Isolation and Structure Determination of Akunolides, Macrolide Glycosides from a Marine <i>Okeania</i> sp. Cyanobacterium

Akunolides A (<b>1</b>), B (<b>2</b>), C (<b>3</b>), and D (<b>4</b>), new macrolide glycosides, were isolated from a marine <i>Okeania</i> sp. cyanobacterium. Their structures were elucidated by spectroscopic analyses and derivatization reactions. Akunolides A–D (<b>1</b>–<b>4</b>) are classified as 16-membered macrolide glycosides, which are relatively rare structures for marine cyanobacterium-derived natural products. Akunolides A–D (<b>1</b>–<b>4</b>) showed moderate antitrypanosomal activities against <i>Trypanosoma brucei rhodesiense</i>, with IC₅₀ values ranging from 11 to 14 μM. Furthermore, akunolides A (<b>1</b>) and C (<b>3</b>) exhibited no cytotoxicity against normal human WI-38 cells even at a concentration of 150 μM.