The metabolism of nicotine-1′-oxide in excised Nicotiana glutinosa leaves

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Aqueous solutions of nicotine-1′-oxide- 14C and nicotine- 14C were absorbed through the stems of excised Nicotiana glutinosa leaves. After varying metabolic periods, the alkaloids were reisolated from the excised leaves and separated by TLC. The 14C content of the regions of the chromatographs corresponding to nicotine and nornicotine were determined by liquid scintillation counting. It was found that nicotine-1′-oxide was converted into both nicotine and nornicotine by the mature N. glutinosa leaf. The extent of the conversion of nicotine-1′-oxide to nornicotine approximated the extent of the conversion of nicotine to nornicotine. However, it was found that nicotine was converted faster than nicotine-1′-oxide to nornicotine, and that nicotine-1′-oxide was converted to nicotine faster than it was converted to nornicotine. In young N. glutinosa leaves it was found that little nicotine-1′-oxide was converted to nornicotine, while the conversion of nicotine-1′-oxide to nicotine was still observed. The increased conversion of nicotine-1′-oxide to nornicotine that was observed as the plants matured could be directly correlated with the increased ability of the maturing N. glutinosa leaves to convert nicotine to nornicotine. The experimental results are readily explained by proposing that the N. glutinosa leaves catalyze a reduction of nicotine-1′-oxide to nicotine and that the observed conversion of nicotine-1′-oxide to nornicotine occurs only via the nicotine so produced. It is concluded, therefore, that nicotine-1′-oxide is not an intermediate in the conversion of nicotine to nornicotine in alkaloid containing N. glutinosa leaves.