DPPH Free-Radical Scavenging Activity, Total Phenolic Contents and Chemical Composition Analysis of Forty-Two Kinds of Essential Oils
CHIA-WEN LIN, CHIA-WEN YU, SUNG-CHUAN WU AND KUANG-HWAY YIH*
Department of Applied Cosmetology, HungKuang University, No.34, Zhongqi Rd., Shalu Township, Taichung, Taiwan, R.O.C.
(Received: March 5, 2009; Accepted:September 16, 2009)
ABSTRACT
Forty-two commonly used essential oils were investigated for the antioxidant capabilities by DPPH free-radical scavenging activity, total phenolic contents and photochemiluminescence (PCL) assay. At the concentration of 5 mg/mL, cinnamon bark (91.4 ± 0.002%), origanum (86.66 ± 0.008%) and thyme wild (52.54 ± 0.016%) were shown to own the strongest DPPH free-radical scavenging activity. Their total phenolic contents were 658.40 ± 4.383, 1107.20 ± 0.768 and 275.50 ± 0.607 (µg GAE / 5 mg essential oil), respectively. To compare with the standard reference BHA (µg/mL), their EC50 were in the order: BHA (25.11 µg/mL) < cinnamon bark (90.63 µg/mL) <origanum (751.51 µg/mL). The photochemiluminescence assay was also employed to investigate the antioxidative capabilities of lipid-soluble substances (ACL). The results were as follow: cinnamon bark (133.9 ± 0.26 µmol trolox/g) > origanum (62.63 ± 1.73 µmol trolox/g) > theme wild (5.88 ± 0.16 µmol trolox/g). The chemical compositions of cinnamon bark, origanum and thyme wild were analyzed by GC-MS and followed by DPPH free-radical scavenging activity assay to confirm that eugenol, carvacrol and thymol were the major compositions contributing the antioxidative capabilities of the essential oils.
Key words: DPPH free-radical scavenging activity, total phenolic contents, photochemiluminescence, essential oil