A Sensitive LC-MS/MS Method for Palytoxin Using Lithium Cationization

Investigating the etiology of Haff disease: Optimization and validation of a sensitive LC-MS/MS method for palytoxins analysis in directly associated freshwater and marine food samples from Brazil

Haff disease typically develops after eating contaminated marine or freshwater species, especially fish. Despite still having an unknown etiology, recent reports have suggested its possible correlation with palytoxins. Therefore, the present work aimed to optimize and perform a validation of a sensitive method using liquid chromatography coupled with tandem mass spectrometry (LC-MS/MS) for the analysis of palytoxin and some of its analogs, with the main purpose of investigating their presence in marine and freshwater food samples associated with Haff disease in Brazil. The method optimization was performed using a central composite rotatable design and fish samples fortified with the palytoxin standard. Then, the optimized method was validated for different food matrices, including freshwater and marine fish, mollusks, and crustaceans. The sample preparation involved a solid-liquid extraction using methanol and water, solid-phase extraction using Strata-X cartridges, and on-column palytoxin oxidation. The detection of the main oxidized fragments (amino and amide aldehydes) was achieved by LC-MS/MS with electrospray ionization in positive mode, using a C18 column, as well as acetonitrile and water as mobile phases, both acidified with 0.1 % of formic acid. After optimization and validation, the etiological investigation involved the analysis of 16 Brazilian Haff disease-related food samples (in natura and leftover meals) from 2022. The method was demonstrated to be appropriate for quantitative analysis of freshwater and marine species. So far, it has proven to be one of the most sensitive methods related to palytoxin detection (LOD 10 μg/kg), being able to work in a range that includes the provisional ingestion limit (30 μg/kg). Regarding the Haff disease-related samples analysis, there is a strong indication of palytoxin contamination since the amino aldehyde (common fragment for all palytoxins) was detected in 15 of the 16 samples. Selected results were confirmed using liquid chromatography coupled with high-resolution mass spectrometry (LC-HRMS).

Detection of Extremely Low Level Ciguatoxins through Monitoring of Lithium Adduct Ions by Liquid Chromatography-Triple Quadrupole Tandem Mass Spectrometry

Ciguatera poisoning (CP) is the most common type of marine biotoxin food poisoning worldwide, and it is caused by ciguatoxins (CTXs), thermostable polyether toxins produced by dinoflagellate Gambierdiscus and Fukuyoa spp. It is typically caused by the consumption of large fish high on the food chain that have accumulated CTXs in their flesh. CTXs in trace amounts are found in natural samples, and they mainly induce neurotoxic effects in consumers at concentrations as low as 0.2 µg/kg. The U.S. Food and Drug Administration has established CTX maximum permitted levels of 0.01 µg/kg for CTX1B and 0.1 µg/kg for C-CTX1 based on toxicological data. More than 20 variants of the CTX1B and CTX3C series have been identified, and the simultaneous detection of trace amounts of CTX analogs has recently been required. Previously published works using LC-MS/MS achieved the safety levels by monitoring the sodium adduct ions of CTXs ([M+Na]+ > [M+Na]+). In this study, we optimized a highly sensitive method for the detection of CTXs using the sodium or lithium adducts, [M+Na]+ or [M+Li]+, by adding alkali metals such as Na+ or Li+ to the mobile phase. This work demonstrates that CTXs can be successfully detected at the low concentrations recommended by the FDA with good chromatographic separation using LC-MS/MS. It also reports on the method's new analytical conditions and accuracy using [M+Li]+.

[Universal Method for Determination of Ciguatoxins by LC-MS/MS]

Ciguatera poisoning (CP) is one of the most frequent seafood poisonings across the globe. CP results from the consumption of fish flesh that has accumulated principal toxins known as ciguatoxins (CTXs), and it mainly occurs in tropical and subtropical regions. In Japan, incidents of CP have been reported primarily from Okinawa and Amami Islands in the subtropical area. Meanwhile, there have also been reports from Mainland sporadically. Since the amount of CTXs contained in fish flesh is extremely low, a highly sensitive detection method by LC-MS/MS is required. But the currently reported detection method is applicable only to specific equipment, and many laboratories have difficulty to respond CP. In this study, to prepare for the risk of nationwide CP, we researched a universal analytical method for CTXs based on LC-MS/MS. Using a water/acetonitrile mobile phase supplemented with lithium hydroxide and formic acid gave rise to prominent peaks of the stable [M+Li]+ions. As the [M+Li]+ions did not produce valid product ions even with high collision energy, the [M+Li]+ions of each analog were set for both precursor and product ions ([M+Li]+>[M+Li]+) and monitored under the multiple reaction monitoring (MRM) mode. With the method described above, analyses of nine CTX congeners were carried out. The limit of detection (LOD, S/N>5) and quantitation (LOQ, S/N>10) were estimated as 0.005-0.030 ng/mL and 0.010-0.061 ng/mL, respectively. When the 1 mL of extract solution is prepared from 5 g of the fish tissue, the LOD and LOQ will be at 0.001-0.006 μg/kg and 0.002-0.012 μg/kg, respectively. This result indicates that we could detect the required level of 0.175 μg/kg CTX1B equivalent in fish flesh which is recommended for safe consumption in Japan. This method is considered to be a universal analytical method without depending on the specific equipment. Thus it could contribute to improving the CP investigations in nationwide laboratories.

Recent advancements in LC-MS based analysis of biotoxins: Present and future challenges

There has been a rising concern regarding the harmful impact of biotoxins, source of origin, and the determination of the specific type of toxin. With numerous reports on their extensive spread, biotoxins pose a critical challenge to figure out their parent groups, metabolites, and concentration. In that aspect, liquid chromatography-mass spectrometry (LC-MS) based analysis paves the way for its accurate identification and quantification. The biotoxins are ideally categorized as phytotoxins, mycotoxins, shellfish-toxins, ciguatoxins, cyanotoxins, and bacterial toxins such as tetrodotoxins. Considering the diverse nature of biotoxins, both low-resolution mass spectrometry (LRMS) and high-resolution mass spectrometry (HRMS) methods have been implemented for their detection. The sample preparation strategy for complex matrix usually includes "QuEChERS" extraction or solid-phase extraction coupled with homogenization and centrifugation. For targeted analysis of biotoxins, the LRMS consisting of a tandem mass spectrometer operating in multiple reaction monitoring mode has been widely implemented. With the help of the reference standard, most of the toxins were accurately quantified. At the same time, the suspect screening and nontarget screening approach are facilitated by the HRMS platforms during the absence of reference standards. Significant progress has also been made in sampling device employment, utilizing novel sample preparation strategies, synthesizing toxin standards, employing hybrid MS platforms, and the associated data interpretation. This critical review attempts to elucidate the progress in LC-MS based analysis in the determination of biotoxins while pointing out major challenges and suggestions for future development.

Functional and Structural Biological Methods for Palytoxin Detection

Palytoxin (PLTX) and its analogues are marine polyethers identified in Palythoa and Zoanthus corals, Ostreopsis dinoflagellates, and Trichodesmium cyanobacteria. Humans can be exposed to these toxins by different routes with a series of adverse effects but the most severe risk is associated with poisonings by the consumption of edible marine organisms accumulating these toxins, as occurs in (sub)-tropical areas. In temperate areas, adverse effects ascribed to PLTXs have been recorded after inhalation of marine aerosols and/or cutaneous contact with seawater during Ostreopsis blooms, as well as during cleaning procedures of Palythoa-containing home aquaria. Besides instrumental analytical methods, in the last years a series of alternative or complementary methods based on biological/biochemical tools have been developed for the rapid and specific PLTX detection required for risk assessment. These methods are usually sensitive, cost- and time-effective, and do not require highly specialized operators. Among them, structural immunoassays and functional cell-based assays are reviewed. The availability of specific anti-PLTX antibodies allowed the development of different sensitive structural assays, suitable for its detection also in complex matrices, such as mussels. In addition, knowing the mechanism of PLTX action, a series of functional identification methods has been developed. Despite some of them being limited by matrix effects and specificity issues, biological methods for PLTX detection represent a feasible tool, suitable for rapid screening.

Toxicity of crude organic extracts from the zoanthid Palythoa caribaeorum: A biogeography approach

Marine isolates such as palytoxin (PTX) are of concern within the Caribbean region due to their toxicity. PTX for example has been described as a one of the most known potent marine toxins, known to prevent predation from larger species (e.g. vertebrates) as well as the prevention of being overgrown from other coral species. PTX is a polyhydroxylated polyether toxin with a very large and complex chemical structure that possesses both hydrophilic and lipophilic properties. Previous acute toxicity tests using brine shrimp (Artemia salina) and PTX extract had shown it to be moderately toxic. In humans, PTX has been credited to be responsible for extreme symptoms such anaphylactic shock, rapid cardiac failure and eventual death occurring within minutes. Extrapolation for human dose ranges has therefore been suggested to be between 2.3 and 31.5 μg. This study isolates a potentially PTX-enriched extract from Palythoa caribaeorum and examines its organic extract toxicity from a biogeography perspective from a within-colony to a variety of reef sites around Trinidad and Tobago that are popular for marine visitors. This research represents an acute study with a high level of crude organic extract toxicity on A. salina whilst postulating potential factors which may contribute to its extreme toxicity and the risk posed to users of these environments.

Emerging Marine Biotoxins

The emergence of marine biotoxins in geographical areas where they have never been reported before is a concern of considerable impact on seafood contamination, and consequently, on public health [...].