Using a combination of gas chromatography, mass spectrometry, and selected ion recording techniques, we have identified nicotine and its major metabolite, continine, in the breast fluid of nonlactating women smokers. As little as 25 picograms could be measured by using the deuterated variants, [5',5'-2H]nicotine and [3,3-2H]cotinine, both as internal standards and as carriers in an inverse isotope dilution method.
Metabolic N-hydroxylation of the potent psychotomimetic amine 1-(2,5-dimethoxy-4-methylphenyl)-2-aminopropane (5) by rabbit liver microsomal preparations has been investigated. Synthetic hydroxylamine 8 was obtained by sequential reduction of the corresponding nitropropene 10 with sodium borohydride followed by zinc reduction of the resulting nitropropane 11. Compound 8 in water (pH 7.4) was rapidly air oxidized to oxime 12; this oxidation was completely blocked by rabbit liver microsomes. Microsomal incubations of amine 5 or its bis(methoxy-d3)hexadeuterio analog 5-d6 resulted in the formation of 8 and 8-d6, respectively, identified as their bis(trifluoroacetyl) derivatives by GLC-MS. Quantitative estimations of metabolite formation employing selected ion monitoring with the aid of an accelerating voltage alternator were accomplished by stable isotope dilution analyses with 5-d6 as substrate and 8-d0 as internal standard. Similar analyses starting with "pseudoracemates" (R)-5-d0:(S)-5-d6 or (R)-5-d6:(S)-5-d0 as substrates established metabolite 8 to be enriched with its R enantiomer.
An acetylenic C-glucuronide of the sedative-hypnotic drug ethchlorvynol was isolated from rabbit urine as the major metabolite. The C-glucuronide represents a novel metabolic pathway for acetylenes and is a rare example of the formation of a carbon-glucuronide bond in mammalian systems.
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