Effect of Phenolic Antioxidants on Lipoxygenase Reaction

Abstract

The effect of conventional antioxidants on soybean lipoxygenase reaction was examined. Inhibitory activities of o-diphenols such as pyrocatechol, homocatechol, propyl gallate and NDGA were higher than those of m- and p diphenols. The mode of inhibition by NDGA, one of the most effective inhibitors among the phenolic antioxidants tested, conformed to a competitive type and not to an induction period type. Under certain conditions, NDGA could be an irreversible inactivator for the enzyme. The effect of NDGA on the enzyme reaction could not be completely explained by the coupled oxidation theory. The inactivation by NDGA were effectively prevented by either of adding catalase, of incubating under anaerobic condition or in low pH medium or of adding borate. These facts showed that the inactivation of lipoxygenase took place in consonance with the autoxidation of NDGA.