Shellfish properties

Three classes of polyethers, okadaic acid derivatives, pectenotoxins, and yessotoxin were isolated from bivalves in connection with diarrhetic shellfish poisoning. The etiology of the toxins, toxicological properties, and determination methods are described. 

A team of more than 40 scientists assembled at the National Research Council of Canada to solve what came to be called the amnesic shellfish poisoning mystery. Scientists had already tested for bacteria, heavy metals, and pesticides that they knew could cause sickness, but none of these were the cause.The mussel samples were a mixture of thousands of different chemical compounds, and scientists didn t even know what many of them were. How can you separate out an unknown when you don t know what you re looking for or what its properties are ... 

The purpose of this report is to review and present the important historical developments leading to the present understanding of the chemical nature of the poison including its chemical structure and properties, the mechanism causing death and the present means of control to make shellfish safer for human consumption. 

The main genera responsible for freshwater toxic blooms are Microcystis, Anabaena, Aphanizomenon and Oscillatoria. Toxins produced include 1. anatoxins, alkaloids and peptides of Anabaena 2. the peptide microcystin and related peptides of Microcystis 3. aphantoxins, compounds of Aphanizomenon with properties similar to some paralytic shellfish poisons. Properties of Oscillatoria toxin suggest they are peptides similar to those of Microcystis. Microcystis toxins are peptides (M.W. approx. 1200) which contain three invariant D-amino acids, alanine, erythro-3-methyl aspartic and glutamic acids, two variant L-amino acids, N-methyl dehydro alanine and a 3-amino acid. Individual toxic strains have one or more multiples of this peptide toxin. The one anatoxin characterized is a bicylic secondary amine called anatoxin-a (M.W. 165). The aphantoxin isolated in our laboratory contains two main toxic fractions. On TLC and HPLC the fractions have the same characteristics as saxitoxin and neosaxitoxin. 

Two other suspected alkaloid producing cyanobacteria strains, Anabaena flos-aquae NRC-525-17 and Aphanizomenon flos-aquae NH-5, are now being studied. The toxin of flos-aquae NRC-525-17 (anatoxin-a(s)) is thought to have CNS stimulating properties (7) and that of Aph. flos-aquae NH-5 (aphantoxin) is thought to produce the paralytic shellfish poisons saxitoxin and neosaxitoxin (Fig. 1)... 

The neurotoxins isolated from Aph. flos-aquae were shown to have similar chemical and biological properties to paralytic shellfish poisons (PSP) (25,29,38) Sawyer et al. in 1968 (25) were the first to demonstrate that the crude preparation of aphantoxins behave like saxitoxin, the major paralytic shellfish poison. They showed that the toxins had no effect on the resting membrane potential of frog sartorius muscle blocked action potential on de-sheathed frog sciatic nerve and also abolished spontaneous contractions in frog heart. Sasner et al. (1981) (29) using the lab cultured strain reported similar results. 

Literature data regarding the fate and transport of hexachlorobutadiene are limited. Much of the available information consists of modeling based on the physical and chemical properties of hexachlorobutadiene, and the monitoring data. These data indicate that hexachlorobutadiene will bind to soil particles and sediments, and is found in air and water bound to particulates. Some volatilization of hexachlorobutadiene from surface waters and soils may also occur. The bioconcentration of hexachlorobutadiene has been reported in fish and shellfish with considerable variability between species (EPA 1976 Oliver and Niimi 1983 Pearson and McConnell 1975). 

Chitosan, a polymer derived from shellfish, has been chemically altered to enhance its metalbinding properties. Chitosan derivatives have potential for treating wastewater contaminated with... 

Yessotoxin (YTX) was first postulated as a causative agent of severe clinical signs and symptoms of diarrhetic shellfish poisoning (DSP) (Terao et al. 1990). However, no diarrhogenic properties of this toxin have been reported (Draisci et al. 2000). The mechanism of action of YTX is not completely clarified even though several studies in this sense have been done. 

Formally defined as A reference material, accompanied by a certificate, one or more of whose properties are certified by a procedure which establishes traceability to an accurate realization of the unit in which the property is expressed, and for which each certified value is accompanied by an uncertainty at a stated level of confidence As pure marine biotoxins are rare and expensive, a CRM used for calibration is generally a dilute solution of stated concentration, for example, micromolar, which is traceable in terms of the chemical property (moles) and volume (liter). Methods for preparing biotoxin CRMs including standard solutions and shellfish... 

There are samples or crude extracts containing the analyte of interest but whose concentration has not been accurately established. For marine biotoxins, such materials may be frozen homogenates of naturally contaminated seafood, crude or partially purified extracts of such seafood, or of harmful algae. Digestive glands of contaminated shellfish are a source of concentrated toxins and their metabolites. Such materials cannot be used to calibrate methods of analysis but can serve very useful functions in method validation and quality control, especially when they contain rare toxins not readily available elsewhere (i) Retention times and spectral properties can be established on a routine basis for LC-UV, LC-FL, or LC-MS methods (ii) Partially purified extracts can be used for fortification experiments during method validation and thus establish recovery and precision data (iii) If concentrations of toxins can be established by reference to CRMs, then the materials can be used as in-house or interlaboratory reference materials for quality control. Issues such as toxin stability and homogeneity then become more important. ... 

We have attempted various manipulations to reduce toxicity—cooking, freezing, canning (sousing) for PSP-contaminated shellfish, but we have been only partly successful. We have reduced toxicity to a half, a third, or a fourth with processes that alter the organoleptic properties and renders selfish unfit for commercialization [13], These processes are a combination of pressure of 1.5-2 atm and temperature of 113°C or higher [13], Many other researchers have attempted cooking treatments to destroy these toxins, but without success [78,79],... 

T Yasumoto, Y Oshima, M Yamagnchi. Ocnrrence of a new type of shellfish poisoning in Japan and chemical properties of the toxin. In D Taylor and HH Seliger, eds. Toxic Dinoflagellate Blooms. Amsterdam Elsevier, 1979, pp. 495-502. 

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