Mitotoxin

Maitotoxin is the toxin that causes ciguatera poisoning. Maitotoxin was named from the ciguateric fish Ctenochaetus striatus&mdash;called “maito” in Tahiti&mdash;from which maitotoxin was isolated for the first time. Later on, it was revealed that maitotoxin is made by the dinoflagellate Gambierdiscus toxicus.

The toxicity of maitotoxin to mice is the highest in nonprotein toxins: the LD50 is 50 ng/kg. Maitotoxin induces Ca2+ influx into cell lines when its concentration is nanomolar to picomolar, and at lower concentrations than picomolar, maitotoxin stimulates degradation of inositol phosphate. The mechanisms of the activities have not been determined yet.

Maitotoxin's molecular formula is C164H256O68S2Na2, and its molecular weight is 3422: it is the largest natural product among compounds that do not have well-known units like proteins or polysaccharides. Maitotoxin includes 32 ether rings, 22 methyls, 28 hydroxyls, and 2 sulfuric acid esters. Maitotoxin has an amphipathic structure: polar radicals localize at the A to O rings, and methyls localize at the R to F' rings.

The chemical structure of mitotoxin was determined in 1996 by using high-resolution nuclear magnetic resonance spectrum, mass spectroscopy, and synthetic chemical methods.