Brevetoxins

November 05, 2018
Red tides produce us.
What molecules are we?

Brevetoxins are a family of complex polycyclic polyethers that are produced by the “red tide” alga Karenia brevis that grows in the Gulf of Mexico. Brevetoxins are often abbreviated PbTx, which derives from their former designation Ptychodiscus brevis.

Brevetoxins come in two basic structures, type A and type B. Each type contains several specific compounds that are differentiated at the J-ring in PbTx-A and at the K-ring in PbTx-B. The images show the structure of one of the most common brevetoxins, PbTx-2, a member of the PbTx-B structure type.

Brevetoxin nomenclature is confusing at best. PbTx-2 is often called brevetoxin B even though there are several other type B structures. PbTx-8, also in the B group, was once referred to as brevetoxin C.

As indicated in the hazard information table, brevetoxins are truly toxic. They have been responsible for many fish, mammal, and mollusk kills in the Gulf; and tainted seafood has caused widespread food poisoning in humans. This year saw an especially virulent K. brevis bloom, especially off the coast of Florida.

MOTW update

L-Alanine and L-serine were the Molecules of the Week for October 29, 2018. They, along with glycine and L-proline, are the chief amino acids that make up spider silk proteins. In the past month, chemists at San Diego State University and Northwestern University (Evanston, IL) discovered that before spiders spin their silk, they store the silk proteins in complex nanoparticles.

Brevetoxin PbTx-2 fast facts.

CAS Reg. No. 79580-28-2
Empirical formula C50H70O14
Molar mass 895.08 g/mol
Appearance White solid
Melting point ≈270 ºC (dec.)
Water solubility Soluble

Brevetoxin PbTx-2 hazard information

GHS classification*: acute toxicity, oral, category 2
H300—Fatal if swallowed Chemical Safety Warning
GHS classification: acute toxicity, deermal, category 2
H310—Fatal in contact with skin Chemical Safety Warning
GHS classification: acute toxicity, inhalation, category 2
H330—Fatal if inhaled Chemical Safety Warning

*Globally Harmonized System of Classification and Labeling of Chemicals. Explanation of pictograms.

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