Ichthyotoxic Active Compounds from Red Tides and Mechanism of Ichthyotoxicity

在对鳉鱼进行毒性试验时，发现发现了由Chattonella antiqua引起的赤潮中存在的饱和和不饱和脂肪酸。在不饱和脂肪酸中，十八碳四烯酸（C &lt;18：4&gt;）的活性最强（LC <100>= 7 ppm）。其它C_<18->不饱和脂肪酸活性较低，但其鱼毒活性随不饱和度的增加而增加。然而，这些不饱和脂肪酸的活性通过在pH 8.1下添加抗氧化剂（α-生育酚和抗坏血酸钠）而消失。结果表明，不饱和脂肪酸<100>在pH 8.1时，自由基肉豆蔻酸和棕榈酸的活性在pH 4.5时由于在水中的溶解度降低而降低。而癸酸（C &lt;10：0&gt;）和月桂酸（C &lt;12：0&gt;）的活性在pH 4.5时较pH 8.1时强。在pH 4.5时，癸酸和月桂酸被电离到小于30%的程度。这些事实表明，鱼类毒性归因于饱和脂肪酸的非离子形式与生物膜的疏水相互作用。

Saturated and unsaturated fatty acids present in the red tides alga Chattonella antiqua showed an ichthyotoxic activity when assayd against killifish. Among the unsaturated fatty acids, stearidonic acid (C_<18 : 4>) had the strongest activity (LC_<100> = 7 ppm). Other C_<18->unsaturated fatty acids assayd were less active, although their ichthyotoxic activities increased with increase of the unsaturation degree. However, the activity of these unsaturated fatty acids disappeared by addition of anti-oxidizing reagents (alpha-tocopherol and sodium ascorbate) at pH 8.1. These facts indicate that the ichthyotoxicity is due to damage caused to the biomembrane by radical species generated form the autoxidation of the unsaturated fatty acids.Among the saturated fatty acids, myristic acid (C_<14 : 0>) and palmitic acid (C_<16 : 0>) had the strongest activity (LC_<100> = 10 ppm) at pH 8.1. The activities of myristic acid and palmitic acid decreased at pH 4.5 due to a diminished solubility in water. However, the activities of decanoic acid (C_<10 : 0>) and lauric acid (C_<12 : 0>) were stronger at pH 4.5 rather than at pH 8.1. At pH 4.5, decanoic acid and lauric acid are ionized to an extent of less than 30%. These facts indicate that the ichthyotoxicity ascribes to the hydrophobic interaction with the biomembrane by the non-ionic form of the saturated fatty acid.