Chemotaxonomy of aromatic plants of the genus Origanum via vibrational spectroscopy.

Fourier transformed-Raman (FT-Raman) and attenuated total reflection-infrared (ATR-IR) spectra of essential oils obtained from marjoram and oregano plants by hydrodistillation are presented. It is shown that the main components of the essential oils can be ascertained through both of these complementary techniques, using spectral information from the pure terpenoids. Spectroscopic analysis is based on the characteristic key bands of the individual volatile substances and therefore, in principle, these techniques allow us to discriminate between different essential oil profiles from individual oil plants of the same species (chemotypes). The combination of vibrational spectroscopy and hierarchical cluster analysis provides a fast, easy and reliable method for chemotaxonomy characterisation. The spectroscopic data presented here correlate very well with those found by gas chromatography (GC) analysis.