Secondary metabolites from the[italic] Actinomadura[/italic] sp. and their cytotoxic activity

Actinomadura sp., which is usually found in muddy habitats, produces various secondary metabolites with biological activities. In this study, five new compounds named formosensin A (1), formosensin B (2), oxanthroquinone-3-O-alpha-D-mannose (8), oxanthromicin A (9), and oxanthromicin B (10) were isolated from the culture of Actinomadura sp. together with five known compounds (3-7). Their structures were elucidated by extensive spectroscopic methods including NMR and MS. In particular, the absolute configurations of compounds 1 and 2 were determined using computational methods. Moreover, compounds 1-2 and 8-10 were screened for cytotoxic activity using a panel of human tumor cell lines. Compound 9 induced significant cytotoxicity in five human tumor cell lines (HL -60, A-549, SMMC-7721, MCF-7, and SW480) with IC50 values of 8.7, 17.5, 15.0, 17.8, and 14.6 mu M, respectively. These findings suggested that compound 9 could provide therapeutic benefits in the treatment of tumor -related diseases.