Quantitative analysis of barakol content in Senna siamea leaves and flowers by TLC-densitometry

To develop a TLC-densitometric method for the determination of barakol content in Senna siamea leaf and flower extracts, and to compare the barakol content in mature leaves, young leaves and young flowers of the plant which are consumed as a vegetable in curry. The extraction of pure barakol was performed by boiling the fresh young leaves of S. siamea with 0.5% sulfuric acid followed by chloroform extraction. The extract was further purified and recrystallized from absolute ethanol. Authentic sample of barakol was used for the validation of the TLC-densitometric method. Chromatography was performed on a TLC aluminium plate precoated with silica gel 60 F[254] as a stationary phase and chloroform-methanol [85:15 v/v] as a solvent system. Fifteen percent ethanolic extracts of mature leaves, young leaves and flowers of S. siamea were analyzed and compared for barakol content using the validated TLC-densitometric method. Both the validation and analysis of barakol by TLC-densitometry were carried out at the absorbance mode of 366 nm. Barakol was extracted as pure lemon-yellow crystals from young S. siamea leaves with 0.1% yield. Linearity was found over the range of 200-900 ng/spot [r2 = 0.997]. The developed method gave high precision [%RSD < 0.50] and accuracy [average 101.12%]. The limit of detection and limit of quantitation were 8 and 50 ng, respectively. Barakol content in young leaves, mature leaves and young flowers were 1.67, 0.78 and 1.43% dry weight, respectively. R[f] value of the barakol in young leaves, young flowers and authentic sample was the same: 0.45 +/- 0.03. The TLC-densitometric method was simple, precise and convenient; hence it is an effective procedure for the simultaneous determination of barakol in plant extracts

Barakol contents in fresh and cooked Senna siamea leaves.

Senna siamea (Lam.) Irwin and 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.