扁桃苷[编辑]
| 扁桃苷 | |
|---|---|
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| IUPAC名 [(6-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy](phenyl)acetonitrile |
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| 识别 | |
| CAS号 | 29883-15-6 |
| PubChem | 34751 |
| SMILES |
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| MeSH | Amygdalin |
| 性质 | |
| 化学式 | C20H27NO11 |
| 摩尔质量 | 457.43 g·mol−1 |
| 若非注明，所有数据均出自一般条件（25 ℃，100 kPa）下。 | |
扁桃苷（Amygdalin，源自希腊语“扁桃”?μυγδ?λη amygdálē ），又译苦杏仁苷，是1803年Pierre-Jean Robiquet[1]与A. F. Boutron-Charlard从扁桃的种子中分离出的一种糖苷。李比希与维勒于1830年对这一物质进行了研究。扁桃苷也存在于其他的李属植物，包括杏和黑樱桃中[2]，也存在于枇杷的叶、果和核里。恩斯特·T·克雷布斯（Ernst T. Krebs）曾将这一物质命名为“维生素B17”，并认为可以治疗癌症，但随后的研究证明这一物质并不具有上述功效。[3][4][5]学界也不认为苦杏仁苷是一种维生素，因为苦杏仁苷并不符合维生素的定义。[6]
化学性质[编辑]
扁桃苷的提取，可用扁桃或杏仁在乙醇中加热，之后蒸发溶剂并添加乙醚，即可得到细小的白色扁桃苷晶体。李比希和沃勒发现扁桃苷分解时生成三种产物：糖类、苯甲醛和氢氰酸[7]。之后的研究表明，硫酸催化下扁桃苷分解成葡萄糖，苯甲醛和氢氰酸，而盐酸使之分解为扁桃酸，D-葡萄糖和氨。[8]
在酶的催化下扁桃苷可进行两种分解：麦芽糖酶使之部分分解，生成D-葡萄糖与扁桃腈葡糖苷（C6H5CH(CN)O·C6H11O5），一种苯乙腈葡糖苷的同分异构体。扁桃酶则可使之分解为苯甲醛、氰化物和两分子葡萄糖。这一反应出现在苦扁桃中，导致苦扁桃中通常含有自由的苯甲醛与氰化物。
左旋扁桃腈[编辑]
毒性[编辑]
Toxicity[edit]
The metabolism of amygdalin produces hydrogen cyanide, a potent toxin. Beta-glucosidase, one of the enzymes that catalyzes the release of cyanide from amygdalin, is present in the human small intestine and in a variety of common foods. This leads to an unpredictable and potentially lethal toxicity when amygdalin or laetrile is taken orally.[3][19][20] Ingestion of purified amygdalin or apricot kernels can cause severe toxicity and death due to cyanide poisoning.[15] Numerous case reports in medical literature describe serious cyanide poisoning in patients who ingested laetrile as a cancer treatment.[9][21] Blood cyanide concentrations may be measured as a means of confirming the diagnosis in hospitalized patients or to assist in the forensic investigation of a fatal overdose.[22]
Some laetrile promoters have claimed that the cyanide generated by laetrile is immediately harmlessly detoxified by the mitochondrial enzyme rhodanese into thiocyanate. However, these claims are false. First, because thiocyanate is also toxic, although to a lesser degree. Second, the body only can use the small amount of rhodanese that is present in the blood, regardless of the stores present in kidneys and liver. Third, the limited factor in this conversion are the stores of cystine, cysteine, and other sulfur compounds, which are rapidly depleted in laetrile poisoning. Fourth, blood analysis shows undetoxified cyanide in persons poisoned with laetrile or with apricot kernels.[9]
