Inhibitory effect of eugenol on non-enzymatic lipid peroxidation in rat liver mitochondria.

The anti-peroxidative activity of eugenol on Fe(2+)-ascorbate- and Fe(2+)-H2O2-induced lipid peroxidation was studied using rat liver mitochondria. Eugenol inhibited thiobarbituric acid reactive substance (TBARS) formation induced by both the systems in addition to oxygen uptake and mitochondrial swelling induced by Fe(2+)-ascorbate. Time course studies on TBARS formation indicated the ability of eugenol to inhibit initiation and propagation reactions. There was no measurable chemical modification of eugenol during the course of mitochondrial peroxidation by both the systems. Mitochondrial peroxidation by Fe(2+)-H2O2 was inhibited by hydroxyl radical (OH) scavengers like mannitol, benzoate, formate and dimethyl sulfoxide apart from eugenol. The OH scavenging ability of eugenol was evident from its inhibitory effect on OH-mediated deoxyribose degradation. The second-order rate constant for the reaction of OH with eugenol was about 4.8 x 10(10) M-1 sec-1. Eugenol reduced Fe3+ ions and Fe3+ chelated to citrate or ADP but it did not exhibit pro-oxidant activity in OH-mediated deoxyribose degradation. Incubation of mitochondria with eugenol resulted in the uptake of small but significant quantities of eugenol which inhibited subsequent lipid peroxidation by acting as a chain breaking antioxidant.