Diversity of shellfish toxins of “diarrhetic” type revealed by biological and chemical assays

Abstract

Extracts of "diarrhetic" shellfish toxins from the edible mussel (Mytilus edulis) were tested with biological and chemical assays to determine toxin content. When tested with the standard mouse bioassay, a higher toxicity was detected in most samples compared to that revealed from detection of the diarrhea-causing substances okadaic acid and dinophysistoxin-1 by high-performance liquid chromatography. Routine extraction of toxins for the two assays was carried out with two different solvents, acetone versus aqueous methanol. Accordingly, we questioned whether the variation in results between the methods could be due to differences in chemical properties of these two solvents. When tested, the two solvent systems showed practically the same efficiency concerning the extraction of okadaic acid and dinophysistoxin-1. This demonstrated that toxins other than those causing diarrhea were present in the samples, and that the mouse bioassay was sensitive to these additional toxins. Subsequent testing of the samples with the mouse bioassay, employing both acetone and methanol extracts, revealed that at least two classes of toxins were present in the mussel samples in addition to okadaic acid and dinophysistoxin-1. It is unclear whether the shellfish toxins revealed in this study are partially from known, nondiarrhetic types, such as pectenotoxins or yessotoxins, or from unknown toxin groups exhibiting ichthyotoxic and hemolytic properties.