Evaluation of Polyphenolic Content and Potential Antioxidant Activity of Japanese Cultivars of Peaches, Prunes, and Plums Based on Reversed- and Normal-Phase HPLC and Principal Component Analyses

We investigated the amount of polyphenols present in three types of stone fruits (peaches, plums, and prunes) that were produced in Japan during 2018 and 2019 using reversed-phase high-performance liquid chromatography (HPLC) with photodiode arrays and by normal-phase HPLC with fluorescence-based detection. Principal component analysis revealed the characteristics of the three fruit types: the major contributors of polyphenolic content in peaches were catechin, procyanidin B1, and 5-caffeoylquinic acid; those in plums, procyanidin B4, epicatechin, and procyanidin B5; and those in prunes, 3-caffeoylquinic acid and peonidine-3-rutinoside. Next, their antioxidative activity was assessed using hydrophilic oxygen radical absorbance capacity (H-ORAC). The sum of all polyphenol contents was significantly correlated with H-ORAC values (R² = 0.6205). Both the concentrations of flavan-3-ols and procyanidins measured by reversed- and normal-phase HPLC were significantly correlated with H-ORAC values (R² = 0.7248 and 0.7036, respectively). This work provides a reference for further investigations of stone fruit functions.