Extract from the leaves of ginkgo biloba

Details Extract from the leaves of ginkgo biloba Extract from the leaves of ginkgo biloba

1998-01-15

1999-03-23

Lilling, Herbert J.

Drug, bio-affecting and body treating compositions

Antigen, epitope, or other immunospecific immunoeffector

Conjugate or complex

514 25, A61K 3578, A61K 748

Patent

active

058855823

DESCRIPTION:

BRIEF SUMMARY
The invention relates to a new extract from the leaves of Ginkgo biloba and its method of preparation.
Certain extracts from the leaves of Ginkgo biloba are widely used for the therapy of peripheral and cerebral arterial circulatory disturbances. Various processes for preparing such extracts are described for example in DE-B -1767098, DE-B2117429, EP-A 0 324 197, EP-A 330 567 and EP-A 0 436 129.
The invention also provides a method for preparing a glycolipid extract from Ginkgo biloba leaves comprising the steps of: lipids; media; fraction to provide a concentrated extract.
The process of the invention is a highly efficient extraction process for extracting desired extracts, such as cerebrosides and especially digalactosyldiglycerides from the leaves of Ginkgo biloba. These extracts have applications in topical compositions.
In general terms in the process of the invention; the leaves of Ginkgo biloba are first extracted with an organic solvent such as acetone/water and the resulting solution is concentrated, for example, by evaporation and cooled. The solution is then filtered and a C.sub.1 -C.sub.3 alcohol such as ethanol is added to the precipitate. The solution is agitated and again filtered. The filtrate is adjusted with water and extracted with a suitable organic solvent especially a non polar solvent such as heptane. The particular advantage of extraction with a non polar solvent prior to application to a chromatographic column is that the solvent removes a substantial proportion, typically 30%, of the dry extract. As a result the amount of desired extract, particularly digalactosyldiglycerides, is increased. The aqueous alcoholic phase is then evaporated to dryness, or evaporated and filtered and an organic solvent is added. The resulting solution is filtered, and then purified by chromatographic separation using solvent extraction media.
Preferably the organic solvent in which the concentrated alcoholic solution in dissolved is the same as a first extracting medium applied to the column. This optimises the chromatographic process.
In a preferred embodiment of the invention the concentrated alcoholic solution from which neutral lipids have been removed is treated with at least two different extracting media. The advantage of this feature is in facilitating the targeted extraction of a desired fraction from the material applied to the column.
Preferably at least one of the extracting media is an organic solvent.
In a preferred embodiment of the invention the organic solvent is a mixture of acetone and toluene. We have found that this solvent is particularly advantageous in targeting the extracts of interest. The strength of the mixture depends on the extract being targeted. Preferably the organic solvent in 5% to 80% acetone/toluene. In one case the organic solvent is 20% to 80% acetone toluene, most preferably 40% to 50% acetone/toluene.
In another case where ginkgolic acids, which are generally undesirable, are to be extracted the acetone/toluene is preferably 5 to 30%, especially approximately 20%.
In another embodiment of the invention one of the extracting media with which the concentrated alcoholic solution from which neutral lipids have been removed is treated is a mixture of an organic solvent and an alcohol. Preferably the alcohol is a C.sub.1 to C.sub.3 alcohol, especially ethanol. Preferably also in this case the solvent is acetone. The extracting medium may be 5% to 85% ethanol/acetone depending on the target extract. In one case it is 8% ethanol/acetone and in another 80% ethanol/acetone.
One of the extracting media may be acetone which is again a useful solvent for target extracts.
In a preferred embodiment of the invention the alcoholic solution is concentrated prior to treatment with the extracting medium/media. Typically the alcoholic solution is concentrated by evaporation.
In one embodiment of the invention a desired fraction obtained by extraction is concentrated, redissolved and reprocessed through the chromatographic column to produce a more concentrated desired fraction. Prefe

REFERENCES:
patent: 4981688 (1991-01-01), Ayroles et al.
patent: 5077046 (1991-12-01), Tanaka et al.
patent: 5322688 (1994-06-01), Schwabe
patent: 5389370 (1995-02-01), O'Reilly et al.
patent: 5399348 (1995-03-01), Schwabe
patent: 5512286 (1996-04-01), Schwabe

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