A novel bioactive depsipeptide, thiocoraline, was isolated from the mycelial cake of a marine actinomycete strain L-1 3-ACM2-092.Based on morphological, cultural, physiological, and chemical characteristics, strain L-13-ACM2-092was ascribed to the genus Micromonospora. Thiocoraline showed a potent cytotoxic activity against P-388, A-549 and MEL-28cell lines, and also a strong antimicrobial activity against Gram-positive microorganisms. This compoundbinds to supercoiled DNAand inhibits RNAsynthesis.

Thiocoraline (1) is a new antitumor antibiotic isolated from the mycelium of Micromonospora sp. L-13-ACM2-092. Its structure was elucidated to be a novel cyclic thiodepsipeptide on the basis of spectroscopic methods.In the course of screening for new antitumor compounds, thiocoraline (1) was isolated from the mycelium of Micromonospora sp. L-13-ACM2-092 (Fig. 1) by bioassay-guided fractionation.The taxonomy, fermentation, isolation and biological activities are the subject of a preceeding paper1}. We will report herein the physico-chemical properties and structural elucidation of thiocoraline.

Two new indolocarbazole alkaloids, 4'-Af-methyl-5'-hydroxystaurosporine (2) and 5'-hydroxystaurosporine (3), were isolated together with the known staurosporine (1) from the culture broth of a marine Micromonospora sp. (strain L-31-CLCO-002). The fermentation, structural data and cytotoxic activities of these compounds against various tumorcell lines aregiven.