Cytoprotective Effect of Acid-Hydrolyzed Sesame Leaves against Oxidative Stress in HepG2 Cells

In this study, we investigated the cytoprotective effects of acid-treated sesame leaf extracts against oxidative damage in HepG2 cells. Treatment with 0.1 M HCl of sesame leaves significantly increased their verbascoside content (4.398 g/100 g) compared to non-acid-treated leaves (3.950 g/100 g). Acid-treated sesame leaf extract (ASLE) showed no cytotoxicity in HepG2 cells. ASLE conferred a greater cytoprotective effect against oxidative insult than a methanol extract of sesame leaves (SLE), verbascoside, and a vehicle control group. ASLE treatment also significantly inhibited reactive oxygen species generation in response to oxidative stress. Treatment with tert-butyl hydroperoxide increased malondialdehyde (MDA) levels, and depleted reduced glutathione (GSH). However, ASLE treatment significantly ameliorates this MDA and GSH depletion. Moreover, ASLE increased the activities of antioxidant enzymes including catalase, glutathione reductase, and glutathione peroxidase. Phenolic compounds in ASLE and SLE were characterized using UPLC-Q-TOF/MS analysis. A total of 29 iridoid and phenol compounds were tentatively identified in ASLE, and 27 compounds were observed in SLE. These results suggest that acid treatment of sesame leaves enhances the protective effects of their extract against oxidative stress by modulating antioxidant enzymes in HepG2 cells.