Almond, bitter, hydrocyanic acid

F. L. Winckler found that crude oil of bitter almonds, containing hydrocyanic acid, with hydrochloric acid forms a new acid which he called mandelic acid. In a note (1836) Liebig suggested that the hydrocyanic acid is hydrolysed into ammonia and formic acid which combines with the benzaldehyde (C HfiO + H2CO2 = CgHgOg (mandelic acid is CeH6-CH(0H)-C02H). 

As early as 1908, Rosenthaler found in the ferment mixture of emulsin a u-oxynitrilase , which directed the addition of hydrocyanic acid (hydrogen cyanide) to benzaldehyde asymmetrically to give x-hydroxybenzeneacetonitrilc (mandelonitrile)9. This result was confirmed1 °, however, it was not until 1963 that Pfeil ct al. first isolated and characterized the enzyme (R)-oxyni-trilase [EC 4.1.2.101 from bitter almonds (Prunus amygdalus)1 12. The yellow-colored enzyme contains a flavin-adenine dinucleotide (FAD)11 and loses its activity by splitting off this prosthet-... 

A). Cyanide ions (CN ) enter the organism in the form of hydrocyanic acid (HCN) the latter can be inhaled, released from cyanide salts in the acidic stomach juice, or enzymatically liberated from bitter almonds in the gastrointestinal tract The lethal dose of HCN can be as low as 50 mg. CN binds with high affinity to trivalent iron and thereby arrests utilization of oxygen via mitochondrial cytochrome oxidases of the respiratory chain An internal asphyxiation (histotoxic hypoxia) ensues while erythrocytes remain charged with O2 (venous blood colored bright red). 

Hydrocyanic acid Bitter almond 2,000 Stone fruits... 

Cyanogen does not exist in nature ready formed the kernels of peaches, plums, bitter almonds, et cetera, and the leaves of the cherry-laurel, yield, by distillation, Abundance of hydrocyanic acid, but it Is ouly then produced by the decomposition of other substances containing nitrogen. 

Amygdalin (the glucoside of bitter almonds) is a white crystalline compound, soluble in water, readily hydrolysed on heating with dilute sulphuric acid to benzaldehyde, hydrocyanic acid and glucose. 

This consists essentially of sugar and almond paste. Besides the determination of the sugars, which is made as in biscuits, and the microscopic examination for the detection of other seeds and extraneous flours, tests for hydrocyanic acid (from the bitter almonds) and nitrobenzene (added as an adulterant) are also necessary. 

Artificial products, obtained by addition of aromatic substances to commercial alcohol, may however be recognised, as they contain little or no hydrocyanic acid and are rich in benzaldehyde. Kirschwasser and similar spirits are prepared, although rarely, from alcohol and bitter almond or cherry laurel water and in such cases hydrocyanic acid is present. Artificial products are generally prepared from rectified alcohol and thus have a low coefficient of impurity and contain only very small amounts of higher alcohols. 

Do not confuse sweet almond with bitter almond (Prunus amygdalus var umu. a). The essential oil is extracted by steam distillation after maceration of pressed nuts. A major component is benzaldehyde (95%), which is moderately toxic. Hydrocyanic acid is also formed, which is poisonous. It is not suitable for aromatherapy but is used in the food industry. 

Dilute hydrochloric acid hydrocyanic acid, HCN, with an odour reminiscent of bitter almonds, is evolved in the cold. It should be smelled with great caution. A more satisfactory method for identifying hydrocyanic acid consists in converting it into ammonium thiocyanate by allowing the vapour to come into contact with a little ammonium polysulphide on filter paper. The paper may be conveniently placed over the test-tube or dish in which the substance is being treated with the dilute acid. Upon adding a drop of iron(III) chloride solution and a drop of dilute hydrochloric acid to the filter paper, the characteristic red colouration, due to the iron(III) thiocyanate complex, Fe(SCN)3, is obtained (see reaction 6 below). Mercury(II) cyanide is not decomposed by dilute acids. 

Pure anhydrous hydrocyanic acid is a clear colourless liquid with a peculiar odour which is usually compared with that of bitter almonds. It has been observed, however, that this substance has an indefinite odour which varies with the degree of its dilution with air and the period of exposure to it. ... 

Hydrocyanic acid is most easily prepared from its potassium salt, K(CN), which is obtained principally by the decomposition of the complex double cyanides of iron as we shall soon consider. The acid is also obtained by the hydrolysis of certain glucosides, e.g., amygdalin, in bitter almonds. It is prepared synthetically by reactions to be discussed presently in connection with the constitution of it and its salts. It is a colorless liquid with a characteristic odor and burns with a violet flame. It boils at 26.1 and solidifies to crystals which melt at —14°. It is an extremely strong poison the best antidotes being chlorine and hydrogen dioxide. It is readily absorbed by metallic nickel which is thus used in gas masks for this purpose. It is stable in dry air but in presence of water is readily hydrolyzed yielding ammonia and formic acid as the chief products. 

Emxdsin (synaptase), found in the seeds of the Bitter Almond, Cherry Laurel leaves, in the barks of the Wild Black Cherry and Choke Cherry and in other Rosaceous plant parts, in Manihot utilissima, Polygala species, etc., hydrolyzes the glucoside present (either amygdalin or 1-mandelonitrile glucoside) to hydrocyanic acid, benzaldehyde and glucose. 

The use of coumarin, tonka bean, safrole, sassafras oil, dihydrosafrole, isosafrole, agaric acid, nitrobenzene, dulcamara, pennyroyal oil, oil of tansy, rue oil, birch tar oil, cade oil, volatile bitter almond oil containing hydrocyanic acid, and male fern as flavouring agents is prohibited. 

See amygdalin. Note Bitter almonds contain amyg-dalin together with an enzyme that catalyzes its hydrolysis. When the kernels are ground and moistened, a volatile oil produced by the hydrolysis can be distilled from them consisting mainly of benzal-dehyde and hydrocyanic acid. This is the oil of bitter almond used in pharmacy as a food flavor after removal of the hydrocyanic acid) (Eckey, Vegetable Fats and Oils.). 

Amygdalin, CaoHjrNOn—157—exists in cherry-laurel and in bitter almonds, but not in sweet almonds. Its characteristic reaction is that, in the presence of emulsin, which exists in sweet as well as in bitter almonds, and of water, it is decomposed into glucose, benzoic aldehyde, and hydrocyanic acid. The same reaction is brought about by boiling with dilute HaSO< or HCl. Bitter almonds contain about 2 per cent, of amygdalin. 

Hydrocyanic Acid, HCN, commonly called prussic acid, occurs in the free condition in certain plants. It is produced as the result of the decomposition of a substance called amygdalin (352), which occurs in the leaves of the cherry and laurel, in bitter almonds, peach kernels, and other substances. It can be formed by exposing a mixture of hydrogen and nitrogen to an electric arc between carbon poles under these conditions about 4.7 per cent of the gases is converted into hydrocyanic acid. 

Hydrocyanic acid is a colorless liquid which boils at 26°, and when cooled forms crystals which melt at —14°. It has an odor which is similar to that of the oil of bitter almonds. It burns with a pale blue flame. Hydrocyanic acid is one of the most powerful poisons 0.05 gram is said to be a fatal dose. Hydrogen peroxide or the inhalation of air containing chlorine are said to be antidotes for hydrocyanic acid. The poisonous property of the acid is in some way associated with the CN ion. Substances from which this ion is produced are poisonous,whereas those, like potassium ferrocyanide, which do not give a simple CN ion are not poisonous. 

Benzaldehyde, benzoic aldehyde, CeHs.CHO, occurs in amygdalin, a glucoside which is present in bitter almonds and in the kernels of various fruits it yields the aldehyde, hydrocyanic acid, and glucose on hydrolysis (353). The aldehyde is called oil of bitter almonds. It is used in flavoring extracts and perfumery, in the manufacture of certain dyes, and in the preparation of other compounds. 

---