Stability of Trans‐Resveratrol Encapsulated in a Protein Matrix Produced Using Spray Drying to UV Light Stress and Simulated Gastro‐Intestinal Digestion

Trans‐resveratrol has demonstrated the potential to provide both therapeutic and preventive activities against chronic diseases such as heart disease and cancer. The incorporation of trans‐resveratrol into food products would allow for broader access of this bioactive compound to a larger population. However, this strategy is limited by instability of trans‐resveratrol under environmental conditions and within the digestive system leading to isomerization of trans‐resveratrol (bioactive form) to cis‐resveratrol (bio‐inactive form). Studies in the stabilization of trans‐resveratrol into protein microparticles are presented. Trans‐resveratrol was encapsulated using whey protein concentrate (WPC) or sodium caseinate (SC), with or without anhydrous milk fat (AMF). Binding of resveratrol and aromatic residues in protein was estimated utilizing the Stern–Volmer equation and the number of tryptophan residues. The stability of encapsulated resveratrol was evaluated after exposure to ultraviolet A (UVA) light and 3‐stage in vitro digestion. After UVA light exposure, SC‐based microcapsules maintained a higher trans:cis resveratrol ratio (0.63, P < 0.05) than WPC‐based microcapsules (0.43) and unencapsulated resveratrol (0.49). In addition, encapsulation of resveratrol in both protein microparticles led to an increased digestive stability and bioaccessibility in comparison to unencapsulated resveratrol (47% and 23%, respectively, P < 0.05). SC‐based microcapsules provided a higher digestive stability and bioaccessibility (86% and 81%; P < 0.05) compared to WPC‐based microcapsules (71% and 68%). The addition of AMF to the microcapsules did not significantly change the in vitro digestion values. In conclusion, SC‐based microencapsulation increased the stability of trans‐resveratrol to UVA light exposure and simulated digestion conditions. This encapsulation‐system‐approach can be extended to other labile, bioactive polyphenols.     

Resveratrol Preserves Mitochondrial Function,Stimulates Mitochondrial Biogenesis,and Attenuates Oxidative Stress in Regulatory T Cells of Mice Fed a High‐Fat Diet

Consumption of high‐fat diet (HFD) is related with increased oxidative stress and dysfunctional mitochondria in many organs. The effects of resveratrol (trans‐3,5,4′‐trihydroxystilbene) that can protect T lymphocytes in various disease conditions on the HFD‐induced apoptosis of CD4⁺CD25⁺CD127^low/? regulatory T cells (Tregs) were studied, and the possible mechanism was postulated. Resveratrol significantly decreased Tregs death induced by 20‐wk HFD, being associated with the reduction of reactive oxygen species production and the alleviation of HFD‐induced loss of mitochondrial membrane potential (Δψm) in Tregs. Furthermore, resveratrol increased the expression of factors that regulated mitochondrial biogenesis in Tregs. Finally, resveratrol recovered the HFD‐induced activation of apoptotic markers in Tregs. Resveratrol protected Tregs against HFD‐induced apoptosis by reducing oxidative stress, restoring mitochondrial functional activities, and stimulating mitochondrial biogenesis.     

Bioavailability study of a polyphenol‐enriched extract from Hibiscus sabdariffa in rats and associated antioxidant status

The aqueous extracts of Hibiscus sabdariffa have been commonly used in folk medicine. Nevertheless, the compounds or metabolites responsible for its healthy effects have not yet been identified. The major metabolites present in rat plasma after acute ingestion of a polyphenol‐enriched Hibiscus sabdariffa extract were characterized and quantified in order to study their bioavailability. The antioxidant status of the plasma samples was also measured through several complementary antioxidant techniques. High‐performance liquid chromatography coupled to time‐of‐flight mass spectrometry (HPLC‐ESI‐TOF‐MS) was used for the bioavailability study. The antioxidant status was measured by ferric reducing ability of plasma method, thiobarbituric acid reactive substances assay, and superoxide dismutase activity assay. Seventeen polyphenols and metabolites have been detected and quantified. Eleven of these compounds were metabolites. Although phenolic acids were found in plasma without any modification in their structures, most flavonols were found as quercetin or kaempferol glucuronide conjugates. Flavonol glucuronide conjugates, which show longer half‐life elimination values, are proposed to contribute to the observed lipid peroxidation inhibitory activity in the cellular membranes. By contrast, phenolic acids appear to exert their antioxidant activity through ferric ion reduction and superoxide scavenging at shorter times. We propose that flavonol‐conjugated forms (quercetin and kaempferol) may be the compounds responsible for the observed antioxidant effects and contribute to the healthy effects of H. sabdariffa polyphenolic extract.     

Bioavailability of iron from a heat treated glucose‐lysine model food system: assays in rats and in Caco‐2 cells

The influence of Maillard reaction products (MRP) from glucose–lysine on iron bioavailability was investigated. Equimolar glucose–lysine mixtures (GL, 40% moisture) were heated (150 °C, for 30, 60 and 90 min) to prepare samples GL30, GL60 and GL90, respectively, and were used to study the influence of MRP on iron solubility, iron uptake and transport in Caco‐2 cells and iron balance in rats. After an initial increase with GL30, in vitro iron solubility decreased in the presence of most of the heated samples. The Caco‐2 cell experiments showed that Fe cell content increased in the presence of heated mixtures with respect to GL, whereas transport was less affected. Iron balance was determined in rats fed diets containing the GL30 and GL90 samples (3%) for a 21 day period and compared with that measured in a control group. Consumption of glucose–lysine heated mixtures increased total iron retention, although hemoglobin values decreased. Iron accumulations in organs such as the spleen, kidney and small intestine were observed. Copyright © 2004 Society of Chemical Industry     

Solubilization and Activity Detection in Polyacrylamide Gels of a Membrane‐Bound Esterase from an Oenological Strain of Saccharomyces cerevisiae

Due to the importance of esters in determining wine aroma, the presence of different esterases in soluble and insoluble cell fractions of an oenological strain of Saccharomyces cerevisiae was studied. Cells of an oenological yeast strain were separated into three fractions corresponding to the cytoplasm, periplasm and plasma membrane, all showing esterase activity. The conditions for optimal solubilization of the membrane‐bound esterase were found, as well as those allowing its electrophoretic analysis, using the detergent disodium‐n‐lauryl‐β‐iminodipropionate (Deriphat) in the cathodic buffer. Comparison of the activity bands detected on gels revealed the presence of different esterase iso‐forms in the three sub‐cellular fractions. The method can also be used as the first electrophoretic step in two‐dimensional PAGE. Therefore, the procedures described are also a promising tool for the study of the yeast enzymes in relation to their effects during winemaking.     

Bioavailability of zinc from infant foods by in vitro methods (solubility,dialyzability and uptake and transport by Caco‐2 cells)

The aim of this study was to evaluate the bioavailability of zinc from infant foods (adapted, follow‐up and toddler milk‐based formulas and fruit juices containing milk and cereals, FMC) using solubility, dialyzability and a model combining simulated gastrointestinal digestion and zinc uptake and transport by Caco‐2 cells. The greater solubility of zinc from infant formulas compared with fruit juices (FMC) could be due to the greater casein phosphopeptide content resulting from casein hydrolysis. The highest zinc dialysis percentage corresponded to FMC, which on the other hand had the lowest zinc contents of the analyzed samples. The presence of organic acids in samples of this kind favors the formation of soluble low molecular weight complexes with zinc, thereby increasing the solubility of the latter. Bifidobacterium addition exerted no effect upon zinc bioavailability. Transport and uptake efficiency in Caco‐2 cells were significantly greater for toddler formulas, which presented the highest casein contents. The greater efficiency in zinc transport and uptake from the powdered toddler formula compared with the liquid formulation could be explained by the effect of Maillard reaction products. Copyright © 2006 Society of Chemical Industry     

Comparison of the in vitro metabolism of isoflavones by fecal flora from human flora‐associated mice and human

Recently there has been great interest in the biological effects of equol (4′,7‐dihydroxyisoflavan), a metabolite of daidzein produced by intestinal flora. In this study, the in vitro metabolism of daidzein, daidzin and genistein by fecal flora, in human flora‐associated (HFA) mice and a human donor was investigated. The in vitro incubation of feces with isoflavones demonstrated that the potential for equol production had been successfully transferred from human feces to HFA mice. The average equol concentrations were higher in feces from HFA mice than in those from their donor. In both HFA mice and their donor, the fecal equol production from daidzin was comparable to that from daidzein. The results suggest that daidzin would be an effective substrate for bacterial equol production in vivo. The HFA mice produced in these experiments and maintained in an isolated environment might also be useful for investigating the biological activity of equol in detail. Copyright © 2006 Society of Chemical Industry     

The bioavailability of an omega‐3‐rich algal oil is improved by nanoemulsion technology using yogurt as a food vehicle

Global trends show that habitual omega‐3 intakes are short of recommended guidelines, particularly among vegetarians. Subsequently, alternative dietary sources of long‐chain omega‐3 polyunsaturated fatty acids (LC3PUFA) from vegetarian sources are needed. Food technology methods are advancing, and nanoemulsion technologies have improved the bioavailability of certain lipid‐based nutrients. This study examined whether ingestion of an omega‐3 algal oil nanoemulsion led to improved bioavailability compared to the bulk oil. Eleven subjects completed a single‐blind, randomised crossover trial, with a 21‐day washout between interventions. Results demonstrated that LC3PUFA absorption from the nanoemulsion was significantly higher than the bulk oil. Percentage blood fatty acids were significantly increased for docosahexaenoic acid (DHA; P ≤ 0.05) while LC3PUFA: PUFA ratios increased (P ≤ 0.05) and omega‐6:omega‐3 ratios were reduced (P = 0.028). Larger and longer intervention studies are now needed, but these preliminary findings demonstrate that nanoemulsion technology may improve the absorption of omega‐3 fatty acids.