Linamarin, in cassava

The cyanide in cassava that is not properly prepared can be released by the action of enzymes in our gut and can poison an individual. It does this by binding to an enzyme in the mitochondria inside the cell which blocks the production of energy. In vulnerable tissues, like the nerves of the spinal cord, this causes damage. The detoxication of cyanide with sulphur, derived from sulphur-containing amino acids in protein, produces thiocyanate, which is excreted into the urine, but this system is easily overwhelmed especially in those deficient in sulphur. Drought and poor soil seem to increase the production of linamarin in cassava, and it is possible that other dietary deficiencies may contribute to the nerve damage. 

Elias, M., Nambisan, B. and Sudhakaran, P.R. (1997) Catabolism of linamarin in cassava Manihot esculenta Crantz). Plant Sci., 126, 155-62. 

Glycosides cvanoeenic prunasin (Ang. BR) linamarin (Euphorbiaceae, Ang., notably found in Cassava starch BR) amygdalin (seeds ofRosaceae, Ang. BR). 

Nambisan, B. and Sundaresan, S. (1994) Distribution of linamarin and its metabolising enzymes in cassava tissues. /. Sci. Food Agric., 66, 503-7. 

ANDERSEN, M.D., M0LLER, B.L., Cytochromes P450 from Cassava (Manihot esculenta Crantz) catalyzing the first steps in the biosynthesis of the cyanogenic glucosides linamarin and lotaustralin cloning, functional expression in Pichia pastoris and substrate specificity of the isolated recombinant enzymes, J. Biol. Chem., 2000,275, 1966-1975. 

Bitter almonds contain amygdalin, which is the P-D-glucoside of prunasin, so it hydrolyses sequentially to the same products. Cassava, which is used in many parts of the world as a food plant, contains linamarin, which is the P-D-glucoside of acetone cyanohydrin. Preparation of the starchy tuberous roots of cassava for food involves prolonged hydrolysis and boiling to release and drive off the HCN before they are suitable for consumption. 

The levels of HCN equivalent (HCN, linamarin and cyanohydrins combined) must not exceed 50mg/kg in the complete feed and the maximum level of cassava permitted in poultry in Canada is 200g/kg. (From CFIA, 2005.)... 

A potential source of cyanide poisoning is cassava, a starch from the root of Manihot esculenta, used as food in much of Africa. The root contains cyanogenic linamarin, which is normally removed in processing the root for food. Widespread cases of a spinal cord disorder called konzo and characterized by spastic paralysis have been attributed to ingestion of linamarin from inadequately... 

Thiocyanate ion, SCN-, inhibits formation of thyroid hormones by inhibiting the iodination of tyrosine residues in thyroglobulin by thyroid peroxidase. This ion is also responsible for the goitrogenic effect of cassava (manioc, tapioca). Cyanide, CN-, is liberated by hydrolysis from the cyanogenic glucoside linamarin it contains, which in turn is biodetoxified to SCN. 

Cyanide in linamarin is in a form where it is attached to a sugar, the combination being known as a glycoside. The cyanide content can be loo mg or more per kilogram of cassava. In some areas of Africa 1.5 kg of cassava may be eaten every day A safe level in properly prepared cassava would be less than 20 mg cyanide per kilogram of cassava. 

Linamarin is isolated from cassava, a woody shrub grown as a root crop in the humid tropical regions of South America and Africa. Amygdalin is present in the seeds and pits of apricots, peaches, and wild cherries. Amygdalin, also known as laetiile, was once touted as an anticancer drug, and is still available in some countries for this purpose, although its effectiveness is unproven. 

Both linamarin and amygdalin are toxic compounds because they are metabolized to cyanohydrins, which are hydrolyzed to carbonyl compounds and toxic HCN gas. This second step is merely the reconversion of a cyanohydrin to a carbonyl compound, a process that occurs with base in reactions run in the laboratoiy (Section 21.9A). If cassava root is processed with care, linamarin is enzymatically metabolized by this reaction sequence and the toxic HCN is released before the root is ingested, making it safe to eat. 

Antinutrient Cassava [18] Suppression of enzymes (CYP79D1 and CYP79D2) involved with the biosynthesis of cyanogenic glucosides (decrease in linamarin)... 

Over the years, through trial and error, cassava eaters have identified a variety of processes that render the tuber safe. South American native peoples who spat bitter-tasting cassava back into their food bowls and then sampled it again later discovered that the bitterness had vanished. That s because salivary enzymes can also cause linamarin to break down, liberating hydrogen cyanide, which then escapes into the air. In Africa, the traditional method of detoxifying cassava is to pile cassava roots and allow them to ferment in the sun for about seven days. This also releases the enzyme needed to degrade linamarin. 

For detection and for removal of linamarin from foods (Phaseolus, Cassava) and animal fodder (flaxseed) by enzymatic cleavage and extraction processes, see Lit.. Linamarin and lotaustralin occur in the hemolymph of caterpillars of the butterfly Zygaena trifolii. ... 

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