CZ286430B6 - Isolation process of crystalline silybin and silymarin - Google Patents

Abstract

In the present invention there is disclosed a process of isolating silybin and silymarin from fruits of milk thistle by extraction of drug with aqueous acetone and by treating the extract, particularly by crystallization of silybin and distribution the residue into two fractions, from which one contains predominantly silychristin, taxifolin and polar ballast substances and is excluded from the process and the other fraction contains nearly all silybin and a portion of silychristin and is treated to form silymarin.

Description

Process for isolating crystalline silybin and silymarin

Technical field

The invention relates to the isolation of crystalline silybin and silymarin from seeds of the silybin variety of Silybum marianum Gaertn.

BACKGROUND OF THE INVENTION

The fruit of the milk thistle contains a group of substances derived from flavifol taxifolin, collectively referred to as flavolignans. The complex of flavolignans isolated from this drug is also referred to as silymarin and has been used for many years as a hepatoprotective for its protective action on the liver membrane (eg, Arzneimittel Forschung 25, 82 (1975)). The major components of silymarin are the isomeric compounds of the formula C25H22O10: silybin, isosilybin, silydianin and silychristin, the complete structure of which has been elucidated in a number of leading journals (Tetrahedron Lett. 25, 2911 (1968)); Chem. Ber. 108, 1481 (1975); J. Chem. Soc. Chem. Commun., 16, 696 (1979); Tetrahedron Lett. 31, 2675 (1970); Tetrahedron Lett. 51, 4547 (1977)].

The hepatoprotective effect is attributed to the whole summary of flavolignans - synergism of the action of the individual components of silymarin is expected. Therefore, most known processes deal with the isolation of the so-called silymarin complex - silymarin (DE 19 23 082, DE 20 17 789, J 8 091 212, BE 766 228, CS 216 997, CS 162 722, CS 223 986, FR 2 181 188, DD 112 261, DE 1 767 666, DE 2 020 407, DE 2 914 330, DE 3 225 688, DE 2 459 388, US 3 773 932, US 4 368 195, AT 290 223, CH 646 69Z5 or Belgian Pat. Application BE 08 800 376).

The procedures differ both in the isolation procedure used and in the quality of the product obtained; however, the quality of the product depends mainly on the raw material used - the milk thistle drug. The above-mentioned flavolignans - silybin, silydianin and silychristin are contained in the red flowering variety, while the white variety contains other flavolignans that differ in the absence of one hydroxyl group and the spatial arrangement of the molecule. The ratio of silybin, silydianin and silychristin in the red flowering variety is different in different varieties; silydianin dominant varieties exist - silydianin varieties and silybin dominant varieties silybin varieties. Older patents dealing with the isolation of the silymarin complex do not even mention the ratio of the individual components. In the more recent patent of Madaus (DE 2 914 330), the ideal ratio of silybin - silydianin - silychristin is 3: 1: 1, the so-called standardized silymarin.

Isolation of pure silybin appears only in the newer patent literature. The aim is to obtain pure silybin for the preparation of water-soluble silybin derivatives suitable for the production of injectable dosage forms or solid dosage forms with higher bioavailability. In DE 3,537,656, silybin is isolated from the silymarin obtained according to DE 1 923 082 by repeated crystallization from ethyl acetate. In the procedure according to MS. No. 266809 isolates silybin from the drug through a relatively complex process, difficult to implement on an industrial scale.

SUMMARY OF THE INVENTION

The process of the invention solves the simultaneous isolation of crystalline silybin and silymarin from the silybin variety of Milk Thistle variety by extracting the drug with acetone containing 5 to 15% water. The extract obtained is concentrated to one-half to one-fifth of the original volume and the concentrated extract is refined with petroleum ether. In the refined extract, the acetone concentration is further reduced by evaporation and / or addition of water. This eliminates the concentrate which is separated

From the aqueous phase and diluted with methanol. Crude silybin crystallizes from the methanol solution obtained, from which pure silybin is obtained by crystallization from ethanol. The methanolic mother liquors, after isolation of the crude silybin, are further separated into two fractions by shaking in methylene chloride-methanol-water. The aqueous fraction containing mainly silychristin, taxifoline and polar ballast substances is removed from the process. The methylene chloride fractions mainly contain silybin and isosilybin are combined with the mother liquors from the recrystallization of crude silybin and processed to silymarin by a known method, either dried in a fluidized bed or spray dryer, or silymarin is precipitated by addition of water and the precipitate obtained is filtered and dried.

The main advantage of the process according to the invention over the previously known processes is the simultaneous isolation of silybin and silymarin directly from the milk thistle drug. This is achieved, in particular, by the process of treating the mother liquors after isolating the crystalline crude silybin. These mother liquors contain mainly silychristin (20-30% in dry matter), silybin (including isosilybin 10-20% in dry matter). Also present are minor substances from the flavolignan family (for example taxifoline) and polar ballast substances.

Shaking these mother liquors in the methylene chloride-methanol-water system separates the substances into two fractions, the aqueous fraction containing mainly silychristine, taxifoline and polar ballasts, and being eliminated from the process and the methylene chloride fraction containing mainly silybin (including isosilybin 25 to 35%) dry matter) and silychristin (15-20% dry matter). This methylene chloride fraction, together with the mother liquors from the recrystallization of crude silybin (containing mostly silybin - about 50%), can be processed into silymarin of satisfactory quality. In the preparation of standardized silymarin, silydianin may be supplemented by the addition of silymarin obtained by isolation from the silydianin variety of Milk Thistle.

The following example illustrates the process according to the invention.

Exemplary embodiment

1.0 kg of Milk Thistle (silybin variety) milled drug is extracted by macerating five times with just the necessary amount of acetone containing 10 vol% water. 3.1 L of extract are obtained, which is concentrated to a volume of 900 ml. The solution obtained is refined by extracting three times with 100 ml of petroleum ether, and the raffinate is further concentrated to a volume of 600 ml, followed by the addition of 600 ml of water. The precipitated product is separated from the aqueous phase, diluted with 200 ml of methanol and the solution is concentrated to 100 ml. The precipitated crude silybin was collected by filtration after 5 hours of crystallization at 0 ° C. 16.2 g of crude silybin are obtained, which is recrystallized from 160 ml of ethanol. 9.5 g of pure silybin are thus obtained (silybin content 97.2% in the dried substance; water content 2.1%; ethanol content 0.5%).

The mother liquors after isolation of the crude silybin are diluted with 100 ml of methanol and 200 ml of methylene chloride and 150 ml of water are added. After stirring for 5 minutes, the phases are separated and the aqueous phase is extracted 5 more times with 50 ml of methylene chloride. The combined methylene chloride extracts are concentrated to a residue which is then dissolved in ethanol mother liquors after recrystallization of crude silybin and the ethanol solution is poured into 500 ml of 1% aqueous sodium chloride solution. The precipitate formed is dried. 21.2 g of silymarin (silybin content 25.1%, isosilybin content 15.2%, silychristine content 19.5%) are thus obtained.

Industrial applicability

The invention is useful in the pharmaceutical industry in the manufacture of silybin and silymarin substances. These substances are widely used as hepatoprotectives and drugs for disorders of the body associated with the induction or suppression of a number of enzymes.

Claims (1)

PATENT CLAIMS Method for the isolation of crystalline silybin and silymarin from a silybin variety of Silybum marianum Gaertn, characterized in that the milled drug is extracted with acetone containing 5 to 15% by volume of water, the extract obtained is concentrated to one-half to one fifth of the original volume, concentrated The extract is refined with petroleum ether, then the refined extract is reduced in acetone concentration by evaporation and / or addition of water, thereby eliminating the silymarin concentrate which is separated from the aqueous phase and diluted with methanol and the crude solution silybin crystallizes from the solution which is recrystallized from ethanol. the pure silybin and mother liquors from both crystallizations are processed to silymarin in a manner known per se, with the methanol mother liquors separated after separation of the crude silybin into two fractions by shaking in methylene chloride-methanol-water, using only silymarin for processing methy lenchloride fraction containing mainly silybin and isosilybin.