Structurally diverse steroidal saponins from the bulbs of Lilium lancifolium Thunb. and their neuroprotective activities.

Eleven undescribed steroidal saponins (1-11) and seven known steroidal saponins (12-18) were isolated from the bulbs of Lilium lancifolium Thunb. Their structures with absolute configurations were deduced from spectroscopic data, acidic hydrolysis, and comparison with reported compounds. Biological evaluations of neuroprotective activities of these compounds were carried out in vitro. Compounds 1-2, 5-7, 10, 13, and 18 demonstrated significant neuroprotective activity at a concentration of 20 μM. Notably, 2 exhibited the most potent activity. Mechanistic investigations disclosed that it conferred a protective effect through the regulation of Nrf2 pathway expression.