Brevetoxin

Brevetoxins are neurotoxic algae toxins of dinoflagellates Karenia brevis (formerly Gymnodinium breve ).

Occurrence and significance

Karenia brevis is a marine alga tropical regions and is observed regularly in the Caribbean and especially in the Gulf of Mexico. Here she appears as one of the causes of red tides, so-called Red Tides, which form through mass reproduction of these algae on. In the course of such red tides occur again and again (eg dolphins ) caused by toxic metabolites of algae, in particular by brevetoxins to mass mortality of fish and animals of higher trophic levels.

Within the food chain can result in an accumulation of these toxins. This means that toxin- contaminated fish, shellfish, crabs find their way to people as end member such food chains. In humans, the poisoning is known as Paralytic Shellfish Poisoning ( PSP).

Structure and Properties

Brevetoxins belong to the reduced non-aromatic polyketides. Is a polyether, the presence of tetrahydrofuran and / or tetrahydropyran is characteristic of this polyketides. Also have this more ether bonds. Currently, ten different brevetoxins are known, which can be divided into groups A and B. The brevetoxins A have ten five -to nine- membered rings B eleven five -to eight- membered rings.

• Brevetoxin -1 ( PbTx -1 ) R = - CH 2 C ( = CH2) CHO
• Brevetoxin -7 ( PbTx -7 ) R = - CH 2 C ( = CH 2) CH 2 OH
• Brevetoxin -10 ( PbTx -10 ) R = - CH 2 CH ( CH3 ) CH2OH

• Brevetoxin -2 ( PbTx -2 ) R = - CH 2 C ( = CH2) CHO
• Brevetoxin -3 ( PbTx -3 ) R = - CH 2 C ( = CH 2) CH 2 OH
• Brevetoxin -8 ( PbTx -8 ) R = - CH2COCH2Cl
• Brevetoxin -9 ( PbTx -9 ) R = - CH 2 CH ( CH3) CH2OH

More brevetoxins:

• Brevetoxin -5 ( PbTx -5): as PbTx -3, however, the hydroxyl group is acetylated in position 38
• Brevetoxin -6 ( PbTx -6): as PbTx -2, in place of the 27-28 double bond there is an epoxide

The structure elucidation as well as the total synthesis of these toxins was not an easy task. 1981 brevetoxin B was the first of these poisons enlightened in its structure; 1995 published Nicolaou et al.dessen total synthesis. Brevetoxin A in 1986 was elucidated in its structure and in 1998, again for the first time totalsynthetisiert by Nicolaou et al., .

Toxicity

Brevetoxin is a neurotoxin that causes the irritation of the mucous membranes and respiratory tract. The effect is similar to that of ciguatoxin, but it is less toxic. It binds to voltage-gated sodium channels and thus leads to a membrane potential and a depolarization. It is also highly toxic to fish ( Ichthyotoxin ) dar. Not only when bathing is a danger of poisoning. In the restaurants can cause with brevetoxin -contaminated fish neurotoxic shellfish poisoning ( neurotoxic shellfish poisoning ). Poisoning by brevetoxin is considered harmless and leaves no permanent damage. In vitro studies of John Ramsdell of the National Oceanic and Atmospheric Administration ( NOAA) in Charleston / South Carolina showed that one of the two above-mentioned toxins may very well cause permanent damage. It binds to the DNA and forms adducts which cause mutations and defects in the cell division. Thus, they are deemed as a possible carcinogen, according to the NOAA view, however, it is too early to say this is safe, because there is the possibility that endogenous repair enzymes eliminate the error again.