Streptomyces albogriseolus SY67903 Produces Eunicellin Diterpenoids Structurally Similar to Terpenes of the Gorgonian Muricella sibogae, the Bacterial Source

Microeunicellols A (1) and B (2), two undescribed eunicellin diterpenoids, were isolated from the culture of a bacterial symbiont, Streptomyces albogriseolus SY67903. Their structures, including absolute configurations revealed by spectroscopic data and single-crystal X-ray diffraction analysis, are closely related with the diterpenoids from its host, a South China Sea gorgonian, Muricella sibogae. This is the first report of eunicellin diterpenoids, commonly coral-derived, from a bacterial symbiont of coral. The chemical metabolic relationship between the bacterium and its host is discussed. Biological evaluation revealed that compound 1 possessed cytotoxicities against several human cancer cell lines.