The invention relates to a process for the preparation of diacetylrhein in pharmaceutically acceptable purity with a remainder of undesired aloe emodin derivatives of less than 20 ppm in total. The process consists in subjecting aloe emodin components of the diacetylrhein to a liquid-liquid partition followed by crystallisation and drying the product under particularly mild conditions. The invention also relates to the diacetylrhein which can be obtained by this process, and to a pharmaceutical composition containing this compound.
