DE1062890B - Process for the production of hecogenin - Google Patents

Description

GERMAN

The invention relates to improvements in the recovery of hecogenin, and is more particularly related the extraction of hecogenin from a raw concentrate and the preparation of purified hecogenin from this.

Hecogenin occurs naturally in plants of the Agave genus and related genera, in particular in the sisal plant, which is a useful starting material due to its cultivation in plantations.

In these plants, hecogenin occurs in the form of water-soluble glycosides, while hecogenin occurs itself is largely insoluble in water.

There are various methods of obtaining hecogenin from plant material by hydrolysis of the glycosides Procedures have been developed in which in each case hecogenin is combined with difficult-to-remove colored impurities is precipitated.

From Chemistry and Industry, 1952, pp. 426 to 428, it is known that hecogenin can be obtained by hydrolysis ao of the saponin contained in the pressed juice of sisal leaves. The juice is here with salt or Sulfuric acid heated for a few hours or subjected to natural fermentation, whereupon the raw Sapogenin that has precipitated with other products that have become insoluble or on added adsorptive carbon has been bound, is isolated. The precipitate or the carbon adsorbate is then with Ether, especially isopropyl ether, which is a particularly selective solvent, extracted. The from The solution resulting from the extraction of the concentrate with isopropyl ether contains a relatively small solution Amount of impurities that give the concentrate a green color, and one can get out of it Isolate crystallized hecogenin in almost quantitative yield by concentration and cooling.

However, if large amounts of hecogenin concentrate are to be worked up, then a complete extraction of the hecogenin from the concentrate with the aid of isopropyl ether takes an inexpediently long time. In addition, isopropyl ether is a solvent that must be handled with great care because of the danger of explosion and its high flammability. Accordingly, it is an object of the invention to provide a method by which 4-5 chem hecogenin can be obtained faster, safer and more expediently than with isopropyl ether from contaminated hecogenin, as is present in the form of the above-mentioned crude concentrate, and the hecogenin simultaneously effective from water-insoluble, colored and other impurities are freed.

The use of lower aliphatic alcohols as extractants is apparently contrary to that A-alcohols a relatively large amount of colored processes for the production of hecogenin

Applicant:
National Research
Development Corporation,
London

Representative: Dr.-Ing. F. Wuesthoff and Dipl.-Ing. G. Puls, Patent Attorneys, Munich 9, Schweigerstr. 2

Claimed priority:
Great Britain June 15, 1954

Philip Calvert Spensley, London,
and William White Easton, Edinburgh
(Great Britain),
have been named as inventors

Absorb impurities from the water-insoluble hecogenin concentrate. Nonetheless it was using the new process found that relatively harmless alcohols as extraction agents can be used with better results than isopropyl ether.

According to the invention, a hecogenin concentrate containing water-insoluble impurities is extracted with methyl, ethyl, propyl, isopropyl, butyl or isobutyl alcohol, then heats the extract with caustic alkalis and receives the hecogenin from this by precipitation with water.

After the alcohol extraction is complete, the extract is preferably prepared before the addition of caustic alkali constricted to a relatively small volume. Treatment with caustic alkali has the effect of that most of the water-insoluble colored contaminants that come with the alcohol had been extracted, saponified and thus water-soluble, so that when the Extract with water will keep the impurities in solution while the hecogenin precipitates.

In one example, a solid concentrate of hecogenin becomes continuous extracted with hot methyl or ethyl alcohol in a large percolator for 96 hours, after which the extraction is complete. This period is in contrast to a period of about 14 days, which one with an extraction of the same amount with

909 580/389

Claims (5)

Isopropyl ether required. The extract is then concentrated by distilling off the alcohol until the concentration of the total extractive substances is 10 to 35% of the extract. At this point, caustic alkali or caustic sodium, expediently as a concentrated solution, is added to the alcoholic extract, so that a 4 to 20% alkali solution is produced and a ratio of Vs to Va caustic alkali per part of the extractive substance is present. The alkaline solution is then refluxed for 1 to 3 hours. Now the alkaline alcoholic liquid is diluted with the same volume of water while stirring, heated to the boil, kept boiling for 2 to 5 minutes and filtered while hot. When water is added, the hecogenin precipitates out of the solution in a relatively pure form and is washed thoroughly with hot water on the filter until it is free of residual alkali. The hecogenin obtained in this way can furthermore be purified by converting it into its acetate and recrystallizing the acetate from higher-boiling gasoline. Instead of simply diluting the concentrated alkaline alcoholic liquid with water to precipitate the hecogenin, in some cases it is preferable to use steam distillation to remove the alcohol and then replace it with water, as this gives an end product with a good crystalline structure. An adsorbent, such as. B. activated charcoal, can be mixed with the hecogenin concentrate before extraction with alcohol to reduce the amount of colored substances going into solution. It may also prove expedient to use charcoal to remove the last remains of colored substances from the gasoline solution of the acetate when the hecogenin acetate is recrystallized during the final cleaning. The procedure can be used with equal success in small-scale trials. In the following it will be explained in more detail using examples: Example 1 50 g of powdered concentrate is extracted in a Soxhlet extractor or other device for continuous liquid extraction of solids with methyl or caustic alcohol for 24 hours under so low boiling that only about six extractions take place. The extract is then concentrated to about 150 ecm. 7.5 g of potassium hydroxide are then dissolved in 7.5 ecm of water and 15 ecm of methyl or ethyl alcohol and added to the concentrated extract, whereupon the whole is refluxed for 1 hour. Now no less than 2Z3 of the alcohol are removed by steam distillation. When using ethyl alcohol, the steam distillation is expediently carried out until pronounced foaming can be observed. If methyl alcohol is used, foaming can occur considerably earlier and must be contained by adding octyl alcohol or another such antifoam agent. The crude hecogenin crystals are then collected, washed thoroughly with hot water, dried and weighed. If the concentrate is satisfactory, the yield is about 5 to 15 g. The purification is carried out, if necessary, by the usual method of conversion to acetate. The lower aliphatic alcohol used according to the invention to extract the hecogenin from the concentrate can contain a proportion of water. It has been found that aqueous alcohol solvents are generally more selective than pure alcohol for the present purpose, although extraction may take somewhat longer when aqueous alcohol is used. Example 2 In an example of the use of aqueous alcohol, 462 kg (1020 lbs.) Of crude powdered hecogenin concentrate was extracted in a large continuous extractor with 4050 l (900 gallons) of hot 95% ethyl alcohol for 106 hours after which it was demonstrated by laboratory testing it could be determined that the extraction was complete. The alcoholic extract was then concentrated to a volume of 675 liters (150 gallons) by distillation. Then 68 kg (150 lbs.) Of potassium hydroxide was added with stirring until completely dissolved and the alkaline solution was refluxed for 3 hours. More than half of the remaining alcohol was recovered by steam distillation until this had to be broken off as a result of the disruptive foaming. Then, as described above, hecogenin was precipitated from the alcoholic solution by adding water. The hecogenin was collected by filtration through a filter press or on a hydroextractor, washed and weighed, the yield being 69 kg (154 lbs.). The hecogenin was then further purified by acetylation and crystallization. Patent claims: 1. Process for the production of hecogenin from a water-insoluble hecogenin-containing concentrate, characterized in that the concentrate in powder form with methyl, ethyl, Propyl or butyl alcohol extracted, the alcoholic extract heated with caustic alkali for so long until the colored impurities are saponified, and that one then removes the hecogenin from the solution fails. 2. The method according to claim 1, characterized in that the hecogenin is added by adding from water to the saponified alkaline alcoholic extract precipitates. 3. The method according to claim 1, characterized in that the hecogenin is removed by steam distillation of the saponified alkaline alcoholic extract fails. 4. The method according to claim 1 to 3, characterized in that the alcoholic extraction takes place with hydrous aliphatic alcohols. 5. The method according to claim 1 to 4, characterized in that the alcohol extract is on brings a concentration with a content of 10 to 35% extractive substances and then 4 to 20% Adding caustic alkali. Considered publications:
Chemistry and Industry, 1952, pp. 426-428, 1953. © 909 580/389 7.