New amino butenolides from the bulbs of Fritillaria unibracteata.

Five new amino γ-butenolides, fritenolide A (1), B (2), C (3), D (4), and E (5), along with four known compounds, were isolated from the bulbs of Fritillaria unibracteata. Their structures were determined by spectroscopic analysis, including 1D NMR, 2D NMR, HRESIMS, HRESIMS/MS, IR, and CD techniques. All isolates were evaluated for the protective activity on injured hepatocytes and cytotoxic activity on human cancer cells in vitro. The unusual amino butenolides were isolated from the Liliaceae family for the first time.