New sesquiterpene lactones from Inula montbretiana DC

The genus Inula (Asteraceae) comprises more than 100 species distributed in Asia, Europe and Africa. Many of these species have been used as traditional medicines and were reported to possess anti-inflammatory, anti-infective and other activities [1]. Sesquiterpene lactones (STL) have frequently been reported as active constituents. In the course of our studies on STL in Asteraceae, we have now investigated for the first time Inula montbretiana DC, a species occurring in Turkey. From the dichloromethane extract of aerial parts we isolated several esters of 9β-hydroxy-parthenolide, whose structures were determined by HR-ESI-MSMS and extensive NMR measurements. A mixture of 1a-2b was obtained in crystalline form which was separated by prep. HPLC to yield diastereomeric mixtures of 1a+1b and 2a+2b. Compounds 3 and 4 were obtained by CC from further fractions. While 3 and 4 have previously been described as constituents of Inula verbascifolia [2], compounds 1a and 1b as well as 2a and 2b are new natural products, to the best of our knowledge. Further compounds of this type were detected in the extract by UHPLC-ESI-MSMS; their isolation is still ongoing. Studies on the anti-cancer and anti-protozoal activity of the isolated compounds are in progress.

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Acknowledgements: The presented work was performed at IPBP, Münster, during an ERASMUS fellowship.

References: 1. Zhao, Y-M. et al. (2006) Chem. Biodivers. 3: 371–384.

2. Harvala, E. et al. (2002)J. Nat. Prod. 65: 1045–1048.