Variation in Cytostatic Constituents of a Sponge-Derived <i>Gymnascella dankaliensis</i> by Manipulating the Carbon Source

The Halichondria sponge-derived fungus, Gymnacella dankaliensis, was cultured in two different media conditions. A modified malt extract medium containing soluble starch instead of glucose resulted in two extremely unusual steroids, dankasterones A (2) and B (3), while four additional unusual steroids, gymnasterones A (4), B (5), C (6), and D (7), were isolated from the original malt extract medium. Their stereostructures have been established on the basis of spectroscopic analyses along with X-ray crystal structure analyses, modified Mosherʼs method, CD exciton method, and a chemical transformation. All the steroids except for 4 exhibited significant growth inhibition against the murine P388 cancer cell line. Dankasterone A (2) also exhibited potent growth inhibition against human cancer cell lines.