Abstract: Honey pomelo pulp is rich in dietary polyphenols with great health benefits. However, the deep processing industry of honey pomelo is restricted due to the lack of theoretical research on these phenolic compounds. In this study, we extracted and characterized dietary polyphenols from the fruit pulp of Meizhou honey pomelo, and we further investigated the protective effect and underlying mechanism of the polyphenols on H2O2-induced oxidative stress in HepG2 cells. A total of 7 individual polyphenols were identified in the polyphenol extract: naringin, narirutin, rhoifolin, vanillic acid, methyl hesperidin, vicenin-2, and ferulic acid. The content of naringin was 50.54 mg/g, significantly higher than the contents of the other six phenolic compounds. Vicenin-2 and rhoifolin were identified for the first time in the pulp of pomelo. The dietary polyphenols at concentrations of 20 and 100 μg/mL had a protective effect against H2O2-induced oxidative damage in HepG2 cells, and decreased in lactate dehydrogenase (LDH) release and reactive oxygen species (ROS) accumulation. Our results also revealed that the dietary polyphenols promoted the translocation of nuclear factor erythroid 2-related factor 2 (Nrf2) from the cytoplasm to the nucleus and up-regulated the expression of the genes encoding its target antioxidant enzymes such as quinone oxidoreductase 1 (NQO1), heme oxygenase-1 (HO-1), glutathione S-transferase A2 (GSTA2), and glutamate-cysteine ligase catalytic subunit (GCLC). Therefore, the dietary polyphenols from honey pomelo pulp could serve as a potential therapeutic agent for oxidative stress-related disorders.

Key words: antioxidant; reactive oxygen species; dietary polyphenols; HepG2; nuclear factor erythroid 2-related factor 2