Nine Virginia soybeans grown in a single location were compared for their antioxidant properties and isoflavone profiles. The extracts were evaluated for their total phenolic contents (TPC), Oxygen Radical Absorbance Capacity (ORAC), and DPPH™ radical scavenging activities. In order to evaluate efficient preparation methods for soybean antioxidants, three Virginia-grown soybeans were extracted using different extraction strategies. The extraction techniques included soxhlet extraction, conventional solvent extraction, and ultrasonic-assisted extraction (UAE) with 5 different common solvent systems including 50% and 80% aqueous acetone, 50 and 70% aqueous ethanol, and 80% aqueous methanol. The TPC in the soybean extracts and isoflavone compositions were significantly different among cultivars. Malonylgenistin was the major isoflavone in all soybean seeds, accounting for 75-83% of the total measured isoflavones. The V01-4937 variety had the highest total isoflavone and malonylgenistin contents, followed by V03-5794. The antioxidant activities of the soybean extracts were also significantly different. Overall, the V01-4937 soybean was the variety that stood out from the other tested Virginia soybeans because it had the highest TPC, ORAC value, and isoflavone contents as well as the second highest DPPH™ scavenging activity. Ultrasonic treatment improved the extraction of soybean phenolics by more than 50% compared to solvent alone. The UAE with 50% aqueous acetone was the most efficient for extraction of phenolic compounds in the soybean seeds. The conventional and UAE with 70% aqueous ethanol extracts had the highest ORAC values, while the soxhlet methanol extracts had the highest DPPH™ radical scavenging activities. Our results suggest that different extraction technologies have a remarkable effect on soybean antioxidant estimation and the UAE is more appropriate for soybean phenolic extraction because it is less time and solvent consuming than the conventional solvent and soxhlet extractions. The V01-4937 soybean with the highest TPC was evaluated for its antioxidant activity and isoflavone contents in an in vitro digestive system. After gastrointestinal digestion, soybean extracts contained higher TPC and ORAC values than cooked soybean (before digestion) but they were relatively low in DPPH™ radical scavenging capacity. The glucosides, daidzin, genistin, and malonylgenistin showed stability during simulated digestion with 83.3 %, 59.4 %, and 10.7 % recovery, respectively. Aglycones, including daidzein and genistein, were recovered at 37 % and 73.7 %, respectively, after in vitro digestion. In this study, daidzin was the most stable and bioaccessible isoflavone determined using the in vitro digestive system. Among the aglycones, genistein was more stable and bioaccessible than daidzein after digestion. In conclusion, soybean antioxidant activities were different among cultivars and efficient extraction for TPC was found using UAE with 50% aqueous acetone. Furthermore, antioxidant activities were stable during digestion and genistein, within aglycones tested, was the most stable and bioaccessible compound following in vitro digestion. This information may provide manufacturers or researchers information required to develop food or nutraceutical products processed for better bioaccessibility of soybean bioactive components. / Ph. D.

Actuellement, le public et surtout dans les pays industrialisés est de plus en plus conscient du fait que la dégradation de l’environnement peut dépasser les avantages du progrès rapide dans les domaines industriels et technologiques et que des dommages sérieux et irréversibles peuvent être imposés aux futures générations. L'occurrence des POPs dans l'environnement, qui résulte essentiellement des activités anthropogéniques, est l'une des préoccupations permanentes chez les scientifiques. Ces composés ont été trouvés dans toutes les matrices environnementales telles que l'air, le sol, l'eau et les sédiments et en raison de leurs propriétés lipophiles, ils risquent de rebondir dans la chaîne alimentaire humaine. Durant cette dernière décennie, le Liban a connu une grande explosion démographique qui a été accompagnée par des activités anthropogéniques diverses. La dégradation de la qualité de l’environnement est bien ressentie par la population locale et les conséquences sur la santé humaine sont lourdes et affreuses. Les travaux de cette thèse ont permis d’évaluer concrètement l’effet de POPs sur la qualité de l’environnement au Liban, ces travaux ont abouti à la détermination des niveaux de quelques POPs les plus globalement étudiés tels que les HAPs, les PCBs et les OCPs dans les différents compartiments environnementaux au Liban. A cette fin, des protocoles d'analyse comprenant une méthode GC/MS pour la séparation et la détection des HAPs, une méthode UAE pour l'extraction des HAPs à partir du sol et des sédiments et une méthode SPE pour l'extraction des HAPs à partir de l'eau ont été développés. Ces méthodes ont été ensuite appliquées pour évaluer les niveaux de 17 HAPs dans des sols de différents usages et pour étudier la distribution de HAPs dans la phase aqueuse et les sédiments sur les côtes libanais et dans des rivières côtières et internes. Les principaux résultats ont montré que les niveaux de contamination des sols par les HAPs décroissent dans l’ordre suivant: industriels, urbains, transport et agricoles et que les sols industriels et urbains étaient 777 et 256 fois plus toxiques que les sols ruraux de référence selon l'approche TEF. De plus, l'eau et les sédiments des sites côtiers affectés par l'industrie et le transport maritime ont montré une contamination plus élevée par les HAPs. Certains échantillons de sédiments ont montré des niveaux de quelques HAPs individuels supérieures à l'ERL, ce qui pourrait occasionnellement provoquer des effets écologiques négatifs. Les travaux de cette thèse incluent aussi la détermination des niveaux des PCBs et des OCPs dans les sédiments de la rivière Litani qui est une source d’une grande préoccupation environnementale actuelle au Liban. / Currently, the public and especially in industrialized countries is increasingly aware that environmental degradation can outweigh the benefits of rapid progress in the industrial and technological fields and that serious and irreversible damage can be imposed on the future generations. The occurrence of POPs in the environment, which results mainly from anthropogenic activities, is one of the permanent concerns of scientists. These compounds have been found in all environmental matrices such as air, soil, water and sediments and because of their lipophilic properties, they are likely to rebound in the human food chain. During the past decade, Lebanon has experienced a large population explosion that has been accompanied by various anthropogenic activities. The degradation of the quality of the environment is felt by the local population and the consequences for human health are heavy and horrendous. The work of this thesis allowed to evaluate concretely the effect of POPs on the quality of the environment in Lebanon, this work led to the determination of the levels of some POPs most widely studied such as PAHs, PCBs and OCPs in the different environmental compartments in Lebanon. To this end, analytical protocols including a GC/MS method for the separation and detection of PAHs, a UAE method for the extraction of PAHs from soil and sediments and an SPE method for the extraction of PAHs from water were developed. These methods were then applied to evaluate the levels of 17 PAHs in soils of different uses and study the distribution of PAHs in the aqueous phase and sediments on the Lebanese coasts and in coastal and inner rivers. The main results showed that soil contamination levels by PAHs decreased in the following order: industrial, urban, transport and agricultural and that industrial and urban soils were 777 and 256 times more toxic than rural reference soils according to the TEF approach. In addition, water and sediments from coastal sites affected by industry and shipping have shown higher contamination by PAHs. Some sediment samples showed concentrations of a few individual PAHs greater than the ERL, which could occasionally cause negative ecological effects. The work of this thesis also includes the determination of levels of PCBs and OCPs in the sediments of the Litani River which is a source of great environmental concern currently in Lebanon.