ABSTRACT
Niacin is the generic descriptor for two vitamers, nicotinic acid and nicotinamide, which have equal bioactivity in the free form. American usage of the term “niacin” to denote specifically nicotinic acid, and “niacinamide” to denote the amide is not used in this text. In living tissues nicotinamide is the reactive moiety of the coenzymes nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP). The coenzymes function as proton and electron carriers in a wide variety of oxidation-reduction reactions. Examples are reactions concerned with the release of energy from carbohydrates, fatty acids, and amino acids, and with the synthesis of amino acids, fatty acids, and pentose sugars.
