Solvent Effect on the Hydroxyl Radical Scavenging Activity of New Isothiocyanate Compounds

The role of natural-based isothiocyanates Cp1-Cp4, i.e., allylisothiocyanate, 1-isothiocyanate-3-methylbutane, 4-methylphenyl isothiocyanate, and 2-phenylethyl isothiocyanate in scavenging highly reactive HOꞏ-radical was studied using Density Functional Theory at M06-2X/6-311++G(3df,3pd)//M06-2X/6-311++G(d,p) level of theory. Formal hydrogen transfer, radical adduct formation, and single electron transfer mechanisms were considered in water and pentyl ethanoate (PEA, to mimic the lipid environment). The results illustrated the high HOꞏ-scavenging activity of the isothiocyanate compounds with rate constants of about 108 - 109 M-1s-1. Allylisothiocyanate Cp1 represents the most efficient HOꞏ-scavenger with koverall of 5.20 × 109 M-1s-1 in water, and 1.85 × 109 M-1s-1 in PEA. Moreover, the rate constants of HOꞏ-reactions with the studied isothiocyanates in the aqueous medium are comparable with that of several biological molecules. These results allow us to enrich the data source on effective antioxidants to reduce excess free radicals and limit damaging effects on biological molecules.