Detoxification of cyanide

Noncyanogenic fungi can degrade cyanide to formamide followed by hydrolysis by a hydratase to formate and ammonia (Dumestre et al. 1997). This pathway is also used by some bacteria (Jandyala et al. 2003). Bacteria also use a number of reactions for the detoxification of cyanide, including monooxygenation to COj and ammonia (Wang et al. 1996). 

Chemical oxidation technology is primarily used for the detoxification of cyanide and other oxi-dizable organics such as aldehydes, mercaptans, phenols, unsaturated acids, and certain pesticides.40... 

Manning, K. 1988. Detoxification of cyanide by plants and hormone action. Pages 93-110 in D. Evered and S. Harnett (eds.). Cyanide Compounds in Biology. Ciba Foundation Symposium 140. John Wiley, Chichester. 

Methaemoglobin forming compounds should be used cautiously in victims suffering from concurrent carbon monoxide poisoning or hypoxia. The second approach calls for provision of additional sulfur groups to enhance the detoxification of cyanide and thiocyanate by endogenous rhodanese this comes about by giving sodium thiosulphate. 

Schulz, V., and B.Roth. 1982. Detoxification of cyanide in a new-born child. Klin. Wochensch. 60 527-528. 

Basu TK. 1983. High-dose ascorbic acid decreases detoxification of cyanide derived from amygdalin (laetrile) Studies in guinea pigs. Can J Physiol Pharmacol 61 1426-1430. 

The metabolic pathway for the detoxification of cyanide involves conversion to the less toxic thiocyanate by a reaction requiring thiosulfate or colloidal sulfur as a substrate ... 

Nazly N, Knowles CJ, Beardsmore AJ, Naylor WT, Corcoran EG. Detoxification of cyanide by immobilised fungi. J Chem Technol Biotechnol 1983 33B 119-126. 

After the initial therapy of methemoglobin inducers, the cyanide has to be converted to thiocyanate which is eliminated in urine. This enzymatic detoxification of cyanide is facilitated by a sulfur donor like sodium thiosulfate. The mechanism of this reaction was discussed earlier under elimination of cyanide. High tissue oxygen markedly potentiates the effects of this reaction. In cases where methemoglobin formation is not desirable, sodium thiosulfate together with oxygen alone is sufficient. The utility of... 

Limited information on absorption is available. After ingestion, the onset of symptoms of cyanide toxicity is expected in 30 min to 2h however, symptoms could be delayed. The delay in symptoms may be due to the rate at which the hydrocyanic acid is yielded when hydrolyzed by the enzymes during digestion. The major route for detoxification of cyanide is the... 

Wood JL, Cooley SL. Detoxification of cyanide by cystine. J Biol Chem, 1956 218 449 57. 

Rapid detoxification of cyanide occurs in mammals for example, rates of detoxification have been estimated at 0.076 mg CN kg-1 min-1 for guinea pigs (Lendle, 1964) and 0.017 mg CN kg 1 min 1 in humans (McNamara, 1976). Several pathways exist for the biodetoxification of cyanide of which the major one, responsible for conversion up to 80% of a dose of CN, is by the enzymatic conversion of cyanide to the significantly less acutely toxic thiocyanate (SCN)... 

Cyanide hydrolyzing enzymes (i. e. reaction schemes 12.1-4 and 12.1-5) have, with the exception mentioned above, not been reported to hydrolyze organic nitriles and thus appear to be highly specific for inorganic cyanide. Therefore, they are mainly of interest in waste water treatment as a biological alternative to conventional chemical detoxification of cyanide by alkaline chlorination and will not be treated further. 

This reaction normally represents hepatic detoxification of cyanide ions produced from nitroprusside in erythrocytes. The SCN- is 99% less toxic than CN-. NaSCN was also still official in the NF X (1960) as an antihypertensive drug. A nitroprusside mechanism on vascular smooth muscle by interference with the role of Ca2+ in the muscle contraction process has also been suggested. 

Figure 7. Enzymatic detoxification of cyanide as it occurs in vivo (31)...

Thiocyanate [SCN ], the anion of thiocyanic acid, is an important waste product from the chemical industry, it is present in various food items, it may be added to dairy milk to promote bacteriostatic processes, and it is synthesixed in the human liver as part of detoxification of cyanide. A special case in medicine has been generation of large amounts of thiocyanate leading to hypothyroidism after sodium nitroprusside infusion for hypertension (Nourok et at, 1964). After oral ingestion thiocyanate is readily absorbed. It is partly bound to albumin in blood, and mainly eliminated by excretion in urine. The half life of thiocyanate in humans is in the order of 1—2 weeks (Scherer, 2006), but varies between individuals. Thiocyanate may have a number of... 

The basic aim of rapid detoxification of cyanide is prevention or reversal of inhibition of cytochrome oxidase by cyanide. This is usually facilitated by providing a large pool of ferric iron in the form of methemoglobin to complex cyanide. Cyanide preferentially competes with the Fe + of methemoglobin as compared with that of cytochrome oxidase and eventually binds with the former to form cyanmethemoglobin. Thereby, the activity of inhibited cytochrome oxidase is restored (Baskin et al., 1992). The various methemoglobin inducers used as cyanide antidotes are discussed. 

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