Abstract
Focusing on tetramine, tetramethylammonium ion, contained in the salivary glands of marine carnivorous snails, this paper gives an overview of analytical methods, distribution in marine snails, and toxicological aspects. Some Neptunea snails have often caused food poisoning in North Atlantic and Northeast Asia regions, especially in Japan. The toxin of both N. arthritica and N. antiqua was first proven to be tetramine in 1960. Subsequent research on marine snail tetramine has progressed with the development of analytical methods. Of the various methods developed, the LC/ESI-MS method is most recommended for tetramine analysis in terms of sensitivity, specificity, and versatility. Accumulated data show that tetramine is ubiquitously contained at high concentrations (usually several mg/g) in the salivary glands of Neptunea snails. Tetramine is also found in the muscle and viscera of Neptunea snails and even in the salivary gland of marine snails other than Neptunea species, although mostly at low levels (below 0.1 mg/g). Interestingly, the major toxin in the salivary glands of Fusitriton oregonensis and Hemifusus tuba is distinguishable from tetramine. In tetramine poisoning, diverse symptoms attributable to the ganglion-blocking action of tetramine, such as visual disturbance, headache, dizziness, abdominal pain, and nausea, develop within 30 min after ingestion of snails because of rapid absorption of tetramine from the gastrointestinal tract. The symptoms are generally mild and subside in a short time (within 24 at most) because of rapid excretion through the kidney. However, it should be kept in mind that tetramine poisoning can be severe in patients with kidney dysfunction, as shown by two recent case reports. Finally, given the diffusion of tetramine from the salivary gland to the muscle during boiling and thawing of snails, removal of salivary glands from live snails is essential to avoid tetramine poisoning.
Highlights
A variety of toxins are distributed in marine carnivorous snails [1]
Based on the results described above, we propose that the best way to prevent tetramine poisoning incidents due to ingestion of Neptunea snails is to remove salivary glands from live specimens
This review summarized the findings obtained about tetramine in the salivary glands of marine carnivorous snails, which have often caused food poisoning
Summary
A variety of toxins are distributed in marine carnivorous snails [1]. Some of them, such as tetrodotoxin [2,3,4] and surugatoxins (neosurugatoxin and prosurugatoixn) [5,6,7], are exogeneous. Apart from the exogeneous toxins, endogenous toxins are present in the venom glands, hypobranchial glands, or salivary glands of marine carnivorous snails. Tetramine in marine snails has attracted little attention of researchers, such as natural products chemists and toxicologists. Reflecting on this situation, there has been no review article focusing on tetramine in marine snails for more than 30 years since that of Anthoni et al [23] published in 1989, tetramine has been only briefly mentioned in some reviews [1,24,25,26,27] on marine toxins or mollusk toxins. It should be noted that some of the scientific names described in this review are different from those in the original papers, since the taxonomy follows the World Register of Marine Species (WoRMS, https://www.marinespecies.org/, accessed on 10 November 2021)
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