Neolignans and amide alkaloids from the stems of Piper kadsura and their neuroprotective activity

Four undescribed neolignans and three undescribed amide alkaloids, along with twelve known compounds, were isolated from the stems of Piper kadsura (Choisy) Ohwi. The structures of the new compounds were determined by spectroscopic analysis, quantum-chemical calculations, and Mo2(OAc)4-induced ECD analysis. The neuroprotective effects of these compounds against Aβ25-35-induced cell damage in PC12 cells were investigated, and eight compounds exhibited significant neuroprotective effects against Aβ25-35-induced PC12 cell damage, with the EC50 values of 3.06-29.3 μM. Three of these compounds were selected for further experiments, and they appear to reduce apoptosis and enhance autophagy against Aβ25-35-induced PC12 cell damage.