DFT-Based Quantum Chemical Studies on Conformational, Electronic and Antioxidant Properties of Isobavachalcone and 4-Hydroxyderricin

Isobavachalcone and 4-hydroxyderricin which exhibit numerous biological activities are two major chalcone constituents isolated from the roots of Angelica keiskei KOIDZUMI. The conformational and antioxidant activity properties have been investigated by quantum chemical calculations based on the density functional theory, with the aim of verifying dominant antioxidant mechanisms. Three parameters of the O-H bond dissociation enthalpy (BDE), ionization potential (IP) and acidity in the presence of an implicit solvent for methanol are computed to estimate the antioxidant capacities. Results reveal that the order of antioxidant efficacies predicted by BDE and IP, different from that predicted by acidity, is in agreement with that obtained by experimental data. This demonstrates the importance of the hydrogen atom transfer and single electron transfer mechanisms to explain their capacities to scavenge 2, 2-diphenyl-1-picrylhydrazyl (DPPH) free radical.