1,2-NRH, 1,4-NRH, and 1,6-NRH are oxidized to NR by NQO2 in the presence of FAD and menadione. 1,2-NRH and 1,6-NRH are oxidized to NR+ more slowly than 1,4-NRH. Slow oxidation of all three isomers is observed in the presence of FAD only, with 1,4-NRH being the most reactive toward FAD.