Triterpene saponins with neuroprotective effects from the leaves of Diospyros kaki Thunb.

Seven undescribed triterpene saponins, named kakisaponin I-VII (1-7), together with nine known ones (8-16) were isolated from the leaves of Diospyros kaki Thunb. by various chromatographic methods. Compounds 1-5 were novel 18, 19-secoursane triterpenoids, which were an uncommon type of triterpenoids. Their structures were elucidated by different spectroscopic methods, combining HRESIMS, 1D and 2D NMR. All isolated compounds were evaluated for their protective effects on HO-induced damage in human dopaminergic neuroblastoma cells (SH-SY5Y). Compound 2 showed significant neuroprotective effect at a certain concentration, and compounds 3 and 12 exhibited moderate bioactivities. Current study suggests that triterpene saponins in Diospyros kaki may play an important role in the neuroprotective properties.