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Portimine, a new polycyclic ether toxin containing a cyclic imine moiety, was isolated from the marine benthic dinoflagellate Vulcanodinium rugosum collected from Northland, New Zealand. The structure of portimine, including the relative configurations, was elucidated by spectroscopic analyses. The cyclic imine moiety consists of an unprecedented five-membered ring with a spiro-link to a cyclohexene ring. This is the only structural similarity to the pinnatoxin group of polycyclic ethers also produced by V. rugosum, which all contain a six-membered cyclic imine ring. The LD50 of portimine to mice by intraperitoneal injection was 1570 μg/kg, indicating a much lower toxicity than many other cyclic imine shellfish toxins. In contrast, portimine was highly toxic to mammalian cells in vitro with an LC50 to P388 cells of 2.7 nM, and activati...
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...
The microcystin content and cyanobacterial community structure of Antarctic microbial mat samples collected from 40 ponds, lakes and hydro-terrestrial environments were investigated. Samples were collected from Bratina Island and four of the Dry Valleys; Wrights, Victoria, Miers and Marshall. Enzyme-linked immunosorbent assays (ELISA), liquid chromatography mass spectrometry (LC-MS), and protein phosphatase inhibition assays (PP-2A) resulted in the identification of low levels (1 - 16 mg/kg dry weight) of microcystins in all samples. A plot of indicative potencies of microcystins (ratio PP-2A:ELISA) versus total microcystins (ELISA) showed a general decrease in potency as total microcystin levels increased and a clustering of values from discrete geographic locations. LC-MS/MS analysis on selected samples identified eight novel microc...
animals and people consuming seafood. Brevetoxin-B2 (5) is a toxic metabolite produced in shellfish exposed to algae that contain brevetoxin-B (1). S-Desoxybrevetoxin-B2 (4) has been proposed as a cometabolite produced during this transformation, and while LC-MS analyses suggest its presence in shellfish, it has not yet been isolated and characterized. Studies on these materials are severely constrained by the difficulty of obtaining and purifying them from natural sources. We have developed a convenient one-pot conversion of commercially available brevetoxin-B (1) into S-desoxybrevetoxin-B2 (4), and a simple method for converting 4 into brevetoxin-B2 (5). Full NMR and mass-spectral characterization of 4 and 5 confirmed their structures and showed that the ratio of diastereoisomers in the synthetic 4 and 5 was similar to that observed ...
Two novel pectenotoxins (PTXs), PTX-13 and -14, were isolated from extracts of Dinophysis acuta collected from the west coast of South Island, New Zealand. The compounds were identified as oxidized analogues of PTX-2 by NMR spectroscopic and LC-MS studies. PTX-13 (32R-hydroxyPTX-2) corresponds to the unidentified analogue PTX-11x reported by [Suzuki et al., 2003. Liquid chromatography-mass spectrometry of spiroketal stereoisomers of pectenotoxins and the analysis of novel pectenotoxin isomers in the toxic dinoflagellate Dinophysis acuta from New Zealand. J. Chromatogr. A 992, 141–150]. PTX-13 underwent slow deuteration at the 13β-position during NMR analysis. PTX-14 corresponds to the 32,36-dehydration product of PTX-13, and may be an artifact.
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