This chapter describes the chemical characteristics of azaspiracids (AZAs) to complete the view on this toxin group, with two other chapters in this book dedicated to toxicological1 and ecological aspects.2 AZAs are a group of polyether toxins first reported to cause food poisoning in 1995.3,4 Since then, a small number of food poisoning incidents have occurred, and it is now accepted that this group of compounds requires regulation to protect public health.5–8 At least six risk assessments have been carried out over the last decade to determine appropriate levels for regulatory limits in order to protect public health,1 yet all these assessments are based on a single poisoning incident in 1997 and attempt to set levels based on the presence of just three analogues: AZA1, AZA2, and AZA3. Over the last 5 years, more than 30 additional analogues have been described, with both biotransformation in shellfish and chemical interconversion shown to contribute to the chemical diversity of this toxin group.
In the following sections, we review AZAs to distinguish those analogues that are formed by the microalgae themselves from those that are formed by biotransformation or by chemical modification during extraction or sample treatment. Subsequently, chemical characteristics such as solubility and pH and thermal stability are reviewed. Methods for discovery of AZA analogues are discussed, including bioassays and chemical techniques. Finally, methodology for detection and quantitation is reviewed with consideration of quality control in routine analytical settings.