Method of extracting sennosides A, B and A1

摘要

Sennosides A, B and Al of the formula: <IMAGE> which are substantially free from sennosides C, D and Dl, and from aloe-emodin derivatives, are prepared by a process wherein a) a sennoside mixture is reduced to rhein-9-anthrone-8-glucoside and aloe-emodin-9-anthrone-8-glucoside, b) a liquid-liquid partitioning of the compounds obtained is carried out between a polar organic solvent which is only partly miscible with water and an aqueous phase and c) the rhein-9-anthrone-8-glycosides contained after the partitioning in the aqueous phase is again oxidized to the corresponding sennosides and these are recovered.