Abstract: Objective: To evaluate whether a tea extract rich in polysaccharides and polyphenols (TEPP) can improve the intestinal response to oxidative stress induced by D-galactose in mice, and to explore its antioxidant mechanism. Methods: Mice were injected intraperitoneally with 10% D-galactose for eight weeks to establish an oxidative stress model. After the model was successfully established, the normal and model groups were gavaged with distilled water, the positive group was gavaged with 200 mg/kg mb of reduced glutathione, the low-, medium- and high-dose TEPP groups were respectively administered with 40, 100 and 250 mg/kg mb of TEPP, and the tea polyphenol group was administered with 50 mg/kg mb of tea polyphenols. Enzyme-linked immunosorbent assay kits were used to detect the total antioxidant capacity (T-AOC), reactive oxygen species (ROS) content, glutathione reductase (GR) activity, heme oxygenase (HO) activity in the intestinal tissues of the mice in each group, and the mRNA expression levels of toll-like receptors (TLR4), p38, nuclear factor-erythroid 2-related factor 2 (Nrf2), GR and HO were detected by fluorescent quantitative real-time polymerase chain reaction (qPCR). Results: Compared with the model group, the T-AOC of the high-dose TEPP group increased by 2.2 times, and the activities of GR and HO increased by 2.8 times and 1.7 times, respectively. The ROS content decreased by 72.8%, the mRNA expression of TLR4 and p38 declined by 39.1% and 82.4%, and the mRNA expression of Nrf2, GR and HO increased by 83.6%, 8.3 times and 96.3%, respectively. All of these changes were statistically significant (P < 0.05). Conclusion: TEPP can improve the intestinal response of mice to oxidative stress induced by D-galactose through the TLR4/p38 mitogen-activated protein kinase (MAPK)/Nrf2 pathway.

Key words: tea extract rich in polysaccharides and polyphenols; intestinal oxidative stress; antioxidant; TLR4/p38 MAPK/Nrf2 pathway