Content area
Full text
Among marine toxins, tetrodotoxin (TTX) and paralytic shellfish poisons (PSPs) have frequently been found along the coasts of Southeast Asia, including China [1], Vietnam [2,3], Thailand [4,5], Cambodia [6,7], Malaysia [8], and the Philippines [9,10]. TTX was originally discovered and isolated from puffer fish in 1964 [11]. Later, it was found in many other organisms from terrestrial [12] and marine habitats [13–15]. The molecular formula of TTX is C11H17O8N3 (molecular weight ＝ 319 Da), which has more than 10 analogs, and TTX owns the highest toxicity among them [11,14]. The molecule consists of a positively charged guanidinium group and a pyrimidine ring that helps stabilize the TTX–sodium channel binding complex at the aqueous interface (Fig. 1A).
In the past decades, PSPs have been responsible for the most severe seafood poisoning in humans worldwide [1,15–20]. The source of PSPs in Vietnam was thought to be the toxic dinoflagellates, including Alexandrium minutum and Alexandrium affine [3,21,22]. The PSP toxins from a group of closely related tetrahydropurine compounds can be categorized into up four subgroups: carbamate, N-sulfocarbamoyl, decarbamoyl, and deoxydecarbamoyl components, including saxitoxin (STX), neosaxitoxin (neo-STX), several gonyautoxins (GTXs), and their variants (Fig. 1B), which act by blocking the flux of sodium ions through voltage-gated sodium channels on excitable cell membranes. GTXs, especially GTX 1,4 epimers and GTX 2,3 epimers, are most abundant in mollusk extract samples, being around 75–85% of the total toxin content in most of the samples analyzed, indicating that they account for the high toxicity of the shellfish in China, Chile, and South America. Different GTXs may have different toxicities and may be converted to/from each other through various mechanisms [3,7,23].
In Vietnam, the first evidence of TTX association with food poisoning was the intoxication of six humans after ingesting puffer fish [2]. PSP and TTX compounds have been linked to seafood poisoning involving gastropods of the genera Nassariidae, Naticidae, and Olividae in China, Taiwan, Japan, Hong Kong, Malaysia, and Australia [17,20,24–27].
We undertook further examination of the lethal potency of gastropods consumed in Vietnam because of food safety concerns. To determine the toxicity of various compounds,...