Cyanogenic Glycosides

Each is built from an amino acid, and the amino acid decides the family:

Amygdalin and prunasin

from phenylalanine; stone-fruit kernels, apple seeds, bitter almond and wild cherry bark

Sambunigrin

a stereoisomer of prunasin; elder leaves, stems and unripe berries

Linamarin and lotaustralin

from valine and isoleucine; cassava, flaxseed, lima beans and white clover

Dhurrin

from tyrosine; sorghum

Taxiphyllin

from tyrosine; bamboo shoots

Gynocardin and tetraphyllin B

a ring-shaped type; passionflower relatives and damiana

Most cyanogenic foods are made safe by preparation. Cassava is peeled, grated, soaked, fermented or cooked, which lets the plant's own enzyme release the cyanide and lets it escape before eating. Flaxseed and bamboo shoots are cooked.

Bitter almonds are not sold for eating in most countries. The almonds in shops are the sweet variety, which makes almost no amygdalin.

Wild cherry bark is the one traditional medicine in which these compounds are the point. It has long been used in cough syrups as a calming expectorant, and its prunasin is credited with the sedative effect on cough. It is used dried and in modest doses.

The members do not have a range of effects. Each one does one thing, which is to release cyanide, and the amount released is what matters. The plant, the part and the preparation decide how much.

Cyanide stops cells using oxygen by blocking cytochrome c oxidase, the last enzyme of cellular respiration. The body can detoxify small amounts, converting them to thiocyanate with the enzyme rhodanese, which is why a few swallowed apple pips are harmless.

Amygdalin, and a semi-synthetic relative sold as laetrile or vitamin B17, has been promoted as a cancer treatment since the 1950s. It is not a vitamin. A clinical trial run through the Mayo Clinic in 1982 found no benefit, and a Cochrane review found no reliable evidence that it works against cancer.

Taken by mouth it is more dangerous than injected, because gut bacteria release the cyanide. Serious cyanide poisonings have followed laetrile tablets and apricot kernels eaten as a cancer remedy.