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Abstract. Senna siamea (Lam.) Irwin & Barneby is a medicinal plant popularly used in Thailand. Young leaves and/or young flowers of this plant have been consumed by Thai people as a Khi Lek curry for a long time. The fresh young leaves and flowers are boiled with water 2-3 times to get rid of the bitterness and the boiled mush is used for curry cooking. Barakol, a major constituent of Senna siamea leaves was analyzed for its content in the fresh young leaves, the boiled leaves and the boiled filtrates by a high-performance thin-layer chromatographic method. Fresh young leaves of S. siamea contained 0.4035% w/w barakol. The amount of barakol in the first and second boiled filtrates were 0.2052 and 0.1079% fresh weight, while the first and second boiled leaves samples were 0.1408 and 0.0414% fresh weight, respectively. The results show the process of preparation of Khi Lek curry by boiling S. siamea young leaves twice with water reduced barakol content up to 90 % and the content of barakol in boiled leaves used for curry has much less tendency to cause liver toxicity. This may explain the reason why Thai Khi Lek curry has not caused hepatotoxicity, unlike S. siamea leaves consumed as a powdered capsule.
INTRODUCTION
Senna siamea (Lam.) Irwin & Barneby is found indigenously in Thailand and locally called "Khi Lek". It has a long history of use as a folk medicine and its therapeautic efficacy is well recognized. Different parts of S. siamea can be used for various medical purposes (Fiorino et al, 1998; Subhadhirasakul et al, 2000; Sukmaef al, 2002). The fresh young flowers and/or young leaves have been used as vegetables in Thailand. They can be prepared as food by boiling with water at a ratio of 1:3 for 1 hour 2-3 times to reduce the bitterness. The water is then discarded and the boiled leaves are cooked by mixing with coconut milk and curry paste and cooked as a curry which is used as a mild laxative and sleeping aid. An aqueous extract of fresh or dried leaves of S. siamea has also been recommended for treatment of insomnia (Thongsaard et al, 1996). For the past few decades, barakol, a major biologically active constituent of S. siamea,...