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| Names | |
|---|---|
| Preferred IUPAC name 5-(Hydroxymethyl)-4-(methoxymethyl)-2-methylpyridin-3-ol | |
| Other names 4'-O-methylpyridoxine; 4-O-methylpyridoxine | |
| Identifiers | |
3D model (JSmol) | |
| ChEBI | |
| ChEMBL | |
| ChemSpider |
|
| |
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| Properties | |
| C9H13NO3 | |
| Molar mass | 183.207 g·mol−1 |
| Hazards | |
| GHS labelling: | |
 | |
| Danger | |
| H300,H330 | |
| P260,P264,P270,P271,P284,P301+P310,P304+P340,P310,P320,P321,P330,P403+P233,P405,P501 | |
Except where otherwise noted, data are given for materials in theirstandard state (at 25 °C [77 °F], 100 kPa). | |
Ginkgotoxin (4'-O-methylpyridoxine) is aneurotoxin naturally occurring inGinkgo biloba. It is anantivitamin structurally related tovitamin B6 (pyridoxine). It has the capacity to induceepileptic seizures.
Seeds and phytopharmaceuticals derived from the plantGinkgo biloba aredietary supplements used to improve memory,[1] brain metabolism,[2] andblood flow,[3] and to treatneuronal disorders.[4][5] It has been long used for a wide range of medicinal purposes. For instance, inJapan andChina,Ginkgo biloba is used to treatcough,bronchial asthma, irritablebladder andalcohol use disorder.[6]
Ginkgotoxin is found in the seeds and, in lesser amounts, in the leaves ofGinkgo biloba. The seeds can be consumed as is and the leaves can be used to prepare the dietary supplements. Analyses of raw seeds from eight different locations in Japan byhigh-performance liquid chromatography showed concentrations of ginkgotoxin varying from 0.173 to 0.4 mg/g of seeds.[7] Also, there is aseasonal variation of ginkgotoxin concentration in the seeds. The maximum has been observed in August.[8] Analyses of the powder ofGinkgo biloba capsules revealed the presence of ginkgotoxin. However, as most oral supplements are made from the leaves, which contain only small amounts of ginkgotoxin,[9] below the level of toxicological relevance.[10]
Ginkgotoxin-5'-glucoside is a derivative of ginkgotoxin that possesses aglycosyl in the 5' position. Its content is higher than the concentration of ginkgotoxin in heated seeds (boiled or roasted).[11] Liberation of ginkgotoxin byenzymatic hydrolysis of theglycosidic linkage is possible. Nevertheless, thetoxicity or the mechanism of action of the glucoside form is not fully understood.
Ginkgotoxin can also be found in plants of the genusAlbizia.[8] However, these plants have no known dietary use for humans, so their production of ginkgotoxin is of lesser concern.
Ginkgotoxin is the 4'-O-methyl derivative of vitamin B6 (pyridoxine), but the presence of the vitamin is not required for thebiosynthesis of ginkgotoxin. It indicates that the pyridoxine system can be synthesizedde novo in the cells ofGinkgo biloba.[12]
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The first step of the biosynthesis involvesribulose 5-phosphate anddihydroxyacetone phosphate. They react in the presence of asynthase complex consisting ofPdx1 andPdx2, and formpyridoxal phosphate. The second step is hypothetical and consists of the removal of ahydride in the presence of adehydrogenase to produce pyridoxine. The last step involves the O-methylation of pyridoxine to form 4'-O-methylpyridoxine (ginkgotoxin).[6]
A few cases reported poisoning from commercially available products. The consumption of seeds represent a greater concern. Overconsumption ofGinkgo biloba seeds, especially by children, can result inloss of consciousness,convulsions, and death.[11]
Ginkgotoxin is structurally related to vitamin B6. It is suspected that ginkgotoxin interferes with the synthesis of the vitamin by decreasing the activity ofpyridoxal kinase in mammals.[13] This decrease leads to the decreased availability ofglutamate decarboxylase. In turn, it causes an imbalance between excitation and inhibition ofneurotransmitters, resulting inepileptic seizures.[13] The toxicity of ginkgotoxin consequently can be relieved by taking vitamin B6 supplements.
Media related toGinkgotoxin at Wikimedia Commons
