Method for purifying diacetylrhein for obtaining a diacetylrhein free of aloe-emodin

摘要

PCT No. PCT/IB96/00093 Sec. 371 Date Mar. 18, 1997 Sec. 102(e) Date Mar. 18, 1997 PCT Filed Feb. 7, 1996 PCT Pub. No. WO96/24572 PCT Pub. Date Aug. 15, 1996The present invention discloses a method for preparing purified diacetylrhein to be used in the preparation of drugs which includes the steps of: (a) suspending a diacetylrhein containing various impurities and, in particular, relatively high amounts of aloe-emodin derivatives, in a mixture of organic solvent/water; (b) adding a tertiary amine; (c) adding to the solution obtained a salt of an acid and of an alkali metal or of an alkaline-earth metal; (d) carrying out a hydrolysis in a weakly acidic medium; (e) collecting the purified diacetylrhein, by filtration.!