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Okadaic acid (OA) and dinophysistoxins (DTXs) are a group of polyethers known to sometimes contaminate filter-feeding shellfish that cause symptoms classified as diarrhetic shellfish poisoning. The algae Dinophysis acuta is one pro-genitor of okadaic acid, DTX-1 and 2, and is found in coastal waters of Norway. The chemistry of the algal toxins is of particular importance, as testing methods are becoming more specific towards particular structures. DTX-2 for analysis by NMR was obtained through four isolation experiments. The isolated toxin will become standard reference material as set forth by EU’s BIOTOX program. DTX-2 from these experiments was used in NMR analyses for full assignment of the molecule in two deuterated solvents (CDCl3 and CD3OD). Concurrent analysis of DTX-1 by NMR in three different solvents (CDCl3, CD3OD, and CD3CN...
Okadaic acid (OA), dinophysistoxin-1 (DTX-1), and dinophysistoxin-2 (DTX-2) are algal toxins that can accumulate in shellfish and cause diarrhetic shellfish poisoning. Recent studies indicate that DTX-2 is about half as toxic and has about half the affinity for protein phosphatase 2A (PP2A) as OA. NMR structural studies showed that DTX-1 possessed an equatorial 35-methyl group but that DTX-2 had an axial 35-methyl group. Molecular modeling studies indicated that an axial 35-methyl could exhibit unfavorable interactions in the PP2A binding site, and this has been proposed as the reason for the reduced toxicity of DTX-2. Statistical analyses of published data indicate that the affinity of PP2A for DTX-1 is 1.6-fold higher, and for DTX-2 is 2-fold lower, than for OA. We obtained X-ray crystal structures of DTX-1 and DTX-2 bound to PP2A. T...
A cis-isomer of a C8-diol ester of okadaic acid (1) was isolated during large-scale purification of pectenotoxins (PTXs) from extracts of Dinophysis acuta collected from the west coast of South Island, New Zealand. The compound was identified by NMR spectroscopic and liquid chromatography-mass spectrometry (LC-MS) studies, and is the first reported cis-isomer of an okadaic acid C₈-diol-ester identified in Dinophysis. The more abundant trans-C₈-diol ester of okadaic acid (2) isolated from the same Dinophysis extract was rapidly hydrolyzed to okadaic acid in vitro by the supernatant from green-lipped mussel hepatopancreas.
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