Theoretical evaluation of the antioxidant activity of some stilbenes using the Density Functional Theory

•QTAIM shows the intramolecular Diels Alder cyclization of cis oxy res.•The BDE and ETS-NOCV confirmed that the oxyresveratrol and T-CYCLE-OXY possess higher radical scavenging potency.•The HAT, SET–PT, and SPLET mechanisms have been investigated.•HAT is a thermodynamically preferred mechanism in DMSO.•The SPLET and HAT are competitive in inactivating free radicals of different characteristics.