Caramboxin (CBX) is a

toxin A toxin is a naturally occurring organic poison produced by metabolic activities of living cells or organisms. Toxins occur especially as a protein or conjugated protein. The term toxin was first used by organic chemist Ludwig Brieger (1849 ...

found in star fruit (''Averrhoa carambola''). Individuals with some types of kidney disease are susceptible to adverse neurological effects including intoxication,

seizure An epileptic seizure, informally known as a seizure, is a period of symptoms due to abnormally excessive or synchronous neuronal activity in the brain. Outward effects vary from uncontrolled shaking movements involving much of the body with l ...

s and even death after eating star fruit. Caramboxin has been identified as the neurotoxin responsible for these effects. Caramboxin is a

non-proteinogenic amino acid In biochemistry, non-coded or non-proteinogenic amino acids are distinct from the 22 proteinogenic amino acids (21 in eukaryotesplus formylmethionine in eukaryotes with prokaryote organelles like mitochondria) which are naturally encoded in the ge ...

that stimulates the

glutamate receptor Glutamate receptors are synaptic and non synaptic receptors located primarily on the membranes of neuronal and glial cells. Glutamate (the conjugate base of glutamic acid) is abundant in the human body, but particularly in the nervous system ...

s in neurons. Its chemical structure is similar to the amino acid phenylalanine. Caramboxin is an agonist of both

NMDA ''N''-methyl--aspartic acid or ''N''-methyl--aspartate (NMDA) is an amino acid derivative that acts as a specific agonist at the NMDA receptor mimicking the action of glutamate, the neurotransmitter which normally acts at that receptor. Unlike ...

and

AMPA α-amino-3-hydroxy-5-methyl-4-isoxazolepropionic acid, better known as AMPA, is a compound that is a specific agonist for the AMPA receptor, where it mimics the effects of the neurotransmitter glutamate. There are several types of glutamatergic ...

glutamatergic ionotropic receptors with potent excitatory, convulsant, and neurodegenerative properties. A possible interaction between caramboxin and oxalic acid in starfruit can lead to both neurotoxic and nephrotoxic effects. Consuming large amounts of starfruit or its juice on an empty stomach is not recommended, even for individuals with normal kidney function.

References

{{reflist Neurotoxins Amino acids Phenols Benzoic acids Toxic amino acids Plant toxins