The method of identification and qu

The method of identification and quantification of polyphenols in apples has been reported previously (19). Briefly, the separation was carried out in a C18 column with a binary mobile phase consisting of 6% acetic acid in 2 mM sodium acetate buffer and acetonitrile and a diode array detector. The total polyphenolic index (TPI) was calculated according to the method given in our previous paper (23). TPI is the sum of concentrations of all polyphenolic compounds separated and detected by HPLC. All samples were prepared and analyzed in duplicate