类胡萝卜素是自然界中广泛存在的天然色素，在人体内发挥重要的生理功能。部分顺式类胡萝卜素的抗氧化活性优于全反式构型，并可被人体选择性吸收。除通过简单被动扩散方式，全反式类胡萝卜素还可通过脂质转运蛋白协助扩散方式进入肠上皮细胞。然而顺式类胡萝卜素跨膜运输机制尚不明确。本项目将研究类胡萝卜素异构体的消化稳定性和跨膜运输机制，明确顺式类胡萝卜素在体内的形成阶段及选择性吸收原因。通过溶剂载体和乳液体系搭配体外模拟消化模型和分配系数扩散模型，系统研究类胡萝卜素几何异构体在消化过程中的结构稳定性和生物可给率，明确顺式类胡萝卜素在体内的形成阶段；采用体外模拟消化液进行肠上皮细胞吸收实验，结合分子模拟对接技术，阐明顺式类胡萝卜素跨膜运输机制。本项目的开展，将为提高类胡萝卜素等脂溶性植物化合物的生物利用率提供理论依据，推动高生物利用率类胡萝卜素的产业化发展，具有重要的理论和实践意义。

Carotenoids are widely-found natural pigments with various physiological activities. Certain cis- (Z-) carotenoids are selectively absorbed in human body and exhibit higher antioxidant activity than their all-E-isomers. Except for simple passive diffusion process, certain lipid transporters of the epithelial layer have been reported to facilitate the transport of some all-E-carotenoids. However, the facilitated diffusion mechanism of Z-carotenoid is yet to be studied. In this project, the digestive stability and transmembrane transport mechanism of carotenoid geometric isomers will be systematically investigated to clarify the phases where the Z-carotenoids are formed after the oral administration of meals rich in all-E-carotenoids and explain the selective absorption of Z-carotenoids. Two vehicles including solvent and emulsion are coupled with in vitro digestion model and partition factors diffusion model to study the digestive stability and bioaccessibility of carotenoid geometric isomers and decide the potential phases where the Z-carotenoids are formed. Besides, the Caco-2 cellular transport data of digesta will be combined with molecular docking results to further illuminate the potential facilitated transport mechanism of Z-carotenoids. This project will provide the theoretical basis for the study of improving the bioavailability of carotenoids and other lipophilic phytochemicals, and will also promote the industrial production of lycopene with high bioavailability.