The antioxidant potential of retrochalcones isolated from liquorice root: A comparative DFT study

Polyphenolic compounds are known to exhibit potent antioxidant properties owing to the presence of various phenolic groups. The present study reports the antioxidant potentials of six retrochalcones, namely echinatin, and licochalcone A, B, C, D and E, isolated from the root of the Glycyrrhiza species, toward various reactive oxygen and nitrogen species. Different mechanistic pathways, viz. hydrogen atom transfer (HAT), single electron transfer (SET), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET), have been considered. In addition, two other pathways, i.e. sequential double proton loss electron transfer (SdPLET) and sequential proton loss hydrogen atom transfer (SPLHAT), which are significant for the scavenging of reactive species by the mono-deprotonated forms of retrochalcones, have also been considered. All the calculations were performed using density functional theory at the B3LYP/6-311++G** level in the gas phase and in aqueous solution. The results suggest the predominance of the HAT mechanism in the gas phase, while in aqueous solution, the SPLET mechanism is thermodynamically favored. The possibility of SdPLET increases at higher pH.