Detection of DSP-toxins, okadaic acid, and dinophysis toxin-1 in shellfish by serine/threonine protein phosphatase assay.

A relatively rapid protein phosphatase-based assay was developed for detecting okadaic acid in extracts of shellfish, using oysters (Crassostrea virginica) as a model. The assay has good sensitivity, detecting okadaic acid in crude methanolic extracts of oysters at > or = 4 ng/mL (> or = 0.1 ng/assay). Assay accuracy for detecting toxic shellfish was validated through a series of spike recovery experiments. In more than 320 assessments, all oysters containing toxic amounts of okadaic acid (> or = 0.2 microgram/g) were detected. Results of analysis of the same extract by phosphatase assay and liquid chromatography gave very high correlation.