Neurotoxins saxitoxins

Figure 1. PSP neurotoxins saxitoxin-STX, gonyautoxin-GTX, neosaxitoxin-NEO, and B1-C4 are sulfocarbamoyl toxins.

Neurotoxin Saxitoxin. Shell fish toxin ganglion blocker where the guanidinium groups act as an NR4+ group cf. curare (see text)... 

The powerful human neurotoxin saxitoxin, present in the dinoflagellate Alexandrium (Gonyauhix) cantenella, incorporates a reduced form of the purine-2,8-diamine cation in its... 

Cyanobacteria toxins (sometimes referred to as blue green algal toxins) are represented in this entry by Aplysiatoxins, which are toxic to the skin, and anatoxin a (CAS 64285-06-9, C10H15NO) and anatoxin a (S) (very fast death factor), which are neurotoxins. Saxitoxin, discussed earlier, and neo-saxitoxin are both neurotoxins that may also be classified as cyanobacterial toxins. A large variety of other toxins is produced by cyanobacteria, but is not as well documented. These include lyngbyatoxin (dermatotoxic) cyclic peptides predominantly microcystins, nodularins, and cylindro-spermopsin (hepatotoxins) endotoxins and other substances as yet undescribed, including additional tumor promoters. 

Stiiken A, Orr RJ, Kelhnann R, Murray SA, Neilan BA, Jakobsen KS (2011) Discovery of nuclear-encoded genes for the neurotoxin saxitoxin in dinoflagellates. PLoS One 6 e20096. doi 10.1371/joumal.pone.0020096... 

Figure 9 A stereo view of a superposition of two marine neurotoxins, saxitoxin (8 dashed line) and tetrodotoxin (9), using the method of Danzinger and Dean. The atoms superimposed are shown in bold.

Cusick, K.D., Sayler, G.S., 2013. An overview on the marine neurotoxin, saxitoxin genetics, molecular targets, methods of detection and ecological functions. Mar. Drugs 11 (4), 991-101. ... 

The tetrodotoxins (TTXs) and saxitoxins (STXs) have in common the ability to block sodium channels of excitable membranes (1—5), Saxitoxin and tetrodotoxin are some of the most potent non-proteinaceous neurotoxins known and are responsible for significant human morbidity and mortality (6, 7). Although for many years the biosynthetic origin(s) of TTXs and STXs has not been identified, recent evidence indicates that bacteria may be a source. 

Neurotoxins, such as saxitoxin and anatoxin-a, have been implicated in mediating competitive interactions between toxic cyanobacteria and other photoautotrophs, but few studies have explicitly examined the allelopathic effects of these compounds (e g., Kearns and Hunter 2001). Although it is reasonable to assume that these compounds bind to algal and cyanobacterial sodium channels in a similar fashion as in vertebrate neurons, support for this hypothesis is currently lacking. 

The saxitoxins from dinoflagellates of the genus Protogonyaulax may accumulate in shellfish and, being potent neurotoxins, pose a serious threat to public health. Six of the saxitoxins are sulfamates which have relatively low toxicity, but are easily hydrolyzed to the respective carbamates with corresponding increases in potency. This paper presents some of the chemistry and public health implications of these toxins. 

The neurotoxins isolated from Aph. flos-aquae were shown to have similar chemical and biological properties to paralytic shellfish poisons (PSP) (25,29,38) Sawyer et al. in 1968 (25) were the first to demonstrate that the crude preparation of aphantoxins behave like saxitoxin, the major paralytic shellfish poison. They showed that the toxins had no effect on the resting membrane potential of frog sartorius muscle blocked action potential on de-sheathed frog sciatic nerve and also abolished spontaneous contractions in frog heart. Sasner et al. (1981) (29) using the lab cultured strain reported similar results. 

A number of compounds listed in Table 16.1 have not proved suitable as drug candidates but are being used as molecular probes that may facilitate the identification of new targets and the discovery of new drug candidates. These compounds include manoalide, okadaic acid, and neurotoxins such as saxitoxin and tetrodotoxin.25... 

Saxitoxin is a neurotoxin produced by certain species of dinoflagellates, cyanobacteria and, most famously, many species of both marine and freshwater pufferfish. The toxin is found throughout these fish, from internal organs through... 

Saxitoxin (32) is listed in Schedule 1 of the CWC. It is a polar, cationic, relatively low molecular mass toxin and is one of 18 structurally related neurotoxins collectively known as paralytic shellfish poisoning (PSP) toxins. Analogues are formed by addition of sulfate, A-sulfo and A-hydroxyl groups, and by decarbamylation. They block neuronal sodium channels, and thereby neurotransmission, death resulting from respiratory paralysis. Saxitoxin is produced by dinoflagellate species (and by some freshwater cyanobacteria), and accumulates in shellfish. The cationic nature of saxitoxin makes capillary electrophoresis combined with... 

Saxitoxin (STX) is a potent neurotoxin that can cause paralytic shellfish poisoning (PSP). Produced by certain strains of dinoflagellates, saxitoxin leads to the contamination of commercial shellfish and cause severe outbreaks of seafood poisoning. The public health problems caused by these outbreaks have led to significant interest in the development of analytical methods for the analysis of saxitoxin in environmental and biological samples. Saxitoxin is also one of a series of several closely related... 

Marine dinoflagellates produce a number of toxins, such as saxitoxin, surugatoxin, tetrodotoxin, and gonyautoxin, that affect ion channels (Table IV). These algae are eaten by some copepods, fish, and molluscs that also store these neurotoxins 4,17,28,29,494,495). As a consequence, these animals have acquired chemical defense compounds, which they can use against predators. 

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