Exploring the Antioxidant and Degradation Mechanisms of Hydroxy‐α‐sanshool as the Key Pungent Dietary Component in Sichuan Peppers and Pungent Foods: A DFT Study

To better understand the structural changes of the key pungent dietary component hydroxy-α-sanshool in Sichuan peppers and pungent foods under different processing and storage conditions, its antioxidant and structural degradation mechanism as a free radical scavenger has been firstly explored computationally. Our results show that hydroxy-α-sanshool may act in parallel as an excellent antioxidant via favorably donating its allylic hydrogen atoms or beneficially accepting radicals through its conjugated C═C bonds, as well as a pro-oxidant via the radical adduct formation pathways in yielding reactive radical species. The hydrogen abstraction from its allylic C─H bonds and the radical addition to its C═C─C─C─C═C group by model peroxy radicals are found to be the most thermodynamically and kinetically preferable reaction channels, where the radical addition steps are more rapid than the corresponding epoxide formation steps in most addressed sites. Besides, the reaction between hydroxy-α-sanshool and peroxy radicals exhibits lower energy barriers in a polar solvent environment. Finally, its possible autoxidative degradation mechanism has been proposed. This work is helpful for the better understanding or prediction of the pungent changes of Sichuan peppers and pungent foods. PRACTICAL APPLICATIONS: Based on the largely unknown antioxidant and degradation mechanisms, or tendency, the effects of the structural changes on the oral pungency, pungent mechanism or biological activities of sanshools, as well as their mutual relationships, have been largely overlooked. The present work provides an alternative novel solution to get a mature understanding or prediction of the pungent changes during the process and storage operations on the Sichuan peppers and pungent foods.