Polyphenols of Traditional Apple Varieties in Interaction with Barley β-Glucan: A Study of the Adsorption Process

Lidija Jakobek,Ivana Buljeta,Andrew R Barron,Jozo Ištuk

doi:10.3390/foods9091278

Abstract

Apple polyphenols have been studied for various beneficial bioactivities. Especially interesting are traditional, old varieties of apples for which some initial studies have suggested significant bioactivities, but they are still not completely understood. Polyphenol bioactivities can be affected by interactions with dietary fibers such as β-glucans. The aim of this study was to investigate for the first time interactions between individual polyphenols from traditional, old apple varieties (“Božićnica” and “Batulenka”) and β-glucans by studying the adsorption process. Polyphenols were extracted from the peel and flesh of traditional apples by using an ultrasonic bath and characterized with high-performance liquid chromatography. The amounts of adsorbed (qe) and un-adsorbed (ce) polyphenols were modeled with adsorption isotherms (Langmuir, Dubinin–Radushkevich, and Hill) by using improved non-linear fitting in a novel R algorithm, developed specifically for the modeling of adsorption isotherms. Polyphenols adsorbed onto β-glucan from 9 to 203 (peel, “Božićnica”), 1 to 484 (peel, “Batulenka”), 5 to 160 (flesh, “Božićnica”), and 19 to 28 mg g−1 (flesh, “Batulenka”). The adsorption was concentration dependent (polyphenols present in higher amount adsorbed in higher amounts). Physical sorption can be suggested. Polyphenols from traditional apples adsorb onto β-glucan and should be further studied.

Highlights

Many potential beneficial effects of dietary polyphenols have been studied [1,2,3,4]
Β-glucans can be used for developing delivery systems for apple polyphenols. β-glucans have already been studied as delivery systems for various pharmaceuticals such as doxorubicin [39], for single-strand DNA [40], for mucosal antigen [41], or even for polyphenols such as quercetin and curcumin [42]. β-glucan showed beneficial effects itself [43], which has made it a good candidate for this purpose
Polyphenols from apples interacted with β-glucan and adsorbed onto β-glucan in a concentration dependent manner

Summary

Introduction

Many potential beneficial effects of dietary polyphenols have been studied [1,2,3,4]. Dietary polyphenols have been mentioned as “a promising strategy for the alleviation of autism spectrum disorder symptoms” [1]. They have the potential in reducing the risk of developing type 2 diabetes mellitus [4]. More studies are necessary to enhance knowledge of these potential effects Apples and their polyphenols are interesting because they are a good source of polyphenols in everyday diet. Apple polyphenols have been studied in particular for their potential beneficial effects in relieving hypoxia-induced pulmonary arterial hypertension [5] or for their therapeutic potential for obesity and related metabolic disorders [6]. Some people can develop intolerance to apples, and, in these cases, old, traditional apple varieties can be tolerated better than commercial varieties [7]

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