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The HAB Five: Saxitoxin

Posted by Stephanie A. Smith, Ph.D., on Mon, May 11, 2015

Clams_muscles_shellfish_foodIn this fourth installment of the HAB Five, we’ll look at a little toxin with a big reputation.   Saxitoxin is one of the most potent natural neurotoxins ever described, and is best known as one of the “paralytic shellfish poisonings,” or PSPs.  If shellfish graze on algae that make saxitoxin, the shellfish can concentrate the toxin to dangerously high levels.  If you’re the unlucky consumer of saxitoxin-contaminated shellfish (raw oysters, anyone?), the outcome can range from perspiration to cardiac failure.   Due to its association with global foodborne illnesses, saxitoxins is thus one of the best-studied algae toxins.  Below are five fun facts about sax:

  • Saxitoxin was first isolated from the Alaskan butterclam (which I love saying out loud) in 1957 by Schantz et al. (J. Am. Chem. Soc. 79:5230).
  • There are now 57 analogs of saxitoxin found worldwide (Casero et al., 2014, Harmful Algae 37:28).
  • It wasn’t until the 1990s that it was realized that freshwater cyanobacteria could also produce saxitoxin (Humpage et al., Med. J. Aust., 1993, 159:423). In fact, today there are more known freshwater cyanobacteria than there are marine algae that can make saxitoxin!
  • In 1984 saxitoxin was artificially synthesized by Jacobi et al (J. Am. Chem. Soc. 106:5595). This is actually a lot harder to do than it sounds, so don’t get the misperception that someone can make mounds of saxitoxin.
  • The reason you don’t want that misperception is that saxitoxin is the only algal toxin on the “select agent” list of the Centers for Disease Control, due to its potential to be used as a biological weapon.

So I’ll leave you with that creepy last fact, which might make you relieved to learn that the next toxin we’ll talk about, microcystin, is much less deadly, even though it’s getting a LOT of attention these days.  Until next time…

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