SOLVENT EFFECT IN THE STUDY OF ANTIOXIDANT ACTIVITY

Antioxidant activity is capacity of the compound to inhibit lipid oxidation and thus to shorten the oxidation chain length as a result of its reaction with lipid peroxyl radicals. The activity of antioxidants depends on complex factors including nature of the antioxidants, conditions of experiments, properties of substrate, being oxidized and stage of oxidation. Complex formation based on the intermolecular hydrogen bond between hydrogen atom of phenolic antioxidants (AOH) and polar solvents reduces significantly the activity of AOH to scavenge free radicals. Phenols contained a methoxy group in the ortho-position represent an important class of natural compounds. Hydroxylated biphenyl unit, recognized as C2-symmetric phenol dimer, is embedded in many structures of bioactive natural products. Compared to ortho-methoxy phenols, hydroxylated biphenyls manifests higher antioxidant activity and generally they are less toxic than the corresponding phenolic monomer [1,2]. Based on our previous results in hydroxylated biphenyls with antiproliferative activity, dimer of eugenol and dimer of creosol were synthesized by Dettori et al [3]. Natural methoxyphenols: eugenol (Eu), creosol (Cr), and their C2-symmetric biphenyls: dimer of eugenol (DEu) and dimer of creosol (DCr) in presence of dimethyl sulfoxide (DMSO) were selected for this study. Theoretical (DFT calculations) and experimental (lipid autoxidation) approaches were applied to study and to explain the solvent effect on the activity of the selected methoxyphenols. Experimental results obtained confirmed the higher antioxidant efficiency of DCr and of DEu than that of Eu and Cr. The antioxidant efficiency of DCr decreased significantly in presence of DMSO as a solvent. In case of Cr there is no decrease of its efficiency.