Tactfully improve the antioxidant activity of 2′-hydroxychalcone with the strategy of substituent, solvent and intramolecular hydrogen bond effects

Abstract

The substituent and solvent effects on the antioxidant activity of 2′-hydroxychalcone (2′Cha) were systematically explored in gas and three solvent phases by designing six novel compounds (2′Cha-3′NH2, 2′Cha-4′NH2, 2′Cha-5′NH2, 2′Cha-3′CN, 2′Cha-4′CN, and 2′Cha-5′CN) based on the density functional theory (DFT) approach. Significant parameters involved in three primary antioxidant mechanisms, namely the hydrogen atom transfer (HAT), single electron transfer followed by proton transfer (SET-PT), and sequential proton loss electron transfer (SPLET) were computed to confirm the thermodynamically preferred reaction pathway in different media. Besides, 4′-hydroxychalcone (4′Cha) was introduced to unveil the intramolecular hydrogen bond (IHB) effect on the radical scavenging capacity of 2′Cha utilizing the DFT and 2,2-Diphenyl-1-picrylhydrazyl (DPPH) ultraviolet–visible (UV–Vis) spectroscopic methods. Energy barriers and kinetic parameters for HAT reaction of 2′Cha and 4′Cha with hydroperoxyl (HOO) radical were calculated to further compare the radical-trapping process. The photophysical properties of 2′Cha in benzene, chlorobenzene and ethanol are in good agreement with the measured experimental data and the excited-state antiradical capacity improving mechanism was also confirmed experimentally. The current work not only provides valuable guidance for synthesizing high-efficiency antioxidants but also exploits the potential application fields for 2′Cha.