A method comprising the indirect electrochemical regeneration of NAD(P)H in enzymatic substrate conversions which are catalyzed by monooxygenases, for example, is described. In particular, a method for the electroenzymatic preparation of 2,3-dihydroxyphenyl derivatives, which is catalyzed by the enzyme 2-hydroxybiphenyl 3-monooxygenase and in which simultaneously the NAD⁺ formed by reductive cleavage of oxygen is electrochemically reduced, is described.