Theoretical study on the radical scavenging activity and mechanism of four kinds of Gnetin molecule

•The 12-OH on the A1 ring of all Gnetins has a higher radical scavenging activity.•Antioxidant order is: Gnetin-C ≈ Gnetin-L > Resveratrol > Gnetin-D > Gnetin-F.•Type A has a high radical scavenging activity than type B in the thermodynamic.•The OH can nonselective react with Gnetins, while for OOH is extremely difficult.•The most preferred mechanism relies on solvent effects environment.