Studies in detoxication. 39. Nitro compounds. (a) The metabolism of o-, m- and p-nitrophenols in the rabbit. (b) The glucuronides of the mononitrophenols and observations on the anomalous optical rotations of triacetyl β-o-nitrophenylglucuronide and its methyl ester

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Abstract
O-, m- and p-nitrophenols are excreted in conjugated forms, there being only small amount (< 1%) of the unchanged free phenols excreted. The main metabolites are the nitrophenylglucuronides which account for about 70% of the dose. The corresponding ethereal sulfates are also excreted. The nitro group of the nitrophenols undergoes reduction in vivo only to a minor extent, and some 80% of it is excreted unchanged. The extent of reduction is about 6% for o-, 10% for m- and 14% for p-nitrophenol. The nitrophenols also undergo oxidation to a very small extent (< 1%); o- yields traces of nitroquinol; m-, nitroquinol and 4-nitrocatechol; and p-, and p-4-nitrocatechol. The dihydric phenols produced are similar to those formed during the Elbs persulfate oxidation of the mononitrophenols. The significance of the similarity in relation to free radicals is discussed. The paper chromatography of the mono- and dihydric nitrophenols was studied. The beta-glucuronides of the nitrophenols were isolated and characterized as amines and triacetyl methyl esters. The abnormal positive rotations of triacetyl beta-o-nitrophenyl-D-glucuronide and its methyl ester were investigated, and it was shown that in the case of the ester this rotation becomes negative on raising the temp., a behavior reminiscent of tetra-acetyl-beta-o-nitrophenylgluco-side. The metabolic results were discussed in relation to the toxicity of p-nitrophenol and the non-toxicity of o-nitrophenol.