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

As an important subgroup of resveratrol oligomers, Gnetins received much attention due to their antioxidants. The four Gnetin molecules are divided into two major categories according to different structures, type-A (Gnetin-C, Gnetin-D) and type-B (Gnetin-L, Gnetin-F). Density functional theory (DFT) has been performed thermodynamically and kinetically in detail to analyze the structure and antioxidant activity of four Gnetins toward OH/OOH radical in the gas and solvents phase with four possible antioxidant mechanisms, namely, Hydrogen-atom transfer (HAT), Single electron transfer followed by proton transfer (SET-PT), Sequential proton-loss electron transfer (SPLET), and Radical adduct formation (RAF). From these calculations; Gnetins' order of antioxidant activity was estimated as: Gnetin-C ≈ Gnetin-L > Resveratrol > Gnetin-D > Gnetin-F. All investigations suggested that type A has a higher radical scavenging activity compared to type B. On the basis of the structure–activity relationship, type A structure may have more vital antioxidant potential in the future.