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Medicinal and aromatic plants are garnering an increasing interest in industry, academia and health sciences. In passing from plant production to the bioactive product used by Human, many research studies are involved. The current research aimed to determine the chemical composition and to evaluate the antimicrobial effects of the essential oil extracted from the black psyllium (Plantago afra L.). The aerial parts essential oil obtained by hydrodistillation was analyzed using gas chromatography coupled to mass spectrometry (GC–MS) and flame ionization detection (GC-FID), whereas the microdilution technique was developed to evaluate its antimicrobial efficacy. The main identified constituents were thymol (14.3%), 3-[4-(t-Butyl) phenyl] furan-2,5‑dione (12.7%), palmitic acid (8.9%) and eudesmane (4.7%). The antimicrobial activities were assessed against five standard bacterial strains: Escherichia coli (ATCC 8739), Salmonella enterica (CIP 8039), Pseudomonas aeruginosa (ATCC 9027), Staphylococcus aureus (ATCC 6538) and Bacillus subtilis (ATCC 6633) along with the yeast Candida albicans (ATCC 30031). The results demonstrated that the effective Plantago afra essential oil could be potentially utilised in controlling some phytopathogenic fungi and bacteria.

Essential oils possessing several therapeutic benefits are considered of a paramount importance in human life. They have been used since antiquity in flavour as condiments and in medicine as antimicrobial agents. Carrot is one of the main vegetables displaying numerous interesting nutritional and pharmacological benefits. The present study was undertaken to determine the interspecific chemical variability and evaluate the antibacterial effects of the essential oils from two Daucus carota subspecies; D. carota subsp. drepanensis (Lojac.) Heywood (EOCD) and D. carota subsp. hispidus (Ball) Heywood (EOCH) growing wildly in Tunisia. Analysis of both resulting essential oils using gas chromatography-flame ionization detector (GC/FID) and GC-mass spectrometry (GC/MS) allowed to observe variations in contents of the main constituents. Thus, sixty-two volatiles representing respectively, 98.6% (EOCD) and 98.3% (EOCH) of the total essential oils were identified. Major constituents are (E)-methyl isoeugenol (58.7%) and elemicin (24.3%) for (EOCD) and α-cadinol (13.6%), premnaspirodiene (11.4%) and (E)-methyl isoeugenol (11.4%) for (EOCH). Both essential oils were individually tested against the pathogenic strains: Salmonella typhimurium ATCC 1408, Escherichia coli ATCC 35218, Staphylococcus aureus ATCC 25923 and Enterococcus faecalis ATCC 29212. The inhibitory effect of D. carota subs. hispidus essential oils was detected over all the strains studied, the MIC ranged from 1.25 to 2.50 mg mL−1.

The hydro-distilled essential oil from flowering aerial parts of Vernonia cinerea Less. (Asteraceae) was investigated by using GC-FID and GC/MS. Thirty-eight components, represented 95.1% of the total oil were identified. The major constituents of the essential oil were β-caryophyllene (23.2%), δ-cadinene (10.3%), γ-amorphene (7.5%), cis-β-guaiene (6.8%), premnaspirodiene (6.3%) and 9-epi-β-caryophyllene (4.8%). The oil was found to be rich in sesquiterpene hydrocarbon type constituents (81.2%).