Standardization and toxicity evaluation of Cassia fistula pod pulp extract for alternative source of herbal laxative drug

The ripe pod pulp of Cassia fistula Linn. (Fabaceace) has long been used as a traditional laxative drug due to anthraquinone glycosides constituent. Rhein is the major anthraquinone in the pod pulp. In this study, extracts from ripe pod pulp of Cassia fistula collected from 10 different provinces in Thailand were standardized for physical and chemical properties. Using UV-vis spectrophotometric analysis, total anthraquinone content in the pod pulp extracts was more than 0.10% w/w (average 0.1365 ± 0.001% w/w) while total anthraquinone glycosides was more than 0.03% w/w (average 0.0445 ± 0.002% w/w), both calculated in terms of rhein. Quantitative analysis of rhein content in the pod pulp extracts was performed by high performance liquid chromatographic (HPLC ) method. It was found that rhein content in pod pulp extracts was more than 0.02% w/w (average 0.0518 ± 0.003% w/w). Acute toxicity of the pod pulp extracts in rats and mice showed no mortality or any signs of toxicity. Total aerobic bacteria count and total fungi count in the extracts did not exceed 10 and 11 cfu/g, respectively while no pathogenic bacteria were found. This information would be a useful guideline for quality control and standardization of C. fistula pod pulp extracts for a good quality herbal laxative raw material.