INHIBITION OF MITOCHONDRIAL RESPIRATION BY MODEL PHENOLIC-COMPOUNDS

A variety of model phenolic compounds were tested for their ability to inhibit the beef heart mitochondrial NADH-oxidase and succinoxidase enzyme systems in vitro. Specifically, we determined the hydroxy and methoxy configurations of the model phenolic compounds that were mandatory for inhibition of mitochondrial respiration. Data are presented that supported the conclusion that the relative potency of inhibition of the beef heart mitochondrial succinoxidase enzyme system was methyl hydroquinone > hydroquinone > 4-methyl catechol > 3-methyl catechol > catechol, whereas o-cresol, p-cresol, resorcinol, 2- methyl resorcinol and orcinol were non-inhibitory. None of the model phenolic compounds tested were inhibitory toward the beef heart mitochondrial NADH-oxidase enzyme system. These findings indicate that the site of inhibition for the catechol and hydroquinone derivatives is in complex II. Furthermore, it is proposed that a capacity for ortho- or para-quinone formation is mandatory for inhibition of mitochondrial succinoxidase activity by model phenolic compounds. © 1979.