Fates of N'-methylnicotinamide and nicotinamide N-oxide in mice.

This experiment was performed to investigate the possibility that N'-methylnicotinamide (N'-methyl-3-pyridinecarboxamide) and nicotinamide N-oxide have niacin activity or not in animals. When 20 mg N'-methylnicotinamide per mouse was administered, urinary excretion of nicotinamide, N1-methylnicotinamide (MNA), N1-methyl-2-pyridone-5-carboxamide (2-Py), and N1-methyMpyridone-3-carboxamide (4-Py) increased 24-, 3-, 3-, and 3-fold, respectively, compared with the control values. The increased ratios of MNA, 2-Py, and 4-Py were almost the same as those when 20 mg nicotinamide was administered. Therefore, the relative activity of N'-methylnicotinamide to nicotinamide as niacin was considered to be about 1. When 20 mg nicotinamide N-oxide per mouse was administered, urinary excretion of nicotinamide, MNA, 2-Py, and 4-Py increased 6.4-, 1.8-, 1.6-, and 1.7-fold, respectively, compared with the control values. The increased ratios of MNA, 2-Py, and 4-Py were about 1/2 of those when 20 mg nicotinamide was administered, so the relative activity of nicotinamide N-oxide to nicotinamide as niacin is considered to be about 1/2. In conclusion, it was found the possibility that the reactions N'-methylnicotinamide→nicotinamide and nicotinamide N-oxide→nicotinamide occur, at least in mice, and that therefore N'-methylnicotinamide and nicotinamide N-oxide have niacin activity.