Cyanogenic Glycosides and Biogenetically Related Compounds in Higher Plants and Animals

Lechtenberg M

Zusammenfassung

Cyanogenesis describes the ability of living organisms to liberate hydrogen cyanide from stored cyanogenic glycosides upon tissue damage by hydrolysis and/or decomposition. It has been described for more than 3000 species of higher plants. Chemically, cyanogenic glycosides are glycosides of α-hydroxynitriles (cyanohydrins). Cyanogenic glycosides together with plant glycosidases and hydroxynitrile lyases form a preformed defence system. The structures are biogenetically related to only a few precursor amino acids. In the biosynthetic pathway, two multifunctional P450 enzymes and a glucosyltransferase act in a sequence. Biogenetically, glucosides of β- and γ-hydroxynitriles are closely related. Cyanogenic glycosides and their related nitriles also may serve as storage forms for reduced nitrogen. A recycling pathway has been proposed to recover reduced nitrogen for primary metabolism. Many food plants are cyanogenic, and great efforts are made to optimise their detoxification. The presence of cyanogenic glycosides in the animal kingdom appears to be restricted to arthropods. Some insects, often aposematically coloured, synthesise cyanogenic glycosides de novo and/or sequester them from their host plants.