The polyphenols content in the RE was determined using Folin–Ciocalteu reagent. A volume of 1 ml of reaction solution, prepared in ethanol at a concentration of 0.1 mg/ml, was mixed with 7.5 ml Folin–Ciocalteu reagent diluted 10 times.
The mixture is left 5 min at room temperature before mixing with 7.5 ml of 60 mg/ml of aqueous sodium bicarbonate solution Na2CO3. The prepared mixture is placed at room temperature and darkness for 2 h. The absorbance of the sample was measured at 725 nm using spectrophotometer (Varian, Inc., CA, USA). The concentration was determined using gallic acid as reference and the result is expressed in gallic acid equivalents per gram extract (GAE/g).reaction was added to this mixture. A control was prepared with the same amounts of oils and obviously without any extract.