VITAMINS 241 



occurs in two forms, dextrorotatory and levorotatory, and of these only 

 the dextrorotatory form has biological activity. Since free pantothenic 

 acid can readily be obtained only as a sirupy, gummy mass, it is usually 

 converted to the calcium salt, which is a w^iite powder and the form in 

 which the synthetic product is supplied. 



Since it is an amide, pantothenic acid is readily hydrolyzed by heating 

 in either acid or alkaline solution. Hydrolysis results in complete de- 

 struction of the vitamin activity. It is rather stable to boiling in neutral 

 aqueous solutions, although it is destroyed by long heating at 120°C. 



It appears that pantothenic acid is not" extensively destroyed by ordi- 

 nary cooking of food. Losses of approximately 50 per cent may, however, 

 occur if the cooking water from vegetables is discarded. 



Occurrence 



Yeast, liver, egg yolk, and rice polishings are very rich sources of 

 pantothenic acid, while dairy products, whole cereals, muscle meats, 

 green leafy vegetables, and certain other vegetables like cauliflower and 

 sweet potato, may be classed as good sources. Fruits and egg white are 

 low in pantothenic acid. 



The assay of foods for this vitamin is based on the growth response 

 of chicks when fed the test material. A bacterial method very similar 

 to the one described above for riboflavin has also been developed. The 

 human requirement for pantothenic acid has not yet been determined, 

 but it has been suggested that about 10 mg. per day is adequate. 



PYRIDOXINE (VITAMIN B^) 



Physiological function 



Rats receiving an inadequate supply of this vitamin develop a derma- 

 titis, which makes its appearance in a characteristic manner. The paws 

 and tips of the ears and nose are first affected, becoming red and swollen. 

 The area immediately surrounding the nostrils becomes bare, and there 

 may be a nasal discharge. The administration of pure pyridoxine ma- 

 terially improves the condition of the rat, but even more striking improve- 

 ment results from the use of certain fats, especially those which supply 

 the so-called "essential fatty acids." The relation between the physio- 

 logical action of these fatty acids and pyridoxine is not yet clear. It 

 may well be that both are required for the normal nutrition of the rat. 

 Neither black-tongue, pellagra, nor chick dermatitis is cured by pyri- 

 doxine. It has been shown, however, that pyridoxine is required by 

 dogs, swine, pigeons, and chickens, and several reports indicate that it 

 is also important in human nutrition. Deficiency symptoms that have 



