A theoretical study of the conformational behavior and electronic structure of taxifolin correlated with the free radical-scavenging activity

Based on the most stable conformations of taxifolin, its electronic structure was calculated using AM1 and RHF/6-31G* treatments. BDE of the OH groups was calculated and this confirms the predominant H-transfer capacity of the 3′-OH and 4′-OH groups, compared to the 3-OH group and the OH groups of the A-ring. HOMO, characteristic of the electron-transfer capacity, is delocalized in the B-ring but, compared to quercetin, π-electron delocalization does not occur to the 2,3-bond and the 4-keto group, which confirms the minor role of the 3-OH group in taxifolin. Also the singly-occupied molecular orbital (SOMO) of the 3-OH radical are localized on the O-atom, whereas SOMO of the 3′-OH and the 4′-OH radicals are delocalized. This is in agreement with high BDE for the first one and low BDE for the latter two. All calculations are in agreement with the structure–activity relationship established for taxifolin in the literature concerning its antioxidant activity.