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

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