Solid phase extraction for removal of matrix effects in lipophilic marine toxin analysis by liquid chromatography-tandem mass spectrometry

The potential of solid phase extraction (SPE) clean-up has been assessed to reduce matrix effects (signal suppression or enhancement) in the liquid chromatography-tandem mass spectrometry (LC¿MS/MS) analysis of lipophilic marine toxins. A large array of ion-exchange, silica-based, and mixed-function SPE sorbents was tested. Polymeric sorbents were found to retain most of the toxins. Optimization experiments were carried out to maximize recoveries and the effectiveness of the clean-up. In LC¿MS/MS analysis, the observed matrix effects can depend on the chromatographic conditions used, therefore, two different HPLC methods were tested, using either an acidic or an alkaline mobile phase. The recovery of the optimized SPE protocol was around 90% for all toxins studied and no break-through was observed. The matrix effects were determined by comparing signal response from toxins spiked in crude and SPE-cleaned extracts with those derived from toxins prepared in methanol. In crude extracts, all toxins suffered from matrix effects, although in varying amounts. The most serious effects were observed for okadaic acid (OA) and pectenotoxin-2 (PTX2) in the positive electrospray ionization mode (ESI+). SPE clean-up on polymeric sorbents in combination with the alkaline LC method resulted in a substantial reduction of matrix effects to less than 15% (apparent recovery between 85 and 115%) for OA, yessotoxin (YTX) in ESI¿ and azaspiracid-1 (AZA1), PTX2, 13-desmethyl spirolides C (SPX1), and gymnodimine (GYM) in ESI+. In combination with the acidic LC method, the matrix effects after SPE were also reduced but nevertheless approximately 30% of the matrix effects remained for PTX2, SPX1, and GYM in ESI+. It was concluded that SPE of methanolic shellfish extracts can be very useful for reduction of matrix effects. However, the type of LC and MS methods used is also of great importance. SPE on polymeric sorbents in combination with LC under alkaline conditions was found the most effective method

Not all shellfish "allergy" is allergy!

The popularity of shellfish has been increasing worldwide, with a consequent increase in adverse reactions that can be allergic or toxic. The approximate prevalence of shellfish allergy is estimated at 0.5-2.5% of the general population, depending on degree of consumption by age and geographic regions. The manifestations of shellfish allergy vary widely, but it tends to be more severe than most other food allergens

The role of interactions between Prorocentrum minimum and Heterosigma akashiwo in bloom formation

We examined the growth and interactions between the bloom-forming flagellates Prorocentrum minimum and Heterosigma akashiwo using bi-algal culture experiments. When both species were inoculated at high cell densities, growth of H. akashiwo was inhibited by P. minimum. In other combinations of inoculation densities, the species first reaching the stationary phase substantially suppressed maximum cell densities of the other species, but the growth inhibition effect of P. minimum was stronger than that of H. akashiwo. We used a mathematical model to simulate growth and interactions of P. minimum and H. akashiwo in bi-algal cultures. The model indicated that P. minimum always out-competed H. akashiwo over time. Additional experiments showed that crude extracts from P. minimum and H. akashiwo cultures did not affect the growth of either species, but both strongly inhibited the growth of the bloom-forming diatom Skeletonema costatum. Further experiments showed that it was unlikely that reactive oxygen species produced by H. akashiwo were responsible for the inhibition of P. minimum growth

Azaspiracid Toxins: Toxicological Profile

Azaspiracids (AZAs) are a toxin group that originate from marine dinoflagellates of the genera Azadinium and Amphidoma. After accumulation of these toxins in edible marine organisms and their subsequent consumption, humans develop a gastrointestinal syndrome referred to as azaspiracid shellfish poisoning (AZP). This syndrome is very similar to diarrheic shellfish poisoning (DSP), with main symptoms appearing after a few hours from consumption and including diarrhea, vomiting, and stomach cramps. Due to extensive metabolism in shellfish, more than 30 analogues have been reported to date, and purified compounds for selected analogues have recently been made available for toxicological studies. Currently, only AZA1, AZA2, and AZA3 are regulated in Europe and internationally; however, more recent evidence suggests that AZA6, AZA17, and AZA19 may also be analogues of importance for estimating the full risk of seafood. Even though animal studies have pointed out target organs (digestive tract, liver, heart, and lung), mechanism of action studies at cellular level are not yet conclusive. While a number of common targets have been excluded (protein phosphatases, kinases, actin depolymerization, G protein-coupled receptors), some evidence points toward ion channel activity of AZAs. Still, in vitro studies do not correlate well with symptoms observed in humans. Also, while some animal studies point toward longer-term effects, no such evidence has been reported from human poisoning events. However, it should be noted that in-depth epidemiological studies are still lacking. Even though all risk assessments have based their evaluation on a single, relatively early poisoning event in 1997, in Arranmore Island, Ireland, producing organisms and toxin occurrences have been reported worldwide, and further occurrence studies should provide a better base for such epidemiological studie