Thio-nicotinamide adenine dinucleotide (thio-NAD) is a coenzyme closely related to nicotinamide adenine dinucleotide (NAD+) and nicotinamide adenine dinucleotide phosphate (NADP+). It plays a role in cellular redox reactions and energy metabolism, similar to these other coenzymes. Thio-NAD is often used as a research tool to study specific enzymatic reactions and mechanisms. It is the main raw material for the preparation of total bile acid(TBA) detection reagents.