Four new tirucallane-type triterpenoids from Sapindus mukorossi Gaertn. flowers induced neurite outgrowth in PC12 cells related to insulin-like growth factor 1 receptor/phosphoinositide 3-kinase/extracellular regulated protein kinase signaling pathway

Four new tirucallane-type saponins (i.e., sapinmusaponin S–V, which include one new structure and three new stereoisomers) and a known compound sapinmusaponin G were isolated from the flowers of Sapindus mukorossi . All of them could significantly induce neurite outgrowth of PC12 cells. The structures of active compounds were determined using spectroscopic data and chemical derivatization. Specific inhibitor experiments and Western blot analysis of sapinmusaponin S, which is the most active compound, were performed. Results indicated that the insulin-like growth factor 1 receptor/phosphoinositide 3-kinase/extracellular regulated protein kinase signaling pathway is involved in this action.