Estimation of Anthraquinones and their Glycosides from Rhizomes of Rheum emodi

Background: Rheum emodi an Indian variety of the Chinese Rhubarb plays a vital role in traditional Chinese and Indian forms of medicine. The plant majorly consists of pharmacologically and therapeutically significant free 1,8-dihydroxy- anthraquinones and their glycosides. Objective: The present work focuses on estimation of the free anthraquinones and their glycosides from Indian Rhubarb (Rheum emodi) viz. emodin, physcion and chrysophanol by an HPLC method using fluorescence detection. Materials and Methods: The anthraquinone aglycones were extracted from the crude drug by treatment with aqueous alkali, subsequent acidification and partitioning using an organic solvent. The glycosides present in the plant material were first subjected to hydrolysis with acid and then treated in the same manner as that of parent aglycones, and both samples were estimated for their quinone content. Results: The total quinone content prior to and after hydrolysis was found to be 1.91% and 4.52% respectively. The specific aglycone content for emodin, chrysophanol and physcion were analyzed by HPLC and were found to be 0.9%, 0.76% and 0.25% respectively in native form while their respective glycosides were found to be 0.6%, 1.52% and 0.25%. Conclusion: The work presents a simple and efficient method for estimation of anthraquinone glycosides, besides the acid hydrolysis of glycosides can lead to enriched source of anthraquinones from R. emodi, which can be exploited at industrial level for commercial maximization of the pharmacologically important quinones.