Stimulation of Nicotine Demethylation by NaHCO3 Treatment Using Greenhouse-Grown Burley Tobacco

• Published in: Journal of agricultural and food chemistry 2003-12, Vol.51 (26), p.7679-7683
• Main Authors: Shi, Hongzhi, Kalengamaliro, Newton E, Krauss, Marc R, Hempfling, Walter P, Gadani, Ferruccio
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Biological and medical sciences; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; Generalities. Agricultural and farming systems. Agricultural development; Generalities. Production, biomass, yield. Quality
• ISSN: 0021-8561; 1520-5118
• DOI: 10.1021/jf030136r

Experiments were conducted in tobacco (Nicotiana tabacum L.) to investigate the effect of sodium bicarbonate (NaHCO3) on the conversion of nicotine to nornicotine, a secondary alkaloid that can form the tobacco-specific nitrosamine N-nitrosonornicotine (NNN). The results showed that, under optimum conditions, NaHCO3 stimulated nicotine conversion in converter plants to the maximum level predetermined by the genetic background. The conversion level in NaHCO3-treated leaves was 2−3 times higher than that in control leaves. For young seedlings the optimum concentration of sodium bicarbonate was 0.8% aqueous solution, and for adult plants the optimum concentration was 1%. Lower concentrations resulted in partial stimulation, whereas higher concentration damaged leaf tissue and resulted in a lower conversion level. Studies with different temperatures (from 22 to 43 °C) showed that 37 °C was optimal. This temperature allowed the least amount of time, 2−3 days for mature leaves and 4−6 days for green leaves, for the major converters to reach >95% of nicotine conversion. An examination of leaves from different growth stages and stalk positions showed that the amount of time needed for conversion was longer for young leaves and shorter for mature leaves. Treatment of leaves with NaHCO3 affords a rapid and convenient means of identifying and removing nornicotine converter plants during growth in the greenhouse or field. Keywords: Tobacco; nornicotine; nicotine; conversion; NaHCO3; demethylation