Utilization of Niacin Precursors and Derivatives by the Rat and Neurospora

Abstract

Of numerous niacin derivatives and precursors tested, only niacinamide, 3-hydroxyanthranilic acid, l- and dl-tryptophan and quinolinic acid proved active in correcting niacin deficiency in the rat. Kynurenine, kynurenic acid, anthranilic acid, N-formyl kynurenine, N-formyl anthranilic acid, N¹-methylnicotinamide, 3-cyanopyridine, and acetyl kynurenine proved inactive in this respect. The incubation of 3-hydroxyanthranilic acid with fresh liver slices resulted in a large percentage conversion to quinolinic acid. Tryptophan was not so converted under similar conditions. The relative activity of quinolinic acid for rats is so low compared with that of other niacin precursors that it is suggested that it may be produced as a side reaction rather than as a direct intermediate in the conversion of tryptophan to niacin, in a manner similar to that suggested for Neurospora. The basis for this suggestion is discussed.