Abstract

This study aimed to evaluate the chemical stability of Cassia fistula Linn. pod pulp extracts which were freshly prepared and were stored under accelerated and real time storage conditions for 6 months according to ASEAN guideline on drug stability study. A thin layer chromatography (TLC)-densitometric method was developed and validated for quantitative analysis of the content of rhein, a major anthraquinone constituent, in the extracts. The TLC was carried out on aluminium sheet of silica gel 60 F₂₅₄ using ethyl acetate:methanol:water (100:17:10, v/v/v) as a mobile phase. The wavelength of the ultraviolet (UV) detector was set at 435 nm. The proposed TLC-densitometric method showed acceptable validation parameters. The content of rhein in the decoction extracts remained more than 95% (96.40 to 99.65%) of the initial amount (0.1446% w/w) for all storage conditions. There was no significant change of the extracts kept in glass vials and in aluminium foil bags. TLC-densitometric method is simple, rapid, sensitive, and economical for routine analysis of rhein content in C. fistula pod pulp extracts. The good chemical stability of the extracts indicates the suitability of C. fistula pod pulp extract as a raw material for the development of modern herbal laxative formulations.

Key words: Cassia fistula, chemical stability, laxative, thin layer chromatography (TLC)-densitometric method.