Caramboxin
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| IUPAC name
2-Carboxy-3-hydroxy-5-methoxy-L-phenylalanine
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| Systematic IUPAC name
2-[(2S)-2-Amino-2-carboxyethyl]-6-hydroxy-4-methoxybenzoic acid | |
| Identifiers | |
3D model (JSmol)
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PubChem CID
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CompTox Dashboard (EPA)
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| Properties | |
| C11H13NO6 | |
| Molar mass | 255.226 g·mol−1 |
| Density | 1.5 ± 0.1 g/cm3 |
Refractive index (nD)
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1.625 |
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references
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Caramboxin (CBX) is a neurotoxin that is found in star fruit (Averrhoa carambol). The fruit was used as traditional Chinese medicine, for treating fever, cough, and asthma, and it is believed to have more beneficial effects.
Caramboxin is a non-proteinogenic amino acid similar to phenylalanine, but containing hydroxyl, methoxy and carboxyl substituents on the aromatic ring. Like phenylalanine, it contains a single chiral atom, meaning thre are two enantiomers possible, with the (S) form being the one found in nature.
Next to caramboxin, star fruit also contains oxalic acid. This is also found in other food sources like cabbage, broccoli, and quinoa. Oxalic acid can bind to calcium forming calcium oxalate. Calcium oxalate can form crystals in kidney tubules which is linked to “an acute and/or chronic decrease in kidney function”. Eating too much starfruit in a short time can cause acute kidney injury (AKI) to occur, which in term increases the risk of caramboxin doing severe damage to the body. Therefore, oxalate also influences the effect of caramboxin.
The consummation of substantial amounts of starfruit or its juice on an empty stomach is not recommended, regardless of whether individuals have a normal kidney function or not. When this happens, intense haemodialysis is used to lower the concentration of caramboxin and oxalic acid, as these are water soluble.