Bioactivity and bioavailability of minerals in rats loaded with cholesterol and kiwi fruit

Abstract

The aim of this study was to compare the content of polyphenols (TP), minerals, ascorbic acid (AA) and total antioxidant capacities (TAC) of conventional and organic kiwifruit ‘Hayward’ treated with ethylene after harvest and to determine their influence on plasma TAC, mineral content in the liver and bioavailability (RBV — relative bioavailability value) in rats fed diet containing cholesterol. Organic and conventionally grown kiwifruits ‘Hayward’ as supplementation to rat diet were investigated in vitro for their bioactive compounds (polyphenols, flavonoids, flavanols, tannins, dietary fiber, and ascorbic acid), minerals, trace elements and TAC. In the in vivo investigation, 36 male Wistar rats (111±5g) were randomly divided into six diet groups, each of 6 rats: control without cholesterol (C) and 5 groups with 1% cholesterol (ch). Four cholesterol groups were supplemented with 5% lyophilized kiwifruit: ethylene treated, organic (chOHE) or conventional (chCHE) and untreated, and organic (chOHC) or conventional (chCHC). During a period of 33days of ad libitum feeding feed intake, body weight and feed utilization ration (FER) were controlled. In the end of the experiment rats were anesthetized using Narcotan and sacrificed, and blood and liver were assessed. Testing of antioxidant activity in plasma, minerals and trace elements in the diet and in the liver was performed. Ethylene-treated organic kiwifruit (OHE) had the highest content of TP and TAC. Mg content was significantly higher and Mn was lower in organic kiwifruit ‘Hayward’. Inverse relationship in the case of Mn in conventional kiwifruit was found. Supplementation of kiwifruit in ch diet groups improved diet palatability, influenced the increase of feed intake and body gain and also improved FER (lower values). Significant increase of plasma TAC for DPPH (19%), FRAP (68%) and ABTS (62%) in rats fed diets with kiwifruits was obtained. Ethylene treated conventional and organic kiwifruit improved (vs ch group) the antioxidant status of the rat body. Bioavailability of Mn and Zn in rats, calculated on the basis of its content in the liver was significantly lower in chOHC in comparison with ch group. Supplementation of ch diet groups with kiwifruit significantly decreased Mg bioavailability. Ethylene treated kiwifruit had no effect on mineral bioavailability in rats. Organic kiwifruit ‘Hayward’ contains more bioactive compounds, and showed higher antioxidant capacity than the conventional. Ethylene treatment of kiwifruit after harvest increases its bioactivity. Growing conditions of kiwifruit affect their Mg and Mn contents. Supplementation of kiwifruit in atherogenic diet increased plasma antioxidant capacity in rats. Similar effect was estimated for organic and conventional fruits. The ethylene treated kiwifruit significantly decreased magnesium bioavailability determined on the basis of its concentration in the liver. Supplementation of Mg in hypercholesterolemia is an important factor.