Marmycins A and B, cytotoxic pentacyclic C-glycosides from a marine sediment-derived actinomycete related to the genus Streptomyces.

Two new cytotoxic quinones of the angucycline class, marmycins A and B ( 1, 2), were isolated from the culture broth of a marine sediment-derived actinomycete related to the genus Streptomyces. The gross structures and absolute configurations of both compounds were determined by spectroscopic and crystallographic methods. Marmycin A ( 1) displayed significant cytotoxicity against several cancer cell lines, some at nanomolar concentrations; while compound 2, a chloro analogue of 1, was less potent. For marmycin A ( 1), tumor cell cytotoxicity appeared to coincide with induction of modest apoptosis and arrest in the G1 phase of the cell cycle.