Determination of PSP Toxins in Moroccan Shellfish by MBA, HPLC and RBA Methods: Links to Causative Phytoplankton Alexandrium minutum

Abstract

Paralytic shellfish poisoning (PSP) toxins are secondary metabolites of the toxic species of phytoplankton. The consumption of shellfish accumulating these toxins can cause neurological symptoms and even death. Within the framework of the surveillance program of seafood safety along the Moroccan littoral environment established by National Institute of Fisheries Research (INRH), a study of PST was conducted from 2004 to 2016 in south Moroccan’s shellfish, mussels from south Agadir region and Razor Shell from Dakhla bay. The surveillance was carried out bi-monthly or weekly using the AOAC official method of analysis (AOAC 959.08) mouse bioassay (MBA). In parallel, monitoring of toxic phytoplankton in water was conducted.  With the aim to determine the shellfish toxin profile, ion-pair high-performance liquid chromatography with post-column derivatisation and fluorescence detection (HPLC-FD) was performed. The Receptor Binding Assay (RBA) also was used for determination of total toxicity of PSP toxins in Agadir’s mussels. In both regions, the analysis of seawater revealed the presence of the toxic algae Alexandrium spp during toxics events. Along the coast of Agadir, PSP toxins in shellfish were associated with the presence of Alexandrium cf. minutum in seawater. These toxic events were widely distributed in time and space and mainly detected during the summer and fall seasons. In some samples concentrations exceeded the sanitary threshold (ST) of 800 μg eq STX /kg. HPLC analysis revealed that Saxitoxin and Gonyautoxins dominated the toxin profile. The comparison between different methods showed a strong uphill (positive) linear relationship, with a coefficient correlation of r=0.79 between MBA and HPLC and r = 0.809 between MBA and RBA.