Biological and Nonbiological Antioxidant Activity of Some Essential Oils.

Fifteen essential oils, four essential oil fractions, and three pure compounds (thymol, carvacrol, and eugenol), characterized by gas chromatography and gas chromatography-mass spectrometry, were investigated for biological and nonbiological antioxidant activity. Clove oil and eugenol showed strong DPPH (2,2-diphenyl-1-picrylhydrazyl) free-radical scavenging activity (IC50 = 13.2 μg/mL and 11.7 μg/mL, respectively) and powerfully inhibited reactive oxygen species (ROS) production in human neutrophils stimulated by PMA (phorbol 12-myristate 13-acetate) (IC50 = 7.5 μg/mL and 1.6 μg/mL) or H2O2 (IC50 = 22.6 μg/mL and 27.1 μg/mL). Nutmeg, ginger, and palmarosa oils were also highly active on this test. Essential oils from clove and ginger, as well as eugenol, carvacrol, and bornyl acetate inhibited NO (nitric oxide) production (IC50 < 50.0 μg/mL). The oils of clove, red thyme, and Spanish oregano, together with eugenol, thymol, and carvacrol showed the highest myeloperoxidase inhibitory activity. Isomers carvacrol and thymol displayed a disparate behavior in some tests. All in all, clove oil and eugenol offered the best antioxidant profile.