Natural Products Discovery Group, Department of Chemistry and Biochemistry, 620 Parrington Oval, Room 208, University of Oklahoma, Norman, OK 73019, USA.
Toxicon. 2010 Jun 15;55(7):1396-404. doi: 10.1016/j.toxicon.2010.02.017. Epub 2010 Feb 23.
Within the last two decades, Prymnesium parvum (golden algae) has rapidly spread into inland waterways across the southern portion of North America and this organism has now appeared in more northerly distributed watersheds. In its wake, golden algae blooms have left an alarming trail of ecological devastation, namely massive fish kills, which are threatening the economic and recreational value of freshwater systems throughout the United States. To further understand the nature of this emerging crisis, our group investigated the chemical nature of the toxin(s) produced by P. parvum. We approached the problem using a two-pronged strategy that included analyzing both laboratory-grown golden algae and field-collected samples of P. parvum. Our results demonstrate that there is a striking difference in the toxin profiles for these two systems. An assemblage of potently ichthyotoxic fatty acids consisting primarily of stearidonic acid was identified in P. parvum cultures. While the concentration of the fatty acids alone was sufficient to account for the rapid-onset ichthyotoxic properties of cultured P. parvum, we also detected a second type of highly labile ichthyotoxic substance(s) in laboratory-grown golden algae that remains uncharacterized. In contrast, the amounts of stearidonic acid and its related congeners present in samples from recent bloom and fish kill sites fell well below the limits necessary to induce acute toxicity in fish. However, a highly labile ichthyotoxic substance, which is similar to the one found in laboratory-grown P. parvum cultures, was also detected. We propose that the uncharacterized labile metabolite produced by P. parvum is responsible for golden algae's devastating fish killing effects. Moreover, we have determined that the biologically-relevant ichthyotoxins produced by P. parvum are not the prymnesins as is widely believed. Our results suggest that further intensive efforts will be required to chemically define P. parvum's ichthyotoxins under natural bloom conditions.
在过去的二十年中，Prymnesium parvum（金藻）迅速蔓延到北美洲南部的内陆水道，并且这种生物现在已经出现在分布更北的流域。在其之后，金藻大量繁殖，留下了令人震惊的生态破坏痕迹，即大量鱼类死亡，这威胁到了美国整个淡水系统的经济和娱乐价值。为了进一步了解这一新兴危机的性质，我们小组研究了 P. parvum 产生的毒素的化学性质。我们使用了一种双管齐下的策略来解决这个问题，包括分析实验室培养的金藻和野外采集的 P. parvum 样本。我们的结果表明，这两种系统的毒素特征有明显的差异。在实验室培养的 P. parvum 中鉴定出一组由 stearidonic 酸组成的强烈的鱼类毒性脂肪酸，尽管脂肪酸的浓度足以解释培养的 P. parvum 的快速发作的鱼类毒性特性，但我们还在实验室培养的金藻中检测到了第二种类型的高度不稳定的鱼类毒性物质，这种物质仍然没有特征。相比之下，在最近的藻类大量繁殖和鱼类死亡地点的样本中，stearidonic 酸及其相关同系物的含量远低于在鱼类中引起急性毒性所需的水平。然而，还检测到了一种高度不稳定的鱼类毒性物质，类似于在实验室培养的 P. parvum 中发现的物质。我们提出，P. parvum 产生的未鉴定的不稳定代谢物是金藻造成毁灭性鱼类死亡的原因。此外，我们已经确定，P. parvum 产生的具有生物学相关性的鱼类毒素不是人们普遍认为的 prymnesins。我们的结果表明，需要进一步进行化学研究，以确定自然繁殖条件下 P. parvum 的鱼类毒素。
