Antioxidant Activity of Eugenol: A Structure–Activity Relationship Study

Eugenol (4-allyl-2-methoxyphenol), a major phenolic component from clove oil (Eugenia caryophyllata), has several biological activities. To estimate the capacity of eugenol to act as an antioxidant, the following were studied: 1,1-diphenyl-2-picryl-hydrazyl–, 2,2′-azino-bis(3-ethylbenzthiazoline-6-sulfonic acid)–, and N,N-dimethyl-p-phenylenediamine–scavenging activity; total antioxidant activity; and ability to reduce ferric ions and cupric ions. Eugenol inhibited 96.7% (r2=0.9319) lipid peroxidation of a linoleic acid emulsion at a 15-μg/mL concentration. Butylated hydroxyanisole, butylated hydroxytoluene, α-tocopherol, and Trolox® displayed 95.4% (r2=0.8482), 99.7% (r2=0.7798), 84.6% (r2=0.9272), and 95.6% (r2=0.8511) inhibition of peroxidation, respectively, at the 15-μg/mL concentration. According to the results of this study, eugenol had the most powerful antioxidant activity and radical-scavenging activity. This study should prompt further studies of the antioxidant properties of eugenol.