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Etude chimique et statistique de la composition d'huiles essentielles d'origans (Lamiaceae) cultivés issus de graines d'origine méditerranéenne

Abstract : Present in numerous Mediterranean countries, the plant Origan (Origanum genre) has been classed in 74 species, under species, varieties or hybrids. The chemical composition of the essential oils (EO) of around thirty species has been studied in this work. The vegetable material has been furnished by the CNPMAI at Milly-la-Forêt, who realized cultures from seedlings collected in their original countries. Plants thus obtained have been gathered and dried, and the EO have been extracted by hydrodistillation, according to the process described in the Pharmacopée Européenne (5th edition). Analysis of the 457 EO samples has been carried out using GC techniques, coupled with either mass spectrometry for compound identification, or with a flame ionisation detector for their quantification. Analysis of the results shows that phenols are present in almost all of the studied species, carvacrol being the most represented, making up more than 40% of the EO in 22 species, while the thymol content reaches more than 40% in the EO of 8 species. Oxygenated monoterpenes are present at more than 50% in 7 species, with linalool, a-terpineol, sabinene trans-hydrate and terpinen-4-ol being the most significant. Only one species renders an EO containing monoterpene hydrocarbons in important quantities. This work has allowed the identification of EO compositions not previously studied, as well highlighting some intra and inter species specificities. In fact, when enough EO samples could be analysed, a statistical study, by PCA and Student's test showed the presence of different chemotypes within the same species. The geographical origin could be an important variable, since the EO of some species native to geographically isolated areas (Cyprus) generally have an unique composition, as opposed to the EO of continental species, where the presence of 2 or 3 chemotypes has at times been shown. This work has also shown that the species O. dubium and O. majorana var. tenuifolium, initially confused, are in fact 2 different botanic species. The composition of their EO confirms this distinction : the EO of the first species presents 2 chemotypes (one thymol, the other carvacrol), whereas the EO of the second is principally composed by a-terpineol, sabinene trans-hydrate and terpinen-4-ol. However, it was not possible to formally establish a chimiotaxonomic link between the chemical composition of Origan's EO and the classification proposed by Iestwaart.
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Submitted on : Friday, July 13, 2012 - 3:26:20 PM
Last modification on : Tuesday, December 14, 2021 - 10:38:06 AM
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  • HAL Id : tel-00717749, version 1

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Gilles Figueredo. Etude chimique et statistique de la composition d'huiles essentielles d'origans (Lamiaceae) cultivés issus de graines d'origine méditerranéenne. Chimie organique. Université Blaise Pascal - Clermont-Ferrand II, 2007. Français. ⟨NNT : 2007CLF21732⟩. ⟨tel-00717749⟩

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