Estimation of nicotinic acid in animal tissues, blood and certain foodstuffs

Abstract

A quantitative study is made of various factors influencing the accuracy of the estimation of nicotinic acid in biological material by means of the cyanogen-p-aminoacetophenone method of Harris & Raymond, such as alternative methods of extraction, rate of hydrolysis, removal of interfering substances with ethyl alcohol, effects of changes in pH and of the final acidification, specificity of the color reaction. The method is more sensitive than those in which metol and aniline are used. As little as 1-2 7 of nicotinic acid can be detected in 1 g. of material; quantitative recovery of added nicotinic acid was effected in control tests. In some animal tissues nicotinic acid is apparently bound to substances easily extracted by boiling water but partly precipitated by ethyl alcohol. In some cereals only a small fraction of the chromogen is readily extracted by boiling water. Only this fraction (or a portion of it) appears to be the "true" or "active" nicotinic acid; otherwise yellow maize which is known to be deficient in nicotinic acid would test as though the concentration were high.