Amygdalin
From Freepedia
Amygdalin (from the Greek amugdale, almond), C20H27NO11, is a glucoside isolated from bitter almonds by H. E. Robiquet and A. F. Boutron-Charlard in 1830, and subsequently investigated by Liebig and Wöhler, and others. Some sources claim Ernst T. Krebs was the discoverer of the substance, and Krebs is generally credited with popularizing it as a purported cancer cure and as "Vitamin B17." It is extracted from almond cake by boiling alcohol; on evaporation of the solution and the addition of ether, amygdalin is precipitated as white minute crystals. Sulfuric acid decomposes it into d-glucose, benzaldehyde, and prussic acid (hydrogen cyanide); while hydrochloric acid gives mandelic acid, d-glucose, and ammonia. The decomposition induced by enzymes may occur in two ways. Maltase partially decomposes it, giving d-glucose and mandelic nitrile glucoside, C6H5CH(CN)O·C6H11O5; this compound is isomeric with sambunigrin, a glucoside found by E.E. Bourquelot and Danjou in the berries of the common elder, Sambucus nigra. Emulsin, on the other hand, decomposes it into benzaldehyde, cyanide, and two molecules of glucose; this enzyme occurs in the bitter almond, and consequently the seeds invariably contain free cyanide and benzaldehyde. An "amorphous amygdalin" is said to occur in the cherry-laurel. Closely related to these glucosides is dhurrin, C14H17O7N, isolated by W. Dunstan and T. A. Henry from the common sorghum or "great millet," Sorghum vulgare; this substance is decomposed by emulsin or hydrochloric acid into d-glucose, cyanide, and p-hydroxybenzaldehyde.
Amygdalin is also called laevomandelonitrile, or Laetrile (some claim that Laetrile is derived from a Latin word meaning "joyfulness") for short, and has been advocated by some as a "cure" or a "preventative" for cancer: as there is no evidence of its efficacy, it has not been approved for this use by the FDA. The US government's National Institutes of Health reports that two clinical trials with laetrile have been published. One Phase I study found that amygdalin caused minimal side effects; the side effects that were seen were similar to the symptoms of cyanide poisoning. One Phase II study with 175 patients had some patients reporting improvements in symptoms, but all patients showed cancer progression 7 months after completing treatment, and it was determined no further tests were necessary.
While no double-blind clinical trials may have been conducted, a clinical trial was carried out in 1982 by the Mayo Clinic and three other U.S. cancer centers under NCI sponsorship. Laetrile and "metabolic therapy" were administered as recommended by their promoters to 178 patients with advanced cancer for which there was no proven treatment. None was cured or stabilized or had any improvement of cancer-related symptoms. The median survival rate was about five months. In survivors after seven months, tumor size had increased. Several patients suffered from cyanide poisoning.
In 1974, the American Cancer Society officially labelled Laetrile as "quackery," but even today many American and Canadian cancer patients travel to Mexico for treatment with the substance, under the auspices of Dr. Ernesto Contreras. Curiously, Laetrile's foremost advocates within the United States can be found both on the far left of the political spectrum (e.g., The Village Voice) and the far right (e.g., The John Birch Society).
Though it is sometimes sold as "Vitamin B17", it is not a vitamin, as no disease is associated with a dietary deficiency of Laetrile. This commercial product is extracted from apricot seeds, which are in the same genus (Prunus) as the almond.
This article incorporates text from the 1911 Encyclopædia Britannica, which is in the public domain.
