Antioxidant Activity of Polysaccharide Degradation Based on Nrf-2/Keap-1 Signaling Pathway in HepG2 Cells with Oxidative Stress Induced by HO.

The objective of this research was to investigate the antioxidant activity of polysaccharide degradation and its underlying mechanism involved in the Nrf-2/Keap-1 signaling pathway in HepG2 cells with oxidative stress induced by HO. The result of the scavenging ability of free radicals showed that GLP-HV (polysaccharide degraded by HO-vitamin C (Vc)) performed a better scavenging ability than GLP ( polysaccharide). Moreover, the scavenging ability of polysaccharide to these free radicals from strong to weak was as follows: superoxide radical, ferric ion, ABTS, and DPPH radical, and their IC values were 3.56 ± 0.0028, 4.97 ± 0.18, 9.62 ± 0.35, and 23.85 ± 1.78 mg/mL, respectively. Furthermore, GLP-HV obviously relieved oxidative stress in HepG2 cells, which strengthened the activity of T-AOC, CAT, GSH-PX, and SOD, and diminished the intensity of MDA, intracellular ROS, and calcium ion based on the Nrf-2/Keap-1 signaling pathway. The PCR result revealed that polysaccharide upregulated the expression of the genes Nrf-2, HO-1, NQO-1, and ZO-1 and downregulated Keap-1. The correlation between chemical properties and antioxidant mechanism of GLP-HV was evaluated via a heat map. The results illustrated that reducing sugar and active groups presented a positive correlation, and molecular weight and viscosity exhibited a negative relation with antioxidant activity.