Electrochemical hydrogenation of nicotinamide adenine dinucleotide

In an electroylsis process wherein nicotinamide adenine dinucleotide (NAD.sup.+) is hydrogenated to (NADH) by an indirect electrochemical reduction in which the electrolysis is carried out in the presence of an electron carrier, the improvement which comprises:

• employing as the electron carrier a metal complex having a reduction potential which is not more negative than -1.3 volt, based on a reference electrode consisting of an Ag/AgCl electrode in saturated aqueous potassium chloride, and wherein the electrolysis is carried out in a cell at a temperature of from about 10.degree. to 70.degree. C., a pH of from about 5 to 10 and a current density of from 1 to 100 mA/cm.sup.2.