Performance of an integrated approach for prediction of bond dissociation enthalpies of phenols extracted from ginger and tea

Integration of the (RO)B3LYP/6-311++G(2df,2p) with the PM6 method into a two-layer ONIOM is found to produce reasonably accurate BDE(O–H)s of phenolic compounds. The chosen ONIOM model contains only two atoms of the breaking bond as the core zone and is able to provide reliable evaluation for BDE(O–H) for phenols and tocopherol. Deviation of calculated values from experiment is ±(1–2) kcal/mol. BDE(O–H) of several curcuminoids and flavanoids extracted from ginger and tea are computed using the proposed model. The BDE(O–H) values of enol curcumin and epigallocatechin gallate are predicted to be 83.3 ± 2.0 and 76.0 ± 2.0 kcal/mol, respectively.