Evaluation de la qualité nutritionnelle des jus d'agrumes : estimation in vitro de la biodisponibilité des carotenoïdes

Les jus d'agrumes sont des aliments riches en phytonutriments antioxydants tels que la vitamine C, les polyphénols et particulièrement les caroténoïdes. Bien qu'il soit établi que ces micronutriments/microconstituants soient bénéfiques pour la santé humaine, leur teneurs dans les jus d'agrumes et leur absorption lors de la digestion restent encore mal connues. L'objectif général de cette étude a été d'identifier les déterminants principaux de la variabilité de la qualité nutritionnelle des agrumes associés aux caroténoïdes du fruit frais jusqu'à la biodisponibilité en tenant compte des facteurs génétiques, environnementaux et technologiques. Afin d'estimer la biodisponibilité in vitro des caroténoïdes (et en particulier de la [bêta]-cryptoxanthine sous forme libre ou ester) de jus d'agrumes sélectionnés, un modèle de digestion in vitro couplé à des cellules intestinales de type Caco-2 a été utilisé afm de mieux comprendre les mécanismes associés aux processus digestifs. Nos résultats montrent que la [bêta]-cryptoxanthine esterérifiée est partiellement hydrolysée durant l'étape de digestion in vitro. La bioaccessibilité de la [bêta]-cryptoxanthine libre (soit le transfert micellaire) est plus élevée que celle du [bêta]-carotène et des formes esters. Par ailleurs, les résultats sur l'absorption entérocytaire ont montré que le [bêta]-carotène et la [bêta]-cryptoxanthine libre sont préférentiellement captés par les cellules Caco-2 (cloneTC7) par rapport aux formes estérifiées. La dernière partie de ce travail a permis de mettre en évidence les interactions des flavanones contenues dans les agrumes, lesquelles semblent augmenter l'absorption des caroténoïdes par les cellules intestinales du modèle Caco-2. (Résumé d'auteur

Fruit carotenoids affect the bioaccessibility and cellular uptake of ß-carotene from orange fleshed sweet potato

Context and motivation of the work: To fight against vitamin A deficiency in developing countries, consumption of orange fleshed sweet potato (OFSP) which contains high concentrations of beta-carotene (provitamin A) is currently promoted. Indeed, clinical studies show that the vitamin A status was increased in children fed with OFSP (1). However, information on how well provitamin A was absorbed by intestinal cells is unclear and depends of bioaccessibility. Bioaccessibility of carotenoids depends on various factors included food matrix, food preparation method, presence of fiber and dietary fat or other microconstituants in the food (2).This last point and especially the interaction between carotenoids could be well documented. Moreover, few studies reports informations about the interaction through food matrix. The objective of this study is to assess the effect of carotenoids from fruits juices on the bioaccessibility and cellular uptake of BC from OFSP by using the in vitro digestion coupled with Caco-2 cell culture model. Materiel and methods: To simulate gastric and small intestinal phases of digestion, boiled OFSP (5g) mixed with fruit juice samples (30 ml) in saline solution were incubated at 37 °C (pH 4, pepsin, 30 minutes).Then, the pH was adjusted 6 and bile extract and pancreatin were added for 30 minutes. Micelles were collected in aqueous fraction after centrifugation and filtration (0.22?m). A micellarisation test without food matrix was also investigated (equimolar quantity of carotenoids, 5 ml of 100 mg/ml bile, 17h, 37 °C). Digestat from in vitro digestion were incubated (1h30) on Caco-2 TC7cells cultivated 21 days on wells in order to study the intestinal absorption. Extraction and HPLC analysis of carotenoids from micelles and from OFSP food products were carried out according previous study (3). Results: Effect of fruit juice on the micellarization of beta-carotene from OFSP showed that addition of Pink grapefruit reduces BC micellarization whereas kiwi juice and Clementine increased all-trans BC, but decreased 13-cis BC. Lycopene, beta-cryptoxanthine and lutein carotenoids as standard carotenoids were added to OFSP instead of fruit juices during in vitro digestion and confirmed some carotenoid interactions particularly for lycopene. Micellarization test showed that lycopene decreased and BCX increased. Cellular uptake of all- trans BC from digested OFSP (36%) and 13-cis BC (13 %) significantly decreased in presence of fruit juices. Conclusion: This study shows that carotenoids from fruit juice modify the bioaccessibility and cellular uptake of BC from OFSP. However, further investigations are needed to identify other components responsible of interactions in order to show efficacy of OFSP for maintaining adequate vitamin A status in a meal. (Texte intégral

Autofluerescence visualization of phenolic compound uptake by microscopic and spectroscopic techniques in caco-2 cell line model

Polyphenols are the most abundant health benefits in the human diets. However, there is a little understanding on the bioavailability particularly the localization of these compounds in the human intestinal cells. In the present study, two polyphenols (quercetin, and hesperidin) chosen according to their structural characteristics, were used to evaluate the localization from their natural fluorescence properties in human intestinal Caco-2 cell lines. Through the technique of fluorescence and confocal microscopy, such compounds were found to exhibit a specific fluorescence. According to the structure of the phenolic compounds (aglycone or glycosylated), the absorptive conditions showed themselves differently. Indeed, the rate and the route of transporting through the cellular monolayer did not seem to be identical, passing time varied from 10 to 90 min depending on which type of phenolic compounds, quercetin or hesperidin. The results showed that the passage of quercetin occurred rapidly with transcellular mechanism while the passage of hesperidin was visualized with transcellular mechanism as well at the first time then paracellular mechanism after incubation time of 90 min. Furthermore, by the detection of polyphenol absorbance, the correlation was observed with cellular uptake and polyphenol visualization by confocal microscopy. (Texte intégral

Citrus flavanones enhance carotenoid uptake by human intestinal Caco-2 cells

The health benefit of a diet rich in fruits and vegetables could be attributed to the complex mixture of phytochemicals. It is now widely believed that the actions of the antioxidant microconstituents is a result of additive and/or synergistic effects of these phytochemicals present in whole food. Because citrus juices are considered as a rich source of antioxidants including ascorbic acid (or vitamin C), phenolics compounds, and carotenoids, these different molecules may affect bioavailability or intestinal absorption of each other microconstituent. For these reasons, our study focused on effects of flavonoids and acid ascorbic on intestinal carotenoid uptake. This study was conducted using the differentiated Caco-2 cellline as experimental in vitro model and interactions of different flavanones such as hesperidin (HES-G) and hesperetin (HES) with carotenoid uptake were examined. Effect of ascorbic acid (AA) added to HES-G was also investigated. The data showed an enhancing effect of HES-G and HES on ?-carotene (b-C) and ?-cryptoxanthin (b-CX) uptake. For instance, at 5h incubation in presence of a mixture b-C:b-CX, HES-G and HES significantly increased total carotenoid uptake by 1.7 and 1.6-fold, respectively. Moreover, AA was able to cancel the enhancing effect of HES-G by decreasing significantly the cellular uptake of carotenoids from 48.2 to 39.8 % (P<0.05). In order to attribute the enhancing effect of HES-G to its already known iron-chelating effect, another experiment was conducted by incubating cells with b-CX in presence of either iron or a metal chelator (deferoxamine). b-CX uptake decreases in presence of iron and increases in presence of deferoxamine In sum, the results indicate that citrus flavanones enhance the carotenoid uptake by intestinal cells and that iron inhibits this process. Thus, the present data suggest that the citrus polyphenols could act through their iron-chelating properties. (Texte intégral

Understanding carotenoid losses in orange-fleshed sweet potato in drying and storage

Biofortified orange-fleshed sweet potato (OFSP) is being promoted to tackle vitamin A deficiency, a serious public health problem affecting children and pregnant/lactating women in sub-Saharan Africa. The aim of the study was to quantify and understand the factors influencing provitamin A losses in OFSP dried chips. Losses were determined after drying and storage. A preliminary pilot-scale study demonstrated that carotenoid levels were not significantly different after either solar or sun drying. Field conditions using locally-promoted varieties in Uganda and Mozambique showed losses associated with drying were less than 40%. Flour made from OFSP could therefore be a significant source of provitamin A. In contrast, storage of chips at room temperature in Uganda for four months resulted in high losses of pro-vitamin A (ca. 70% loss from the initial dried product). Low-cost pretreatments, such as blanching, antioxidants and salting, did not improve carotenoid retention during storage. To understand the cause of the losses, dried sweet potato chips were stored under controlled conditions of temperature (10; 20; 30; or 40ºC), aw (0.1; 0.3; 0.5 or 0.7) and oxygen (0 [under nitrogen]; 2.5; 10 or 21% [air]). Losses in provitamin A were the least during storage at the lowest temperature and oxygen level and at the highest humidity level. Enzymatic catabolism of [bêta]-carotene in the flour was considered unlikely because of low peroxidase activities at low water activities and the loss of peroxidase activity during storage. (Résumé d'auteur