Neuroprotective polyhydroxypregnane glycosides from Cynanchum otophyllum.

Five new polyhydroxypregnane glycosides, namely cynanotosides A-E (1-5), together with two known analogues, deacetylmetaplexigenin (6) and cynotophylloside H (7), were isolated from the roots of Cynanchum otophyllum. Their structures were established by spectroscopic methods and acid hydrolysis. The neuroprotective effects of compounds 1-7 against glutamate-, hydrogen peroxide-, and homocysteic acid (HCA)-induced cell death were tested by MTT assay in a hippocampal neuronal cell line HT22. Compounds 1, 2, and 7 exhibited protective activity against HCA-induced cell death in a dose-dependent manner ranging from 1 to 30μM, which may explain the Traditional Chinese Medicine (TCM) use of this plant for the treatment of epilepsy.