foods Article Pectin Influences the Absorption and Metabolism of Polyphenols from Blackcurrant and Green Tea in Rats Gunaranjan Paturi 1, * ,† , Christine A. Butts 2, * ,† , Nigel I. Joyce 3 , Paula E. Rippon 3 , Sarah C. Morrison 3 , Duncan I. Hedderley 2 and Carolyn E. Lister 3   Citation: Paturi, G.; Butts, C.A.; Joyce, N.I.; Rippon, P.E.; Morrison, S.C.; Hedderley, D.I.; Lister, C.E. Pectin Influences the Absorption and Metabolism of Polyphenols from Blackcurrant and Green Tea in Rats. Foods 2021, 10, 813. https://doi.org/ 10.3390/foods10040813 Academic Editors: Maria Paula Duarte and Claudia Sánchez-Lara Received: 19 February 2021 Accepted: 1 April 2021 Published: 9 April 2021 Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affil- iations. Copyright: © 2021 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). 1 The New Zealand Institute for Plant and Food Research Limited, Private Bag 92169, Auckland 1142, New Zealand 2 The New Zealand Institute for Plant and Food Research Limited, Private Bag 11600, Palmerston North 4442, New Zealand; duncan.hedderley@plantandfood.co.nz 3 The New Zealand Institute for Plant and Food Research Limited, Private Bag 4704, Christchurch 8140, New Zealand; nigel.joyce@plantandfood.co.nz (N.I.J.); paula.rippon@plantandfood.co.nz (P.E.R.); sarah.morrison@plantandfood.co.nz (S.C.M.); carolyn.lister@plantandfood.co.nz (C.E.L.) * Correspondence: gunaranjan.paturi@plantandfood.co.nz (G.P.); chrissie.butts@plantandfood.co.nz (C.A.B.) † The two authors contributed equally to the paper. Abstract: Consumption of polyphenols and dietary fiber as part of a normal diet is beneficial to human health. In this study, we examined whether different amounts of dietary soluble fiber (pectin) affect the absorption and metabolism of polyphenols from blackcurrant and green tea in rats. After 28 days, the rats fed blackcurrant and green tea with pectin (4 or 8%) had significantly lower body weight gain and food intake compared to the rats fed a control diet. Rats fed a blackcurrant and green tea diet with 8% pectin had significantly higher fecal nitrogen output and lower protein digestibility. No polyphenols were observed in the urine, feces and plasma of rats fed the control diet. Parent catechins and flavonols were absent in urine obtained from all diet groups. Gallocatechin glucuronide was only observed in the plasma of rats fed the blackcurrant and green tea diet without pectin. Meanwhile, epicatechin and catechin gallate were present in the feces of rats fed a blackcurrant and green tea diet with and without 4% pectin. Pectin (4 or 8%) added to the blackcurrant and green tea diet increased the plasma antioxidant capacity in rats. Inclusion of pectin in the diet altered the host absorption and metabolism of polyphenols from blackcurrant and green tea. Keywords: dietary fiber; functional foods; metabolites; plant-based foods 1. Introduction Polyphenols found in fruit and vegetables offer numerous health benefits, including protection against cardiovascular disease [1]. The biological activity of polyphenolic com- pounds has been attributed to their antioxidant properties due to free radical scavenging activity, metal chelating properties andenzymatic activity. The bioavailability of polyphe- nols is highly variable and dependent on factors such as the structure and conjugation of the polyphenol, food matrix components and interactions with the gastrointestinal system [2,3]. The in vivo effect of a compound depends on its absorption and elimination kinetics, the nature and extent of its metabolism and the activity of circulating compounds. Flavonoids are a diverse group of polyphenols found naturally in several fruits and vegeta- bles. Flavonoid metabolism occurs in the small intestine and liver, whereas the unabsorbed flavonoids undergo microbiota-mediated ring-fission, producing phenolic acids that are absorbed and excreted in the urine [4]. The health benefits of polyphenols have been associated with the parent compounds in food, but it may in fact be the presence of their metabolites in the blood and tissues that confers these biological properties [3,5]. Polyphenols can directly influence the cellular Foods 2021, 10, 813. https://doi.org/10.3390/foods10040813 https://www.mdpi.com/journal/foods