Among all the substances belonging to the category of cyanogenic glycosides, amygdalin is undoubtedly the most common and representative. Like the other members of this group, it has the ability to originate hydrogen cyanide when subjected to enzymatic hydrolysis. Amygdalin, in in particular, it undergoes the action of B-glycosidases, releasing two molecules of glucose, a molecule of benzaldehyde and a molecule of hydrogen cyanide. The enzymes involved in this reaction are not produced directly by the human organism, but by the intestinal bacterial flora and by that possibly present in the ingested drug.
Due to its ability to release hydrogen cyanide, amygdalin is responsible for the toxicity of the leaves and seeds of many plants belonging to the Rosaceae family.
As shown in the table, amygdalin abounds mainly in bitter almonds, but also in the seeds of peaches, apples, plums and cherries. A bitter almond contains about one milligram of hydrogen cyanide. For a child, the simple ingestion of one ten bitter almonds can therefore be fatal, while for an adult it takes 50-60.
Food sources of cyanogenic glycosides and quantity of hydrogen cyanide produced
Amygdalin and tumors
In the oncology field, amygdalin represents one of the many "hoaxes" perpetrated to the detriment of consumers. The discovery of the alleged anticancer properties of this cyanogenic glycoside is attributed to the American doctor Ernest T. Krebs, but it is thanks to the "studies" of his son Ernest T. Krebs Junior, biochemist, that amygdalin has risen to the headlines all over the world, so much so as to justify the opening overseas of real clinics dedicated to anti-cancer therapy with amygdalin.
In the form of laetrile (a molecule very similar to the original), the substance was the subject of marketing campaigns and studies that had very little scientific: small case studies, generic results, publication in third-rate journals, conflicts of interest and so on. . To justify the alleged empirical efficacy with scientific evidence, several hypotheses were advanced; denied the ability to selectively release hydrocyanic acid at the level of cancer cells (rich, according to Krebs, in B-glycosidase and poor in the enzymes necessary to detoxify it), amygdalin was even renamed vitamin B17, given that tropical populations that ingested significant quantities of this substance through the diet seemed to suffer less from some forms of cancer. It is just a pity that the major American health authorities, together with prestigious oncological institutions, applying the scientific method to the study of the anti-cancer virtues of amygdalin, have repeatedly emphasized the absence of anticancer properties on experimental animals and humans, as well as the danger of hydrocyanic acid intoxication in case of long-term use or in high doses.
