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.

Antioxidants have been considered essential for preventing cell damage by scavenging deleterious free radicals. The consumption of antioxidant-rich plants is associated with a reduced risk of some chronic diseases. This study evaluates the antioxidant and acetylcholinesterase inhibition activities of aqueous extracts obtained from different parts of Diplotaxis simplex and Diplotaxis harra from Tunisia. The study also aimed to investigate the action of simulated gastrointestinal juice on antioxidant activities of both extracts. The total phenolic, flavone and flavonol, and flavanone and dihydroflavonol contents were determined by Folin–Ciocalteau, aluminum chloride and 2,4-dinitrophenylhydrazine colorimetric methods, respectively. The metal ion chelating activity, acetylcholinesterase inhibition capacity, and free radical scavenging potential of the extracts towards ABTS (2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid), DPPH (2,2-diphenyl-1-picrylhydrazyl), hydroxyl, superoxide and nitric oxide were also evaluated. The action of simulated gastro-intestinal fluids on the flavone and flavonol content and total antioxidant activity of the flower extracts was surveyed. Extracts from the seeds and flowers of D. simplex and D. harra displayed the highest amounts of phenols (2691.7 and 2694.5 mg Caffeic Acid Equivalent (CAE)/100 mg; 3433.4 and 2647.2 mg CAE/100 mg, respectively) and flavonols/flavones (2144.4 and 2061.1 mg Rutin Equivalent (RE)/100 g; 1922.6 and 1461.1 mg RE/100 g, respectively). The flower and seed extracts exhibited the highest rates of antioxidant and acetylcholinesterase inhibition activities. A decrease in the flavonoid content and antioxidant activity was observed after extract exposure to simulated saliva. Antioxidant and acetylcholinesterase inhibition activities were noted to depend on plant species and plant parts. In vitro gastrointestinal digestion is useful in assessing the bio-accessibility of compounds with biological activities from food. The simulated gastrointestinal fluids influenced the flavonoid concentration and antioxidant activity.

In this study, the chemical composition and biological activities of the essential oil (EO) extracts (from leaves and cones) of the Tunisian Thuja occidentalis were evaluated. The composition of the leaf EO extract was more complex than that of the cones. The major components of the leaf EO extract were α-Pinene (34.4%), cedrol (13.17%), and β-Phellandrene (8.04%), while the composition of the cone EO extract was characterized by the predominance of α-Pinene (58.55%) and 3-Carene (24.08%). All EO extracts showed much better antioxidant activity than Trolox against 2, 2′-diphenyl-1-picryl hydrazyl (DPPH) radical scavenging, but EOs extracted from leaves exhibited the highest total antioxidant activity. All EOs showed strong antibacterial and antifungal activities against nine tested foodborne microorganisms (Bacillus cereus American Type Culture Collection (ATCC) 1247, Listeria monocytogenes ATCC 7644, Staphylococcus aureus ATCC 29213, Aeromonas hydrophila EI, Escherichia coli ATCC 8739, Pseudomonas aeruginosa ATCC 27853, Salmonella typhimurium NCTC 6017, Aspergillus flavus (foodborne isolate), and Aspergillus niger CTM 10099. The highest antimicrobial activities by disk diffusion assay were recorded for the EOs extracted from leaves, while no difference in potency was marked between leaf and cone EO extracts by the agar dilution method. The most potent antimicrobial activity was recorded among fungi. This study confirms the strong antimicrobial and antioxidant potential of EO extracts from the Tunisian T. occidentalis (from the Sidi Bou Said site), highlighting its potential as a natural preservative against foodborne pathogens, particularly against E. coli and S. typhimurium.

The extraction yield of the essential oil (EO) extracted by hydrodistillation from the cones of TunisianCupressus sempervirensL. was of 0.518%. The chemical composition was analyzed by GC-MS. Results showed that this essential oil was mainly composed of monoterpene hydrocarbons (65%) withα-pinene as the major constituent (47.51%). Its antioxidant activity was ascertained by evaluating the total antioxidant capacity and also by evaluating its inhibitory effect against DPPH and ABTS radicals. In addition, it showed a strong antioxidant power against the DPPH (IC50= 151 µg/mL) and ABTS (IC50= 176.454 µg/mL) radicals scavenging. Moreover, its antibacterial activity was tested against different species of pathogenic bacteria (three Gram-positive and eight Gram-negative bacteria). The bacterial strains susceptible to the evaluated oil wereBacillus subtilis,Escherichia coli,Klebsiella oxytoca,Morganella morganii,Shigella, andVibrio cholerae.