Zooxanthellae are typical symbiotic dinoflagellates associated with a wide range of marine invertebrates and they play important roles such as CO_2 fixation and production of organic molecules at marine environments. While screening symbiotic microorganisms from marine invertebrates for bioactive compounds, we discovered potent vaso-constrictive polyols named Zooxanthellatoxin-A (ZT-A) and ZT-B from a cultured zooxanthella, Symbiodinium sp. isolated from the flat worm Amphiscolops sp. collected at Okinawa. Zooxanthellatoxins are sulfate esters of highly unsaturated polyols with a molecular weight of ca. 2900. Periodate oxidation of ZT-A gave seven fragments (A〜G). Among these fragments, the most charactristic fragment E (C_<47>H<76>O_<14>) was established to be an allylic alcohol-rich polyhydroxypolyene with a diepoxide unit. The structure of fragment A (C_<56>H_<91>O_<22>SNa) was shown to be a sulfate ester of a polyol having an elongated structure of fragment E. The other fragments are peracetylated and the structures of the acetates were determined by homo-spin decoupling and NOE experiments. These results revealed that Zooxanthellatoxins are a new type of marine toxins.
