Two high-mass polar compounds were observed in aqueous side-fractions from the purification of okadaic acid (
1) and dinophysistoxin-2 (
2) from
Dinophysis blooms in Spain and Norway. These were isolated and shown to be 24-
O-β-
d-glucosides of
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Two high-mass polar compounds were observed in aqueous side-fractions from the purification of okadaic acid (
1) and dinophysistoxin-2 (
2) from
Dinophysis blooms in Spain and Norway. These were isolated and shown to be 24-
O-β-
d-glucosides of
1 and
2 (
4 and
5, respectively) by nuclear magnetic resonance (NMR) spectroscopy, mass spectrometry, and enzymatic hydrolysis. These, together with standards of
1,
2, dinophysistoxin-1 (
3), and a synthetic specimen of 7-deoxy-
1 (
7), combined with an understanding of their mass spectrometric fragmentation patterns, were then used to identify
1–
5, the 24-
O-β-
d-glucoside of dinophysistoxin-1 (
6),
7, 7-deoxy-
2 (
8), and 7-deoxy-
3 (
9) in a range of extracts from
Dinophysis blooms,
Dinophysis cultures, and contaminated shellfish from Spain, Norway, Ireland, Canada, and New Zealand. A range of
Prorocentrum lima cultures was also examined by liquid chromatography–high resolution tandem mass spectrometry (LC–HRMS/MS) and was found to contain
1,
3,
7, and
9. However, although
4–
6 were not detected in these cultures, low levels of putative glycosides with the same exact masses as
4 and
6 were present. The potential implications of these findings for the toxicology, metabolism, and biosynthesis of the okadaic acid group of marine biotoxins are briefly discussed.
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