TOXIC SUBSTANCES, HETEROCAPSATOXIN A AND B TOWARDS OYSTER FROM RED TIDES, HETEROCAPSA CIRCULARISQUAMA, APPREARED IN SETO INLAND SEA

有害的浮游植物大量繁殖已造成严重的社会和环境问题，并对全世界的渔业造成严重损害。近年来，一种新的甲藻Heterocapsa circuliquama在日本的几个内湾引起了双壳类，如牡蛎和珍珠牡蛎的大规模死亡。本研究从养殖的圆鳞藻中分离到两种对牡蛎有毒性的新化合物，用1-BuOH提取圆鳞藻，1-BuOH提取液在正己烷和80%MeOH中进行分配。将来自80%MeOH可溶性级分的残余物在反相硅胶上进行柱色谱，得到生物活性级分。通过硅胶柱色谱、凝胶渗透色谱和HPLC（反相）进一步分离得到两种有毒物质，命名为杂capsatoxin A（HTX-A，分子量5024）和杂capsatoxin B（HTX-B，分子量1980）。通过对HTX-A和HTX-B的~ 1H和~ 1C <13>NMR谱的分析，发现它们具有非常相似的结构，都含有多个C=C双键和多个氧官能团，为了阐明HTX-A的结构，我们将HTX-A进行臭氧化，得到两个主要产物，分别命名为HTX-A1和HTX-A2。经高分辨快原子轰击质谱（FABMS）测定，HTX-A1分子式为C_<46>H_<84>O_<22>。HTX-A1的结构解析主要通过NMR实验进行，包括^1H和11 <13>C NMR、COSY、HMQC和HMBC。

Harmful phytoplankton blooms have caused serious social and environmental problems and heavy damage to fisheries throughout the world. In recent years, a novel dinoflagellate Heterocapsa circularisquama has caused mass mortality of bivalves, e.g. oysters and pearl oysters, in several inner bay of Japan. In our research the toxic substance in this plankton, two novel compounds exhibit the toxicity towards oyster were isolated.The algae of cultured H.circularisquama was extracted with 1-BuOH, and the 1-BuOH extract was partitioned between hexane and 80% MeOH. The residue from the 80% MeOH-soluble fraction was subjected to column chromatography on reversed phase silica gel to afford the biologically active fractions. Further separation by silica gel column chromatography, gel permeation chromatography, and HPLC (reverse phase) yielded two toxic substances named heterocapsatoxin A (HTX-A, molecular weight 5024) and heterocapsatoxin B (HTX-B, molecular weight 1980). Analysis of ^1H and ^<13>C NMR spectra of HTX-A and HTX-B, they have a very similar structures which contained the several C=C double bonds and many oxygen functionalities.In order to elucidate the structure of HTX-A,HTX-A was subjected to ozonolysis to give two major products, which were named HTX-A1 and HTX-A2. HTX-A1 was determined to have the molecular formula C_<46>H_<84>O_<22> by high-resolution FABMS. The structural elucidation of HTX-A1 was performed mainly by NMR experiments consisting ^1H and ^<13>C NMR,COSY,HMQC, and HMBC.