VITAMINS 229 



vitamin supply, thereby inducing a form of neuritis. Since infectious 

 diseases likewise increase the needs of the body for this vitamin, they may 

 be causal agents in the production of thiamine deficiencies. 



Chemical nature 



This vitamin, which has been synthesized by two distinctly different 

 methods, contains the familiar pyrimidine ring (cytosine, thymine, and 

 uracil of the nucleic acids are pyrimidines) together with the thiazole ring, 

 in which the sulfur is contained. In addition to these two rings note 

 in the formula below that this vitamin is an amine. 



CH3 

 I 

 N=C— NH2— HCl .C=C-CH2-CH20H 



I I >^ 

 CH3-C C— CH2— nC 



II II I \ 

 N— CH CI ^C— S 



H 



. Thiamine chloride hydrochloride, C12H18N4SCI2 



In addition to being water-soluble, thiamine dissolves in acids and 

 dilute alcohol. It is fairly stable to heat in acid solution, but in an 

 alkaline medium it is rapidly destroyed by heat. Although the evidence 

 is somewhat conflicting, it appears to be fairly well established that ap- 

 preciable destruction of thiamine occurs during the cooking of food. 

 Thus it has been reported that up to 57 per cent of the thiamine may 

 be lost by stewing meat, about an equal amount by roasting or baking, 

 and 10 to 30 per cent by frying. Baking bread causes about 15 to 20 

 per cent loss. The destruction of thiamine by boiling vegetables has 

 been reported to amount to as much as 22 per cent, with an additional 

 15 per cent present in the cooking water. The amount of destruction 

 increases rapidly at temperatures above 100° C. Pressure cooking, there- 

 fore, causes considerably more destruction of thiamine than cooking at 

 ordinary pressure. 



An enzyme (thiaminase) in certain fish, mostly of fresh water origin, 

 has the specific property of destroying thiamine. Foxes fed diets contain- 

 ing raw carp develop a paralysis which was found to be actually a thiamine 

 deficiency, brought about through the agency of thiaminase. Cooking 

 the carp, or feeding extra amounts of thiamine to the animals prevented 

 the disease. 



In the last few years several relatively quick chemical methods of 

 assaying foods for their thiamine content have been proposed. Perhaps 

 the most widely used is the "thiochrome method," which is based on the 

 oxidation of thiamine, in an extract of the food, to thiochrome, which 

 shows a characteristic bluish fluorescence in ultraviolet light. The in- 



