RESPIRATORY INHIBITION OF ISOLATED RAT-LIVER MITOCHONDRIA BY EUGENOL

Eugenol inhibited mitochondrial respiration dose-dependently in vitro and uncoupled oxidative phosphorylation from electron transfer. This phenol derivative appeared to compete at higher concentrations with the known uncoupler of oxidative phosphorylation, 2,4-dinitrophenol. Isoeugenol was less active than eugenol, and homovanillic acid was the least active of the three compounds. The effect of eugenol on mitochondrial respiration was different according to the site of entry of electrons from substrates. Eugenol inhibited respiration at a lower concentration with glutamate rather than succinate as substrate. The suggestion was made that the effect of eugenol on a nicotinamide adenine dinucleotide (NAD)-linked substrate was one of electron chain inhibition, but beyond Co-enzyme Q, both NAD-linked and flavin-linked substrates uncoupled oxidative phosphorylation. The results suggest that at the mitochondrial level all three agents can mediate cell injury by acting as potent uncouplers of the respiratory assembly. © 1979.