Amygdalin

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. 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. Sulphuric 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[?].

(from an old encyclopedia)

Amygdalin is also called laevomandelonitrile, or Laetrile for short, and used to prevent cancer, though this is not approved by the FDA. It is claimed to be a vitamin and assigned the number B17. For this use, it is extracted from apricot pits, which are in the same genus (Prunus) as the almond.