Optimization of extraction yield, chemical composition, antioxidant, and antimicrobial activities of Thymus algeriensis Boiss. & Reut essential oils

This research focuses on the extraction of the essential oil from aerial part of Thymus algeriensis Boiss. & Reut, collected in flowering (April) and fruiting period (August). It was conducted to optimize the hydro-distillation method to improve the influence of four factors (time, temperature, plant/water mass ratio, and sampling period) on the yield of essential oil extraction using the full factorial design 24. Statistical treatments with Minitab software showed that the maximum desirability of extraction yield was estimated to be 1.43% under operational conditions: plant collected in flowering period, time = 240 min, temperature = 250 °C, mass/water ratio = 0.25. The extracted essential oils obtained were analyzed by GC/MS. The essential oils consisted of camphor, as the most abundant component (13.59–14.06%), followed by 1, 8-cineole (10.47–13.71%) and α-pinene (6.43–8.55%).Therefore, Thymus algeriensis Boiss. & Reut essential oil collected in April showed slightly higher antioxidant and antimicrobial activity than that collected in August (IC50 = 4.22 ± 0.13 and IC50 = 4.04 ± 0.09 μg/ml, respectively). Antimicrobial study showed that, except for P. aeruginosa, Thymus algeriensis Boiss. & Reut, EOs have a bacteriostatic activity against all the strains tested. The range of inhibition zones and minimal inhibitory concentration values were 11–19 mm and 1.25–5 μL/mL, respectively.