Nitrogen oxidation in ferrihaemoglobin formation

Evidence for p-hydroxylation of N-ethyl-N-methylaniline

1. N,N-Dialkyl- and N-alkyl-4-aminophenols derived from N-ethyl-N-methylaniline have been isolated from incubation mixtures of rabbit hepatic microsomes fortified with an NADPH-generating system. 2. This is the first report of metabolic ring (4-C) hydroxylation in vitro of an N,N-dialkylaniline. 3. N-Ethyl-N-methyl-4-aminophenol was the major ring-hydroxylation product, whilst N-ethyl-4-aminophenol and N-methyl-4-aminophenol were formed in approx. equal amounts at about 15% of the tertiary compound. 4. An apparent Vmax of 1.8 nmol/mg protein per min and Km of 1.7 x 10(-4)M were determined for N-ethyl-N-methyl-4-aminophenol formation using an optimized incubation time of 10 min.

Mechanism of the autocatalytic formation of ferrihemoglobin by N,N-dimethylaniline-N-oxide. Structure and ferrihemoglobin forming activity of the purple dye

The structure of the leuco compound of the purple dye which is formed in mixtrues of N,N-dimethylaniline-N-oxide (DANO) and ferrihemoglobin or ferricytochrome c was elucidated. IR, NMR, mass spectroscopy, and synthesis by oxidation of mixtures of N-methylaniline and 2-dimethylaminophenol showed that the leuco compound is produced by condensation of these two compounds. But only X-ray analysis proved the structure: 2-dimethylamino-4-(N-methylanilino)-phenol. The purple dye was produced from the leuco compound by withdrawal of two electrons and may be considered as resonance hybrid of the p-quinonimine and the o-quinonimine. When DANO was incubated with ferrihemoglobin or ferricytochrome c the oxygen of DANO was used for the production of the dye by oxidation of N-methylaniline and 2-dimethylaminophenol. The amount of N,N-dimethylaniline found in the incubation mixtures corresponded with the amount of purple dye produced. In the absence of molecular oxygen from incubation mixtures of DANO with cytochrome c the purple dye was formed at the same rate as under air. In blood in vitro the purple dye catalytically transferred electrons from ferrohemoglobin to molecuar oxygen. Its ferrihemoglobin-forming activity was lower than that of 4-dimethylaminophenol but higher than that of 2-dimethylaminophenol. The chemical mechanism of the autocatalytic formation of ferrihemoglobin by DANO is described.