Antioxidant activity of 3-hydroxyphenol, 2,2'-biphenol, 4,4'-biphenol and 2,2',6,6'-biphenyltetrol: theoretical and experimental studies

A set of selected phenolic compounds (phenol, 3-hydroxyphenol (resorcinol), 2,2'-biphenol, 4,4'-biphenol and 2,2',6,6'-biphenyltetrol) is designed in order to study the structure - antioxidant activity relationship for the compounds with one benzene ring and two C-C bridged benzene rings. The corresponding "dimeric" structures (biphenols and biphenyltetrol) of phenol and resorcinol are handpicked in order to study the influence of the number and mutual position of the substituents (OH group(s) in the aromatic ring) on the antioxidant activity. A combination of theoretical and experimental approaches is applied. Chain-breaking antioxidant activities of compounds under study are determined from the main kinetic parameters of bulk lipid autoxidation. Full geometry optimization of neutral molecules and their corresponding phenoxyl radicals for all compounds under study are obtained by using DFT (B3LYP/6-31+G**) calculations. Good correlation between experimental and predicted activity is achieved.