Cytotoxic angucyclines from Amycolatopsis sp. HCa1, a rare actinobacteria derived from Oxya chinensis.

Two new angucyclines, named (2R,3R)-2-hydroxy-8- O-methyltetrangomycin (1) and (2R,3R)-2-hydroxy-5-O-methyltetrangomycin (2), together with eight known compounds (3-10), were isolated from the culture of Amycolatopsis sp. HCa1, a rare actinobacteria isolated from the gut of Oxya chinensis. The new structures were elucidated through extensive spectroscopic data analysis, and their absolute configurations were assigned by application of the modified Mosher's method and CD spectrum comparison. Their IN VITRO cytotoxic activities against four cell lines including human cervical cancer cell line (HeLa), human gastric adenocarcinoma cell line (SGC-7901), human lung adenocarcinoma cell line (SPC-A-1), and mouse macrophage cell line (RAW264.7) were then investigated. Compounds 3, 4, 9, and 10 showed potent cytotoxic activities towards the HeLa cells with IC (50) values of 0.27, 0.11, 0.56, and 0.39 µM, respectively.