Donor-acceptor interactions as descriptors of the free radical scavenging ability of flavans and catechin

Abstract

Interest in food phenolics has increased in recent years largely due to their antioxidant capacity, free radical scavenging, and potential health benefits. In literature two main reaction mechanisms have been proposed for their role as free radical (FR) scavengers, i.e., the mechanism of a hydrogen atom transfer (HAT) governed by the O H bond dissociation enthalpy (BDE), and the mechanism of single electron transfer (SET) governed by an electron transfer process, the ionization potential (IP) playing an important role. Thirty nonplanar structures were analyzed. The study of (+)-catechin (CTQ) and (4α → 6″, 2α → O → 1″)-phenylflavans with a R′ = H, R = OH; R′ = OH, R = H, and R′ = OH, R = OH substitution is performed herein. Catechol, phenol, and resorcinol are also included as references. Results obtained with B3LYP hybrid functional with 6-311++G(d,p) and 6-31G(d,p) basis set are analyzed. Two new indicators arising from electron delocalizations are presented herein, thus showing that there is a different set of donor-acceptor interactions to explain FR scavenging mechanisms.