Determination of Anthraquinone Glycoside Content in Cassia fistula Leaf Extracts for Alternative Source of Laxative Drug

The pod of Cassia fistula Linn. has been used as a laxative drug in Thai traditional medicine for a long time. The pods and leaves contain anthraquinone aglycones and anthraquinone glycosides which are the active laxative form, while rhein is a major component. The degree of laxative potency is depended on the content of anthraquinone glycosides. This study determined the content of total anthraquinone glycosides in leaves of C. fistula collected in early summer (February-March, 2008) from 10 provinces in the North, North-East, Central, and South of Thailand. The leaves were extracted by decoction which was found to be a suitable method for extraction of anthraquinone glycosides from C. fistula. All extracts were analyzed using a UV-visible spectrophotometric method. The contents of total anthraquinone glycosides in the decoction leaf extracts were 0.62-2.01% dry weight (average 1.52% dry weight) while in the dried leaves were 0.090.63% w/w (average 0.36% w/w) calculated as rhein. The leaves collected from the Central and the North-East area, where the weather is warm in summer, contained high amounts (average 0.46 and 0.45% dry weight of total anthraquinones glycosides, respectively) while the samples from the South, where the weather is cool and raining throughout the year, contained a lower amount (average 0.13% dry weight). According to the standard of ASEAN Herbal Medicine, the central and north-eastern leaf samples of C. fistula, which contained about 0.5% of total anthraquinone glycosides, might be used as a source of laxatives just as the ripe pods. The decoction extract of the leaves containing an average total anthraquinone glycosides 1.52% w/w might be used as an alternative source of raw material for various laxative preparations. _____________________________________________________________________________________________________________