Linamarin: The Toxic Compound of Cassava

Abstract

Cassava is a widely grown root crop which accumulates two cyanogenic glucosides, linamarin and lotaustralin. Linamarin accounts for more than 80% of the cassava cyanogenic glucosides. It is a ß-glucoside of acetone cyanohydrin and ethyl-methyl-ketone-cyanohydrin. Linamarin ß-linkage can only be broken under high pressure, high temperature and use of mineral acids, while its enzymatic break occurs easily. Linamarase, an endogenous cassava enzyme, can break this ß-linkage. The enzymatic reaction occurs under optimum conditions at 25ºC, at pH 5.5 to 6.0. Linamarin is present in all parts of the cassava plant, being more concentrated on the root and leaves. If the enzyme and substrate are joined, a good detoxification can occur. All the cassava plant species are known to contain cyanide. Toxicity caused by free cyanide (CN¯) has already been reported, while toxicity caused by glucoside has not. The lethal dose of CN¯ is 1 mg/kg of live weight; hence, cassava root classification into toxic and non-toxic depending on the amount of cyanide in the root. Should the cyanide content be high enough to exceed such a dose, the root is regarded as toxic. Values from 15 to 400 ppm (mg CN¯/kg of fresh weight) of hydrocyanic acid in cassava roots have been mentioned in the literature. However, more frequent values in the interval 30 to 150 ppm have been observed. Processed cassava food consumed in Brazil is safe in regard to cyanide toxicity

Characterization of cassava (Manihot esculenta Crantz) varieties in Nigeria and Tanzania, and farmers’ perception of toxicity of cassava

“…Although bitter cassava is described generally in the literature as a toxic crop, which must be processed extensively to produce safe foods (Spencer et al, 1993;Cereda and Mattos, 1996), farmers in this study do not perceive cassava as a toxic crop. Farmers did not describe sweet cassava as safe, or bitter cassava as toxic or poisonous crop that must always be processed before consumption.…”

Traditional and novel fermented foods and beverages from tropical root and tuber crops: review

“…All the above references Chickwangue Streptococcus faecalis, Bacillus lichenoformis Good palatability, improved texture, and protein enriched Nwankwo et al,1989;Cereda & Mattos, 1996 Cyanogens reduction Improves shelf-life, texture quality, cooking quality, puffing quality suitable for baking products and reduces cyanogens glucosides Dufour et al, 1996;Padmja et al, 1994;George et al, 1995;Moorthy and Padmaja, 1995;Mestres et al, 1996;Balagopalan, 2000 Sweet potato Sour starch Lactobacillus cellobiosus, Streptococcus lactis, Corynebacterium sp.…”

Use of cassava wastewater treated anaerobically with alkaline agents as fertilizer for maize (Zea mays L.)

“…The organic matter is variable and it can surpass 100 gCOD.L -1 , with 4 to 6% soluble sugars as sucrose, fructose and glucose (Damasceno et al, 2003). This residue may also contain high cyanide glycoside due to the linamarine decomposition (Cereda and Mattos, 1996;Moraes et al, 2000). Investigations on the use of the crude wastewater were also proposed considering its use as pesticide (Magalhães et al, 2000), insecticide (Ponte, 2000), heavy metals adsorption (Horsfall Jr and Abia, 2003) and biosurfactants adsorption (Nitschke et al, 2004).…”