing it into agueous solution bg the additio~ of a base, for examp~e sodium hgdro~ide or potassium bydroxide, to a p~ value of abput 6 to 7, extracting the solution with butan-2-ol, butan-2-one or acetone and again precipitating out the product bg the additiou of an acid to a p~
va~ue of about 2 to 4, 20 ~03L1O
Step b) In this step, the aloe-emodin components and especially aloe-emodin-9-anthrone-8-glucoside are removedO For this purpose, a liquid-liquid partitioning of the product obtained is carried out ina polar organic solvent which is only partlg miscible with water and an aqueous phase. Appropriate polar organic solvents include C4-C5-alkanols and di-Cl-C3-alkyl ketones, for example butan-l-o~, butan-2-ol, butan-2-one and acetone, butan-2-ol and acetone preferably being usedO
To the aqueous phase is preferablg added a reducing agent in order to impart to the aqueous phase during the whole of the liquid-liquid partitioning a redox potential of -210 mV or more negative. It is preferred to use the same reducing agent as in step a).
In the case of using an alkali metal dithionite as reducing agent, in general a 2 to 4~ by weight solution at a pH value of 7 to 10.5 is sufficient i~ order to maintain the mentioned potential conditions. The p~
2~ value is preferabl~ maintained in this range by the addition of a buffer.
The volume ratio of aqueous phase (heav~ phase) to organic phase (light phase) is generally in the range of from 1:5 to 1:40.
The liquid-liquid extraction preferably takes place in countercurrent. ~he mixture of the anthrone compounds is therebg i~troduced in the form of the solution obtained after the reduction or, when the anthrone . 9 compounds ~ave bee~ isolated, in the form of a 3 to 15~ by wei~ht solulion.
After 'he parti~ioning, the desired rhein-9-anthrone-8-glucoside is present in the aqueous phase. It is pre-cipitated out D~ the addition of an acid up to a pHvalue of about 2 to 4 and recovered in the usual wa~.
Step c) In tbis step, the rhei~-9-anthrone-8-glucoside is again oxidised to the corresponding sennoside compounds.
Oxidation agents appropriate for this purpose include h~drogen peroxide, manga~ese dioxide, permanganates and manganic acetonylacetonate. ~owever, the oxidation is preferably carried out with oxy~en. As t~e source of oxygen, air can, for example, be used.
Since rhein-9-a~throne-8-glucoside is insoluble in water, for the oxiaG~ion it is converted into a soluble form. This can ~-~ake p~ace, for example, by converting it into an alkali metal salt or into the calcium salt bg the addition of an appropriate base up to a p~ value of about 6 to 7. If desired, a small amount (up to about 30% bg volu~e) OL a solvent which is onlg partly miscible with water, especially butan-~-ol, can be added to tbe solu ionO
The oxidation ~8 carried out in 8 solution wbich is as concentrated as possible because, in this wag, the formation of the desired sennosides is favoured. ~he oxidation iD preferably carried out with a solutio~
which contains about 250 to ~00 g of rhein-9-anthrone-20~03~0 -lC-8-glucoside per Litre of solvent In t~e case of using oxygen as oxidation agent, this is preferably passed ~hrough the solutio~.
T~e oxidation with ox~ge~ can be facilitated bg the use of a catal~st. Appropriate catalgsts include, for example, palladium black and ferric salts, especially ferric chloride. In general, the amount of catal~st lies in the range of 0.2 to 2~ bg weight, referred to the amount of rhein-9-anthrone-8-glucoside, and especiallg in the range of 0.5 to 1% b~ weight.
Alternatively, the oxidation can be carried out with a ferric salt, for example ferric sulphate or ferric chloride, at a p~ value of 8 to 8.5. It is t~ereby pre-ferred to work at 3C to 50~C and in the presence of trisodium citrate.
~ he oxidation is carried out ~ntil the rhein-9-anthrone-8-glucoside can no longer be detected (absence of the ultra-violet fluorescence of the anthrone compounds).
The sennosides are obtained in the usual way by acidi~ication of the solution obtsined. The solution is 2referably di~uted before the addition of the acid with the solvent used, fo~ e~ample water/b~tan-2-ol, to 2 to 3 times the volume present. In this wag, it is achieved that the rhein-8-glucoside formed as b~-product remains substantially in solution in the case of the precipit-ation of the sennosides.
20903~10 The separation of the rhein-8-glucoside can also take place via the calcium salt because the calcium salt of rhein-8-gluco8ide is insolubie and precipitates out, whereas the calcium calts of the senno8ide5 remain in 901ution.
The sennosides are preci?itated out by the addition of an acid to a p~ of about 2 to 4 and then recovered in the usual way.
The sennosides obtained are substantially the 10 sennosides A, B and Al. They are substantially free h~sennosides C, D and Dl and ~m other aloe-emodin contaminations. The contents of sennosides C, D and Dl -n the product obtained according to the present invention is less than 100 ppm, determined according 15 to the methods of analysis described in the following Examples.
The present invention is also concerned with the mixture of sennosides A, B and Al obtainable according to the present invention, as well as with pharma-20 ceutical compositions which contain the said mixture.
The field of use, the dosage to be administeredand the appropriate forms of dosage are known from and described in the initially mentioned publications.
The following Examples are given for the purpose 25 of illustrating the present invention:
A - 1 4 ~ 2 ~ ~ o 3 ~ o Example 1.
O~.aining rhe sennosid~ mixture used as startin~
~,- er al.
In each case, 40 Xg of senna drug are i~.~rc-. ced into two percolators, .onnected in series, wit.~ ~
volume of 250 litres and covered with a perfora~ steel plate. 7070 methanol is used as solvent for t~e extraction which is passed to the drug in the ~ t percolator. The solution formed in the first percola-tor i9 pa~sed to the drug which is present in thesecond percolator. The solvent i8 thereby allowed to flow freely through the firqt percolator.
For the extraction of 40 kg of senna drug, there is used, in all, 160 li~res of methanol. After this 15 volume of ,0% methanol has passed through the two percolators and the corresponding amount of percolate has been collected, the emptying pipe of the percolator is coupled with a post-?ercolate container and then 60 litres of 70% methanol are passed through the percolators. Thereafter, the remaining free solvent is passed from the firs~ percolator into the upper part of the second percolator and the post-percolate is collected until it makes up a total of 120 litres.
The first percolator is then emptied and again filled with 40 kg of senna drug and the post-percolate is pu~ped on to the drug, 120 litres of post-percolate ~ thereby sufficing in order to cover the drug in the 20903~o percolator. Subsequently~ tbe temperature OL the solution is ~,oug~t to +30 C. Thereafter, il is left to stand overnight. This percoLator is connected with the o~e which ~as been previously extracted and the extraction is carried out as described above.
In each case, for 40 kg of dru3 there are collected 16C litres of percolate from which the methanol is removed in a vacuum rotar~ evaporator which is eguipped with a ~ac~ed coLumn. About 3G litres of bottom product are obtained. TbiS concentrate is extracted with an equal volume of butan-2-ol which is saturated with ~ater.
The phases are then separated and the agueous phase is furt~er worked up.
Step a Reduction of the sennosides to r~ein-9-ant~rone-8-glucosides l.0 litre of the extracted concentrate is b,ou~ht to pH 7.5 with a 48% agueous solution of sodiu~ ~ydro~ide.
It is ~eated to 60~C and, w~ile s~irring, 90 g of sodium dithionite in solid form are added to the solution over ~he course of half an hour. After completion of the addition, stirring is continued for a further hour.
Subse~uently, while stirring, concentrated sulpburic acid is added thereto until the p~ value is 2. Cooling to ambient temperature is carried out over the course of 2 hours and the precipitated crystalline material is ~iltered off and washed with 9ulp~ur dioxide-containing water.
If desired, crude rhein-9-anthrone-8-glucoside is re~recipitated. The stiLl moist filter cake is dissolved in a mixture of ~5 parts by volume of butan-2-ol and 85 parts by volume of water which contains 0.5~ b~ weight of sodium pyrosulphite in such a manner that, b~ the addition of a 48% aqueous solution of sodium hydroxide up to a pH va~ue of7, a 10% solution (w/v) is obtained.
~he solution is acidified with concentrated hydrochloric acid to a pH Yalue of 2.8 or below and left to stand for 2 hours. ~e precipitate obtained is filtered off, washed with water containing sulphur dioxide or sodium pgro-sulphite and dried, The yield is 90%.
A renewed reduction (post-reduction) is carried out in the following wa~ with the product obtained in this ma~ner: 3.0 g of the crude, dried rhein-9-an'hrone-8-glucoside or the corresponding amount of the moist product are dissolved in 15 ml of water, together with 1.4 ~ of sodium ditbionite and 2,3 ml 5N aqueous sodium hydroxide solution. Subsequently, it is made up with water to 24 m~ and the so~ution is heated for 20 minutes at 55~C, Thereafter, a further 1.5 g of sodium dithionite is added to the solution~ followed b~ heating to 55~C
for 20 minutes. 0.9 ml of 5N aqueous sodium h~droxide solution and 105 g of sodium dithionite are tben added there~o. After beating for 20 minutes to 55~C, a furtber 0,9 m~ of 5N aqueous sodium hydroxide solution are again added thereto. The solution obtained is then introduced direct~ into the following liquid-liquid extraction.
20~03~0 Step b) Separatin~ off of t~e aloe-emodin components The separating off of the aloe-emodin components takes place b~ Liquid-liquid partitioning of t~e 9-anthrone-8-glucosides in countercurren' witn an apparatus of 6C mixer-settlër units. As aqueous, heavier phase, there is used a solution of 3.0 g.
sodium ~ithionite in 3.5 ml 5N aqueous sodium h~droxide solutio~ and 96 ml of water. As organic, lighter phase, there is used water-saturated buta~-2-ol or acetone.
T~e two phase are supplied to the apparatus in such a manner that t~e volume ratio of the ~eavier phase to the lighter phase is 1:10.
The mixture to be separated is supplied to ~he apparatus in the form of the freshly reduced solution or in t~e form of a solution of approp-iate p~; value and of appropriate concentration which contains t~e 9-anthrone-8-glucosides obtainedlfrom step a) in such a ma~ner that 30 parts by volume of the orga~ic phase are used per one part by volume of mixture to be separated.
The p~ of the solution containing the mixture is maintained at 9 to 9.5 ~ith t~e help of a glycine ~uffer. The buffer of 3 parts by volume of a 7.5%
g~ycine solution and 1 part by volume of lN aqueous sodium hydroxide solution is i~troduced in an amount of 240 ml of buffer solution per 150 g of crude rhein-9-anthrone-8-glucoside. The undesired aloe-emodin compounds enrich in the organic phase, whereas the rhein-9-anthrone-8-glucoside remains in the aqueous phase. The aqueous phase is acidified with sulphuric acid to pH 2.8, the precipitate formed is filtered off and washed with water and acetone and dried in the air at ambient temperature. In this way, there is obtained rhein-9-anthrone-8-glucoside with a content of aloe-emodin components of 49 ppm (determined as aloe-emodin); yield 97%, referred to rhein-9-anthrone-8-glucoside.
Step c) Oxidation of the rhein-9-anthrone-8-glucosides 18.8 g of the rhein-9-anthrone-8-glucoside obtained are dissolved in 56 ml of water and 11 ml of butan-2-ol, 17N aqueous sodium hydroxide solution being added thereto until the pH is 6.5. While stirring, air is blown through this solution for 5 hours in a cylindrical vessel with the help of a glass frit, the rate of flow of the air being 40 ml/minute. The course of the oxidation is monitored by means of HPLC.
When rhein-9-anthrone-8-glucoside can no longer be detected, the solution is diluted to about 200 ml with water/butanol (65:11 v/v). Concentrated hydrochloric acid is added thereto until the pH is 1.5 to 2, followed by stirring for 2 hours at ambient temperature. The precipitated crystals are filtered 20903iO
off, washed with water and acetone and dried. Tbere are obtained 14.4 g (76% of theor~) of pure sennoside mixture with a content of 41 ppm aloe-emodi~ components (determined as aloe-emodin), according to the analysis procedure described for step c) in Example 2.
E~ample 2 ~ he process is as described in E~ample 1 but the oxidation i~step c) is carried out as follows:
150 g of the pure rhein-9-anthrone-8-glucosides and 0.75 g ferric chloride hexahydrate are dissolved in 480 ml of water and l20 m~ of butan-2-ol. A 4~% aqueous solutio~ of sodium hydrQxide is added thereto until a pH value of 6.5 is reached and the rhein-9-anthrone-8-glucoside has dissolved. ~he solution is introduced i~to a vessel with a sinter bottom plate. Subseguentlg~
a vi~orous curre;nt of air is passed through the solution. ~he oxidation is finished after about 3C
minutes. The solution is subsequentlg diluted with a mixture of 120 ml butan-2-ol and 480 ml of water.
7.5 g sodium dithionite are added tbereto and the p~
value of the soLutio~ is adjusted to 2.0 b~ the addition of concentrated hydroch~oric acid. The solution is stirred for 18 hours. Subsequently~ the precipitate obtained is filtered off, washed with 600 ml of water and 800 ml of acetone and dried. ~he conte~t of 2 0 9 0~ ~ o ~n.~ noid co~pounds in the prc~uct obt~ined is fr~
~_ ~ 95,~.
The product is taken up in 200 ~1 of butan-~a~d ?reci?ita~ed with 800 ml o. water :i~h the add ~ion of 5.5 g sodium pyrosulphite. ~fter filtering off ~nd dryin~ the precipitate obtained, there are obtainec 95.4 g of a product of anthanoid compounds of the following composition (according to HPLC, analysis of a ty?ical experiment):
rhein-8-glucoside 1.5%
sennoside B 49.7%
sennoside Al 13.3%
sennoside A 33.6%
sennidine monoglucosides 1.1%
rhein 0.02%
99.22%
Sennosides C and D and aloe-emodin glucoside could not be detected by HPLC. The total content of aloe-emodin and of the derivatives thereof was determined as being 30 ppm according to the following method:
Sennosides C and D and aloe-emodin-8-glucoside can no longer be dependably determined as sennosides in the ppm range by means of HPLC chromatography. There-fore, it is necessary to convert the substance to beinvestigated by oxidation with ferric chloride and 2û~03~10 ~i~ultaneous hydrolysis ~ith. hyd.~chlc-i~ c_id -n a ~o-?has2 mixture of aqueous sol~~ion _a~c~ te-ra-_hloride into rhein or aloe-2mod~ e r~in s then converted into a salt so thct it ~an -~ ext act~d into the aqueous phase and the al~e-er~di~ in th~ or,anic phase can be determined by means of HPLC. In t:~is way, there can be given the total content of sennosides C
and D, aloe-emodin-8-glucosides 2nd other cloe-emodin components, expressed as aloe-emodin.
Example 3.
The extraction of the senna drug and the reduction of the sennosides described in Example 1 i9 repeated. 1~e subsequent reduction is then carried out as follows:
14.0 g saccharose, 4.5 g 8S% sodium dithionite and 13.3 g potassium acetate are di~olved in 133 ml of water and 1.3 ml of 48% ~odium hydroxide solution and 17.3 g potassium carbonate are added thereto.
Subsequently, the reaction mixture is mixed with 293 ml acetone snd 50 ml of water. The mixture is shaken in a separating funnel and the phases are ~eparated, 375 ml of upper phase (acetone phase) and 130 ml of lower phase thereby being obtained.
20903~o 1.4 ml of a 48% sodium hydroxide solutio~ and 10 g of crude rhein-9-~nthrone-8-glucoside are dissolved in 98 ml of the lower phase. The solution is.warmed to 45 to 50~C and maintained at this temperature for 2C to 30 minutes. Subsequentlg~ 1.0 ml of a 48% sodium hydroxide solution and 3.4 g sodium ~ithionite are added thereto and ~eated for a further 20 to 30 minutes to 45 to 50~C. Subseguently, there are again added 1.0 ml of 48~ sodium hydroxide solution and 3.4 g sodium dithionite, followed b~ hesting for 20 to 30 minutes to 45 to 50~C.
The separation of the aloe-emodin components takes place by liquid-liquid partitioning of the reduced solutio~ in countercurrent against tbe above-mentioned upper phase (scetone phase). The raffinate phase flowing off an~ containing the rhein-9-anthrone-8-glucosid~ is concentrated to 400 ml and mixed with 20 ml butan-2-ol. Hbdrochloric acid or sulphuric acid is added thereto up to a p~ value of 4.0 to 4.2. ~he precipitate formed is filtered off, washed with 40 ml of water and 30 ml of acetone and subse~ entl~ drled.
The subsequent oxidation takes place in the manner described in Example 2.
E~amp~e 4 The concentrate obtained after extraction of the senna drug is mixed with about 2 litres of butan-2-ol. The reduction of the mixture of the senna fruit co~centrate snd butan-2-ol is then carried out in 7 steps under nitrogen as protective ~as. After reduction step I, there follows the precipitation of the crude rhein-9-anthrone-8-g~ucoside.
Reduction step I
100 ~itres of a mixture of senna fruit conceutrate and butan-2-ol contai~ing about 4 ~g of sennosides are placed in a stirrer container and covered with ~itrogen. While stirring, 6 litres of a 20% b~ weight aqueous solution of sodium hg~roxide and thereafter 350 litres of water-saturated butan-2-ol, for exzmple from step II, are added thereto and stirred for 15 minutes. T~e batch is heated to 42 to 50~C, mixed with 7 kg sodium dithionite a~d further stirred for 45 minutes, The p~ vaLue is maintained at 7.5 to 8 with 20% b~ weight aqueous sodium hydroxide so~ution.
The reductio~ potential (against an Ag/AgCl electrode) is, if necessar~, maintained below -6~0 mV by the addition of sodium dithionite. After cooling to 30 to 35~C, precipitation is carried out witbin 1.5 hours with lOX by weig~t sulphuric acid t~ p~ ~ 4.
The resultant suspension is stirred for about 10 hours at ~ 25~C with a slow speed of sti~ring and the resultant precipitate is filtered off. T~e precipitate is suspended in 60 litres of 15~ by weight butan-2-ol, stirred for ~0 minutes at 50 to 60~C and subsequentlg filtered, The residue is washed with 100 litres A-14~
- 22 - 20903~0 of demineralised water. The crude yield of rhein-9-anthrone-8-glucoside is more than 82~, referred to the sennosides used.
Reduction steP II.
3.3 kg crude rhein-9-anthrone-8-glucoside from step I are suspended in a mixture of 42 litres of demineralised water and 7.4 litres butan-2-ol.
The suspension is brought into solution with 2 litres of 20% by weight aqueous sodium hydroxide solution and 9.9 kg trisodium citrate and thereafter mixed with 3.3 kg sodium dithionite and 350 litres water-saturated butan-2-ol, for example from step III. The batch is heated to 42 to 45~C, the pH value being maintained at 8.5 to 9 with 20% by weight aqueous ~odium hydroxide solution. The reduction potential (against an Ag/AgCl electrode) is, if necessary, maintained below -750 mV by the addition of sodium dithionite. After st~n~ng for 30 minutes, the upper phase is e...o~ed and the lower phase further worked up in step III.
Reduction step III.
The reduction/ extraction proce~s described in step II is repeated with the lower phase from step II, with the addition of the following chemi-25 calss 1.65 kg sodium dithionite, 0.8 litres 20% by weight aqueous sodium hydroxide ~olution and 350 litres water-saturated butan-2-ol, for erample from ~tep IV.
20903~0 Reduction steps IV and VII
The reduction/extrsction process described in step II is repeated wi~h, in each case, the lower phase from t~e precedin~ step with the addition of the following chemicals:
0.825 kg sodium dithionite G.4 litres of 2GX by weight aqueous sodium hydroxide solution and 350 litres of water-saturated butan-2-ol, for example in each case from the following step - countercurrent principle.
The lower pnase separated off in step VII is cooled to 30 to 35~C and the rhein-9-anthrone-8-glucoside precipitated out as described in step I. ~he resultant precipitate is fi~tered off and washed with 100 litres o~ demineralised water. Subsequent~g~ it is covered with lQ litres of ferric sulphate solution (28 kg ferric sulphate in 100 ~itres of demineralised water).
~he rhein-9-anthrone-8-glucoside is then converted into tQe sennosides in the manner described i~ Example 1 or 2.
Example 5 The oxidation of rhei~-9-anthrone-8-glucoside can also take place according to the following process:
6.0 kg of filter-moist rhein-9-anthrone-8-glucoside are mixed with 12.6 ~g trisodium citrate. ~his mixture is dissolved in 7.C litres of lN aqueous sodium h~droxide solution with vi~orous stirring and mixed 20903~0 with 0.7 litres of butan-2-ol. Subsequentl~ it is mixed with 8.8 Litres of ferric sulphate solution (28 kg ferric sulphate in 100 Litres of demineralised wate,) a~d sufficient 20~ aqueous sodium hydroxide solution added to give a pH value of about 8.3. ~he solution is left to react for 3 to 4 hours at about 40~C, then acidified with ~2~ sulphuric acid to pH
value 1.8 to 2,0 and worked up in the manner described in Example 1.
Example 6 Alte.~atively, rhein-9-a~throne-8-glucoside is dissolvea in 50 ml o~ water bg the addition of calcium hgdroxide-saccharose solution (prepared by suspending 7.0 g czlcium-hgdroxide i~ a solution of 30.0 g saccharose in lOC ml of water and removal of the undissolved ca~cium h~droxide). 20 ml butan-2-ol are added thereto and a vigorous current of air is passed through the solution over the course of 90 mi~utes.
5.0 g calcium cbloride dihydrate are added thereto and the pH value is adjusted to 8.5 with the calcium nydroxiàe-saccharose solution. ~he precipitate formed is filtered off and the filtrate is diluted with water to 340 ml, mixed with 60 ml butan-2-ol and adjusted to pH value 2.C with concentrated hydrochloric acid.
Further wor~ing up takes place in the ma~ner described in ~xample 1.
20903~0 Pharmacolo~ical investi~ations Laxative action The laxative effect of the sennoside mixture according to the present invention was determined o~
mice. Male I~I mice were used which were ~ept duri~g the experiment i~ Plexiglas cages and whicb received sta~dard feed mixed with tap water (1:1) o mushy consistencg. A separate supply of drinking water was not provided during the experiment.
~e animals received ~00, 200 and 400 mg/kg of the sennoside mixture in 10 ml of 0.5% aqueous sodium hydrogen carbonate/kg by means of a stomac~ probe.
Aft2r administration of the compounds to be tested, faeces and urine of the animals were collected over ~he course of 24 hours and the~ determined. The results obtained, referred to kg of body weight, are summar-ised in the following Table.
Table ~a~ative effect of the sen~oside mixture according ~o the present invention on mice dossge number number of number of soft faeces as (mg/kg) of normaL soft ~aecal % of the total animaLs faecal pellets faecal pellets ~ excretio~
100 40 587 144 2a.0 2~0 3~ 223 2~9 56.0 400 30 236 282 60.0 -It can be see~ that the sennosides display a good laxative action which commences relatively guickly.
~he time up to the appe~rance of the first soft faeces (2 hours) is, however, also to be combined with the previous transit to the large intestine and a brea~down of the sennosides bg the flora of the large intestine, A dosage-action relationship is present, Acute toxicitg I~ each case, male and female Wistar rats were given sennosides once i~ dosages of from 200 to 25,000 mg/kg by means of a stomach probe.
Macroscopic orga~ damage caused b~ the administered substances could not be observed. The following ID50 values were ascertained:
+ 840 male rats: 5200 - 720 mg/kg female rats: + 380 mg/kg In the case of male and fema~ mice (n = 8, strain NI~I), the maximum administerable dose of 50C0 mg/kg did not result in any deaths, In all mi~e ~ diarrhoea occurred, although to a lesser extent than in the case of rats, For both sexes, the ~D50 values were > 5000 mg/kg,
The sennosides are laxative-acting substances which occur in the dried drugs of the genus Cassia and Rheum. The senna drug consists of the dried leaves and pods of the senna plant, for example of Indian senna (Cassia angustifolia)~
The laxative-active sennosides are dianthrone glucosides derived from rhein and aloe-emodin, the most important ones being sennosides A, B, Al, C, D
and Dl. They correspond to the general formula:-6 11~5 ~ 0 OH
~-~ ~ ~ COOH
C6 11~5 ~ OH
- In the case of sennosides A, B and Al, R stands for COOH and in the case of sennosides C, D and Dl, R
stands for CH20H. Sennosides A, B and A1 and C, D and D1 are stereoisomers and differ from one another by the configuration on carbon atoms 10 and 10'.
Besides the sennosides, the crude drug also contains aglycones (sennidines), semi-glycosylated sennidines, polymers, decomposition products of the sennosides, aloe-emodin and derivatives thereof etc.
which can bring about undesired side effects, such as ill-feeling, vomiting, flatulence and colic.
Processes for obtaining sennosides from senna drug are described, for example in German Patent No.
1,617,667, French Patent No. M 6,611, Canadian Patent No. 1,203,800 and U.S. Patent No. 4,595,592. Depending upon the drug, the sennosides obtained according to these known processes contain a sennoside mixture with 1.5 to 5% of sennosides C, D and D1. As has already been indicated above, these contain in their molecule a moiety derived from aloe-emodin of the formula:
~
HO O OH
~
It would be desirable if sennosides could be obtained which are substantially free from sennosides C, D and D1.
A substantially complete separation of sennosides C, D and D1 from a sennoside mixture is not known from the present state of the art.
20903~u Therefore, it is an object of the p.ese~t invention to provide a process for obtaining sennosides A, B and Al which are substantiall~ free from u~esi-ed acco~pany-ing materials ~ndespecial~y from sennosides v, D and Dl.
ThUs~ accordin~ to the present inventio,., there is provided a process for obtaining sennosides A, B and Al of t~e formula:-C6H11 5 ~ O OH
lcco~
CCOH
~o 13 C6~11~5 ~ OH
wherein al a sennoside mixture is reduced to rhein-9-anthrone-8 glucoside and aloe-emodin-9-ant~rone-8-glucoside, b) a liquid-liquid partitioning of the compounds obtained is carried out between a polar organic solve~t which is only partly miscible with water and a~ aqueous p~ase and c) t~e rhein-9-anthrone-8-glucoside contained after partitioning in the agueous phase is again oxidised to the corresponding sennosides and these are recove~d.
~0~40 Step a) As starting material for the process according to the present invention, there are, in general, used sennoside mixtures such as are obtained in the extraction of senna drug according to the above-mentioned processes. For example, as starting material, a sennoside mixture can be used which is obtained by the process described in Canadian Patent No. 1,203,800 and U.S. Patent No. 4,595,592.
Thereafter, the senna drug is first extracted with aqueous methanol. The concentrate remaining after complete removal of the methanol contains the sennosides in the form of the potassium salts. This concentrate can be used as starting material for the process according to the present invention.
The concentrate can also be purified by liquid-liquid extraction with alcohols or ketones which are partly soluble in water, for example butan-2-ol, butan-2-one or acetone. The raffinate is acidified to a pH of about 1.5 to 2.0 and the sennosides are brought to crystallisation by seeding. The crude sennoside mixture obtained can also be used as starting material for the process according to the present invention. If desired, the crude sennoside mixture can also be recrystallised.
Alternatively, the concentrate mixed with an alcohol or ketone which is partly soluble in water, especially butan-2-ol, can be used as starting material.
In the case of the extraction of the senna drug, the ratio of drug to extraction solvent is preferably 1:4 to 1:15 and especially 1:4 to 1:10.
20903~0 The extraction is ?referably carried out in the prese~ce of a buf er, for example trisodium citrate, glycine, sodium bicarbonate or sacc~arose According to the process of the present invention, t~ese starti~g materials are completely reduced to the corresponding rhein-9-anthrone-8-glucoside (R = COO~) a~d to the corresponding aloe-emodin-9-anthrone-8-glucoside (R = CE20H) of the ge~eral formula:-C5~1C5 ~ O OH
~ R
~educi~g agents with an appropriate reduction pote~ial ind~de, for example, stannous chloride, sulphur dioxide, alkali metal boron hydrides and preferab~ a~kali metal dithionites, especial~y sodiuE di~hionite.
For carrying out the reduction, the startin~
material can be present i~ aqueous solution or suspension a~d the reducing agent added thereto in o solid form or dissolved in water. Especially in thecase of using senna fruit primary extract according to Canadian Patent No. 1,203,800 and U.S. Patent No.
4,595,592 (aqueous concentrate), it is also possible to work in a two-phase mixture by adding a polar organic solvent which is partly miscible with water, especially butan-2-ol or acetone.
The reduction can be carried out at ambient temperature or at an elevated temperature. The reduction is preferably carried out at 40 to 60~C and especially at 50 to 55~C. Working can be carried out at a weakly acidic to weakly alkaline pH value of the solution or suspension of the starting sennoside solution and preferably at a pH value of from 5 to 10.5. If desired, the reduction can be carried out several times, especially 2 to 10 times.
20~03~0 The 9-a~throne-8-glucoside formed is precipitated out by the addition of an acid, for example of sulphuric acid, up to a p~ value of about 2 to 4.5.
The temperature s~ould thereb~ preferably be ~ot more than 40~C, In t~e case of precipitating out the antbrone glucosides, a~d i~ the case of of the isolation thereof, for example b~ fi~tration, it is preferab~e to work u~der an atmosphere of nitrogen in order to prevent an uncontrolled oxidatio~ of t~ese compounds.
It is importsnt that the reduction proceeds to completion. ~herefore, it IS preferable to use the reducing age~t in large excess, Ditbionites and especially sodium dithionite are, in ge~eral, used in a l to 4 ~old amount bg weight, referred to the content of sennosides i~ the starting material, Furthermore, the reducing age~ is allowed to act for at least 2 ~ours and preferably for at least ~ hours. In general, the reduction takes place for ~ot longer tban lO bours, h post-reduction is preferablg carried out u~der the given conditions.
Before its use in step b), the product obtai~ed is preferably reprecipitated b~ bringing it into agueous solution bg the additio~ of a base, for examp~e sodium hgdro~ide or potassium bydroxide, to a p~ value of abput 6 to 7, extracting the solution with butan-2-ol, butan-2-one or acetone and again precipitating out the product bg the additiou of an acid to a p~
va~ue of about 2 to 4, 20 ~03L1O
Step b) In this step, the aloe-emodin components and especially aloe-emodin-9-anthrone-8-glucoside are removedO For this purpose, a liquid-liquid partitioning of the product obtained is carried out ina polar organic solvent which is only partlg miscible with water and an aqueous phase. Appropriate polar organic solvents include C4-C5-alkanols and di-Cl-C3-alkyl ketones, for example butan-l-o~, butan-2-ol, butan-2-one and acetone, butan-2-ol and acetone preferably being usedO
To the aqueous phase is preferablg added a reducing agent in order to impart to the aqueous phase during the whole of the liquid-liquid partitioning a redox potential of -210 mV or more negative. It is preferred to use the same reducing agent as in step a).
In the case of using an alkali metal dithionite as reducing agent, in general a 2 to 4~ by weight solution at a pH value of 7 to 10.5 is sufficient i~ order to maintain the mentioned potential conditions. The p~
2~ value is preferabl~ maintained in this range by the addition of a buffer.
The volume ratio of aqueous phase (heav~ phase) to organic phase (light phase) is generally in the range of from 1:5 to 1:40.
The liquid-liquid extraction preferably takes place in countercurrent. ~he mixture of the anthrone compounds is therebg i~troduced in the form of the solution obtained after the reduction or, when the anthrone . 9 compounds ~ave bee~ isolated, in the form of a 3 to 15~ by wei~ht solulion.
After 'he parti~ioning, the desired rhein-9-anthrone-8-glucoside is present in the aqueous phase. It is pre-cipitated out D~ the addition of an acid up to a pHvalue of about 2 to 4 and recovered in the usual wa~.
Step c) In tbis step, the rhei~-9-anthrone-8-glucoside is again oxidised to the corresponding sennoside compounds.
Oxidation agents appropriate for this purpose include h~drogen peroxide, manga~ese dioxide, permanganates and manganic acetonylacetonate. ~owever, the oxidation is preferably carried out with oxy~en. As t~e source of oxygen, air can, for example, be used.
Since rhein-9-a~throne-8-glucoside is insoluble in water, for the oxiaG~ion it is converted into a soluble form. This can ~-~ake p~ace, for example, by converting it into an alkali metal salt or into the calcium salt bg the addition of an appropriate base up to a p~ value of about 6 to 7. If desired, a small amount (up to about 30% bg volu~e) OL a solvent which is onlg partly miscible with water, especially butan-~-ol, can be added to tbe solu ionO
The oxidation ~8 carried out in 8 solution wbich is as concentrated as possible because, in this wag, the formation of the desired sennosides is favoured. ~he oxidation iD preferably carried out with a solutio~
which contains about 250 to ~00 g of rhein-9-anthrone-20~03~0 -lC-8-glucoside per Litre of solvent In t~e case of using oxygen as oxidation agent, this is preferably passed ~hrough the solutio~.
T~e oxidation with ox~ge~ can be facilitated bg the use of a catal~st. Appropriate catalgsts include, for example, palladium black and ferric salts, especially ferric chloride. In general, the amount of catal~st lies in the range of 0.2 to 2~ bg weight, referred to the amount of rhein-9-anthrone-8-glucoside, and especiallg in the range of 0.5 to 1% b~ weight.
Alternatively, the oxidation can be carried out with a ferric salt, for example ferric sulphate or ferric chloride, at a p~ value of 8 to 8.5. It is t~ereby pre-ferred to work at 3C to 50~C and in the presence of trisodium citrate.
~ he oxidation is carried out ~ntil the rhein-9-anthrone-8-glucoside can no longer be detected (absence of the ultra-violet fluorescence of the anthrone compounds).
The sennosides are obtained in the usual way by acidi~ication of the solution obtsined. The solution is 2referably di~uted before the addition of the acid with the solvent used, fo~ e~ample water/b~tan-2-ol, to 2 to 3 times the volume present. In this wag, it is achieved that the rhein-8-glucoside formed as b~-product remains substantially in solution in the case of the precipit-ation of the sennosides.
20903~10 The separation of the rhein-8-glucoside can also take place via the calcium salt because the calcium salt of rhein-8-gluco8ide is insolubie and precipitates out, whereas the calcium calts of the senno8ide5 remain in 901ution.
The sennosides are preci?itated out by the addition of an acid to a p~ of about 2 to 4 and then recovered in the usual way.
The sennosides obtained are substantially the 10 sennosides A, B and Al. They are substantially free h~sennosides C, D and Dl and ~m other aloe-emodin contaminations. The contents of sennosides C, D and Dl -n the product obtained according to the present invention is less than 100 ppm, determined according 15 to the methods of analysis described in the following Examples.
The present invention is also concerned with the mixture of sennosides A, B and Al obtainable according to the present invention, as well as with pharma-20 ceutical compositions which contain the said mixture.
The field of use, the dosage to be administeredand the appropriate forms of dosage are known from and described in the initially mentioned publications.
The following Examples are given for the purpose 25 of illustrating the present invention:
A - 1 4 ~ 2 ~ ~ o 3 ~ o Example 1.
O~.aining rhe sennosid~ mixture used as startin~
~,- er al.
In each case, 40 Xg of senna drug are i~.~rc-. ced into two percolators, .onnected in series, wit.~ ~
volume of 250 litres and covered with a perfora~ steel plate. 7070 methanol is used as solvent for t~e extraction which is passed to the drug in the ~ t percolator. The solution formed in the first percola-tor i9 pa~sed to the drug which is present in thesecond percolator. The solvent i8 thereby allowed to flow freely through the firqt percolator.
For the extraction of 40 kg of senna drug, there is used, in all, 160 li~res of methanol. After this 15 volume of ,0% methanol has passed through the two percolators and the corresponding amount of percolate has been collected, the emptying pipe of the percolator is coupled with a post-?ercolate container and then 60 litres of 70% methanol are passed through the percolators. Thereafter, the remaining free solvent is passed from the firs~ percolator into the upper part of the second percolator and the post-percolate is collected until it makes up a total of 120 litres.
The first percolator is then emptied and again filled with 40 kg of senna drug and the post-percolate is pu~ped on to the drug, 120 litres of post-percolate ~ thereby sufficing in order to cover the drug in the 20903~o percolator. Subsequently~ tbe temperature OL the solution is ~,oug~t to +30 C. Thereafter, il is left to stand overnight. This percoLator is connected with the o~e which ~as been previously extracted and the extraction is carried out as described above.
In each case, for 40 kg of dru3 there are collected 16C litres of percolate from which the methanol is removed in a vacuum rotar~ evaporator which is eguipped with a ~ac~ed coLumn. About 3G litres of bottom product are obtained. TbiS concentrate is extracted with an equal volume of butan-2-ol which is saturated with ~ater.
The phases are then separated and the agueous phase is furt~er worked up.
Step a Reduction of the sennosides to r~ein-9-ant~rone-8-glucosides l.0 litre of the extracted concentrate is b,ou~ht to pH 7.5 with a 48% agueous solution of sodiu~ ~ydro~ide.
It is ~eated to 60~C and, w~ile s~irring, 90 g of sodium dithionite in solid form are added to the solution over ~he course of half an hour. After completion of the addition, stirring is continued for a further hour.
Subse~uently, while stirring, concentrated sulpburic acid is added thereto until the p~ value is 2. Cooling to ambient temperature is carried out over the course of 2 hours and the precipitated crystalline material is ~iltered off and washed with 9ulp~ur dioxide-containing water.
If desired, crude rhein-9-anthrone-8-glucoside is re~recipitated. The stiLl moist filter cake is dissolved in a mixture of ~5 parts by volume of butan-2-ol and 85 parts by volume of water which contains 0.5~ b~ weight of sodium pyrosulphite in such a manner that, b~ the addition of a 48% aqueous solution of sodium hydroxide up to a pH va~ue of7, a 10% solution (w/v) is obtained.
~he solution is acidified with concentrated hydrochloric acid to a pH Yalue of 2.8 or below and left to stand for 2 hours. ~e precipitate obtained is filtered off, washed with water containing sulphur dioxide or sodium pgro-sulphite and dried, The yield is 90%.
A renewed reduction (post-reduction) is carried out in the following wa~ with the product obtained in this ma~ner: 3.0 g of the crude, dried rhein-9-an'hrone-8-glucoside or the corresponding amount of the moist product are dissolved in 15 ml of water, together with 1.4 ~ of sodium ditbionite and 2,3 ml 5N aqueous sodium hydroxide solution. Subsequently, it is made up with water to 24 m~ and the so~ution is heated for 20 minutes at 55~C, Thereafter, a further 1.5 g of sodium dithionite is added to the solution~ followed b~ heating to 55~C
for 20 minutes. 0.9 ml of 5N aqueous sodium h~droxide solution and 105 g of sodium dithionite are tben added there~o. After beating for 20 minutes to 55~C, a furtber 0,9 m~ of 5N aqueous sodium hydroxide solution are again added thereto. The solution obtained is then introduced direct~ into the following liquid-liquid extraction.
20~03~0 Step b) Separatin~ off of t~e aloe-emodin components The separating off of the aloe-emodin components takes place b~ Liquid-liquid partitioning of t~e 9-anthrone-8-glucosides in countercurren' witn an apparatus of 6C mixer-settlër units. As aqueous, heavier phase, there is used a solution of 3.0 g.
sodium ~ithionite in 3.5 ml 5N aqueous sodium h~droxide solutio~ and 96 ml of water. As organic, lighter phase, there is used water-saturated buta~-2-ol or acetone.
T~e two phase are supplied to the apparatus in such a manner that t~e volume ratio of the ~eavier phase to the lighter phase is 1:10.
The mixture to be separated is supplied to ~he apparatus in the form of the freshly reduced solution or in t~e form of a solution of approp-iate p~; value and of appropriate concentration which contains t~e 9-anthrone-8-glucosides obtainedlfrom step a) in such a ma~ner that 30 parts by volume of the orga~ic phase are used per one part by volume of mixture to be separated.
The p~ of the solution containing the mixture is maintained at 9 to 9.5 ~ith t~e help of a glycine ~uffer. The buffer of 3 parts by volume of a 7.5%
g~ycine solution and 1 part by volume of lN aqueous sodium hydroxide solution is i~troduced in an amount of 240 ml of buffer solution per 150 g of crude rhein-9-anthrone-8-glucoside. The undesired aloe-emodin compounds enrich in the organic phase, whereas the rhein-9-anthrone-8-glucoside remains in the aqueous phase. The aqueous phase is acidified with sulphuric acid to pH 2.8, the precipitate formed is filtered off and washed with water and acetone and dried in the air at ambient temperature. In this way, there is obtained rhein-9-anthrone-8-glucoside with a content of aloe-emodin components of 49 ppm (determined as aloe-emodin); yield 97%, referred to rhein-9-anthrone-8-glucoside.
Step c) Oxidation of the rhein-9-anthrone-8-glucosides 18.8 g of the rhein-9-anthrone-8-glucoside obtained are dissolved in 56 ml of water and 11 ml of butan-2-ol, 17N aqueous sodium hydroxide solution being added thereto until the pH is 6.5. While stirring, air is blown through this solution for 5 hours in a cylindrical vessel with the help of a glass frit, the rate of flow of the air being 40 ml/minute. The course of the oxidation is monitored by means of HPLC.
When rhein-9-anthrone-8-glucoside can no longer be detected, the solution is diluted to about 200 ml with water/butanol (65:11 v/v). Concentrated hydrochloric acid is added thereto until the pH is 1.5 to 2, followed by stirring for 2 hours at ambient temperature. The precipitated crystals are filtered 20903iO
off, washed with water and acetone and dried. Tbere are obtained 14.4 g (76% of theor~) of pure sennoside mixture with a content of 41 ppm aloe-emodi~ components (determined as aloe-emodin), according to the analysis procedure described for step c) in Example 2.
E~ample 2 ~ he process is as described in E~ample 1 but the oxidation i~step c) is carried out as follows:
150 g of the pure rhein-9-anthrone-8-glucosides and 0.75 g ferric chloride hexahydrate are dissolved in 480 ml of water and l20 m~ of butan-2-ol. A 4~% aqueous solutio~ of sodium hydrQxide is added thereto until a pH value of 6.5 is reached and the rhein-9-anthrone-8-glucoside has dissolved. ~he solution is introduced i~to a vessel with a sinter bottom plate. Subseguentlg~
a vi~orous curre;nt of air is passed through the solution. ~he oxidation is finished after about 3C
minutes. The solution is subsequentlg diluted with a mixture of 120 ml butan-2-ol and 480 ml of water.
7.5 g sodium dithionite are added tbereto and the p~
value of the soLutio~ is adjusted to 2.0 b~ the addition of concentrated hydroch~oric acid. The solution is stirred for 18 hours. Subsequently~ the precipitate obtained is filtered off, washed with 600 ml of water and 800 ml of acetone and dried. ~he conte~t of 2 0 9 0~ ~ o ~n.~ noid co~pounds in the prc~uct obt~ined is fr~
~_ ~ 95,~.
The product is taken up in 200 ~1 of butan-~a~d ?reci?ita~ed with 800 ml o. water :i~h the add ~ion of 5.5 g sodium pyrosulphite. ~fter filtering off ~nd dryin~ the precipitate obtained, there are obtainec 95.4 g of a product of anthanoid compounds of the following composition (according to HPLC, analysis of a ty?ical experiment):
rhein-8-glucoside 1.5%
sennoside B 49.7%
sennoside Al 13.3%
sennoside A 33.6%
sennidine monoglucosides 1.1%
rhein 0.02%
99.22%
Sennosides C and D and aloe-emodin glucoside could not be detected by HPLC. The total content of aloe-emodin and of the derivatives thereof was determined as being 30 ppm according to the following method:
Sennosides C and D and aloe-emodin-8-glucoside can no longer be dependably determined as sennosides in the ppm range by means of HPLC chromatography. There-fore, it is necessary to convert the substance to beinvestigated by oxidation with ferric chloride and 2û~03~10 ~i~ultaneous hydrolysis ~ith. hyd.~chlc-i~ c_id -n a ~o-?has2 mixture of aqueous sol~~ion _a~c~ te-ra-_hloride into rhein or aloe-2mod~ e r~in s then converted into a salt so thct it ~an -~ ext act~d into the aqueous phase and the al~e-er~di~ in th~ or,anic phase can be determined by means of HPLC. In t:~is way, there can be given the total content of sennosides C
and D, aloe-emodin-8-glucosides 2nd other cloe-emodin components, expressed as aloe-emodin.
Example 3.
The extraction of the senna drug and the reduction of the sennosides described in Example 1 i9 repeated. 1~e subsequent reduction is then carried out as follows:
14.0 g saccharose, 4.5 g 8S% sodium dithionite and 13.3 g potassium acetate are di~olved in 133 ml of water and 1.3 ml of 48% ~odium hydroxide solution and 17.3 g potassium carbonate are added thereto.
Subsequently, the reaction mixture is mixed with 293 ml acetone snd 50 ml of water. The mixture is shaken in a separating funnel and the phases are ~eparated, 375 ml of upper phase (acetone phase) and 130 ml of lower phase thereby being obtained.
20903~o 1.4 ml of a 48% sodium hydroxide solutio~ and 10 g of crude rhein-9-~nthrone-8-glucoside are dissolved in 98 ml of the lower phase. The solution is.warmed to 45 to 50~C and maintained at this temperature for 2C to 30 minutes. Subsequentlg~ 1.0 ml of a 48% sodium hydroxide solution and 3.4 g sodium ~ithionite are added thereto and ~eated for a further 20 to 30 minutes to 45 to 50~C. Subseguently, there are again added 1.0 ml of 48~ sodium hydroxide solution and 3.4 g sodium dithionite, followed b~ hesting for 20 to 30 minutes to 45 to 50~C.
The separation of the aloe-emodin components takes place by liquid-liquid partitioning of the reduced solutio~ in countercurrent against tbe above-mentioned upper phase (scetone phase). The raffinate phase flowing off an~ containing the rhein-9-anthrone-8-glucosid~ is concentrated to 400 ml and mixed with 20 ml butan-2-ol. Hbdrochloric acid or sulphuric acid is added thereto up to a p~ value of 4.0 to 4.2. ~he precipitate formed is filtered off, washed with 40 ml of water and 30 ml of acetone and subse~ entl~ drled.
The subsequent oxidation takes place in the manner described in Example 2.
E~amp~e 4 The concentrate obtained after extraction of the senna drug is mixed with about 2 litres of butan-2-ol. The reduction of the mixture of the senna fruit co~centrate snd butan-2-ol is then carried out in 7 steps under nitrogen as protective ~as. After reduction step I, there follows the precipitation of the crude rhein-9-anthrone-8-g~ucoside.
Reduction step I
100 ~itres of a mixture of senna fruit conceutrate and butan-2-ol contai~ing about 4 ~g of sennosides are placed in a stirrer container and covered with ~itrogen. While stirring, 6 litres of a 20% b~ weight aqueous solution of sodium hg~roxide and thereafter 350 litres of water-saturated butan-2-ol, for exzmple from step II, are added thereto and stirred for 15 minutes. T~e batch is heated to 42 to 50~C, mixed with 7 kg sodium dithionite a~d further stirred for 45 minutes, The p~ vaLue is maintained at 7.5 to 8 with 20% b~ weight aqueous sodium hydroxide so~ution.
The reductio~ potential (against an Ag/AgCl electrode) is, if necessar~, maintained below -6~0 mV by the addition of sodium dithionite. After cooling to 30 to 35~C, precipitation is carried out witbin 1.5 hours with lOX by weig~t sulphuric acid t~ p~ ~ 4.
The resultant suspension is stirred for about 10 hours at ~ 25~C with a slow speed of sti~ring and the resultant precipitate is filtered off. T~e precipitate is suspended in 60 litres of 15~ by weight butan-2-ol, stirred for ~0 minutes at 50 to 60~C and subsequentlg filtered, The residue is washed with 100 litres A-14~
- 22 - 20903~0 of demineralised water. The crude yield of rhein-9-anthrone-8-glucoside is more than 82~, referred to the sennosides used.
Reduction steP II.
3.3 kg crude rhein-9-anthrone-8-glucoside from step I are suspended in a mixture of 42 litres of demineralised water and 7.4 litres butan-2-ol.
The suspension is brought into solution with 2 litres of 20% by weight aqueous sodium hydroxide solution and 9.9 kg trisodium citrate and thereafter mixed with 3.3 kg sodium dithionite and 350 litres water-saturated butan-2-ol, for example from step III. The batch is heated to 42 to 45~C, the pH value being maintained at 8.5 to 9 with 20% by weight aqueous ~odium hydroxide solution. The reduction potential (against an Ag/AgCl electrode) is, if necessary, maintained below -750 mV by the addition of sodium dithionite. After st~n~ng for 30 minutes, the upper phase is e...o~ed and the lower phase further worked up in step III.
Reduction step III.
The reduction/ extraction proce~s described in step II is repeated with the lower phase from step II, with the addition of the following chemi-25 calss 1.65 kg sodium dithionite, 0.8 litres 20% by weight aqueous sodium hydroxide ~olution and 350 litres water-saturated butan-2-ol, for erample from ~tep IV.
20903~0 Reduction steps IV and VII
The reduction/extrsction process described in step II is repeated wi~h, in each case, the lower phase from t~e precedin~ step with the addition of the following chemicals:
0.825 kg sodium dithionite G.4 litres of 2GX by weight aqueous sodium hydroxide solution and 350 litres of water-saturated butan-2-ol, for example in each case from the following step - countercurrent principle.
The lower pnase separated off in step VII is cooled to 30 to 35~C and the rhein-9-anthrone-8-glucoside precipitated out as described in step I. ~he resultant precipitate is fi~tered off and washed with 100 litres o~ demineralised water. Subsequent~g~ it is covered with lQ litres of ferric sulphate solution (28 kg ferric sulphate in 100 ~itres of demineralised water).
~he rhein-9-anthrone-8-glucoside is then converted into tQe sennosides in the manner described i~ Example 1 or 2.
Example 5 The oxidation of rhei~-9-anthrone-8-glucoside can also take place according to the following process:
6.0 kg of filter-moist rhein-9-anthrone-8-glucoside are mixed with 12.6 ~g trisodium citrate. ~his mixture is dissolved in 7.C litres of lN aqueous sodium h~droxide solution with vi~orous stirring and mixed 20903~0 with 0.7 litres of butan-2-ol. Subsequentl~ it is mixed with 8.8 Litres of ferric sulphate solution (28 kg ferric sulphate in 100 Litres of demineralised wate,) a~d sufficient 20~ aqueous sodium hydroxide solution added to give a pH value of about 8.3. ~he solution is left to react for 3 to 4 hours at about 40~C, then acidified with ~2~ sulphuric acid to pH
value 1.8 to 2,0 and worked up in the manner described in Example 1.
Example 6 Alte.~atively, rhein-9-a~throne-8-glucoside is dissolvea in 50 ml o~ water bg the addition of calcium hgdroxide-saccharose solution (prepared by suspending 7.0 g czlcium-hgdroxide i~ a solution of 30.0 g saccharose in lOC ml of water and removal of the undissolved ca~cium h~droxide). 20 ml butan-2-ol are added thereto and a vigorous current of air is passed through the solution over the course of 90 mi~utes.
5.0 g calcium cbloride dihydrate are added thereto and the pH value is adjusted to 8.5 with the calcium nydroxiàe-saccharose solution. ~he precipitate formed is filtered off and the filtrate is diluted with water to 340 ml, mixed with 60 ml butan-2-ol and adjusted to pH value 2.C with concentrated hydrochloric acid.
Further wor~ing up takes place in the ma~ner described in ~xample 1.
20903~0 Pharmacolo~ical investi~ations Laxative action The laxative effect of the sennoside mixture according to the present invention was determined o~
mice. Male I~I mice were used which were ~ept duri~g the experiment i~ Plexiglas cages and whicb received sta~dard feed mixed with tap water (1:1) o mushy consistencg. A separate supply of drinking water was not provided during the experiment.
~e animals received ~00, 200 and 400 mg/kg of the sennoside mixture in 10 ml of 0.5% aqueous sodium hydrogen carbonate/kg by means of a stomac~ probe.
Aft2r administration of the compounds to be tested, faeces and urine of the animals were collected over ~he course of 24 hours and the~ determined. The results obtained, referred to kg of body weight, are summar-ised in the following Table.
Table ~a~ative effect of the sen~oside mixture according ~o the present invention on mice dossge number number of number of soft faeces as (mg/kg) of normaL soft ~aecal % of the total animaLs faecal pellets faecal pellets ~ excretio~
100 40 587 144 2a.0 2~0 3~ 223 2~9 56.0 400 30 236 282 60.0 -It can be see~ that the sennosides display a good laxative action which commences relatively guickly.
~he time up to the appe~rance of the first soft faeces (2 hours) is, however, also to be combined with the previous transit to the large intestine and a brea~down of the sennosides bg the flora of the large intestine, A dosage-action relationship is present, Acute toxicitg I~ each case, male and female Wistar rats were given sennosides once i~ dosages of from 200 to 25,000 mg/kg by means of a stomach probe.
Macroscopic orga~ damage caused b~ the administered substances could not be observed. The following ID50 values were ascertained:
+ 840 male rats: 5200 - 720 mg/kg female rats: + 380 mg/kg In the case of male and fema~ mice (n = 8, strain NI~I), the maximum administerable dose of 50C0 mg/kg did not result in any deaths, In all mi~e ~ diarrhoea occurred, although to a lesser extent than in the case of rats, For both sexes, the ~D50 values were > 5000 mg/kg,
Claims (15)
1. Process for obtaining a mixture of sennosides A, B and Al of the formula:
which mixture is substantially free from aloe-emodin derivatives and contains less than 100 ppm of sennosides C, D and D1, wherein a) a sennoside mixture is reduced to rhein-9-anthrone-8-glucoside and aloe-emodin-9-anthrone-8-glucoside;
b) a liquid-liquid partitioning of the compounds obtained in step (a) is carried out between a polar organic solvent which is only partly miscible with water and an aqueous phase, and c) the rhein-9-anthrone-8-glucoside contained in the aqueous phase after partitioning is again oxidised to the corresponding sennosides which are recovered.
which mixture is substantially free from aloe-emodin derivatives and contains less than 100 ppm of sennosides C, D and D1, wherein a) a sennoside mixture is reduced to rhein-9-anthrone-8-glucoside and aloe-emodin-9-anthrone-8-glucoside;
b) a liquid-liquid partitioning of the compounds obtained in step (a) is carried out between a polar organic solvent which is only partly miscible with water and an aqueous phase, and c) the rhein-9-anthrone-8-glucoside contained in the aqueous phase after partitioning is again oxidised to the corresponding sennosides which are recovered.
2. Process according to claim 1, wherein the sennoside mixture is obtained by extraction of senna drug with aqueous methanol.
3. Process according to claim 2, wherein the extraction with methanol is carried out in the presence of a buffer.
4. Process according to any of claims 1 to 3, wherein an alkali metal dithionite is used as reducing agent in step (a).
5. Process according to claim 4, wherein working is carried out at a pH value of 5 to 10.5.
6. Process according to any one of claims 1 to 5, wherein butan-2-ol or scetone is used as polar organic solvent in step (b).
7. Process according to any one of claims 1 to 6, wherein an aqueous phase is used in step (b) the redox potential of which is -210 mV or more negative.
8. Process according to any one of 1 to 7, wherein the liquid-liquid partitioning in step (b) is carried out in countercurrent.
9. Process according to any one of claims 1 to 8, wherein the oxidation in step (c) is carried out with oxygen or a ferric salt.
10. Process according to claim 9, wherein the oxidation with oxygen is carried out at a weakly acidic pH value.
11. Process according to claim 9 or 10, wherein the oxidation is carried out in the presence of a catalyst.
12. Process according to claim 11, wherein the catalyst is a ferric salt.
13. A mixture of sennosides A, B and A1, whenever obtained by a process according to any one of claims 1 to 12.
14. A mixture of sennosides A, B and A1 which is substantially free from aloe-emodin derivatives and contains less than 100 ppm of sennosides C, D and D1.
15. A pharmaceutical composition containing as active ingredient a mixture of sennosides as defined in claim 13 or 14, together with a pharmaceutically acceptable carrier therefor.
Applications Claiming Priority (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| DE4120991A DE4120991A1 (en) | 1991-06-25 | 1991-06-25 | PROCESS FOR OBTAINING SENNOSIDES A, B AND A1 |
| DEP4120991.5 | 1991-06-25 |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CA2090340A1 CA2090340A1 (en) | 1992-12-26 |
| CA2090340C true CA2090340C (en) | 1998-08-18 |
Family
ID=6434719
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA002090340A Expired - Fee Related CA2090340C (en) | 1991-06-25 | 1992-06-24 | Method of extracting sennosides a, b and a1 |
Country Status (18)
| Country | Link |
|---|---|
| EP (1) | EP0544886B1 (en) |
| JP (1) | JP2705733B2 (en) |
| AT (1) | ATE157984T1 (en) |
| AU (1) | AU662343B2 (en) |
| CA (1) | CA2090340C (en) |
| CZ (1) | CZ281687B6 (en) |
| DE (2) | DE4120991A1 (en) |
| DK (1) | DK0544886T3 (en) |
| ES (1) | ES2110000T3 (en) |
| FI (1) | FI104902B (en) |
| GR (1) | GR3024842T3 (en) |
| HU (1) | HU210198B (en) |
| IE (1) | IE922048A1 (en) |
| PL (1) | PL173870B1 (en) |
| RU (1) | RU2104281C1 (en) |
| SK (1) | SK23493A3 (en) |
| WO (1) | WO1993000350A1 (en) |
| ZA (1) | ZA924646B (en) |
Families Citing this family (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| FI96692C (en) * | 1993-12-17 | 1996-08-12 | Leiras Oy | Process for producing Sennocide A and B |
| US20010011131A1 (en) | 1997-07-28 | 2001-08-02 | Luyten Frank P. | DNA molecules encoding cartilage-derived morphogenetic proteins |
| US5560913A (en) * | 1995-01-27 | 1996-10-01 | The Procter & Gamble Company | Pharmaceutical compositions |
| ITRM20130294A1 (en) * | 2013-05-16 | 2014-11-17 | Aboca Spa Societa Agricola | SENNA EXTRACTS AND THEIR USES |
| CN113624853A (en) * | 2020-05-07 | 2021-11-09 | 厦门泓益检测有限公司 | Method for simultaneously detecting cathartic components in weight-reducing product based on UPLC-MS/MS |
| CN117224419B (en) * | 2023-11-14 | 2024-01-30 | 山东第一医科大学(山东省医学科学院) | Application of sennoside C in preparing skin whitening and spot-fading skin care product and related product |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB555450A (en) * | 1941-05-13 | 1943-08-24 | Sandoz Ltd | Process for the preparation of active glucosides of senna |
| GB832017A (en) * | 1957-10-02 | 1960-04-06 | Westminster Lab Ltd | Senna preparations |
| DE1617667B1 (en) * | 1966-09-08 | 1970-09-03 | Nattermann A & Cie | Process for the production of a sennosid-rich active ingredient concentrate from sennessee pods |
| JPS54149813U (en) * | 1978-04-10 | 1979-10-18 | ||
| DE3200131A1 (en) * | 1982-01-05 | 1983-07-14 | Madaus & Co Dr | "METHOD FOR OBTAINING LAXATIVE COMPOUNDS FROM SENNADROGE" |
| FR2594337A1 (en) * | 1986-02-17 | 1987-08-21 | Oppag Sa | Sennoside-based composition and process for preparing this composition |
-
1991
- 1991-06-25 DE DE4120991A patent/DE4120991A1/en not_active Ceased
-
1992
- 1992-06-24 SK SK23493A patent/SK23493A3/en unknown
- 1992-06-24 ZA ZA924646A patent/ZA924646B/en unknown
- 1992-06-24 CA CA002090340A patent/CA2090340C/en not_active Expired - Fee Related
- 1992-06-24 HU HU9300506A patent/HU210198B/en not_active IP Right Cessation
- 1992-06-24 RU RU93004900/04A patent/RU2104281C1/en not_active IP Right Cessation
- 1992-06-24 PL PL92298140A patent/PL173870B1/en unknown
- 1992-06-24 AU AU21654/92A patent/AU662343B2/en not_active Ceased
- 1992-06-24 DE DE59208889T patent/DE59208889D1/en not_active Expired - Fee Related
- 1992-06-24 DK DK92913646.3T patent/DK0544886T3/en active
- 1992-06-24 WO PCT/EP1992/001428 patent/WO1993000350A1/en active IP Right Grant
- 1992-06-24 EP EP92913646A patent/EP0544886B1/en not_active Expired - Lifetime
- 1992-06-24 ES ES92913646T patent/ES2110000T3/en not_active Expired - Lifetime
- 1992-06-24 AT AT92913646T patent/ATE157984T1/en not_active IP Right Cessation
- 1992-06-24 JP JP5501333A patent/JP2705733B2/en not_active Expired - Lifetime
- 1992-07-01 IE IE204892A patent/IE922048A1/en not_active IP Right Cessation
-
1993
- 1993-02-23 FI FI930790A patent/FI104902B/en active
- 1993-06-24 CZ CZ93370A patent/CZ281687B6/en not_active IP Right Cessation
-
1997
- 1997-09-24 GR GR970402481T patent/GR3024842T3/en unknown
Also Published As
| Publication number | Publication date |
|---|---|
| DE4120991A1 (en) | 1993-01-07 |
| CZ37093A3 (en) | 1996-12-11 |
| HU210198B (en) | 1995-02-28 |
| EP0544886A1 (en) | 1993-06-09 |
| CZ281687B6 (en) | 1996-12-11 |
| FI104902B (en) | 2000-04-28 |
| HU9300506D0 (en) | 1993-05-28 |
| DK0544886T3 (en) | 1997-10-13 |
| DE59208889D1 (en) | 1997-10-16 |
| FI930790A (en) | 1993-02-23 |
| ATE157984T1 (en) | 1997-09-15 |
| HUT64007A (en) | 1993-11-29 |
| JP2705733B2 (en) | 1998-01-28 |
| IE922048A1 (en) | 1992-12-30 |
| AU662343B2 (en) | 1995-08-31 |
| ZA924646B (en) | 1993-03-31 |
| PL173870B1 (en) | 1998-05-29 |
| EP0544886B1 (en) | 1997-09-10 |
| GR3024842T3 (en) | 1998-01-30 |
| RU2104281C1 (en) | 1998-02-10 |
| FI930790A0 (en) | 1993-02-23 |
| JPH06502191A (en) | 1994-03-10 |
| ES2110000T3 (en) | 1998-02-01 |
| PL298140A1 (en) | 1993-11-02 |
| CA2090340A1 (en) | 1992-12-26 |
| WO1993000350A1 (en) | 1993-01-07 |
| AU2165492A (en) | 1993-01-25 |
| SK23493A3 (en) | 1993-07-07 |
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