The amount of total phenols was determined by the Folin–Ciocâlteu reagent method as described by Scalbert et al. [18]. A 10 μL volume of essential oil was dissolved in 10 mL of methanol, and 0.1 mL of methanol solution was then transferred into a volumetric flask and diluted with 0.4 mL of double distilled water and used for analysis. A Folin–Ciocâlteu reagent solution 1:10 v/v in double distilled water (1 mL) was added to the diluted methanol/oil mixture (0.5 mL), which was then mixed thoroughly and leaved for 10 minutes at room temperature. A 2 mL solution based on 15% sodium carbonate (Na2CO3·10H2O) was added; after 1 h of incubation at room temperature, the absorbance was measured at 740 nm with a UV-Vis 60 Cary spectrophotometer against a blank sample that was concomitantly prepared. The blank sample contained 0.1 mL of methanol without oil, 0.4 mL of water, 1 mL of a Folin–Ciocâlteu reagent solution, and 2 mL of a Na2CO3·10H2O solution. Gallic acid was used as the standard for the calibration curve, which was drawn using solutions of the gallic acid in methanol of different concentrations ranging between 0.01 and 1 mg/mL. Based on the measured absorbance at 740 nm, the concentration of phenolics was read (mg/mL) from the calibration line, and the total phenolics values were then expressed as mg·GAE/g·DW. Each determination was made in triplicate, and average values were reported.