78 OSCILLARIOLIDE, A NOVEL MACROLIDE FROM A BLUE-GREEN ALGA OSCILLATORIA SP.
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Interest in microalgae as new sources of structurally-novel and biologically-active compounds has increased in recent years. In the course of our screening program of bioactive substances from microalgae, we found that a marine cyanobacterium Oscillatoria sp. isolated from Gokashowan-Bay, Mie Prefecture, showed significant activity in the echinoderm egg assay. The reddish blue-green alga was cultured in 1000L plastic tanks. Methanol and methanol/dichloromethane (1:1) extracts of the algal wet cells were partitioned between water and diethyl ether. The lipophilic layer was subjected to silica gel and ODS column chromatography followed by reversed phase HPLC to give an inhibitor of development of fertilized echinoderm eggs (0.0005%yield). It was named Oscillariolide (1). Its molecular formula was deduced as C_<41>H_<69>O_<11>Br from ^<13>C and ^1H NMR and HRFABMS. This compound was suggested to have 7 hydroxy groups from ^1H NMR spectra and formation of heptaacetate (2). The extensive analyses of ^1H-^1H COSY, HOHAHA, HMQC and HMBC spectra revealed the structure of Oscillariolide. Oscillariolide inhibited the cell division of fertilized starfish eggs at a concentration of 0.5μg/ml.
