Synthesis, antioxidant activity, and density functional theory study of catechin derivatives

Catechin derivatives were synthesized, and their structures were characterized by 1H-NMR, 13C-NMR, and mass spectrometry. The target compounds were evaluated for their antioxidant activities. Compound 2 showed the highest antioxidant activity, with an IC50 value of 136.637 μM, whereas methylated derivatives showed weak activity. Density functional theory (DFT) studies were carried out at the B3LYP/6-311++G (d, p) level of theory. According to the geometries, molecular electrostatic potential (MEP), bond dissociation enthalpy (EDE), the HOMO and LUMO, and reactivity indices (η, μ, ω, ω+, and ω−), we predicted the free radical scavenging capacity of catechins and their derivatives from their structures. We also found that the B-ring of catechins is a stronger electron donor than the A- or D-ring, and that there is a good relationship between the bond dissociation enthalpies (BDEs). These theoretical results will be helpful in the development of new or modified antioxidant compounds.