Determination of some flavan-3-ols and anthocyanins in red grape seed and skin extracts by HPLC-DAD: Validation study and response comparison of different standards

Herein is presented a fully validated method that allows simultaneous determination of nine flavonoid compounds (4 flavan-3-ols and 5 anthocyanins) in skin and seed extracts of red grape varieties. On the other hand, the use of the appropriate standard for each compound studied to build the calibration graphs, avoids the error that implies the quantification of anthocyanins by using the malvidin-3-glucoside as the only reference standard. All these considerations ensure the quantification of the compounds studied in real samples. The high performance liquid chromatography (HPLC) with diode array detector (DAD) method developed exhibits good quality parameters: repeatability with R.S.D. < 5.2% and intermediate precision with R.S.D. < 8.1%.