Region and weather of cultivation are important factors effecting the amount of total anthraquinone glycosides in the leaves of C. fistula. The Central and the North-East area of Thailand, where the weather is warm in summer and not too cool in winter, the leaves contained a higher amount (average 0.46 and 0.45% dry weight, respectively) of total anthraquinones glycosides than the leaf samples collected from the South, where the weather is cool and raining all year round. All decoction extracts showed the same pattern of TLC fingerprints, while rhein was a major component just as the pod extract (Sakulpanich and Gritsanapan 2008). Thus, the central and north-eastern leaf samples of C. fistula, which contained about 0.5% of total anthraquinone glyco-sides, might be used as an alternative source for laxative drugs. Also, the leaves of C. fistula, which are available throughout the year, might be used instead of the pods which are available only once a year, for laxative purposes.