Shellfish analogs

Yoon, K.S. and Lee, C.M., Effect of powdered cellulose on the texture and freeze-thaw stability of surimi-based shellfish analog products, J. Food Sci., 55, 87, 1990. 

The paralytic shellfish toxins (PSTs Fig. 5.2a) include saxitoxin (STX) as well as STX analogs such as neo-saxitoxin (neo-STX), gonyautoxin (GTX), and the decar-bamoyltoxins (Sivonen and Jones 1999). These molecules are of particular concern in marine systems, where they have been implicated in human deaths following the consumption of contaminated seafood (Van Dolah 2000). The causative agents in those cases are several genera of marine dinoflagellates that are common components of red tides (e.g., Alexandrium sp. Homer et al. 1997 Van Dolah 2000). 

Although sterols exist as cholesterol in most food and food products including meat, fish, fats and oils, and milk (Kushiro et al., 1980), certain shellfish contain six other analogs of sterol, including 22-frans-24-norcholesta-5,22-diene-3b-ol, 22-dehydrocholesterol,... 

HPLC determination (Osada et al., 1999), and HPLC/MS (Redden and Huang, 1991). In general, enzymatic determination is superior to colorimetry to obtain true cholesterol content. When food such as shellfish contains sterols other than cholesterol, the GC determination is the most adequate method. Although GC/MS also accomplishes good separation between and identification of all sterol analogs, the instrument is too expensive to use for routine analyses of cholesterol. 

Cholesterol oxidase shows relatively wide substrate specificity to 3(3-sterol analogs as shown in Table Dl.3.5 As discussed above, cholesterol contents of certain shellfish, which contain a relatively large amount of 3[3-sterol analogs, may be unreliable when determined by the enzymatic measurement as compared to results found using GC measurement, as shown in Table D 1.3.6 (Kushiro et al., 1980). 

Morohashi, A., Satake, M., Murata, K., Naoki, H., Kaspar, H.F., Yasumoto, T. 1995. Brevetoxin B3, a new brevetoxin analog isolated from the greenshell mussel Perna canaliculus involved in neurotoxic shellfish poisoning in New Zealand. Tetrahedron Letters "id, 8995-8998. 

Commonly used synonyms for these sources and types of toxicity include azaspiracid shellfish poisoning (AZP) caused by five azaspiracid analogs ... 

Chemical Abstracts Service Registry Number CAS 14277-97-5. Domoic acid, a glutamic acid analog that is resistant to temperature extremes, is an excitatory neurotoxin produced by a diatom and concentrated in shellfish. Ingestion leads to amnesic shellfish poisoning, which can also include seizures. Its relevance to use in warfare and terrorism, apart from its being unfamiliar to most disaster-response personnel, is that it is also easily absorbed by inhalation and across mucous membranes. No specific antitoxin is available, and treatment is supportive. 

Yanagi, T., Mnrata, M., Torigoe, K., and Yasumoto, T. Biological activities of semisynthetic analogs of dinophysistoxin-3, the major diarrhetic shellfish toxin. Agric. Biol. Chem., 53(2), 525-529, 1989. 

An important step for any analytical method is the sample extraction. The majority of these post-column derivatization HPLC methods apply, for shellfish samples, an extraction protocol based on the 959.08 AOAC Official Method [4] that uses hydrochloric acid with boiling. This leads to partial hydrolysis of certain PSP toxins (Cl, C2, and GTX5) into more toxic analogs (GTX2, GTX3, STX). 

Since the late 1980s, Sampayo et al. [163] observed an inverse relationship between mussel toxin levels and total phytoplankton concentrations at similar concentrations of Dinophysis spp., that is, toxin content in shellfish depended on the ratio between toxic phytoplankton cells and the total phytoplankton population. Further studies of Blanco et al. [31,164] showed the importance of intrinsic factors linked to bivalve physiology, and developed kinetic models that take environmental conditions (temperature, salinity, water column stability) into account, and the quantity and quality of food (chlorophyll concentration, seston) available to the bivalves. Concentrations of toxigenic cells and toxin content per cell are important parameters in these kinetic models of intoxication and detoxification. Obviously, in waters low in particulate organic matter, filter-feeders need to filter larger volumes to fulfill their nutritional needs. Blanco et al. [164] introdnced a new parameter, toxic quality of food, by analogy with the term food qnality commonly employed in assimilation models for bivalves. Dahl and Johannessen [165] recommended the use of the ratio between... 

FIGURE 13.1 Structures of yessotoxins, shown in their sulfonic acid forms, which were first reported from shellfish. The configuration at C-45 in 5 has been assigned by analogy with 2, as reported by Morohashi et al. ... 

The last YTX-analog from shellfish was found as a metabolic product in Norwegian blue mussels, M. edulis. Its structure, 45-hydroxycarboxyyessotoxin (45-hydroxycarboxyYTX, 15, Figure 13.1), was tentatively assigned on the basis of LC-MS evidence. ... 

Since 1997, when YTX was first isolated from Japanese scallops, more than 30 of its analogs have been identified in toxic shellfish and/or algal cultures. However, some of them represent the major compounds of the YTX-fraction of the biological extract, whereas others are only very minor constituents. 

The toxin profiles in contaminated shellfish clearly point to a structural modification of the absorbed YTX or homoYTX within the mollusk. It is to be noted, however, that, on the basis of the results reported in Table 13.3, the extent of the YTX metabolism within the mollusk greatly depends on the species of the host. Anyway, some YTX analogs, which are reported as very minor constituents of the algal extracts, are present in large quantities in contaminated shellfish 45-hydroxy YTX... 

Takahashi, H., Kusumi, T., and Kan, Y, Determination of the relative and absolute configuration of yessotoxin, a polyether compound implicated in diarrhetic shellfish poisoning, and its analogs, Tennen Yuki Kagobutsu Toronkai Koen Yoshishu, 38, 475, 1996. 

Ishida, H., et al., Brevetoxin B5, a new brevetoxin analog isolated from cockle, Austrovenus stutchburyi, the marker for monitoring shellfish neurotoxicity in New Zealand, Tetrahedron Lett., 45, 29-33, 2004b. 

---