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All plants contain tiny amounts of [https://en.wikipedia.org/wiki/Hydrogen_cyanide hydrogen cyanide] (HCN), however some plants also release high amounts of HCN from a class of glycosides called "cyanogenic glycosides", also called "cyanoglycosides". [https://en.wikipedia.org/wiki/Amygdalin Amygdalin] and [https://en.wikipedia.org/wiki/Linamarin linamarin] are common examples of cyanogenic glycosides <ref name="Gleadow_2014"></ref>. HCN is released from cyanogenic glycosides just like other types of glycosides: beta-glucosidase enzyme or exposure to low pH breaks the bond between a glucose molecule and an unstable compound called "cyanohydrin" (or "alpha-hydroxynnitrile"), which then disassociates into a ketone or benzaldehyde and an HCN molecule. In cyanogenic glycosides, this reaction is called "cyanogenesis". Cyanogenesis is stimulated by maceration, and by bacteria in the human gut. The cyanogenic glycosides themselves are not toxic until the HCN is released <ref name="Speijers">[http://www.inchem.org/documents/jecfa/jecmono/v30je18.htm "Cyanogenic Glycosides", First Draft. Dr G. Speijers. National Institute of Public Health and Environmental Protection Laboratory for Toxicology, Bilthoven, The Netherlands. Retrieved 08/25/2016.]</ref>. Although the optimum pH of cyanogenesis (at least for amygdalin) is 5.0 - 5.8, cyongenesis can occur at a wide range of pH values, and can occur in the presence of acid <ref>[http://www.sciencedirect.com/science/article/pii/S0308814601003132 Total cyanide determination of plants and foods using the picrate and acid hydrolysis methods. M Rezaul Haque, J Howard Bradbury. 2002.]</ref>. If seeds containing cyanogenic glycosides are ground up, the coarseness to which they are ground effects how quickly cyanogenesis occurs. Finely ground seeds extract HCN within an hour, where as coarsely ground seeds extract within 24 hours <ref>[http://www.sciencedirect.com/science/article/pii/030881469599841M The effects of grinding, soaking and cooking on the degradation of amygdalin of bitter apricot seeds. G Tunçel, M.J.R Nout, L Brimer. 1995.]</ref>. HCN boils at a relatively low temperature (25.6°C / 78.1°F) <ref name="Gleadow_2014"></ref>. Soaking, cooking, and/or sometimes fermenting foods with certain bacteria or yeast (this has not been documented with ''Saccharomyces'' or ''Brettanomyces'') that contain cyanogenic glycosides allows the HCN to be released, and then subsequent cooking afterwards will boil off the cyanide <ref>[http://www.sciencedirect.com/science/article/pii/016816059400115M International Journal of Food Microbiology. M.J.R. Nout, G. Tunçe, L. Brimer. 1995.]</ref>.
After being released from cyanogenic glycosides, HCN is highly toxic to animals. The human body is used to breaking down trace amounts of cyanide into the less toxic substance thiocyanate with an enzyme called rhodanese, which then leaves the body via urination <ref name="Gleadow_2014">[http://www.annualreviews.org/doi/full/10.1146/annurev-arplant-050213-040027 Cyanogenic Glycosides: Synthesis, Physiology, and Phenotypic Plasticity. Roslyn M. Gleadow and Birger Lindberg Møller. 2014.]</ref>. Although there are more than 3,000 plant species that are cyanogenic (a number of them cultivated by farmers perhaps because their cyanogenic properties deter animals from eating them), only a few parts of plants that are considered foods contain enough HCN from cyanogenic glycosides to be considered dangerous (generally, other forms of cyanide are considered more dangerous, such as from exposure to air or water that is polluted with cyanide) <ref name="CDC1">[http://www.atsdr.cdc.gov/toxprofiles/tp8.pdf Toxicology Profile for Cyanide. Agency for Toxic Substances & Disease Registry. July 2006. Retrieved 08/25/2016.]</ref>. The location of the cyanogenic glycosides and the enzymes that release them are often each located in different (or all) parts of plants, and those locations are diverse across species. In some plants, the cyanogenic glycosides are concentrated in the stems or leaves of the plant and not the seeds (e.g. sorghum, barley, and lima beans). In fruits sometimes the seeds contain concentrated amounts (e.g. black cherry pits), and other times in the fruit itself (e.g. ''Passiflora edulis''). In rosaceous stone fruits, cyanogenic glycosides are located in the seeds, but the beta-glucosidase enzyme that the plant uses to release HCN is located in the roots of the plant. The concentration of cyanogenic glycosides is generally higher in seedling plants compared to mature plants, however this is there are a few exceptions where this is the opposite (e.g. some ''Eucalyptus'' species, and lima beans).
{| class="wikitable sortable"
|-
! Plant !! mg HCN/kg or mg/liter|| Glycoside
|-
| Cereal grains and their products || 0.001-0.45 <ref name="who">[http://www.who.int/ipcs/publications/cicad/en/cicad61.pdf Concise International Chemical Assessment Document 61. HYDROGEN CYANIDE AND CYANIDES: HUMAN HEALTH ASPECTS. World Health Organization. 2004. Pg 13. Retrieved 08/29/2016.]</ref>||
|-
| Soy protein products || 0.07-0.3 <ref name="who"></ref>||
|-
| Soybean hulls || 1.24 <ref name="who"></ref>||
|-
| Apricot pits, wet weight || 89-2170 (depends on region/species) <ref name="Chaouali"></ref><ref name="who"></ref>|| Amgydalin
|-
| Home-made cherry juice from pitted fruits || 5.1 <ref name="who"></ref>|| Amygdalin
|-
| Home-made cherry juice containing 100% crushed pits || 23 <ref name="who"></ref>|| Amydalin
|-
| Almonds (wild bitter) || 1062-4690 <ref name="Chaouali">[https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3793392/ Potential Toxic Levels of Cyanide in Almonds (Prunus amygdalus), Apricot Kernels (Prunus armeniaca), and Almond Syrup. Nadia Chaouali, Ines Gana, Amira Dorra, Fathia Khelifi, Anouer Nouioui, Wafa Masri, Ines Belwaer, Hayet Ghorbel, and Abderazzek Hedhili. 2013.]</ref><ref>[http://www.ncbi.nlm.nih.gov/pmc/articles/PMC1273391/ Cyanide poisoning after bitter almond ingestion. T A Shragg, T E Albertson, and C J Fisher, Jr. 1982.]</ref> || Amygdalin <ref name="wikipedia_almond">[https://en.wikipedia.org/wiki/Almond "Almnod". Wikipedia. Retrieved 09/06/2016.]</ref>
|-
| Almonds (sweet domesticated) || 25 <ref name="Chaouali"></ref> || Amygdalin <ref name="wikipedia_almond"></ref>
|-
| Cherries with pit || 6.5-9.1 <ref name="daenen"></ref>|| Amygdalin
|-
| Sweet Apricots with kernel (14-24 fruits for 1 kg; single kernel avg weight is 6 grams <ref name="calapricot">[http://www.califapricot.com/marking_regulations.html California Apricots. Marking Regulations. Retrieved 09/01/16.]</ref>) || 4.2 - 7.2 (avg 0.3 mg per kernel <ref name="wiki_apric_kernel">[https://en.wikipedia.org/wiki/Apricot_kernel "Apricot Kernel". Wikipedia. Retrieved 09/01/2016.]</ref>)|| Amygdalin
|-
| Bitter Apricots with kernel (14-24 fruits for 1 kg; single kernel avg weight is 6 grams <ref name="calapricot"></ref>) || 25.2 - 43.2 (avg 1.8 mg per kernel <ref name="wiki_apric_kernel"></ref>)|| Amygdalin
|-
| '''Commercial fruit juices''' ||
|-
| Cherry || 4.6 <ref name="who"></ref>|| Amygdalin
|-
| Apricot || 2.2 <ref name="who"></ref>|| Amygdalin
|-
| Prune || 1.9 <ref name="who"></ref>|| Amygdalin
|-
| '''Tropical foodstuffs''' ||
|-
| Cassava(bitter)/dried root cortex || 2360-2450 <ref name="who"></ref><ref name="Speijers"></ref>|| Linamarin
|-
| Cassava(bitter)/leaves || 300-310 <ref name="who"></ref><ref name="Speijers"></ref>|| Linamarin
|-
| Cassava(bitter)/whole tubers || 380-395 <ref name="who"></ref><ref name="Speijers"></ref>|| Linamarin
|-
| Cassava(sweet)/leaves || 451-468 <ref name="who"></ref><ref name="Speijers"></ref>|| Linamarin
|-
| Cassava(sweet)/whole tubers || 445-462 <ref name="who"></ref><ref name="Speijers"></ref>|| Linamarin
|-
| Gari flour (Nigeria) || 10.6-22.1 <ref name="who"></ref>|| Linamarin
|-
| Sorghum/whole immature plant || 2400-2500 <ref name="who"></ref><ref name="Speijers"></ref>||
|-
| Bamboo/immature shoot tip || 7700-8000 <ref name="who"></ref><ref name="Speijers"></ref>||
|-
| Lima beans from Java (coloured) || 3000-3120 <ref name="who"></ref><ref name="Speijers"></ref>||
|-
| Lima beans from Puerto Rico (black) || 2900-3000 <ref name="who"></ref><ref name="Speijers"></ref>||
|-
| Lima beans from Burma (white) || 2000-2100 <ref name="who"></ref><ref name="Speijers"></ref>||
|-
|}