Nicotinic Acid-13C6 is labelled Nicotinic acid. It is a precursor of the coenzymes NAD and NADP. Widely distributed in nature; appreciable amounts are found in liver , fish, yeast and cereal grains. Dietary deficiency is associated with pellagra. The term “niacin” has also been applied to nicotinamide or to other derivatives exhibiting the biological activity of nicotinic acid. Vitamin (enzyme cofactor).