The variation of antioxidant activities and chemical composition of essential oils of Teucrium orientale L. var. orientale during harvesting stages

The aerial parts of Teucrium orientale L. var. orientale were collected at the budding, flowering and vegetative stages. In the each stage, essential oils were obtained by hydrodistillation and steam distillation. The chemical compositions of the essential oils were analysed by GC and GC-MS; 43 different compounds were determined in total, and more than 96% of the essential oils were identified by GC and GC-MS. They contain mainly linalool, beta-caryophyllene, 3-octanol, phytol, beta-bourbonene and germacrene D. Among the steam distillation oils, the highest 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity was found at the budding stage and the lowest at the vegetative stage. At all stages, the DPPH radical scavenging activities of hydrodistillation oils were markedly lower than those of steam distillation oils. Steam distillation oils of the budding and flowering stages showed the highest antioxidant activities. However, steam distillation oils of the vegetative stage in two doses (200 and 400 mug) did not show antioxidant activities (p > 0.05, between these and control). None of the hydrodistillation oils showed detectable antioxidant activity. In contrast, in the presence of 400 mug hydrodistillation oils of flowering stage, prooxidant activity was found in the linoleic acid emulsion. Copyright (C) 2004 John Wiley Sons, Ltd.