Volume 9 (1978): Issue 5 (December 1978)

This paper illustrates the potential of a computerized spectrophotometer for measuring total alkaloids in tobacco. Prediction equations were developed for three optical parameters. Of the three parameters investigated d² (log (1/R)) /d/² gave the best results and d R / R d l gave better results than log (1/R), where reflectance R is the ratio of the detector signal of the sample to the detector signal of the ceramic standard in the reflectance mode. The coefficient of determination r² for the prediction equation containing d² (log (1/R)) /d/² terms at 10 different wavelengths was 0.975. This equation predicted the total alkaloids in an independent set of samples with a standard error of 0.438 %. Instrument noise contributed 43 % of the variation, the remainder was attributed to anomalies of the chemical methods.

While it is known that ionizing radiation can bring about chemical, biological and physical changes in organic tissue, relatively little is known concerning radiation effects on tobacco and its combustion products. In an effort to study such changes, Virginia bright tobacco was exposed to ionizing radiation at doses up to 50 Mrads, generated electronically by a high-voltage discharge. It was found that tobacco exposed to this high radiation will undergo physical changes such as a darkening, an increase in brittleness, puffing of the stems and a change in aroma characteristics. Chemical changes were found in selected chemicaI components such as water and solvent solubles, nicotine, reducing sugars, dextrin, cellulose, pectin, tannins and lignin. Both physical and chemical changes seem to be dose dependent. Studies on smoke components from cigarettes of both irradiated and non-irradiated tobacco indicate that irradiation had no major effects on the components of the gas phase examined and only minor effects on the composition of the particulate phase.

A compact, portable pressure-drop instrument that incorporates modern electronic pressure-drop measuring techniques has been designed and built. It includes a built-in laminar-flow calibration standard. The new design offers virtual independence from external capillary standards (and the associated problems of maintaining capillary cleanliness), fast digital readout, potential for automatic data processing, and a simple method of flow-rate adjustment at different filter rod pressure drops. Pressure drop measured with the new instrument meets the CORESTA-recommended definition of pressure drop for filter rods. Data collected on the new instrument show that the average and percent coefficient of variation of pressure drops measured on the new instrument compare favourably with data collected by the previously used standard instrument having mainly a vacuum pump, needle valve and water column manometer.

The CORESTA Pesticide Sub-Group has examined various methods for the determination of dithiocarbamate residues in tobacco. As a result of this work the method described in this paper is recommended.

After a brief look at the food law situation, the particular problems of the presence of humic acid in paper are dealt with. Origin and significance as well as physical and chemical properties of humic acid are described. The principle of the method of analysis is that the dyes transferred from the paper to an aqueous solution are freed of humic acid by acidification and extracted from the centrifugate, using isoamyl alcohol. The concentrated aqueous eluate from the amyl alcohol is examined paper chromatographically. The Rf figures for the dyes after their said preparation are quoted and the analytical procedure explained by means of examples.

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.

The constituents of the neutral volatiles in air-cured Burley tobacco were studied, and the following 19 substances were newly added to our lists:

1. 6-Methyl-6,9-oxidonon-4-en-2-ol

2. 5-Isopropylnon-3-en-2,8-dioI

3. 5-Isopropylnonan-2,8-diol

4. 3,3,5-Trimethyl-8-isopropyl-4,9-dioxabicyclo-[3.3.1]nonan-2-oI

5. 2-(1-Methyl-4-isopropyl-7,8-dioxabicyclo[3.2.1]-octan-6-yl)propan-2-ol

6. 3-Oxoactinidol

7. 5-Isopropyl-7-(2-methyltetrahydrofur-2-yl)hept-6-en-2-ol

8. O-Methyl acetophenone

9. 1,5,5-Trimethyl-9-oxabicyclo[4.3.0]nonan-3-one

10. 4-(3-Hydroxybutylidene)-3,5,5-trimethylcyclohex-2-en-1-one

11. (1-Methyl-4-isopropyl-7,8-dioxabicyclo[3.2.1]-octan-6-yl)methyl ketone

12. 6,10-Dimethyl-2-(1-methylethenyl)spiro[4.5]dec-6-en-8-one (solavetivone)

13. 5-Isopropyl-7-(2-methyltetrahydrofur-2-yl)hept-6-en-2-one

14. 4-Ethyl-4-methylbutan-4-olide

15. Phthalide

16. Hydroxydihydrobovolide

17. 1,2-Dimethoxy benzene

18. o-Anisidine

19. Methylanthranilate

A large number of identified compounds may be viewed as degradation products of carotenoids and thunberganoids. These compounds have a characteristic aroma and are thought to be key flavour components in the essential oils of tobacco. The presence of any labdanoid hydrocarbons or their oxygenated products was not recognized in our Burley tobacco extract. Burley tobacco is thought to be deficient in labdanoid compounds.