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.