amygdalin n : a bitter cyanogenic glucoside extracted from the seeds of apricots and plums and bitter almonds

English

Noun

1. a glycoside of benzaldehyde and hydrogen cyanide found in bitter almonds, and in the kernels of some other fruit

Synonyms

• vitamin B17

See also

• laetrile

Amygdalin (from Greek: , almond), C20H27NO11, is a glycoside initially isolated from the seeds of the tree Prunus dulcis, also known as bitter almonds, by Pierre-Jean Robiquet and A. F. Boutron-Charlard in 1803, and subsequently investigated by Liebig and Wöhler in 1830, and others. Several other related species in the genus of Prunus, including apricot (Prunus armeniaca), also contain amygdalin. 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."

Chemistry

Amygdalin is extracted from almond or apricot kernel cake by boiling ethanol; on evaporation of the solution and the addition of diethyl ether, amygdalin is precipitated as white minute crystals. Liebig and Wöhler were already able to find three decomposition products of the newly discovered amygdalin: sugar, benzaldehyde, and prussic acid. Later research showed that 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 4-hydroxybenzaldehyde.

Nomenclature

Amygdalin is also called laevomandelonitrile, or laetrile for short. Some claim that laetrile is derived from a Latin word meaning "joyfulness" as laetari is the Latin verb meaning "to rejoice or exult".

The National Cancer Institute explains that "the names Laetrile, laetrile, and amygdalin are often used in place of one another, but they are not the same product. The chemical make-up of Laetrile patented in the United States is different from the laetrile/amygdalin produced in Mexico. The patented laetrile is a partly synthetic (man-made) form of amygdalin, while the laetrile/amygdalin made in Mexico comes from crushed apricot pits."

Though it is sometimes sold as "Vitamin B17", it meets none of the criteria of a vitamin. Amygdalin/laetrile was claimed to be a vitamin by Ernst Krebs, Jr in the hope that if classified as a nutritional supplement it would escape the federal legislation regarding the marketing of drugs. He could also capitalise on the public fad for vitamins at that time.

Toxicity

Amygdalin contains 6% cyanide by weight. The enzyme, beta-glucosidase, required for release of the cyanide from the amygdalin molecule, is present in human small intestine and in a variety of common foods which leads to an unpredictable and potentially lethal toxicity when amygdalin or Laetrile is taken orally.

Assessment as a Cancer Treatment

Preclinical studies by the U.S. government's National Institutes of Health using laetrile alone and in combination with other substances showed little evidence that it is effective against cancer. Several case studies were recorded involving laetrile and conventional treatments (e.g. radiation and chemotherapy) concurrently, and were therefore inconclusive. However positive results in one case series initiated two published uncontrolled clinical trials using amygdalin. The Phase I study found that amygdalin caused minimal side effects, but the consumption of raw bitter almonds by two patients produced symptoms of cyanide poisoning. The Phase II study gave intravenous amygdalin combined with vitamins and pancreatic enzymes to 175 patients for 21 days followed by oral maintenance as part of a metabolic therapy program that also included dietary changes. Some patients reported improvements in symptoms, but all patients showed cancer progression 7 months after completing treatment, and improvements did not last after treatment. No controlled or double-blind clinical trials have been reported.

Another 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 were 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 advocates for laetrile dispute this label, asserting that financial motivations have tainted the published research. As a result, some North American cancer patients have travelled to Mexico for treatment with the substance, allegedly under the auspices of Dr. Ernesto Contreras. One of these patients was actor Steve McQueen, who died in Mexico, while undergoing treatment for mesothelioma.

Reviews of available clinical evidence published in 2006 concluded that the claim that laetrile has beneficial effects for cancer patients is not supported by sound clinical data, or by data from controlled clinical trials, and that there is considerable doubt about its safety.

Supporters of amygdalin

Laetrile advocates within the United States include a one-time chief chemist of the National Cancer Institute's cytochemistry laboratory, Dean Burk Ph.D., and G. Edward Griffin, author of "The Creature From Jekyll Island: A Second Look at the Federal Reserve".

Jason Vale, a national arm wrestling champion, was a leading spokesman for the legalization of laetrile after claiming to be cured of kidney, pancreatic and spleen cancer, purportedly by eating apricot seeds. However, in 2003 he was convicted of criminal contempt and in June 2004 was sentenced to 63 months in prison for marketing laetrile, for defrauding the U.S. government by claiming that he qualified for Legal Aid, and for ignoring a court order to stop distributing laetrile. Representatives of the Memorial Sloan-Kettering Cancer Center testified on the side of the prosecution during Vale's criminal trial.

Phillip Day, businessman behind Credence Publications, publisher and supplier of alternate medical products, claims in a book published by his company that regular use provides complete protection for a healthy person from cancer, an 80% success (survival after 5 years) when used for treating a newly diagnosed cancer, and 15% success as treatment for a metastasizing cancer. This opinion is based on the idea of cancer being a metabolic disease, a view not supported by current scientific knowledge.

Government regulation in the U.S.

Laetrile is a compound that has been used as an anticancer treatment in humans worldwide. It is not approved by the U.S. Food and Drug Administration (FDA) as a treatment for cancer or any other medical condition. The drug is made and used as a cancer treatment in Mexico.

Since laetrile has not been approved as a treatment for cancer in the United States by the FDA, In Montana this "...does not prevent a physician from prescribing laetrile as a dietary supplement to a patient not suffering from any known malignancy, disease, illness, or physical condition.", while in Indiana a physician who has signed a written informed request can prescribe or administer amygdalin (laetrile) in place of, or as an adjunct to, accepted therapies for the "...treatment of a malignancy, a disease, an illness, or a physical condition of a patient".

In the United States, the Food and Drug Administration continues to seek jail sentences for vendors selling laetrile for cancer treatment, calling it a "highly toxic product that has not shown any effect on treating cancer."

Amygdalin is commonly manufactured in Mexico. Because of the lack of proven efficacy of amygdalin, it may be banned or difficult to locate in some locations.

References

External links

• National Cancer Institute - Laetrile
• A clinical trial of amygdalin (Laetrile) in the treatment of human cancer. - Moertel C and others in New England Journal of Medicine 306:201-206, 1982
• Cancer Research UK on Laetrile
• British Association Festival Of Science BBC news story
• Unproven Methods of Cancer Management: Laetrile - American Cancer Society
• U.S. Supreme Court UNITED STATES v. RUTHERFORD, 442 U.S. 544 (1979). Finding: The Federal Food, Drug, and Cosmetic Act makes no express exception for drugs used by the terminally ill and no implied exemption is necessary to attain congressional objectives or to avert an unreasonable reading of the terms "safe" and "effective" in 201 (p) (1).