Isolation of vitexin and investigation on in vitro antioxidant activities of various extracts from tamarind leaves (Tamarindus indica l., fabaceae)

Abstract

Tamarind (Tamarindus indica L.) is a common plant to Vietnamese people. However, there has been little research on the chemical composition and bio-activity of this medicinal material in Vietnam. This paper was carried out aiming at isolating purified compound and investigating the in vitro antioxidant activities by DPPH radical scavenging assay of tamarind leaf extracts. By the technique of column chromatography and structure elucidation with NMR spectroscopy, a pure C-glucoside flavonoid was first isolated as vitexin. In addition, in the DPPH assay, ethyl acetate fraction had the strongest antioxidant activities with IC₅₀ = 13.19 μg/mL, compared with acid ascorbic (IC₅₀ = 4.71 μg/mL). This results are the premise for further research and orientations on using medicinal herbs for antioxidan activities.

Keywords: Antioxidant, DPPH, Tamarindus indica, vitexin, tamarind leaf