Organic compounds -- part of the class 532-570 series – Organic compounds – Polycyclo ring system containing anthracene configured ring...
Patent
1997-03-18
1998-05-26
Raymond, Richard L.
Organic compounds -- part of the class 532-570 series
Organic compounds
Polycyclo ring system containing anthracene configured ring...
C07C 6760
Patent
active
057567824
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/IB96/00093, filed Feb. 7, 1995.
The present invention is concerned with a new purification method for diacetylrhein and, more particularly, a method which makes it possible to obtain diacetylrhein having a sufficient degree of purity to allow its use in the preparation of drugs.
BACKGROUND OF THE INVENTION
Arthrosis is a disease which is widely spread throughout the world, affecting more particularly elderly people, and manifesting itself by a degradation of the cartilaginous tissues, in particular of articulations and vertebrae, causing pain and having invalidating effects on the persons affected. The aging of the population in the western countries makes all the more necessary treatments capable of relieving pain in people suffering from this disease.
The administration of nonsteroidal anti-inflammatory and analgesic drugs, for example indomethacin, naproxen and aspirin generally makes it possible to relieve temporarily the patient, but has no real curative effect. More recently, it has been shown that certain derivatives of anthraquinone carboxylic acid and more particularly, of diacetylrhein produce good results in the treatment of certain forms of arthritis and arthrosis. Thus, it has been found that diacetylrhein, administered orally, has an anti-inflammatory and analgesic activity, and is effective for the treatment of arthrosis, without exhibiting any harmful secondary effect.
Derivatives of 1,8-dihydroxy-anthraquinone-3-carboxylic acid, including diacetylrhein, are described in the French patent FR-A-2 508 798.
Patent EP-A-243 968 describes alkaline salts of diacetylrhein, such as the sodium and potassium salts, obtained by the dissolution of diacetylrhein in a mixture of acetone and water, addition of triethylamine and conversion into a salt by a weak organic acid in an alcoholic medium (isobutanol). These sodium and potassium salts are used for making solutions designed for intravenous, intramuscular or intraperitoneal administration.
Diacetylrhein is a substance of vegetal origin, obtained from extraction products from aloe or from senna leaves. Thus, for example, it can be prepared by acetylation of 1,8-dihydroxy-anthraquinone-3-carboxylic acid (rhein), which can be obtained from the sennosides extracted from senna leaves. However, the diacetylrhein thus obtained contains important amounts of aloe-emodin, an undesirable secondary product which arises from the raw materials and its purification is difficult. It is also known how to prepare diacetylrhein by acetylation of barbaloin, followed by an oxidation with chromium oxide, but this technique also produces a final product having a high aloe-emodin content and is accompanied by the formation of chromic residues which as wastes, are difficult to eliminate by usual techniques.
Patents DE-A-4 120 989 and DE-A-120 990 describe methods for preparing diacetylrhein from sennosides which can contain aloe-emodin, including several steps consisting in oxidizing rhein-9-anthrone-8-glucosides, in separating the glucose residue and acetylating, the method further including a step of liquid-liquid separation. Although the purity of the diacetylrhein obtained is improved, the level of aloe-emodin in the product obtained remains relatively important (close to 20 ppm), which can result in the need to carry out additional purifications, lengthy and expensive.
SUMMARY OF THE INVENTION
The object of the present invention is a method for preparing a diacetylrhein of a very high purity, with a good yield.
Another object of the invention is a method for purifying diacetylrhein from a composition containing various impurities and in particular aloe-emodin derivatives, for obtaining a diacetylrhein free of aloe-emodin.
The invention extends finally to the diacetylrhein which is pure and substantially free of aloe-emodin thus obtained, to its use in the preparation of a drug for the treatment of arthrosis.
The diacetylrhein obtained by the method according to the present invention is of a purity such that it is substantially free
REFERENCES:
patent: 4244968 (1981-01-01), Friedmann
patent: 4346103 (1982-08-01), Friedmann
patent: 4950687 (1990-08-01), Dall'Asta et al.
patent: 5391775 (1995-02-01), Carcasona et al.
patent: 5393898 (1995-02-01), Carcasona et al.
Browning Clifford W.
Raymond Richard L.
Steba Beheer B.V.
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