Isoquinoline alkaloids from Stephania japonica var. discolor and their neuroprotective effects against OGD/R-induced oxidative injury.

Stephania japonica var. discolor is a traditional medicinal plant reported to contain alkaloids. In this study, eight isoquinoline alkaloids were isolated from the whole plant, including four previously undescribed compounds (1-3, 6). These compounds were evaluated for neuroprotective effects using an oxygen-glucose deprivation/reperfusion (OGD/R) model in PC-12 cells. Several of the isolated alkaloids significantly improved cell viability and reduced intracellular reactive oxygen species (ROS) levels under OGD/R conditions. These results suggest that the neuroprotective activity of these compounds may be closely associated with their antioxidant properties. This is the first study to report the neuroprotective activity of isoquinoline alkaloids from S. japonica var. discolor and to explore their preliminary antioxidant mechanisms. The findings expand the chemical profile of this plant and highlight promising natural product-derived leads for the development of therapeutic agents against ischemic stroke.