Pyranoanthocyanins: a theoretical investigation on their antioxidant activity.

The antioxidant radical scavenging capacity of pyranoanthocyanins present in aged wine and coming from the chemical transformation undergone by anthocyanins was theoretically explored by DFT/B3LYP methods. The two main working mechanisms (H atom donation and single-electron transfer) were investigated, and the O-H bond dissociation energy (BDE) and ionization potential (IP) parameters were computed in the gas phase and in water and benzene solutions. Results indicated that systems possessing the catechol functionality as well as the o-dimethoxy motif are good candidates to donate a H atom to the free radicals, inactivating them. Compounds with a higher degree of electron delocalization may work within the single-electron transfer mechanism. Results provided molecular insight into factors that influence the radical scavenging potential of anthocyanins and then the beneficial health effects of these wine pigments.