Comparative study of the radical scavenging behavior of ascorbic acid, BHT, BHA and Trolox: Experimental and theoretical study

The present study compares, theoretically and experimentally, the antiradical potential of four most commonly used antioxidants, namely butylated hydroxytolune (BHT), butylated hydroxyanisole (BHA), ascorbic acid (Asc) and 6-hydroxy-2,5,7,8-tetramethylchroman-2-carboxylic acid (Trolox). The antiradical activity was evaluated in vitro using DPPH and ABTS assays. DFT calculations at B3LYP/6-311G(d,p) level of theory have been employed to evaluate theoretically the antiradical potential of the investigated compounds in gas phase, ethanol and water. The three well-established antiradical mechanisms, hydrogen atom transfer (HAT), sequential electron transfer proton transfer (SETPT) and sequential proton loss electron transfer (SPLET) have been investigated. The results allowed assigning the antiradical activity to specific moieties and structural features of these compounds. It was found that for Asc the hydroxyl group (4-OH) is the most likely to be abstracted to form radicals and hence define antiradical properties of this compound. For BHA, the isomer 2-BHA is a better antiradical agent than the isomer 3-BHA. The H-benzylic of Trolox contributes to its antiradical properties. For all the studied compounds the HAT was found to be the thermodynamically dominant mechanism in gas-phase, whereas the SPLET mechanism is the thermodynamically favorable pathway in polar solvents. Both experimental and theoretical results indicate that the sequence of the antiradical potential of the investigated compounds is BHT > BHA > Trolox > Asc. (C) 2019 Elsevier B.V. All rights reserved.