This review covers literature data summarizing, on one hand, the chemistry of essential oils and, on the other hand, their most important activities. Essential oils, which are complex mixtures of volatile compounds particularly abundant in aromatic plants, are mainly composed of terpenes biogenerated by the mevalonate pathway. These volatile molecules include monoterpenes (hydrocarbon and oxygenated monoterpens), and also sesquiterpenes (hydrocarbon and oxygenated sesquiterpens). Furthermore, they contain phenolic compounds, which are derived via the shikimate pathway. Thanks to their chemical composition, essential oils possess numerous biological activities (antioxidant, anti-inflammatory, antimicrobial, etc…) of great interest in food and cosmetic industries, as well as in the human health field.

In this research, the chemical composition and biological properties of Tunisian Myrtus communis (McEO) flowers were investigated. The antibacterial effect of McEO toward some bacteria was assessed, alone and in combination with nisin. The major components of McEO were α‐pinene, 1,8‐cineol, limonene, and linalool. McEO exhibited cytotoxicity toward HepG2 and MCF‐7 cell lines. The microbiological data showed that Gram‐positive bacteria were more susceptible to McEO. McEO had a bactericidal effect against L. monocytogenes. McEO is able to prevent lipid oxidation, microbial development at noncytotoxic concentrations, when used alone or in combination with nisin. It can improve sensory attributes within acceptable limits and improve the conservation of shelf life of minced beef meat during the 4°C storage period. The most potent preservative effect was obtained with the mixture: 0.8% McEO with 500 IU/g of nisin. This combination may be a good alternative for the development of natural preservatives.

In the present paper, the essential oil and the volatiles emitted in vivo by leaves of A. herba alba, which grows wild in center of Tunisia, were analyzed by GC-MS and SPME, respectively. The essential oil was characterized by the predominance of oxygenated monoterpenes (93.3%) with α-thujone as the major compound (45.5%) followed by β-thujone (11.4%), trans-sabinyl acetate (10.1%) and 1,8-cineole (7.4%). The SPME analyses showed that oxygenated monoterpenes were the most representative compounds (64.9%). The major ones were α-thujone (37.9%), germacrene D (16.5%), 1,8-cineole (8.4%) followed by β-thujone (7.8%). Moreover, different activities (antioxidant, antibacterial, allelopathic and insecticidal) of the leaf essential oil were investigated. The antioxidant activity was ascertained by evaluating its inhibitory effect against DPPH and ABTS. The results showed that the essential oil had a strong activity and it was more effective against the DPPH radical (IC50 = 6μg/mL) than the ABTS radical (IC50 = 40μg/mL). In antibacterial screening, it inhibited the growth of all bacteria tested except Salmonella anatum and Salmonella salamae which were resistant to this oil type. Staphylococcus aureus and Vibrio cholera were found to be extremely sensitive with the lowest MIC value (0.007 mg/mL). In addition, allelopathic activity was evaluated against Lactuca sativa and Raphanus sativus. Data showed that, with essential oil, seed germination was completely inhibited for both of them, suggesting a potent allelopathic potential for the evaluated oil. Insecticidal activity was investigated against Culex pipiens larvae and a weak activity (LC50 241.1 ppm) for this A. herba alba essential oil

The present study investigated the chemical composition and allelopathic potential of volatile oil from Artemisia campestris originating from Tunisia against four species: Daucus carota, Cicer arietinum, Phaseolus vulgaris and Triticum sativum. The essential oil was extracted using the hydrodistillation method and its composition was analyzed by gas chromatography coupled to mass spectrometry (GC-MS). Furthermore, the essential oil was tested for its inhibitory effect on seed germination of the four precited species. According to the main results, Artemisia campestris essential oil was rich in monoterpenoids and a total of 27 components were identified, accounting for 95.5% of the whole oil. Furthermore, β-pinene (35.0%) and 1, 8-cineole (14.4%) were the two major constituents. The volatile oil was evaluated for its allelopathic potential against the four fore-mentioned species. We noted a significant reduction in germination for all the tested species at 1000 ppm and 2000 ppm concentrations. However, an increase was noticed at the lowest concentration (100 ppm). Moreover, there was a delay in germination for D. carota seeds and this delay was proportional to the essential oil concentration. It is worthy to notice that Artemisia campestris essential oil exhibited allelopathic properties against the tested species and particularly against D. carota.