Insights in the Scavenging Mechanism of Trichloromethyldioxy Radical with Lycopene: a DFT/TD- DFT Study

Abstract

Abstract The antioxidant action of lycopene as an alkyl peroxyl radical (CCl3O•2) scavenger through electron transfer, hydrogen abstraction and radical addition mechanisms has been investigated in the gas, non-polar and polar phases using density functional theory and the conductor like polarizable continuum model, CPCM, to account for solvents effect at the B3LYP/6-31G** level of theory. Results reveal that for fully optimized complexes, there is a stabilizing attraction between CCl3O•2 radical and lycopene that its value in polar phase is more than none-polar phase and in none-polar phase is more than gas phase. Thermodynamic studies reveal that transfer electron process in polar solvent at room temperature is more desirable than other reactions. The global reactivity parameters of ionization potential, IP, electron affinity, EA, electroaccepting, ω+, and electrodonating, ω−, HOMO-LUMO gap, ∆, chemical potential, µ, chemical hardness, η, show that lycopene is considered as a good electron donor compared to CCl3O•2 radical and the antioxidant property of lycopene in polar solvent is more than non-polar solvent and cavity. The calculated λmax via time dependent-density functional theory, TD-DFT, has a bathochromic shift due to interactions of CCl3O•2 radical with lycopene, so that lycopene becomes almost colorless after radical adsorption in polar and non-polar solutions. The calculated values of dipole moment and solubility Gibbs free energy, ∆Gsolv, confirm more solubility of lycopene and its complex with radical in polar phase than non-polar phase. The obtained results can aid in the understanding of different possible mechanisms that may be involved in the prevention of some illness.