Cytotoxic lasiodiplodin derivatives from the fungus Syncephalastrum racemosum.

Chemical investigation of fungal biomass of the fungus Syncephalastrum racemosum led to the isolation of new natural products (3R),(5S)-5-hydroxy-de-O-methyllasiodiplodin (1), 6-oxode-O-methyllasiodiplodin (2), in addition to five known compounds, de-O-methyllasiodiplodin (3), lasiodiplodin (4), (3R),(5R)-5-hydroxy-de-O-methyllasiodiplodin (5), ergosterol (6), and ergosterol peroxide (7). Their structures were elucidated by spectroscopic techniques. The absolute configuration of 1 was determined by a modified Mosher's method. Compound 1 showed cytotoxicity against cholangiocarcinoma, KKU-M139, KKU-M156, and KKU-M213 cell lines with IC(50) values in the range of 14-19 μg/mL, while 3 showed cytotoxicity against KB, BC1, and NCI-H187 cell lines with IC(50) values of 12.67, 9.65, and 11.07 μg/mL, respectively.