In vitro evaluation of antioxidant activity of essential oils and their components

Clove and nutmeg essential oils were analysed by GC and CC-MS. These oils, together with 16-18 components found to be present, were tested for antioxi dant properties at final concentrations of 0.05-2.5 x 10(4) ppm in an egg y olk-based thiobarbituric acid reactive substances (TBARS) assay and also un diluted in a beta -carotene agar diffusion assay. Both the essential oils a nd the components tested in the TEARS assay demonstrated some degree of ant ioxidant activity. Only the clove oil, the nutmeg oil, eugenol and terpinol ene demonstrated any ability to inhibit the oxidative bleaching of the beta -carotene agar. The ability of the oil components to inhibit malondialdehy de formation, and therefore lipid peroxidation, in the TEARS assay, yet app arently to possess no activity in the beta -carotene agar diffusion assay, demonstrates the importance in the screening of plant material for bioactiv ity of using a bank of assays ill vitro before assigning bioactivities. By using a number of assays, not only should the number of false positives and negatives be greatly reduced, but evidence pertaining to the mechanism of action may be obtained. Copyright (C) 2000 John Wiley & Sons, Ltd.