title: Contribution of Nicotine and Nornicotine toward the Production of N'-Nitrosonornicotine in Air-Cured Tobacco (Nicotiana tabacum).
abstract: N'-Nitrosonornicotine (6) is a potent and organ-specific carcinogen found in tobacco and tobacco smoke in substantial amounts. Nicotine (1) and nornicotine (2) are proposed to be the precursors of 6 in tobacco. Since 1 can be rapidly demethylated to 2 in tobacco, to distinguish between the direct formation of 6 from these potential precursors is difficult. A gas chromatography/thermal energy analyzer method using two columns in series was developed to separate the enantiomers of 6, N'-nitrosoanabasine (7), and N'-nitrosoanatabine (8). Tobacco lines with different combinations of three nicotine demethylases inhibited were grown in the field. Air-cured leaves were analyzed for the enantiomeric composition of four main alkaloids and their corresponding tobacco-specific nitrosamines. The percentage of (R)-6 of total 6 varied from 7% to 69% in mutant lines. The measured 6 had the same enantiomeric composition as 2, rather than 1, even when the level of 2 was reduced to 0.6% of 1 in a triple mutant line. The pattern of the enantiomeric composition of 1, 2, and 6 demonstrated that the direct formation of 6 from 1, if it occurs, is negligible in air-cured tobacco. Since (S)-6 is more highly carcinogenic than its R form, the reduction of (S)-2 should be a priority for the reduction of 6.
authors.affiliation: Guizhou Academy of Tobacco Science , Guiyang, Guizhou 550081, People's Republic of China.|Department of Plant and Soil Sciences, University of Kentucky , Lexington, Kentucky 40546-0312, United States.
authors.forename: Bin
authors.initials: B
authors.lastname: Cai
authors.affiliation: Department of Plant and Soil Sciences, University of Kentucky , Lexington, Kentucky 40546-0312, United States.
authors.forename: Huihua
authors.initials: H
authors.lastname: Ji
authors.affiliation: Department of Plant and Soil Sciences, University of Kentucky , Lexington, Kentucky 40546-0312, United States.
authors.forename: Franklin F
authors.initials: FF
authors.lastname: Fannin
authors.affiliation: Department of Plant and Soil Sciences, University of Kentucky , Lexington, Kentucky 40546-0312, United States.
authors.forename: Lowell P
authors.initials: LP
authors.lastname: Bush
mesh_terms: D000470:Alkaloids / Q000737:chemistry*; D002273:Carcinogens / Q000737:chemistry*; D015394:Molecular Structure; D009538:Nicotine / Q000031:analogs & derivatives* / Q000737:chemistry*; D009602:Nitrosamines / Q000737:chemistry*; D009657:North Carolina; D018515:Plant Leaves / Q000737:chemistry; D013237:Stereoisomerism; D014026:Nicotiana / Q000737:chemistry* / Q000235:genetics
chemical_list: D000470:Alkaloids; D002273:Carcinogens; D009602:Nitrosamines; C010257:N'-nitrosoanabasine; D009538:Nicotine; C032978:N'-nitrosoanatabine; C005311:nornicotine; C008655:N'-nitrosonornicotine