Fatty acid esters of azaspiracids identified in mussels (Mytilus edulis) using liquid chromatography-high resolution mass spectrometry

Abstract

Azaspiracids (AZAs) are lipophilic polyether toxins produced by Azadinium and Amphidoma species of marine microalgae. The main dinoflagellate precursors AZA1 and AZA2 are metabolized by shellfish to produce an array of AZA analogues. Many marine toxins undergo fatty acid esterification in shellfish, therefore mussel tissues contaminated with AZAs were screened for intact fatty acid esters of AZAs using liquid chromatography-high resolution mass spectrometry. Acyl esters were primarily observed for AZAs containing hydroxy groups at C-3 with 3- O -palmitoylAZA4 identified as the most abundant acyl ester, while other fatty acid esters including 18:1, 16:1, 17:0, 20:2 and 18:0 acyl esters were detected. The structures of these acyl derivatives were determined through LC-MS/MS experiments, and supported by periodate cleavage reactions and semi-synthesis of palmitate esters of the AZAs. Esters of the hydroxy groups at C-20 or C-21 were not observed in mussel tissue. The relative proportion of the most abundant AZA ester was less than 3% of the sum of the major free AZA analogues. These findings reveal an additional metabolic pathway for AZAs in shellfish.

Current Trends and New Challenges in Marine Phycotoxins

“…It should be also considered that AZAs accumulate in shellfish tissues and have the potential to be metabolized similarly to other lipophilic toxins [ 220 ]. However, AZA analogues have different toxicity, probably due to their specific molecular structures [ 221 ].…”

Emerging Marine Biotoxins in European Waters: Potential Risks and Analytical Challenges

“…The responsible analogue was identified as AZA-1 and the main symptoms were nausea, vomiting, diarrhea, and stomach cramps [ 72 ]. Today, the AZAs group consist of more than 60 compounds [ 21 ] and is mainly produced by dinoflagellates from genera Azadinium and Amphidoma [ 73 ]. For example, the species Azadinium poporum was proofed to produce AZA-2, -11, -36, -37, -40, -41, -42, -59, and -62, while Azadinium spinosum releases AZA-1, -2, -11, 33, -34, -35, -50, and -51; Azadinium dexteroporum produces epi -AZA-7, AZA-35, 54, -55, -56, -57, and -58; and Amphidoma languida produces AZA-2, -38, -39, -43, -52, and -53 [ 70 ].…”

“…For example, the species Azadinium poporum was proofed to produce AZA-2, -11, -36, -37, -40, -41, -42, -59, and -62, while Azadinium spinosum releases AZA-1, -2, -11, 33, -34, -35, -50, and -51; Azadinium dexteroporum produces epi -AZA-7, AZA-35, 54, -55, -56, -57, and -58; and Amphidoma languida produces AZA-2, -38, -39, -43, -52, and -53 [ 70 ]. Some other AZAs are metabolites and products from oxidation, hydroxylation, decarboxylation, and dehydration occurring in shellfish [ 21 , 74 ]. AZA-17 and AZA-19 were found to be the main mussel metabolites of AZA-1 and AZA-2, respectively.…”

“…Among these emerging marine biotoxins, cyclic imines (CIs), which comprise the lipophilic compounds spirolides (SPXs), gymnodimines (GYMs), and pinnatoxins (PnTXs), may entail harmful effects on human health. Another example is the AZAs group which nowadays consists of more than 60 compounds with different toxicity [ 21 ]. In addition, the presence in Europe of toxins from other latitudes like ciguatoxins (CTXs) increases the need for continued renovation of the information available and a methodology update.…”

“…In addition, the presence in Europe of toxins from other latitudes like ciguatoxins (CTXs) increases the need for continued renovation of the information available and a methodology update. Having the same molecular target, brevetoxins (BTXs), responsible for neurotoxic shellfish poisoning syndrome, have become more prevalent in European waters in recent years [ 21 ]. Tetrodotoxins (TTXs) were first reported in Europe in 2008 [ 22 ], and, since then, the number of reports has increased substantially [ 23 , 24 , 25 , 26 ].…”