扁桃苷[編輯]
| 扁桃苷 | |
|---|---|
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| IUPAC名 [(6-O-β-D-glucopyranosyl-β-D-glucopyranosyl)oxy](phenyl)acetonitrile |
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| 識別 | |
| CAS號 | 29883-15-6 |
| PubChem | 34751 |
| SMILES |
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| MeSH | Amygdalin |
| 性質 | |
| 化學式 | C20H27NO11 |
| 摩爾質量 | 457.43 g·mol−1 |
| 若非注明，所有數據均出自一般條件（25 ℃，100 kPa）下。 | |
扁桃苷（Amygdalin，源自希臘語“扁桃”?μυγδ?λη amygdálē ），又譯苦杏仁苷，是1803年Pierre-Jean Robiquet[1]與A. F. Boutron-Charlard從扁桃的種子中分離出的一種糖苷。李比希與維勒於1830年對這一物質進行了研究。扁桃苷也存在於其他的李屬植物，包括杏和黑櫻桃中[2]，也存在於枇杷的葉、果和核裏。恩斯特·T·克雷布斯（Ernst T. Krebs）曾將這一物質命名為“維生素B17”，並認為可以治療癌症，但隨後的研究證明這一物質並不具有上述功效。[3][4][5]學界也不認為苦杏仁苷是一種維生素，因為苦杏仁苷並不符合維生素的定義。[6]
化學性質[編輯]
扁桃苷的提取，可用扁桃或杏仁在乙醇中加熱，之後蒸發溶劑並添加乙醚，即可得到細小的白色扁桃苷晶體。李比希和沃勒發現扁桃苷分解時生成三種產物：糖類、苯甲醛和氫氰酸[7]。之後的研究表明，硫酸催化下扁桃苷分解成葡萄糖，苯甲醛和氫氰酸，而鹽酸使之分解為扁桃酸，D-葡萄糖和氨。[8]
在酶的催化下扁桃苷可進行兩種分解：麥芽糖酶使之部分分解，生成D-葡萄糖與扁桃腈葡糖苷（C6H5CH(CN)O·C6H11O5），一種苯乙腈葡糖苷的同分異構體。扁桃酶則可使之分解為苯甲醛、氰化物和兩分子葡萄糖。這一反應出現在苦扁桃中，導致苦扁桃中通常含有自由的苯甲醛與氰化物。
左旋扁桃腈[編輯]
毒性[編輯]
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]
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