Analysis of Cleistopholis patens Leaf and Trunk Bark Oils Using Combined GC- Flame Ionisation Detection, GC-Retention Index, GC–MS and 13C-NMR
Germacrenes A–C are secondary metabolites produced by various plants. They are sesquiterpene hydrocarbons bearing the (E,E)-1,5-cyclodecadiene structure known to undergo thermal rearrangement through a [3.3]-sigmatropic reaction. Such a rearrangement was evidenced by comparing the contents of a given germacrene and the corresponding elemene calculated by GC-flame ionisation detection (FID) with the relative intensities of the signals of both molecules in the 13C-NMR spectrum of the mixture, recorded at room temperature.
To develop a protocol to identify and quantify germacrenes A, B and C and in parallel the corresponding elemenes, using a combination of GC-FID and 13C-NMR and then provide a correct analysis of Cleistopholis patens essential oils.
The essential oil was submitted to GC-FID, GC-retention index, GC–MS and 13C-NMR analyses. The relative percentages of every couple of germacrene and elemene measured by GC-FID were summed. Then, the relative ratio of the mean intensities of the signals of the protonated carbons of a given germacrene and the corresponding elemene was calculated. The contents of both compounds were obtained by combining GC-FID and 13C-NMR data.
The true content of germacrene A/β-elemene, germacrene B/γ-elemene and germacrene C/δ-elemene in leaf and root oils from C. patens was evaluated by combination of GC-FID and 13C-NMR data. Correct analysis of the essential oils was provided.
Combined analysis of essential oil including 13C-NMR without isolation of the components, appeared really efficient to identify and quantify germacrene isomers and in parallel elemene isomers in essential oils. Copyright © 2013 John Wiley & Sons, Ltd.