Biosynthesis of the nicotine alkaloids in Nicotiana glutinosa: Interrelationships among nicotine, nornicotine, anabasine, and anatabine

Abstract

Biosyntheses from 14CO 2 carried out with both intact Nicotiana glutinosa plants and seedlings have demonstrated that nornicotine is not the precursor of nicotine in either the root or the aerial portions of the plant. This conclusion contrasts with that reached on the basis of 3H incorporations into the alkaloids of Nicotiana rustica. The most probable relationship, based on 14CO 2 biosyntheses and supporting some previous conclusions, is that nornicotine arises by demethylation of nicotine in both the root and aerial portions. The relative specific activities of anabasine and anatabine after the 14CO 2 biosyntheses indicated that anabasine is not the precursor of anatabine. In the case of nicotine, nornicotine, anatabine, and anabasine, higher specific activities were noted in the samples isolated from the root than in those isolated from the aerial portions. This shows that these four alkaloids all can be formed in the Nicotiana root, and furthermore, since the 14C in these experiments first enters into the metabolism of the aerial portion of the plants, these results indicate that the N. glutinosa root is the most active site of formation of each of these alkaloids. Finally, a comparison of the specific activities of anabasine, anatabine, and nicotine suggests that if a precursor-product relationship exists among these alkaloids it must be nicotine → anatabine or anabasine, or both.