Yessotoxin (YTX) and its analogues are disulphated polyether compounds produced by marine algae, in particular Protoceratium reticulatum and Gonyaulax polyedra. YTX is known to accumulate in shellfish meat and is regarded as hepatotoxic and cardiotoxic when ingested above a certain level [1]. The yessotoxins have previously been included in the diarrhetic shellfish poison (DSP) group, but the YTX chemistry and toxicology differ distinctly from the DSP toxin family. The European Commision recently placed the yessotoxins in a separate phycotoxin group, and implemented a maximum permitted level (MPL) of 1 mg YTX eqvivalents/kg shellfish intended for human consumption (Directive 2002/225/EC).

The Direct cELISA Enzyme Linked Immunosorbent Assay (ELISA) has proved to be a sensitive and rapid method for phycotoxin detection. The quantitative YTX ELISA is developed by AgResearch (Hamilton, New Zealand) for the detection of YTXs in water samples, shellfish and algal extracts. The protocol The kit protocol is based on a competitive binding assay where free YTX and YTX analogues in the sample are competing with a plate-coated YTX-conjugated protein for binding to specific anti-YTX antibodies. The anti-YTX antibodies are labelled with horseradish peroxidase (HRP) and the amount bound in the wells is measured by addition of HRP substrate. The colour intensity is inversely proportional to the concentration of YTX in the sample. The assay is calibrated using a standard solution of YTX supplied with the kit.