The Effects of Toxic Metabolites, Violaceol-I and -II, from Emericella violacea on Mitochondrial Respiration

Abstract

Violaceol-I, -II, and violaceic acid from a toxigenic fungus Ernericella violacea were examined for their uncoupling effect on oxidative phosphorylation of isolated rat liver mitochondria. It was found that toxic metabolites violaceol-I and -II were uncouplers to mitochondrial respiration and non-toxic metabolite violaceic acid was not. Violaceol-I and -II induced large amplitude swelling of mitochondria in isotonic alkali salt solutions and violaceic acid again did not. The uncoupling activities of violaceols were found to be gradually diminished and were finally completely lost when violaceols solution was kept at room temperature due to their chemical instabilities. However instead of uncoupling effect, an inhibitory effect on state 3 respiration was increased, causing a prominent decrease in RC index of mitochondrial respiration.