Transformation of Tobacco Alkaloids

Chemical transformation: In air oxidation of nicotine at room temperature, N´-methylmyosmine, which is supposed to be an active intermediate of degradation, cotinine, nicotine-N´-oxide, nicotyrine, myosmine, 3-pyridylpropyI ketone, 3-pyridylmethyI ketone, nicotinic acid, methylamine and ammonia were isolated. N´-Methylmyosmine was first characterized by 1H-NMR. When N´-methylmyosmine was heated, N-methylnicotinamide and nicotyrine were obtained in addition to a large amount of polymerized resinous substances. 2´(S)-nicotine-1´-N-oxide was rearranged to acetyl pseudooxynicotine by reaction with acetyl chloride or acetyl anhydride. This rearrangement could be generally useful for the preparation of Δ1-pyrrolines or Δ1-piperideines. When appropriate acetyl groups were used, the products were effective in improving tobacco taste.

Phytochemical transformation: Transformation of alkaloids in the tobacco plant was investigated by measuring their optical rotatory power, from which it was presumed that nicotine is biosynthesized in the S-form. The nornicotine formed in the leaves is synthesized from S-nicotine, but the one formed in the root is synthesized in the racemic form, indicating a route different from that found in the leaves. Secondary amine alkaloids such as anabasine and anatabine are in the racemic form. From Cherry Red tobacco, a transformation product of nornicotine. 1-(1´-2´(S)-nornicotino)1-β-D-fructofuranoside (m.p. 66-68°C), was isolated for the first time. The structure was confirmed physico-chemically and finally by synthesis. This compound increased markedly during curing, especially at the drying stage, suggesting formation through a non-enzymatic process.

Microbial transformation: 2´(S)-nicotine-1´-N-oxide, which is the most common natural oxidation product of nicotine, was degraded by bacteria abundant on the tobacco leaf surface and in the tobacco field soil. The isolated micro-organisms belong to genus Arthrobacter. Degradation pathway was: nicotine-N´-oxide → N´-methylmyosmine (60 % - 70 % yield) → 4-oxo-4- (3´-pyridyl)butyric acid, whereas nicotine degraded slowly by a different route: S-nicotine → 6-hydroxy-nicotine → 6-hydroxy-N´-methylmyosmine. No analogous and homologous oxides tested were degraded by the bacteria. 1´(R)-2´(S)nicotine-1´-N-oxide was preferentially degraded, compared to 1 ´(S)2´(S)-nicotine-1´-N- oxide.