Analysis of phenolics in the peel and pulp of wild apples (Malus sylvestris (L.) Mill.)

Abstract

© 2017 Elsevier Inc. A simple and efficient ultrasound extraction method for phenolic compounds in the pulp and peel of Malus sylvestris (wild apples) was developed using multivariate methodology. Optimal extraction conditions were obtained using this methodology for peel and pulp samples (2.0 g), including solvent volume 100 mL and 79 mL, methanol concentration 100% (v/v) and 20% (v/v), extraction time 33 min and 40 min, extraction temperature 65 °C and 80 °C, respectively. The peel and pulp extracts were analysed by HPLC-PDA using a C18 Phenomenex Kinetex column. Among the phenolic compounds present in our samples, we quantified (mg/g fresh weight) chlorogenic acid, 0.791; epicatechin, 1.18; and phloridzin, 0.106 in the pulp extract, whereas the peel extract contained chlorogenic acid, 0.568; epicatechin, 1.36; phloridzin, 0.207; catechin, 0.187; hyperoside, 0.261; and quercitrin, 0.256 mg/g. The antioxidant activity of the extracts was measured by spectrophotometric methods Peel extract proved to be a better antioxidant than pulp extract. Additionally, the stability of the analysed phenolic compounds was tested by in vitro digestion procedures. Simulated in vitro digestion showed that the concentrations of all analysed phenolic compounds (except chlorogenic acid) decreased during the intestinal phase of digestion.