Phytosterols (PS) are a group of sterols distributed in foods and plants, where it is prone to oxidation. In this work, we studied the reaction mechanism of phytosterols, using density functional theory (DFT) calculation and experimental methods to study the photooxidation of phytosterols. Under LED light illumination, experimental photooxidation of these phytosterols gives rise to the prior three kind oxides of phytosterol: 6α-OH, 7α-OH, and 7β-OH. The mechanistic investigations by DFT suggest that singlet oxygen (¹O₂)-mediated photooxidation (Type II mechanism) generated radical adds to the C5 and C6 on the B Ring of steroid nucleus and reaction in C7 initiated from C5 products through rearrangement pathway. Furthermore, the stereoselectivity at C5, C6 and C7 provides a mechanistic guide for phytosterols photooxidation. These efforts are expected to serve as an essential exploratory study for the oxidation mechanism of phytosterols in the complex food matrix and antioxidation technology for phytosterols.

植物固醇（PS）是分布在食品和植物中的一组固醇，容易被氧化。在这项工作中，我们使用密度泛函理论（DFT）计算和实验方法研究了植物甾醇的光氧化机理，研究了植物甾醇的反应机理。在LED光照下，这些植物甾醇的光氧化实验产生了植物甾醇的先前三种氧化物：6α-OH，7α-OH和7β-OH。DFT的机理研究表明单重态氧（¹ O ₂）介导的光氧化作用（II型机制）产生的自由基加至类固醇核B环的C5和C6上，并通过重排途径从C5产物引发C7中的反应。此外，在C5，C6和C7处的立体选择性为植物甾醇的光氧化提供了机理指导。预期这些努力将为复杂食物基质中植物甾醇的氧化机理和植物甾醇的抗氧化技术提供重要的探索性研究。