Intraspecific chemical variability of the essential oils of Moroccan endemic Origanum elongatum L. (Lamiaceae) from its whole natural habitats

Abstract

In this study, the chemical variation of the essential oils of the endemic species Origanum elongatum has been studied in its biogeographical context. Essential oils of 168 individual plants collected from 30 populations growing wild in two Moroccan mountains: Rif and Middle Atlas, were analyzed by GC-FID (Gas Chromatography with Flame Ionization Detector), GC/MS (Gas Chromatography/Mass Spectrometry) and 13C NMR (Nuclear Magnetic Resonance). Origanum elongatum produces an EOs yielding after hydrodistillation from 0.81% to 3.12% based on the dry weight of the original biomass. 28 compounds were identified, with a majority of oxygenated monoterpenes among them carvacrol, thymol and p-cymene constitute the most represented compounds. Moreover, a great amount of α-terpinene, limonene, thymoquinone and thymohydroquinone were reported in some samples. Four chemical groups have been identified, namely; carvacrol, carvacrol/thymol, carvacrol/p-cymene and thymol. The geographic distributions of these chemotypes appear to vary since the carvacrol chemotype was the most distributed, while the thymol was found more abundantly in populations from Rif. However, the carvacrol/p-cymene chemotype was revealed only in Taza region. For the first time the whole chemical picture of the EOs of O. elongatum is presented in relation to their geographical distribution such knowledge is primordial in developing a breeding program in order to protect this species widely and intensively used for both medicinal and food uses but also supply the continuous market needs by producing high quality and stable raw material. Keywords: Origanum elongatum, Morocco, Essentials oils, Chemical composition, GC/MS