Azaspiracid-2 Quantitation and Analog Variability Characterisation in Shellfish from Šibenik Bay

Azaspiracids (AZAs) are marine polyether biotoxins produced by dinoflagellates that accumulate in filter-feeding organisms and pose a threat to human health and seafood safety. This study presents the first comprehensive analysis of azaspiracid analogs in shellfish from the Adriatic Sea including use of high-resolution mass spectrometry. AZA-2 was quantified in samples collected from Šibenik Bay between January and May 2024, with the highest concentrations observed in early January. In addition to AZA-2, several known analogs (AZA-6, AZA-9, AZA-10, AZA-19, AZA-41, AZA-43) and a potentially new analog (m/z 884.6066) were also detected. The fragmentation patterns of this new analog indicate a structural similarity to AZA-19 with a possible double bond modification. Potential pitfalls regarding misinterpretation of spectra derived from molecules containing 13C atoms were recognized. The presence of multiple analogs, some of which have high toxic potential, suggests that regulatory practice should consider including more than three analogs in the monitoring program.