Ansamycin antibiotics cytotoxic activities

Ansamycin antibiotics are probably the most complex organic compounds produced by the genus Streptomyces. In addition to the antibacterial, they also exhibit antiviral effects. Ansamitocin P-3 shows a potent cytotoxicity against the human solid tumor cell lines A-549 and HT-29. The compound exhibits a significant activity against P-388 lymphocytic leukemia in mice and both 9PS (murine lymphocytic leukemia) and 9KB (human nasopharyngeal carcinoma) in cell culture systems. [38]. 

A similar strategy has been followed for the preparation of the naphthoquinone nucleus (118) [202], a precursor of awamycin (119), another ansamycin antibiotic isolated from several Streptomyces species and active against Gram-positive bacteria, protozoa and marine tumors in vivo. The compound is also cytotoxic to Hela cells in vitro [203]. The structure of awamycin (119) has been determined by X-ray analysis [204] and it is structurally similar to damavaricin D (120), a degradation product and biosynthetic precursor of streptovaricin D (108). 

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