Synthesis of Small Combinatorial Libraries of Natural Products: Identification and Quantification of New Long-chain 3-Methyl-2-alkanones from the Root Essential Oil of Inula helenium L. (Asteraceae)
Article first published online: 6 AUG 2013
Copyright © 2013 John Wiley & Sons, Ltd.
Volume 25, Issue 1, pages 75–80, January/February 2014
How to Cite
Radulović, N. S., Denić, M. S. and Stojanović-Radić, Z. Z. (2014), Synthesis of Small Combinatorial Libraries of Natural Products: Identification and Quantification of New Long-chain 3-Methyl-2-alkanones from the Root Essential Oil of Inula helenium L. (Asteraceae). Phytochem. Anal., 25: 75–80. doi: 10.1002/pca.2466
- Issue published online: 16 DEC 2013
- Article first published online: 6 AUG 2013
- Manuscript Accepted: 20 JUN 2013
- Manuscript Revised: 18 JUN 2013
- Manuscript Received: 21 FEB 2013
- Anti-staphylococcal activity;
- small combinatorial library;
- root essential oil;
- Inula helenium L
Recently, a potent anti-staphylococcal activity of Inula helenium L. (Asteraceae) root essential oil was reported. Also, bioassay guided fractionation of the oil pointed to eudesmane sesquiterpene lactones and a series of unidentified constituents as the main carriers of the observed activity.
To identify nine new constituents (long-chain 3-methyl-2-alkanones) from a fraction of this root essential oil with a low minimum inhibitory concentration value (0.8 µg/mL) by employing a synthetic methodology that leads to the formation of a small combinatorial library of these compounds.
The identity of these constituents was inferred from mass spectral fragmentation patterns and GC retention data. A library of 3-methyl-2-alkanones (C11–C19 homologous series) was synthesised in three steps starting from methyl acetoacetate and the corresponding alkyl halides. The synthetic library was also screened for in vitro anti-microbial activity.
Gas chromatographic analyses of I. helenium essential oil samples with spiked compounds from the synthesised library corroborated the tentative identifications of the long-chain 3-methyl-2-alkanones. The availability of these anti-microbial compounds from this library made it possible to construct GC/FID calibration curves and determine their content in the plant material: 0.08 − 24.2 mg/100 g of dry roots.
The small combinatorial library approach enabled the first unequivocal identification of long-chain 3-methyl-2-alkanones as plant secondary metabolites, and, also, allowed determination of not only a single compound and biological properties, but those of a group of structurally related compounds. Copyright © 2013 John Wiley & Sons, Ltd.