The chemical composition of essential oils and lipophilic extracts of Silphium integrifolium Michx. and S. trifoliatum L. leaves

The research presented in this paper revealed that secretory ducts in leaf stalks and main nerves of leaf blades of S. integrifolium and S. trifoliatum were of schizogenic origin and were present in varied number around vascular bundles. GC-FID and GC-MS analyses of essential oils and lipophilic extracts made from leaves collected from tested Silphium species in 1999-2001 and 2007 indicated that sesquiterpene compounds were the main constituents: germacrene D, beta-caryophyllene, caryophyllene oxide and silphiperfol-6-en-5-one. Only the oil and extracts from S. integrifolium contained significant amounts of allo-aromadendr-9-ene (8.5 +/- 4.2% in oil achieved in 1999-2001, as well as 3.7 +/- 0.1% and 5.7 +/- 0.3 mu g/ml, respectively in essential oil and extract (1:10) from 2007). Besides volatile compounds, sterols such as gamma-sitosterol and stigmasterol as well as triterpene alcohols (beta-amyrine and alpha-amyrine), higher alkanes, free fatty acids and their derivatives along with vitamin E were present in tested lipophilic extracts. Copyright (c) 2008 John Wiley & Sons, Ltd.