Total phenols were determined using the Folin–Ciocalteu
reagent as described by Roby, Sarhan, Selim, and Khalel (2013) with
slight modifications. Samples of 200 lL of extract at different concentrations,
in triplicate, were mixed with 1.5 mL of Folin–Ciocalteu
reagent and allowed to stand for 5 min at room temperature.
Next, 1.5 mL of sodium bicarbonate solution (60 g/L) were added
to the mixture and the tubes incubated for 90 min at room temperature.