2.5. Quantitation of flavonoids
The calibration curves were run by plotting the ratio between the peak area of each flavonoid and that of the internal standard versus its nominal concentration in the multistandard solutions. For this purpose, 12 calibration levels were prepared in methanol with the target analytes at suited concentrations to define the calibration ranges and evaluate the sensitivity of the method by estimation of the limits of detection and quantitation (LODs and LOQs, respectively). Each calibration level as well as the samples were spiked with 10 mL of a solution of oleuropein at a concentration of 10 mg/mL for its use as internal standard and their analysis were performed in triplicate