Enzymatic hydrolysis of esterified diarrhetic shellfish poisoning toxins and pectenotoxins |
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Authors: | Erin Doucet Neil N Ross Michael A Quilliam |
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Institution: | (1) National Research Council Canada, Institute for Marine Biosciences, 1411 Oxford Street, Halifax, NS, B3H 3Z1, Canada;(2) Department of Process Engineering and Applied Science, Food Science Program, Dalhousie University, Halifax, NS, B3J 2X4, Canada |
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Abstract: | Okadaic acid (OA) and dinophysistoxins-1 and -2 (DTX1, DTX2), the toxins responsible for incidents of diarrhetic shellfish
poisoning (DSP), can occur as complex mixtures of ester derivatives in both plankton and shellfish. Alkaline hydrolysis is
usually employed to release parent OA/DTX toxins, and analyses are conducted before and after hydrolysis to determine the
concentrations of nonesterified and esterified toxins. Recent research has shown that other toxins, including pectenotoxins
and spirolides, can also exist as esters in shellfish, but these toxins cannot survive alkaline hydrolysis. A promising alternative
approach is enzymatic hydrolysis. In this study, two enzymatic methods were developed for the hydrolysis of 7-O-acyl esters, “DTX3,” and the carboxylate esters of OA, “diol-esters.” Porcine pancreatic lipase induced complete conversion
of DTX3 to OA and DTXs within one hour for reference solutions. The presence of mussel tissue matrix reduced the rate of hydrolysis,
but an optimized lipase concentration resulted in greater than 95% conversion within four hours. OA-diol-ester was hydrolyzed
by porcine liver esterase and was completely converted to OA in less than 30 min, even in the presence of mussel tissue matrix.
Esters and OA/DTX toxins were all monitored by LC–MS. Further experiments with pectenotoxin esters indicated that enzymatic
hydrolysis could also be applied to esters of other toxins. Enzymatic hydrolysis has excellent potential as an alternative
to the conventional alkaline hydrolysis procedure used in the preparation of shellfish samples for the analysis of toxins. |
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Keywords: | Diarrhetic shellfish poisoning (DSP) Okadaic acid Dinophysistoxins Pectenotoxins Esters Liquid chromatography– mass spectrometry Enzymatic hydrolysis |
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