Chemical composition and antioxidant activity of Plectranthus grandis and P-ornatus essential oils from north-eastern Brazil

The Plectranthus species (Lamiaceae) have been used in traditional medicine in several places around the world, including Brazil, to treat different diseases. P. grandis and P. ornatus, growing in north-eastern Brazil, were collected at four different times of day and the essential oils from the leaves were analysed by GC-MS. The oil of P. grandis contained mainly trans-beta-caryophyllene (31.3-40.2%), germacrene D (12.5-24.5%) and eugenol (15.4%) and the oil of P. ornatus contained trans-beta-caryophyllene (9.6-62.4%), eugenol (38.0%) and thymol (14.1%) as the major components. The oils were submitted to DPPH antioxidant assay. The oil of P. ornatus showed a higher antioxidant activity than that of P. ornatus, probably due to its higher yield of the phenolic compounds eugenol and thymol. Copyright (c) 2006 John Wiley & Sons, Ltd.