ANTIOXIDANT ACTIVITIES OF ESSENTIAL OILS 401 oregano, wintergreen, and cinnamon bark extra were 4023.49 ± 0.01, 3847.87 ± 0.01, and 1190.23 ± 0.01 μM of trolox mg−1, respectively. The TEAC assay of pepper extra essential oil was 17.17 ± 0.01 μM of trolox mg−1, which was the lowest reported from the TEAC assay. The TEAC assay of Rosmarinus offi cinalis extract, Nigella sativa essential oil (16), Oxytropis halleri, and Lathyrus binatus extract (29) revealed 15700, 2500, 34, and 158 μM of trolox mg−1, respectively. Therefore, the TEAC of the essential oil ajowan (Trachyspermum ammi) is better than that of Nigella sativa, Oxytropis halleri or Lathyrus binatus and worse than that of Rosmarinus offi cinalis extract. FERRIC THIOCYANATE (FTC) ASSAY The inhibition of linoleic acid peroxidation for the FTC assay of the twenty-fi ve essential oils is listed in Table III. At a concentration of 1 mg ml−1, the FTC assay of the twenty- fi ve essential oils was in the range of 0–29.17%. According to the results, oregano was found to have the strongest FTC (29.17 ± 0.02%). This FTC activity was followed by that of ajowan (25.26 ± 0.03%), benzoin (18.59 ± 0.03%), jasmine (arab.) (13.70 ± 0.03%), cinnamon bark extra (10.46 ± 0.05%), nutmeg (5.81 ± 0.05%), and bay laurel (4.89 ± 0.04%) essential oils. The other essential oils showed negligible FTC assay values. Hygrophila auriculata extract (30) at 1 mg ml−1 of concentration shows 55.29% inhibition of linoleic acid peroxidation. Therefore, the FTC of oregano (Origanum vulgare) essential oil is worse than that of the Hygrophila auriculata extract. At a concentration of 1 mg ml−1, the essential oil oregano and four of its main compo- nents (thymol, p-cymene, linalool, and carvacrol) were analyzed via the FTC assay. Figure 4 clearly shows that the inhibition of linoleic acid peroxidation has the following order: carvacrol oregano essential oil thymol p-cymene and linalool. Carvacrol and thymol were the major components of the oregano essential oil attributed to the high inhibition of linoleic acid peroxidation. P-cymene and linalool showed negli- gible FTC assay values. We have studied the DFRS, TPC, and TEAC antioxidant activi- ties of 23 esters, 14 aldehydes, 10 ethers, 14 phenols, 14 monoterpenols, and 10 monoterpenes as chemical components. In the future, we will use these data to make a Figure 3. DPPH free-radical scavenging activity from three major chemical components of cinnamon bark extra compared with its essential oil at a concentration of 1 mg ml−1.

JOURNAL OF COSMETIC SCIENCE 402 table via easy calculations (percentage of the chemical component multiplied by the values of the different kinds of antioxidant activity), to obtain the antioxidant activity of each essential oil. CONCLUSION This study examined the antioxidant activities and major chemical components of twenty- fi ve commonly used essential oils using the DFRS, TPC, TEAC, and FTC assays. Eugenol, of the essential oil cinnamon bark extra, yielded the best DFRS assay values. Carvacrol, of the essential oil ajowan, showed the best results from the TPC and TEAC assays. Thymol, of the essential oil oregano, showed the strongest inhibition of linoleic acid peroxidation via the FTC assay. Those components with high phenolic contents revealed great anti- oxidation properties and contained a positive correlation with the DFRS, TPC, TEAC, and FTC assays. Our research shows that cinnamon bark extra, ajowan, and oregano es- sential oils have the potential to be developed into antioxidant ingredients for functional foods and cosmetic products. ACKNOWLEDGMENTS We thank the National Science Council of Taiwan, the Republic of China, for support (NSC98-2113-M-241-001-MY2-1). We also thank Prof. R. G. Finke and Dr. J. E. Mondloch for helpful discussions. REFERENCES (1) L. I. Daise, D. S. Alviano, C. S. Alviano, and P. P. Kolodziejczyk, Screening of chemical composition, antimicrobial and antioxidant activities of Artemisia essential oils, Phytochemistry, 69, 1732–1738 (2008). (2) M. R. Loizzo, F. Menichini, F. Conforti, R. Tundis, M. Bonesi, A. M. Saab, G. A. Statti, B. Cindio, P. J. Houghton, F. Menichini, and N.G. Frega, Chemical analysis, antioxidant, antiinfl ammatory and anticholinesterase activities of Origanum ehrenbergii Boiss and Origanum Syriacum L. essential oils, Food Chem., 117, 174–180 (2009). Figure 4. Inhibition of linoleic acid peroxidation of the FTC assay from four major chemical components of oregano compared with its essential oil at a concentration of 1 mg ml−1.