Pumiliotoxin

The different divisions of compounds in the pumiliotoxin-A class arise from differences in the carbon backbone and/or the substituents attached to it. The difference between allopumiliotoxins and pumiliotoxins occurs at the 7 position. At this position, pumiliotoxins have a hydrogen whereas allopumiliotoxins have a hydroxyl substituent. Both have methyl and hydroxyl groups at the C-8 position. Homopumiliotoxins contain a quinolizidine ring in the place of the indolizidine ring and methyl and hydroxyl groups at its C-9 position. All three contain an alkylidenyl side-chain. == Nomenclature ==

Pumiliotoxins (or their analogs, allopumiliotoxins and homopumiliotoxins) are named by their class followed by their molecular weight. Isomers are differentiated by a letter after the number. For example, allopumiliotoxin 339A is an allopumiliotoxin with a molecular weight of 339 g/mol, with an axially oriented hydroxyl group at the 7-position in the indolizidine nucleus that differentiates it from allopumiliotoxin 339B. A (+) or (−) sign preceding the name of a pumiliotoxin refers to the compound's rotation of polarized light, with clockwise rotation (dextrorotatation) denoted with (+) and counterclockwise rotation (levorotation) denoted with (-). == Accumulation ==

Frogs obtain pumiliotoxins from their diet in arthropods; by a hydroxylase. Only one of the enantiomers can be hydroxylated to this more potent form of the toxin. The lack of pumiliotoxin 251D in eggs and tadpoles show that the toxin is not passed over from adult frogs to their offspring. The tadpoles are therefore not readily protected from predators. == Physiological Effects ==

Pumiliotoxins and allopumiliotoxins are generally positive modulators of voltage gated sodium channels and increase the strength of heart contraction. One exception is pumiliotoxin 251D, which blocks the flux of Na+ ions and increases the permeability of K+ ions. == See also ==