Radical scavenging activity of three Scirpusins: A kinetic and mechanistic study

Abstract

The strong antioxidant activity of Scirpusin, a polyphenolic compound also known as resveratrol or piceatannol dimer, toward •OH/•OOH in gas phase and solvents was investigated through systematic thermodynamics and kinetics analyses using the density functional theory method. All mechanisms, including hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), sequential proton loss electron transfer (SPLET), and radical adduct formation (RAF), were investigated. The transition state theory was used to calculate potential energy surfaces and rate constants for HAT and RAF. The results revealed that Scirpusins exhibited considerable antioxidant activity, which followed the sequence: Scirpusin-B > Scirpusin-C ≈ Scirpusin-A, the amount of o-bisphenol is essential to enhance their antioxidant activity. Furthermore, Scirpusin-A, Scirpusin-B, and Scirpusin-C with structures of 13′-OH, 12′-OH, and 2-OH, respectively, shared the same parent nucleus but exhibited distinct strongest reactive sites. This result can provide a guidance for Scirpusin application in the future.