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Shellfish are considered a delicacy by many consumers. In NZ, as in many overseas countries, there is a now thriv¬ing shellfish industry servicing both domestic and inter-national markets. Periodically shellfish accumulate harm¬ful levels of a variety of algal toxins, including domoic acid, yessotoxins, pectenotoxins and brevetoxins. When this occurs, regulatory authorities may impose harvesting closures which have a consequential economic impact on both farmers and staff employed to harvest and market shellfish products.
Marine algal toxins of the okadaic acid group can occur as fatty acid esters in blue mussels, and are commonly determined indirectly by transformation to their parent toxins by alkaline hydrolysis. Some data are available regarding the identity of the fatty acid esters, mainly of palmitic acid (16:0) derivatives of okadaic acid (OA), dinophysistoxin-1 (DTX1) and dinophysistoxin-2 (DTX2). Other fatty acid derivatives have been described, but with limited mass spectral data. In this paper, the mass spectral characterization of the [M H]- and [M+Na]+ ions of 16 fatty acid derivatives of each of OA, DTX1 and DTX2 is presented. The characteristic fragmentation of [M+Na]+ ions of OA analogues provided a useful tool for identifying these, and has not been described previously. In addition, a set of negative ion multiple reaction monitoring (M...
Marine algal toxins of the okadaic acid (OA) group can occur as diol esters and sulfated diol esters in algae and as fatty acid esters in shellfish. Several of these ester forms have been identified, but the most common procedure for detecting OA group toxin esters is by measuring the increase in parent toxin after alkaline hydrolysis. Use of this alkaline hydrolysis method led to the discovery of high levels of conjugates of OA and dinophysistoxins-2 (DTX2) in seawater and of OA, DTX1, and DTX2 in blue mussel hepatopancreas (HP) from Flødevigen, Norway, during a bloom of Dinophysis spp. In the water sample, a C8-diol ester, a C9-diol ester, and a previously undescribed C8-triol ester of OA were characterized using HPLC-MS2, -MS3, and -MS4 in combination with various derivatization procedures. Palmitic acid (16:0) ester derivatives of ...
Electrospray ionisation mass spectrometry (ES-MS) has been used to probe the coordination chemistry of metabolites such as sporidesmin D (spdD), found in the saprophytic fungus Pithomyces chartarum, and the related bisdethiobis(methylthio)gliotoxin (dimethylgliotoxin, Megtx). SpdD forms complexes of the type [spdD+M(MeCN)]+ and [2spdD+M]+ (M=Cu, Ag) and, at higher cone voltages, [spdD+M]+. The bis(ligand) ion [2spdD+M]+ was observed at very high cone voltages, indicating it has appreciable stability; the proposed structure of this species has a four-coordinate metal ion with two bidentate spdD ligands, coordinated through their SMe groups. 1H NMR titrations of spdD with K+, Ag+ and Cu+ provided additional evidence for complex formation with the soft metals. SpdD forms only relatively weak complexes with Zn2+, Cd2+, Co2+ and Mn2+, in ke...
Microcystins are a group of cyclic heptapeptides originating from cyanobacteria. Cyanobacteria also produce a range of peptides and other compounds that can result in complex chromatograms when samples are analyzed by LC-MS. Derivatization with appropriate thiols (e.g., mercaptoethanol) of the olefin in the alpha,beta-unsaturated amide present in most microcystins was shown to simplify analysis of LC-MS chromatograms of sample extracts, making it much easier to identify peaks corresponding to candidate microcystins. Furthermore, interpretation of MS2 spectra was facilitated by addition of the mass associated with the thiol to the alpha,beta-unsaturated amide of microcystins. Cyanotoxins containing Mdha or Dha reacted readily with thiols, whereas Mser, Ser, Mdhb, and thiol-derivatives of Mdha or Dha did not react under the conditions us...
Pinnatoxins and pteriatoxins are a group of cyclic imine toxins that have hitherto only been isolated from Japanese shellfish. As with other cyclic imine shellfish toxins, pinnatoxins cause rapid death in the mouse bioassay for lipophilic shellfish toxins, but there is no evidence directly linking these compounds to human illness. We have identified the known pinnatoxins A (1) and D (6), and the novel pinnatoxins E (7), F (8) and G (5), in a range of shellfish and environmental samples from Australia and New Zealand using LC−MS. After isolation from the digestive glands of Pacific oysters, the structures of the novel pinnatoxins were determined by mass spectrometry and NMR spectroscopy, and their LD50 values were evaluated by ip administration to mice. Examination of the toxin structures, together with analysis of environmental samples...
Microcystins are cyclic heptapeptides from cyanobacteria which are responsible for poisonings of livestock and humans. Cyanobacteria also produce a range of peptides and other compounds that can result in complex chromatograms when samples are analysed by LC–MS. Thiol derivatization of the α,β-unsaturated amide present in most microcystins was recently shown to simplify analysis of LC–MS chromatograms of a Microcystis culture, making it easier to identify peaks corresponding to microcystins in complex mixtures. This method was applied to analysis of extracts taken from a natural cyanobacteria bloom in Mwanza Gulf, Lake Victoria, Tanzania, in 2010, revealing the presence of numerous putative microcystin analogues in the sample. Results were verified using LC–MS², LC–MS/MS with precursor-ion scanning, and LC–HRMS, leading to identificati...
The resorcylic acid lactones zearalenone (1), α-zearalenol (2), β-zearalenol (3), α-zearalanol (zeranol) (4), β-zearalanol (taleranol) (5), and zearalanone (6) were converted to their glucuronides on a preparative scale in good yields. Reactions were conducted with bovine uridine 5′-diphosphoglucuronyl transferase (UDPGT) as catalyst and uridine 5′-diphosphoglucuronic acid (UDPGA) as cofactor. The glucuronides were isolated by column chromatography and characterized by NMR spectroscopy and mass spectrometry. Although the principal products were 4-O-glucuronides (i.e., linkage through a phenolic hydroxyl), significant quantities of the 6′-O-glucuronides (i.e., linkage through the aliphatic hydroxyl) of alcohols 2, 4, and 5 were also isolated. In the case of 3, the 2-O-glucuronide was isolated as the minor product. Overall isolated yield...
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