The use of ultrasound-assisted extraction (UAE) for the extraction of chlorogenic acid (CA) from Cynara scolymus L., (artichoke) leaves using 80% methanol at room temperature over 15 min gave a significant increase in yield (up to a 50%) compared with maceration at room temperature and close to that obtained by boiling over the same time period. A note of caution is introduced when comparing UAE with Soxhlet extraction because, in the latter case, the liquid entering the Soxhlet extractor is more concentrated in methanol (nearly 100%) that the solvent in the reservoir (80% methanol) due to fractionation during distillation. The mechanism of UAE is discussed in terms of the effects of cavitation on the swelling index, solvent diffusion and the removal of a stagnant layer of solvent surrounding the plant material.

Essential oils (EOs) have been described as promising eco-friendly secondary products of aromatic plants with several biological activities. The present study aimed to characterize the chemical composition and explore phytotoxic and antimicrobial activities of Teucrium polium and Thymus decussatus EOs extracted using hydrodistillation (HD) and microwave-assisted extraction (MAE) methods. Twenty-seven and twenty-eight compounds were identified from HD and MAE extracted EOs of T. polium, respectively. The oxygenated sesquiterpenes (57.68%) were characterized as the main components of the hydrodistilled EO with a prominence of 6-epi-shyobunol (33.00%), while sesquiterpene hydrocarbons (54.48%) were the main components of the MAE method, with a prominence of delta-cadinene (25.13%). Eighteen and nineteen compounds, were characterized in T. decussatus EOs extracted using HD and MAE methods, respectively, and oxygenated monoterpenes represented the main components of both EOs with carvacrol (94.40% and 75.91%, respectively) as the main compound. The EOs extracted using the MAE method were slightly more phytotoxic than those extracted using the HD method. The T. decussatus EO extracted using the MAE method showed a higher inhibitory effect than T. polium by 16-, 32-, and 24-fold, regarding seed germination, shoot, and root growth of lettuce, respectively. Moreover, EOs extracted by HD method showed a similar pattern with 16-, 28-, and 14-fold effects. Both T. decussatus EOs exhibited potent inhibitory effect against all tested bacteria with an inhibition zone of 34–39 mm and the lowest minimum inhibitory concentration (MIC) of 0.49, 0.98, and 1.95 μg/mL against Aspergillus niger, Escherichia coli, and Staphylococcus aureus, respectively. However, the EOs of T. polium showed weak antibacterial activity and no antifungal effect. Further studies are needed for the characterization of bioactive major compounds, either singular or synergistic, at field scale and to determine their modes of action and safety.

This work aims to highlight the effect of the extraction methods used on the chemical composition and evaluation of antimicrobial activity of the Origanum majorana Essential oil. Accordingly, three different extraction methods namely; Microwave-assisted extraction (MWE), hydro-distillation (HD) and steam distillation (SD) were used for O. majorana essential oils (EOs) extraction. There is variability in the chemical composition of essential oils obtained from the different extraction methods used. Overall, HD showed the highest % of oxygenated monoterpenes (66.8 %), while SD showed the highest % of monoterpene hydrocarbons (46.85 %). Oxygenated sesquiterpenes showed the lowest percentage of the EOs (3.6 % HD, 1.4 % MWE and 0.7 % SD). Terpinene-4-ol was the major components of O. majorana EO with different percentages 28.49 % HD, 22.28 % MWE and 26.72 % SD. EOs was tested for their antimicrobial activity against ten pathogenic microbes (fungi, yeast and bacteria). EOs extracted by SD method showed antimicrobial activities against all tested pathogens with variation degree. This result could be useful in designing the best extraction method. Key word: Microwave-assisted extraction, hydro-distillation, steam distillation, essential oil, antimicrobial activities and Origanum majorana.