Chemical composition and seasonal variation of the volatile oils from leaves of Michelia champaca L., Magnoliaceae

The volatile oils from leaves of Michelia champaca L. collected bimonthly during one year (four times on the fifteenth day of January, March, May, July, September, and November 2004) were subjected to GC/FID and GC-MS analysis, from which thirteen components were identified. Additionally, part of the oil obtained from January collection was subjected to fractionation over silica gel soaked with AgNO3 to afford five of the main sesquiterpenes (β-elemene, β-caryophyllene, α-humulene, β-selinene, and α-cadinol). The obtained data showed a significative variation in the proportions of the components, which could be associated to climatic parameters in each collection periods.