Density Functional Study on the Structure and Antioxidant Activity of Some Bioactive Compounds of Ginger

Oxidative stress is as a result of an imbalance between the increased productions of free radical molecules (FRMs) and the compromised antioxidant protection systems in the cells of the living organism. FRMs play an important role in damaging lipids in cell and intracellular membranes, and disrupting the cell organelle functions which cause many neurological diseases and malignant tumors. Some of FRMs are long-living and can migrate both inside cells and circulated bloodstream thereby can enter other organs, resulting in DNA damage and causing disordering in the cellular genetic functions.In this study, two bioactive compounds in ginger (Paradol and Shogaol) are selected for structural study and analysis of their chain-breaking antioxidant activity. The theoretical method (M۰۶-۲X/۶-۳۱۱++G**) is used to calculate the homolytic O-H and C-H bond dissociation enthalpies (BDEs).Unscaled thermal corrections to enthalpy from the vibrational frequency calculations were added to the total electronic energies. The equation BDE = E (B•) + E (H•) - E(BH) along with addingunscaled thermal corrections to enthalpy from the vibrational frequency calculations is used for the calculation of the BDEs. The results showed the enone part of Shogaol chain is a key importance for efficient chain-breaking antioxidant activity compared to Paradol, probably due to a resonance stabilization of the generated radical.