Antioxidant properties of several coumarin– chalcone hybrids from theoretical insights

Density functional theory (DFT) and time-dependent formulation of DFT (TDDFT) have been employed toelucidate the structural characteristics, the antioxidant ability, and the UV-Vis absorption properties of aseries of coumarin–chalcone derivatives recently synthesized. In addition, to investigate the role ofadjacent hydroxyl groups on the antioxidant properties, five additional hybrids were designed andconsidered in this study. Different antioxidant mechanisms have been investigated. They are hydrogenatom transfer (HAT), electron transfer followed by proton transfer (SET-PT), and sequential proton losselectron transfer (SPLET). Based on the obtained results, the HAT mechanism is proposed as the mostimportant one for the antioxidant protection exerted by this class of compounds. The UV spectra ofcoumarin–chalcone hybrids are characterized by a band in the region between 300 and 450 nm arisingfrom different electronic transitions. Our investigation confirms the antioxidant properties of thesehybrids, and shows that poly-substitution of ring A enhances the antioxidant power of this class ofcompounds. One of the derivatives, designed in the present work, the 5,6,8-trihydroxy-7-methyl-3-(30,40-dihydroxybenzoyl) coumarin, seems to be the most promising candidate as an antioxidant.Accordingly, our calculations strongly encourage the synthesis of coumarin–chalcone hybrids as animportant strategy to develop novel compounds with improved antioxidant properties.