A DFT/TD-DFT Study for the Role of Lycopene as a Trichloromethyldioxy Radical Scavenger

The antioxidant action of lycopene, as a trichloromethyldioxy radical ( ) scavenger has been investigated in the gas, non-polar and polar phases through electron transfer, hydrogen abstraction and radical addition reactions using the density functional theory (DFT) and the conductor like polarizable continuum model (CPCM) to account for solvents effect at the B۳LYP/۶-۳۱G** level of theory. The target solvents are water as a polar solvent and benzene as a non-polar solvent. The results reveal that there is a stabilizing attraction between radical and lycopene for optimized complex. The value of which in the polar phase is more than that in the gas and non-polar phases. Thermodynamic studies demonstrate that transfer electron process in a polar solvent is more desirable than the other reactions. The global reactivity parameters including ionization potential (IP), electron affinity (EA), electroaccepting (ω+), electrodonating (ω-), chemical potential (μ), chemical hardness (η) and HOMO-LUMO gap (∆) have shown that lycopene, being compared to radical is considered as a proper electron donor and the antioxidant property of lycopene in a polar solvent is more than that in the gas and non-polar phases. λmax calculated via time dependent-density functional theory (TD-DFT) has a bathochromic shift because of the interaction of radical with lycopene; so that lycopene after radical adsorption becomes almost colorless in polar and non-polar solutions. The calculated values of dipole moment and Gibbs free energy of solubility (∆Gsolv) indicate a higher solubility of the lycopene-radical complex compared to lycopne alone.

کلیدواژه ها:

lycopene ، trichloromethyldioxy ، radical ، Antioxidant ، DFT ، TD-DFT