Optimisation of the flash extraction process for male catkins of <i>Corylus heterophylla</i> and evaluation of their oxidative stress resistance

The fruit of <i>Corylus heterophylla</i> Fisch is an important nut, while its male catkins remain underutilised despite being rich in various bioactive compounds. To develop this potential resource, this study optimised the extraction process of <i>C. heterophylla</i> male catkins and investigated their antioxidant stress resistance. The results showed that the optimal extraction conditions were: extraction time of 53 s, ethanol concentration of 82%, and a liquid-solid ratio of 33 mL/g. <i>In vitro</i> experiments showed that <i>C. heterophylla</i> male catkin extract (ChCE) reduced ROS production and elevated SOD, CAT activities and GSH content in <i>t</i>-BHP-induced HepG2 cells. Additionally, ChCE promoted the phosphorylation of MAPKs, mediating decreased Keap1 expression in the cytoplasm and increased Nrf2 expression. <i>In vivo</i> experiments confirmed that ChCE alleviated alcohol-induced hepatic oxidative stress in mice. These findings suggest that the male catkins of <i>C. heterophylla</i> represent a valuable resource for applications in the food and pharmaceutical industries.