Variation of the Chemical Composition of Essential Oils in Tunisian Populations of Thymus algeriensisBoiss. et Reut. (Lamiaceae) and Implication for Conservation

Abstract

The variation of the essential-oil composition among 14 Tunisian natural populations of Thymus algeriensis Boiss. et Reut. (=Thymus hirtus Willd. ssp. algeriensis Boiss. et Reut.) was assessed by GC (RI) and GC/MS. The populations were collected from different geographical regions belonging to the sub-humid, upper semi-arid, mean semi-arid, lower semi-arid, and upper-arid bioclimates. A total of 47 constituents, representing 81.0 to 96.5% of the total oil, were identified. The main volatiles at the species level were 1,8-cineole (17.7%), alpha-pinene (15.5%), and camphor (8.2%). A high variation among populations for the majority of the compounds was shown. Camphor (0.2-14.0%), linalool (0.2-22.4%), borneol (<0.01-24.3%), caryophyllene oxide (<0.01-18.8%), thymol (<0.01-54.9%), gamma-terpinene (0.4-6.5%), alpha-copaene (0.4-7.6%), linalyl acetate (<0.01-6.4%), and methyl eugenol (<0.01-6.9%) were the main constituents differentiating the populations. The chemical differentiation among populations, assessed by principal component analysis (PCA) and a UPGMA (unweighted pair-group method with averaging) cluster analysis performed on all populations and compounds, was high. Six chemotypes according to the main compounds have been distinguished, i.e., caryophyllene oxide/1,8-cineole/alpha-pinene, 1,8-cineole/alpha-pinene, 1,8-cineole/alpha-pinene/camphor, borneol/1,8-cineole/alpha-pinene, linalool, and thymol chemotypes. The spatial chemotype distribution was linked to the geographic distance among populations rather than to bioclimates, indicating that local selective environmental factors act on the chemotype diversity. The high chemical variation among populations according to their geographical and bioclimatic distribution imposes that conservation strategies of populations should be made appropriately, taking into account these factors. The in situ and ex situ conservation strategies should concern all populations representing the different chemotypes.

In-vitro assessment of antioxidant and antimicrobial activities of methanol extracts and essential oil of Thymus hirtus sp. algeriensis

“…algeriensis collected in Kairouan is 5.75% and the major components are 1.8-cineole (19.96%) and camphor (19.20%). A similar result was previously described by ElHadj Ahmed [27] who have found that the chemical composition of Thymus hirtus sp. algeriensis resulted in the identification of 25 compounds with a dominance of oxygen-containing monoterpenes, the main constituents were linalool (17.62%) and camphor (13.82%), whereas Ben El Hadj Ali [28] showed that camphor characterized few populations from the semi-arid zone of Tunisia.…”

Effects of Thymus hirtus sp. algeriensis Boiss. et Reut. (Lamiaceae) essential oil on healing gastric ulcers according to sex

“…Extraction procedures for EOTa resulted in a yield of 2.36%. Previous chemical reports of the essential oil obtained from 14 Tunisian natural populations of Thymus algeriensis leaves collected from different geographical regions revealed that the major components were 1,8-cineole (17.7%), α-pinene (15.5%), and camphor (8.2%) [34]. Zouari et al .…”

Chemical composition and antioxidant, antibacterial, allelopathic and insecticidal activities of essential oil of Thymus algeriensis Boiss. et Reut.

“…Gas chromatography (GC) analyses were carried out following the method of Ben El Hadj Ali et al (2010). Gas chromatography-mass spectrometry (GC-MS) analyses were performed with an Agilent 7890A gas chromatograph equipped with a HP-5MS fused silica column (30 m × 250 m coated with 5% phenyl methyl silicone, 95% dimethylpolysiloxane, 0.25 m film thickness), interfaced with an Agilent mass selective detector 5975C inter MSD.…”

“…It's one of the four Thymus species that grows wild in different regions of Tunisia. It is a short lived and gynodioecious shrub (Ben El Hadj Ali et al, 2010;Morales, 1996). It reproduces by seeds and can reach 20-50 cm in height.…”