Antioxidant Activity and HepG2 Cytoprotection of Water-Soluble Chili Pepper Polyphenols

To clarify the purification enrichment of water-soluble polyphenols from chili pepper and their cellular antioxidant mechanisms, crude chili polyphenols (CCP) were prepared via ultrasound-assisted aqueous extraction and purified chili polyphenols (PCP) were obtained via D-101 macroporous resin purification. The total phenolic content (TPC) and in vitro antioxidant activity were compared between the two samples. Ultra-performance liquid chromatography-tandem mass spectrometry was used to identify the phenolic composition of PCP, and the protective effects of PCP against H₂O₂-induced oxidative damage in HepG2 cells were evaluated. The results revealed that TPC of PCP was significantly greater than that of CCP (p < 0.05). UPLC-MS/MS detected 17 polyphenols in PCP, mainly flavonoid glycosides and phenolic acids, with apiin, schaftoside, and luteolin 7-rutinoside as the predominant constituents. The half-maximal inhibitory concentrations for 2,2'-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid), 2,2-diphenyl-1-picrylhydrazyl, and hydroxyl radical scavenging were 18.2 ± 0.4, 24.5 ± 0.7, and 43.2 ± 1.2 µg/mL, which were lower than those of CCP. In the 800 µmol/L H₂O₂ damage model, 50.0 µg/mL PCP increased relative cell viability by 26.6% compared with the model group, significantly reduced intracellular reactive oxygen species and malondialdehyde levels, and restored the reduced glutathione content and superoxide dismutase activity. In conclusion, D-101 macroporous resin significantly enriched antioxidant components from chili pepper. PCP attenuates oxidative stress indicators, potentially through restoring intracellular antioxidant defenses and inhibiting lipid peroxidation, supporting the high-value utilization of water-soluble chili polyphenols. Future animal studies are warranted to confirm in vivo efficacy.