Abstract: Objective: To evaluate the in vitro antioxidant capacity of flavonoids from Lonicera japonica Thunb. leaves and their protective effect against oxidative damage induced by H2O2 in RAW264.7 cells. Methods: Flavonoids from Lonicera japonica Thunb. leave powder were obtained by extraction and purification. Total reducing power and scavenging capacity against hydroxyl (·OH), superoxide anion (O2-·) and DPPH free radicals were determined by using ascorbic acid as a positive control. RAW264.7 cells were cultured in vitro, and the experiment was divided into blank, model, control, and low-, medium- and high-dose flavonoid groups. RAW264.7 cells were injured by H2O2. The cell viability was measured by the methyl thiazolyl tetrazolium (MTT) assay, and the contents of malondialdehyde (MDA) and glutathione (GSH) and the activities of superoxide dismutase (SOD) and lactate dehydrogenase (LDH) in cells and culture supernatant were determined using commercial kits. Results: The flavonoids at sufficient concentrations had strong total reducing power and free radical scavenging ability equivalent to that of ascorbic acid. The flavonoids from Lonicera japonica Thunb. leaves could protect against H2O2-induced toxicity in RAW 264.7 cells in a dose-dependent manner, reduce MDA content in cells and culture supernatant, improve SOD activity and GSH content and increase intracellular lactate dehydrogenase activity. Conclusion: The flavonoids from Lonicera japonica Thunb. leaves has a strong antioxidant capacity, and can repair H2O2-induced toxicity in RAW264.7 cells likely by regulating cell redox system, scavenging free radicals and enhancing the activity of intracellular antioxidant enzymes.

Key words: flavonoids from Lonicera japonica Thunb. leaves, RAW264.7 cells, antioxidant capacity, H2O2-induced injury