Protective effect against oxidation of human low-density lipoprotein and plasmid DNA strand scission of Tamarind seed coat extract in vitro

Methanolic extract from seed coat of Thai Tamarindus indica L. containing polyphenol; procyanidins, (−)-epicatechin was studied in vitro for protective effect against Cu2+-induced human low-density lipoprotein (hLDL) oxidation and oxidative damage of plasmid DNA induced by Fenton reactant. LDL oxidation was monitored by formation of conjugated dienes, fluorescent products, protein carbonylation and thiobarbituric acid reactive substances (TBARS). Supercoiled DNA strand scission was evaluated by gel electrophoresis. The extract inhibited formation of all four products of oxidized LDL in a dose-dependent manner over 25–1000 ng/ml extracts. Furthermore, 1 mg/ml extract also protected supercoiled DNA strand in plasmid pBR322 against scission induced by Fenton-mediated hydroxyl radical similar to that found with reference antioxidant, 0.5 μg/ml Trolox. Thus, seed coat extract from Thai Tamarind shows antioxidant effects against in vitro Cu2+-mediated LDL oxidation and hydroxyl radical–induced supercoiled DNA damage. These results suggest that seed coat extract from Thai Tamarind may be useful for preventing LDL oxidation and DNA damage.