Determination of anthraquinone contents in Cassia fistula leaves for alternative source of laxative drugs

Cassia fistula L. (Fabaceae) is locally called Khun in Thailand [1]. The ripe pods have been populary used as a laxative drug of which active components are anthraquinones [2]. The leaves also contain anthraquinones while rhein is a major component. The leaves of C. fistula collected from 10 provinces in Thailand were extracted by decoction and the aqueous extracts were analyzed for the contents of total anthraquinones and total anthraquinone glycosides, calculated as rhein, by UV-vis spectrophotometric method. The contents of rhein and aloe-emodin were also determined by HPLC. The leaf extracts contained total anthraquinones 1.13–7.96% w/w (average 4.55% w/w), total anthraquinone glycosides 0.62–2.01% w/w (average 1.52% w/w), rhein 0.76–3.37% w/w (average 1.71% w/w) and aloe-emodin 0.01–0.15% w/w (average 0.07% w/w). In dried leaves, total anthraquinones, total anthraquinone glycosides, rhein, and aloe-emodin contents were found to be 0.16–2.12% w/w (average1.12% w/w), 0.09–0.63% w/w (average 0.36% w/w), 0.16–1.06% w/w (average 0.41% w/w), and 0.01–0.05% w/w (average 0.02% w/w), respectively. Compared with C. angustifolia leaf officially in European Pharmacopoeia, which contains not less than 2.5% w/w of total hydroxyanthracene glycosides [3], anthraquinone glycosides in the leaves of C. fistula are about 7 times less than in the leaves of C. angustifolia, while the C. fistula leaf extract contained less hydroxyanthracene glycosides than the leaf extract of C. angustifolia about 3.5 times. Thus, in case that C. fistula leaf extract would be used as an alternative source of laxative drugs, it has to be used for about 3–4 times more than the amount of C. angustifolia leaf extract.

Acknowledgements: This work was granted by Thailand Research Fund (TRF) with Office of Small and Medium Enterprises Promotion (OSMEP).

References: [1] The Forest Herbarium, Royal Florest Department. Flora of Thailand vol. 4, part I Leguminosae-Caesalpinioideae. Bangkok.

[2] Pongbunrond, S. et al. Kasembannakit. Bangkok.

[3] Council of Europe. European Pharmacopoeia-Supplement. Council of Europe. Strasbourg.