Vitamin C from Standardized Water Spinach Extract on Inhibition of Cytotoxicity and Oxidative Stress Induced by Heavy Metals in HepG2 Cells

Inhibitory effects of water extract of water spinach (WEWS) on cytotoxicity and oxidative stress induced by heavy metals were examined. Antioxidant activities of WEWS were expressed as vitamin C equivalent antioxidant capacity in 238 mg/100 g of water spinach using ABTS(center dot-) scavenging assay. Vitamin C was identified as a major bioactive component in WEWS by using UPLC/MS. The content of vitamin C was 42 mg from 100 g of dried powder. 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (a yellow tetrazole) assay and dichlorofluorescein assay were conducted to measure cytotoxicity and generation of reactive oxygen species (ROS) caused by heavy metals, respectively. Cytotoxicity was inhibited at the concentrations of 1.06, 1.06, 1.06, and 2.65 mg/L of WEWS for Cd, As, Pb, and Hg, respectively. Pretreatment of WEWS in HepG2 cell attenuated the generation of ROS in a dose-dependent manner. Results of present study suggest that WEWS mainly containing vitamin C could be effective dietary source for reducing cytotoxicity and oxidative stress-induced heavy metals in HepG2 cell.