ChEBI: Nicotinamide is a pyridinecarboxamide that is pyridine in which the hydrogen at position 3 is replaced by a carboxamide group. It has a role as an EC 2.4.2.30 (NAD(+) ADP-ribosyltransferase) inhibitor, a metabolite, a cofactor, an antioxidant, a neuroprotective agent, an EC 3.5.1.98 (histone deacetylase) inhibitor, an anti-inflammatory agent, a Sir2 inhibitor, a Saccharomyces cerevisiae metabolite, an Escherichia coli metabolite and a mouse metabolite. It is a pyridinecarboxamide and a pyridine alkaloid. It derives from a nicotinic acid.NCI Thesaurus (NCIt): Niacinamide is the active form of vitamin B3 and a component of the coenzyme nicotinamide adenine dinucleotide (NAD). Niacinamide acts as a chemo- and radio-sensitizing agent by enhancing tumor blood flow, thereby reducing tumor hypoxia. This agent also inhibits poly(ADP-ribose) polymerases, enzymes involved in the rejoining of DNA strand breaks induced by radiation or chemotherapy.