Theoretical investigations on the antioxidant potential of 2,4,5-trihydroxybutyrophenone in different solvents: A DFT approach

Abstract

2,4,5-trihydroxybutyrophenone (THBP) is a synthetic molecule possessing phenolic OH groups as well as non-phenolic CHx (x = 2 and 3) groups which are believed to be responsible for its antioxidant behavior. The antioxidant nature of THBP has been systematically investigated through quantum chemical calculation by density functional theory (DFT) method with B3LYP hybrid functional and 6-311G++(d,p) basis set in gas, water and methanol media. The principal pathways such as hydrogen atom transfer (HAT), sequential proton loss electron transfer (SPLET) and single electron transfer-proton transfer (SETPT) were considered for antioxidant reactions. Changes of enthalpy (ΔH) and free energy (ΔG) were computed for OH radical scavenging by THBP. In addition, geometry, highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), energy gap (Eg), the other descriptors (electron affinity (EA), ionization potential (IP), global hardness (η), softness (σ), electrophilicity (ω), chemical potential (μ), electronegativity (χ) etc.), Fukui function, molecular electrostatic potential (MEP) surface and spin density were also taken into account. The calculated data values were compared with those of gallic acid (GA), a well-recognized antioxidant, calculated at the same level and also with literature of those compounds claiming efficient antioxidant. The values of the calculated thermochemical parameters convey evidence in favor of THBP as an antiradical molecule which is strongly supported by the descriptor values. The free radical scavenging reaction may occur preferentially at 5-OH > 4-OH > α-CH2 positions of the molecule.