Chemical constituents of the bulbs of Habranthus brachyandrus and their cytotoxic activities.

The bulbs of Habranthus brachyandrus (Amaryllidaceae) have been extensively analyzed for their chemical constituents, resulting in the isolation of eight flavan derivatives (1-8), four of which are new naturally occurring compounds; a new hydroxybutyric acid glucoside (9); three known phenolic compounds (10-12); and six known alkaloids (13-18). The structures of the new compounds were determined on the basis of spectroscopic analysis, including two-dimensional (2D) NMR data, and chemical evidence. The isolated compounds and a few derivatives were evaluated for their cytotoxic activities against HL-60 human promyelocytic leukemia cells and HSC-2 human oral squamous cell carcinoma cells.