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The present study describes chemical composition, antioxidant, antibacterial, allelopathic and insecticidal properties of essential oil of Thymus algeriensis (Lamiaceae), a North African endemic species. The essential oil from all organs of T. algeriensis were extracted by hydrodistillation and analysed by gas chromatography (GC) and gas chromatography-mass spectrometry (GC–MS). A high variation among organs for the majority of compounds was shown. Caryophyllene oxide (21.1%) and veridiflorol (17.2%) were the main constituents in roots, while elemol (10.2%) and caryophyllene oxide (17.8%) were identified as the main constituents for stems. Leaves were characterized by high levels of α - pinene (19.5%), 1,8-cineole (11.6%) and camphor (10.4%). Based on the determination of the diameter of inhibition and the determination of the minimum inhibitory concentration, a moderate to high antibacterial activity according to oils was revealed against five bacteria strains. However, oils from Dj. Jdidi locality showed higher bactericidal effect (MICs = 1–3.25 μl/ml) than those from other samples. The level of antioxidant activity estimated by DPPH (IC 50 = 4.31–9.23 mg/ml) and ABTS (11.69–28.23 μgTE/mg DW) test was moderate. The obtained results also showed that the leaf oils inhibited the shoot and root growth of Medicago sativa and Triticum æstivum seedlings. Thus, the T. algeriensis oils may be used as a natural herbicide. Furthermore, these oils were found to possess strong insecticidal activity (LC 50 = 44.25–112.75 μl/l air) against cotton leafworm larvae. Thus, the essential oil of this plant could be used as a potential source of natural antioxidants and bioactive molecules in pharmaceutical as well as in food industries. [ABSTRACT FROM AUTHOR]

Abstract: The genetic diversity and the essential oil variations within and among 12 Tunisian natural populations of Thymbra capitata (=Thymus capitatus Hoffm. et Link. = Coridothymus capitatus Rch. f.), from different geographic regions and bioclimates, were assessed using eight isozymes and thirty nine terpenoids. Volatiles were analyzed by gas chromatography (GC) and gas chromatography–mass spectrometry (GC–MS). A high genetic diversity within population which was revealed by isozymes (P =66.64%, Ap =1.85 and He =0.227) resulted from the great number of genotypes in the ancestral population before fragmentation, favored by the outbreeding of the species. Population structure depends on geographic distance between sites rather than bioclimate indicating isolation by distance. Cluster constructed using Nei''s genetic distances showed mainly geographic related population groupings. Essential oil composition varied among populations. UPGMA dendrogram based on Euclidean distance matrix among pairs of populations showed two major population aggregates. The chemical population structure is linked to the geographic distance among populations and ecological factors indicating that the local selective environmental factors act on chemical composition. The correlation between matrices of allozymes and terpenoids was not significant. Population differentiation performed on the two sets of data was similar to that probed by isozymes. The conservation strategies of populations should be made according to their level of genetic and chemical diversity in relation to geographic location of populations. [Copyright &y& Elsevier]

Abstract: Genetic and essential oil variations from eight Tunisian natural populations of Thymus algeriensis Boiss. et Reut. (Synonym Thymus hirtus Willd. subsp. algeriensis Boiss. et Reut.), a North African endemic species, were assessed using 47 terpenoids and 154 RAPD markers amplified by seven selected primers. 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. Essential oil composition varied among populations. Five chemotypes according to main compounds have been distinguished: caryophyllene oxide/1,8-cineole/α-pinene, 1,8-cineole/α-pinene, 1,8-cineole/α-pinene/camphor, linalool and thymol chemotypes. A high genetic diversity within population and high genetic differentiation among them, based on RAPDs, were revealed (H pop =0.303 and G ST =0.339) caused both by the habitat fragmentation, the low size of most populations and the low level of gene flow among them. The genetic and chemical structures are in accordance with geography distances indicating isolation by distance. The UPGMA dendrogram and PCA analysis based on volatiles yielded higher separation among populations indicated specific adaptation of populations to the local environments. While the results obtained through RAPDs separated populations into three distinct clusters each of them including populations closed to their geographical origin. Genetic and chemical data were correlated based on Mantel test. Population differentiation performed on the two sets of data was similar to that shown using RAPDs suggesting higher accuracy of these markers. Given the high differentiation among all populations, conservation strategies should take into account genetic diversity and chemical variation levels in relation to bioclimatic and geographic location of populations. [Copyright &y& Elsevier]