Standardized Cassia fistula pod extracts

Abstract

Cassia fistula L. pods have been used as a laxative drug in Thai traditional medicine for a long time. The pods of C. fistula were collected in summer (April, 2007) from 10 provinces in the North, North-East, Central, and South of Thailand. The pods were extracted by decoction which was found to be a suitable method for extracting anthraquinone glycosides from C. fistula [1]. The pod extracts are brownish-black color with characteristic odour and mild sweet taste. The extract ratio (crude drug: 1g crude extract) were about 1–2: 1. All extracts contained anthraquinone compounds identified by Borntrager's test and TLC. Rhein was a major anthraquinone compound in the pod extracts. Loss on drying of the extracts was not more than 1% w/w. The extracts were freely soluble in water and slightly soluble in 95% ethanol. By UV-vis spectrophotometric analysis, total anthraquinones in the pod extracts were more than 1% w/w, while total anthraquinone glycosides were more than 0.4% w/w calculated as rhein. According to HPLC analysis, the content of rhein in pod extracts was not less than 0.5% whereas aloe-emodin content was not less than 0.0003% w/w. The pod extracts did not contain heavy metals and pesticide residues. Bacterial contamination of the extract was not more than 10 cfu/g while fungi were not more than 11 cfu/g. Also, pathogenic bacteria was not found in the extracts. These informations will be useful for quality assessment of the pod extracts of C. fistula as a raw material for herbal laxative drug.