Quantitative structure-antioxidant activity relationship of trans-resveratrol oligomers, trans-4,4′-dihydroxystilbene dimer, trans-resveratrol-3-O-glucuronide, glucosides: Trans-piceid, cis-piceid, trans-astringin and trans-resveratrol-4′-O-β-D-glucopyranoside

By means of the accurate computations based on the density functional theory, the relationships between the molecular structure and free radical scavenging activity have been studied for dimer of trans-4,4'-dihydroxystilbene, trans-resveratrol-3-O-glucuronide, glucosides: geometric stereoisomers of piceid, trans-astringin, trans-resveratrol-4'-O-beta-D-glucopyranoside and trans-resveratrol dimers: pallidol, geometric stereoisomers of (epsilon)-viniferin, stereoisomers of trans-delta-viniferin and trans-resveratrol trimer-gnetin H. Our results have shown that all oligomers, glucosides and trans-resveratrol-3-O-glucuronide exhibit stronger antioxidant activity than trans-resveratrol and that dimer of trans-4,4'-dihydroxystilbene is a stronger antioxidant than its monomer as well as that cis stereoisomers of piceid and (epsilon)-viniferin are weaker antioxidant than their trans stereoisomers. The homolytic bond dissociation enthalpy values calculated reveal the predominant H-transfer capacity of the OH groups in the trans-stilbene moiety. The hydrogen atom transfer mechanism of free radicals scavenging by the compounds studied is proved more preferable than the single-electron transfer mechanism in the mediums investigated. All the above-mentioned compounds have been proved to have significantly higher ability to electron donation in water medium than in the gas phase. The experimental observations are satisfactorily explained by the results obtained.