Total Phenolic Content (TPC). The Folin-Ciocalteu (FC) reagent method (22) was modified and followed as described in our previous paper (19). TPCs were expressed as micrograms of gallic acid equivalents (GAE) per milliliter of solution. All samples were prepared and analyzed in duplicate.respectively. The antioxidant activity measured by the PCL assay was not correlated with TPC or TPI due to the lack of integratable lag phase in this method with the flavan-3-ols/procyanidins. Among the five major polyphenolic groups, flavan-3-ols/procyanidins had the highest positive correlation with the FRAP and â-CLAMS activities: r ) 0.84 and 0.88 for the peel extracts, respectively; and r ) 0.98 and 0.87 for the flesh extracts, respectively. At individual compound level, epicatechin and procyanidin B2 were the major contributors to the antioxidant activity of apple. Hydroxycinnamic acids may have a significant role in the flesh.