| Research Abstract |
The compositions of fatty acids and sterols were determined in laboratory cultures of the marine dinoflagellate Heterocapsa circularisquama. In the free fatty acids, C_<22 : 6>,C_<16 : 0> and C_<18 : 4> were major components. Polyunsaturated fatty acids account for a substantial portion of the total free fatty acids (63.6 %) and include C_<18>, C_<20> and C_<22> acids. The fraction containig the free fatty acid exhibited potent cytotoxicity towards primary cultured gill cells of oyster. The major components in the fatty acids consisted of triacylglycerols were C_<18 : 2>, C_<16 : 0> and C_<14 : 0>.
Ten kinds of the sterol in H. circularisquama were identified by capillary gas chromatography-mass spectrometry. The major sterol was a 4-methyl sterol, 4α, 23, 24-trimethyl-5α-cholest-22E-en-3β-ol (dinosterol) which is the common sterol in many dinoflagellates. On the other hand, 5, 8α-epidioxy-5α-cholest-6-en-3β-ol was isolated as potent cytotoxic substance.
A novel digalactosyl diacylglycerol has been isolated from H. circularisquama together with two known monogalactosyl diacylglycerols, and their structures were elucidated by spectroscopic methods. The isolated monogalactosyl and digalactosyl diacylglycerols showed potent cytolytic activity towards heart cells of oyster.
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