Wild Thymbra capitata from Western Rif (Morocco): essential oil composition, chemical homogeneity and yield variability.

Essential oils (EO, 15 collective samples and 47 individual samples) of Thymbra capitata collected from Moroccan Western Rif were analyzed using gas chromatography (GC) in combination with retention indices (RI), gas chromatography-mass spectrometry (GC-SM) and 13C NMR spectroscopy. Twenty components were identified. Carvacrol (68.2%-85.9%) was by far the major component of all the samples, while the content of thymol (0.1-0.3%) was very low. Other components present in appreciable amounts were gamma-terpinene (up to 8.9%), p-cymene (up to 7.1%), linalool (up to 4.4%) and (E)-beta-caryophyllene (up to 4.1%). In contrast, the yield of EO varied drastically from sample to sample (0.5-3.7%). No correlation could be established between yield of EO and altitude, pH, chemical composition and granularity of the soil. Cultivation under controlled conditions is suggested to improve the quantitative characteristics of carvacrol-rich Moroccan T. capitata.