Miniaturized QuEChERS-based extraction procedure for determination of (+)-catechin and (−)-epicatechin in red apple peel by HPLC–DAD

Abstract Apple peel constitutes a reliable source of bioactive phenolic substances, especially (+)-catechin and (−)-epicatechin, which have functional and health-promoting effects. In this study, (+)-catechin and (−)-epicatechin were determined in red apple peel using a miniaturized QuEChERS-based extraction procedure and HPLC–DAD analysis for the first time. The proposed miniaturized QuEChERS method was based on the citrate version using primary secondary amine bondesil (PSA) and active earth (AE) for clean-up. The method demonstrated good analytical performance, with linearity (r = 0.999), LOQ ≤ 34 μg kg −1 and RSD ≤ 14%. Under optimized extraction and analysis conditions, we quantified (+)-catechin and (−)-epicatechin in ten red apple peel samples of different varieties. (+)-Catechin and (−)-epicatechin concentrations ranged from 18.84 to 54.56 and 35.08 to 109.34 mg kg −1 of fresh weight (FW), respectively. Overall, this research presents relevant and novel data about the concentration of (+)-catechin and (−)-epicatechin in red apple peel, particularly for those varieties poorly or not yet studied, such as Fengapi/Tessa, Dolcevita, PremA96, and Evelina. Furthermore, the miniaturization of the sample preparation step provided an efficient, simple, and inexpensive procedure for (+)-catechin and (−)-epicatechin quantification in red apple peel.