Benzofuran-stilbene hybrid compounds: an antioxidant assessment - a DFT study

Abstract

The antioxidative activities of the original compound dehydro-δ-viniferin (1) and its three designated derivatives, 5-(2-(4-hydroxyphenyl)benzofuran-3-yl)benzene-1,3-diol (2), (E)-5-(2-(2-(4-hydroxyphenyl)benzofuran-5-yl)vinyl)benzene-1,3-diol (3), and (E)-5-(2-(3-(3,5-dihydroxyphenyl)benzofuran-5-yl)vinyl)benzene-1,3-diol (4), are extensively studied, mainly based on density functional theory (DFT) calculations using the hybrid functional B3LYP and the 6-311G(d,p) basis set. The O-H bond breakage is reasonably responsible for the antioxidative activity, whereas the environment greatly influences results. In solvents, namely water, methanol, and especially acetone, the SPL-ET mechanism (sequential proton loss-electron transfer) is mainly likely to be a antioxidative route for four studied compounds; however, the HAT mechanism (hydrogen atom transfer) is assigned to these compounds in the gaseous phase. Benzofuran-stilbene hybrid compound3with a planar structure is the best antioxidative agent; its 4′-OH induced the lowest PA values in liquid solvents as well as the lowest BDE value in the gas solvent. The kinetic investigation of the interactions of compounds1-4with HOO˙ radicals evidently provides the lowest Gibbs activation energy ΔG#= 4.7 kcal mol−1and the highest rate constantK= 5.702 × 1010L mol−1s−1, which again are assigned to3-4′-OH. At the theoretical level of B3LYP/6-311G(d,p)/LANL2DZ, the complex [La(compound3)3] in gas induces a redshift in the UV-Vis spectrum.