Antioxidant effect and antimicrobial activity of phenolic sulfides

Some phenolic compounds containing both phenolic hydroxyl groups and sulfide groups in the molecules were prepared by Michael addition and radical addition reactions of ethanethiol and ethanedithiol with o-, m- and p-vinylphenol. The antioxidant effect of these products on the autoxidation of lard was examined by an oven test at 60°C. The antimicrobial activities of these products were evaluated by an agar dilution method. Three kinds of gram-positive and three kinds of gram-negative bacterial strains, as well as six kinds of fungal strains were used for the test. It was found that the Michael addition products showed considerably better antioxidant effects than BHT, whereas the radical addition products did not show any antioxidant effect. The antioxidant effects of these compounds were influenced by the positions of the sulfide groups in their molecules. The phenolic sulfides tested in this report showed good antimicrobial activities against bacteria and fungi.