Inadequacy of nutrients and contaminants found in porridge-type complementary foods in Rwanda.

Child malnutrition remains persistently high in Rwanda. Complementary foods play a key role in young child nutrition. This study explores the quality and safety of complementary food products available in the Rwandan market. Ten of the most consumed porridge-type complementary food products in Rwanda have been analysed. Mean values of macronutrient and micronutrient contents were compared against three international standards and evaluated against label claims. Mean mycotoxin, microbiological, and pesticide contamination were compared with maximum tolerable limits. Mean energy density (385 kcal/100 g) and total fat content (7.9 g/100 g) were lower than all three international benchmarks. The mean fibre content of 8.5 g/100 g was above the maximum recommended amount of Codex Alimentarius and more than double the amount claimed on labels. Mean levels of vitamin A (retinyl palmitate, 0.54 mg/100 g) and vitamin E (α-tocopherol, 3.7 mg/100 g) fell significantly short of all three standards, whereas calcium and zinc requirements were only partially met. Average iron content was 12.1 mg/100 g. The analysis revealed a mean aflatoxin contamination of 61 µg/kg, and high mold and yeast infestation. Escherichia coli and pesticide residues were found, whereas no heavy metals could be quantitated. Overall, complementary food products in Rwanda show inadequate nutrient contents and high aflatoxin and microbial contamination levels. Improved regulation and monitoring of both local and imported products are needed to improve the quality and safety of complementary foods in Rwanda.

Intestinal breast cancer resistance protein (BCRP)/Bcrp1 and multidrug resistance protein 3 (MRP3)/Mrp3 are involved in the pharmacokinetics of resveratrol.

The phytoestrogen resveratrol has putative health-promoting effects and is present in several dietary constituents. Resveratrol is metabolized extensively in the gut epithelium, resulting in the formation of hydrophilic glucuronic acid and sulfate conjugates. These polar resveratrol conjugates need specific transporters to cross the cell membrane. We show here that vectorial transport of some of these metabolites is mediated by multidrug resistance protein 3 (MRP3, ABCC3) and/or breast cancer resistance protein (BCRP, ABCG2) located in the basolateral and apical membranes of enterocytes, respectively. In vitro, MRP3 transports resveratrol-glucuronide (Res-3-G). The absence of Mrp3 in mice results in altered disposition of Res-3-G and its parent compound resveratrol, leading to a reduced percentage of resveratrol being excreted via the urine in Mrp3(-/-) mice. Circumstantial evidence suggests that circulating resveratrol is formed by deglucuronidating Res-3-G in vivo, providing a possible explanation for the health beneficial effects of resveratrol in vivo, despite its rapid and extensive conjugation. BCRP transports Res-3-G and resveratrol sulfates in vitro, and its absence in mice results in high plasma levels of resveratrol-di-sulfate, a resveratrol metabolite hardly detectable in the plasma of wild-type mice and in an increased disposal of resveratrol via the urine. The profound effects of ATP-binding cassette transporters on the disposal of resveratrol may be representative for the handling of several other polyphenols of dietary origin.

A novel method to measure both the reductive and the radical scavenging activity in a linoleic acid model system.

The aim of this study was to develop a combined method for measuring the total antioxidant activity, the reductive and the radical scavenging activity. Linoleic acid was used as the substrate for an iron-initiated lipid peroxidation to measure the total antioxidant activity. In addition, methyl esters of linoleic acid hydroperoxides were used as substrates to measure the reductive antioxidant activity. The radical scavenging antioxidant activity was calculated by subtracting the reductive antioxidative activity from the total antioxidative activity. As representative examples, the antioxidants alpha-tocopherol, ascorbic acid, trans-resveratrol and L-glutathione as well as commonly used food additives such as 2(3)-tert-butyl-4-hydroxyanisole (BHA) and 2,6-bis(1,1-dimethylethyl)-4-methylphenol (BHT) were analyzed. The results for the novel antioxidation test showed that alpha-tocopherol, BHA and BHT are primarily acting as radical scavengers, whereas ascorbic acid and L-glutathione show a strong reductive capacity. As linoleic acid as well as its hydroperoxides both are present in foods and in the organism, the test presented here can be considered representative of radical reactions occurring in food matrixes and in vivo. Further experiments are required to document the comprehensive applicability in foods and in vivo.

Concentration-dependent effects of resveratrol and metabolites on the redox status of human erythrocytes in single-dose studies.

Dietary trans-resveratrol (RES) is rapidly metabolized into sulfated and glucuronated conjugates in humans. This study focused on the in vitro determination of the antioxidant capacity of RES and its main physiological metabolites and on its relevance in vivo. In vitro, RES, RES-3-O-sulfate (R3S) and 3-O-glucuronide (R3G) showed antioxidant activities at a concentration of 1mM when compared to Trolox using an assay in which the antioxidant inhibits iron-induced linoleic acid oxidation: 0.87±0.08mM Trolox equivalents (TE) for RES, 0.52±0.01mM TE for R3S and 0.36±0.02mM TE for R3G. At a concentration of 1µM, compounds promoted linoleic acid peroxidation (RES -0.30±0.09mM TE, R3S -0.48±0.05mM TE and R3G -0.57±0.07mM TE). To elucidate whether these effects were reflected in vivo, total antioxidant capacity, reactive oxygen species (ROS), conjugated fatty acid dienes (CD), superoxide dismutase (SOD) and catalase (CAT) activities were determined in human plasma and erythrocytes over 24h, after oral intake of either 0.05g RES as piceid or 5g RES. Oral administration of RES did not show an impact on total antioxidant capacity, ROS or CD. However, enzymatic activities of ROS scavenging SOD and CAT were significantly lower after high-dose compared to low-dose administration of RES (P<.03 and P<.01). In conclusion, in healthy subjects, neither 0.05g nor 5g RES changed blood oxidative state, although our in vitro data point to a prooxidative activity of low concentrations of RES and its metabolites, which could be important in vivo for individuals with compromised antioxidant defense capacity.

High dose of dietary resveratrol enhances insulin sensitivity in healthy rats but does not lead to metabolite concentrations effective for SIRT1 expression.

SCOPE: trans-Resveratrol has been shown to improve insulin sensitivity and to enhance cellular glucose uptake. Evidence from recent studies indicates that these effects depend on SIRT1-pathways. METHODS AND RESULTS: Since ingestion of resveratrol leads to the presence of resveratrol and resveratrol metabolites in the body, we aimed at investigating (i) whether a daily dose of 300 mg resveratrol/kg body weight in healthy male Wistar rats for a period of 8 wk affects the selected parameters of glucose and lipid metabolism and (ii) whether the resulting plasma concentrations of resveratrol metabolites were effective in modulating SIRT1 expression. The dietary dose was based on the results from preceding toxicity studies. The results from the feeding experiment revealed plasma concentrations of resveratrol and its metabolites below 1 µmol/L and showed that fasting glucose and insulin levels were decreased by 35 and 41%, respectively, in the resveratrol group compared with controls. Insulin sensitivity was enhanced by 70%, whereas liver SIRT1 protein expression was not affected. Treatment of HepG2 cells with 10 µM resveratrol (1.49-fold) or its diglucuronides (1.21-fold) increased SIRT1 expression. CONCLUSION: These results suggest that the improved insulin sensitivity after dietary administration of 300 mg resveratrol/kg body weight does not involve increased protein expression of SIRT1.

Quantification of free and protein-bound trans-resveratrol metabolites and identification of trans-resveratrol-C/O-conjugated diglucuronides - two novel resveratrol metabolites in human plasma.

The polyphenol trans-resveratrol (t-RES) is present as t-RES-3-O-beta-D-glycoside, termed piceid, in several plant-derived foods. Although data on the metabolism and on in vivo effects of t-RES have been reported, quantitative data on the metabolites formed after dietary intake of t-RES or piceid are still lacking. In this study, 85.5 mg of piceid per 70 kg of body weight (bw) were administered to healthy volunteers in a bolus dose. t-RES metabolites formed in plasma and urine were identified and quantified by LC-MS/MS, NMR, and HPLC-DAD analysis using chemically synthesized t-RES conjugate standards. In addition, the amount of t-RES metabolites bound noncovalently to plasma proteins was determined for the first time in humans. The metabolites identified and quantified were t-RES-3-sulfate, t-RES-3,4'-disulfate, t-RES-3,5-disulfate, t-RES-3-glucuronide and t-RES-4'-glucuronide, with t-RES-sulfates being the dominant conjugates in plasma and urine. Besides these metabolites, two novel t-RES-C/O-conjugated diglucuronides have been identified and quantified in plasma and urine. Moreover, it could be shown that up to 50% of the plasma t-RES-3-sulfate, t-RES-disulfates, and the novel t-RES-C/O-diglucuronides were bound to proteins. Total recovery of the dietary administered piceid in urine ranged between 13.6 and 35.7%.