脂溶性营养素必须与胆汁酸盐等自组装成“混合胶束”才能有效吸收。大豆皂苷对脂溶性营养素的吸收有显著的影响。但以前的研究是基于大豆皂苷的天然结构，研究证实，近90%的膳食大豆皂苷在机体内发生了代谢转化，我们前期实验解析了三种主要的大豆皂苷肝脏代谢物的分子结构，它们对脂溶性营养素的吸收有何影响？我们推测，大豆皂苷及其肝脏代谢物因其界面活性对自组装“混合胶束”有相互作用，从而影响脂溶性营养素的吸收。为此，我们将首先通过鼠肝脏微粒体孵育制备大豆皂苷代谢物并分析鉴定，再进行体外模拟肠液环境实验，检测其参与自组装时的表面活性行为、热力学及流变学变化，探讨其影响自组装进而影响脂类吸收的机制；然后通过Caco-2细胞模型来验证。本项目旨在生物利用度的基础上，通过大豆皂苷及其肝脏代谢物与“混合胶束”自组装的作用机制探索，为大豆皂苷作为天然表面活性剂的生产及其用来调控脂溶性营养素或活性成分吸收提供科学依据。

Micellar solubilization of lipophilic nutrients or micronutrients by dietary mixed micelles is essential for their absorption in humans. Although many researches have demonstrated that soyasaponins have strong impact on the digestion and absorption of lipophilic nutrients, micronutrients and bioactive dietary compounds, however, previous investigations were carried out by their naturally ocuuring molecular structures, and the bioavailability of soyasaponins maybe underestimated since the metabolites formed in the course of digestion could be related to the bioaccessibility of lipophilic nutrients or micronutrients. .We hypothesize that both dietary soyasaponin and its bile excretion of soyasaponins liver metabolites interact with the self-assembly during the formation of dietary mixed micelles for micellar solubility and uptake of lipophilic nutrients or micronutrients due to their natural amphipathic molecular structures, thus effectively affect the absorption of dietary lipophilic components..This study aims to explore the potential systemic mechanisms of soyasaponin with its liver metabolites on the influence of mixed micelles self-assembly, as well as the interaction with lipophilic nutrients or micronutrients micellarization for delivery and uptake.. The research envisioned comprises four parts: (1) Isolation and purification of soyasaponins. The major native soy saponins, i.e. soyasaponin Ab, Ba, Bb and DDMP soyasaponins αg, βg respectively, will be purified. (2) Preparation and identification of hepatic metabolites of bioavailable soyasaponins. Soyasapogenols will incubate with rat microsome for investigating their metabolism stability and their molecular structures will be determined by liquid chromatography coupled with ion trap mass spectrometry, and NMR. (3) In Vitro models to investigate the effect of soyasaponin and its hepatic metabolites interfacial activity on the self-assambly of dietary mixed micelles and micellar solubilization of lipophilic nutrients or micronutrients. The effect of soyasaponin and its hepatic metabolites interfacial activity on the formation of mixed micelles aggregates, microstructures and structural transition in detail by modulating the molecular structures, molar fractions, concentrations, temperature, etc. will be examined under in vitro conditions with various techniques, such as interfacial tension and interfacial density, isothermal titration calorimetry (ITC), particle size distribution determination, zeta-potential measurements and cryogenic transmission electron microscopy, dynamic light scattering, small angle X-ray scattering, etc. In addition, GC and HPLC will be employed to investigate the effect of soyasaponin and its hepatic metabolites to the micellar solubility of lipophilic nutrients, such as cholesterol, fatty acids, vitarmin D3, vitarmin K, α-tocopherol acetate and/or or monoglyceride by model dietary mixed micelles. (4) Lipophilic nutrients uptake by Caco-2 cells. After simulated digestion, Caco-2 cell model will be applied to measure the uptake of fatty acid, vitarmin K, vitarmin D3, α-tocopherol acetate and/or or monoglyceride under the influence of soyasaponin hepatic metabolites and excreted via bile into gastrointestine. Also, radiolabelled cholesterol, fatty acids and/or cholic acid will be employed to determine the percentage of cholesterol micellarization and uptake by Caco-2 cells in the presence of soyasaponin hepatic metabolites..The proposed project results will highlight the potential of excipient nanoemulsions in controlling the bioaccessibility of lipophilic nutrients and lipophilic bioactive agents and/or boosting the development of soyasaponin as a natural biosurfactant.