Tabaci Folia. Tobacco Leaves. Nicotina, Nicotine. Nicotinae Tartras, Nicotine Tartrate.
Tobacco leaves are obtained from Nicotiana Tabacum, Linn. (N.O. Solanaceae), cured and dried. The plant is a large herb indigenous to America and cultivated, together with other species of Tabacum, in temperate and subtropical countries. The leaves are allowed to wilt, and are then heaped and covered with mats. On these the moisture given off by the leaves condenses. When this "sweating" process is ended, the leaves are tied into bundles and packed in great heaps. The temperature of the heaps rapidly rises, and is kept as near as possible to 50° by turning them. During this process bacteria are active in producing certain, at present not well understood, changes. The leaves are finally dried, and are then ready for the market. They are ovate, ovate-lanceolate, or oval-oblong, brown, and sometimes exceed 50 centimetres in length. The margin is entire, apex acute, surface glandular and hairy, and the texture brittle. The leaves have a characteristic odour, and nauseous, bitter, acrid taste.
Constituents.—The principal constituent of tobacco leaves is the alkaloid nicotine, of which they contain from 1 to 7, sometimes even 10 per cent. They also contain a crystalline substance, nicotianin, and small quantities of alkaloids other than nicotine, viz., nicotinine, nicoteine, and nicoteline, together with traces of a volatile oil, etc. When tobacco is smoked the nicotine and other substances are more or less completely decomposed into pyridine, furfurol, collidine, hydrocyanic acid, carbon monoxide, and other bodies, to which the poisonous effects of tobacco smoke are mainly due.
Action and Uses.—Tobacco leaves are rarely used in medicine except by smoking. The amount of nicotine present in tobacco smoke depends upon the kind of tobacco used, and the manner and apparatus in which it is smoked; some experiments with cigarette smoke showed that it contained 50 per cent. of the nicotine originally in the tobacco. Nicotine closely resembles coniine and lobeline in its pharmacological action: the pyridine bodies present in tobacco smoke modify its action but slightly. Many explanations on the soothing effect of smoking upon the nervous system have been put forward, but agreement is general only in the statement that it is not entirely due to the action of nicotine. Over-indulgence in smoking gives rise to hoarseness and cough, due to congestion of the throat and air-passages. In more severe cases there is a feeble and intermittent action of the heart, depression of the central nervous system, impaired memory, dimness of vision, loss of colour perception, and tremors. The effect of cigar smoking on those who are not accustomed to it is to constrict blood vessels, increase intestinal movements, and raise blood pressure; these effects continue for about twenty minutes, during which time the blood pressure may be raised from 10 to 40 millimetres of mercury. Collapse then ensues, respiration becomes very feeble, the patient breaks out into a cold sweat, and blood pressure falls from 30 to 50 millimetres of mercury. These effects are probably due to the stimulant action of the nicotine on nerve-cells, followed later by the paralytic effect. Those accustomed to tobacco smoking experience none of these symptoms, because their tissues have learnt to oxidise a certain amount of nicotine. Tobacco, mixed with stramonium, lobelia, etc., is smoked for the relief of asthma. Liquid preparations of tobacco, and crude solutions of nicotine, are used as insecticides in horticulture by spraying and by vaporisation. In cases of poisoning by preparations of tobacco, the treatment recommended in the case of nicotine should be resorted to.
C10H14N2 = 162.132.
Nicotine, C10H14N2, is a liquid alkaloid which exists chiefly as malate in the leaves of Nicotiana Tabacum, Linn. (N.O. Solanaceae), the dried Virginian leaf sometimes containing as much as 7 per cent. It may be obtained by digesting the leaves in acidified water, evaporating to a small bulk, and distilling with excess of potassium hydroxide; shaking the distillate with ether, distilling the ethereal solution, and placing the residual nicotine in contact with quicklime to remove water, and finally distilling it in a current of hydrogen. Commercially it is extracted from the leaves with kerosene, and purified. It occurs as a very hygroscopic, colourless or yellowish, oily liquid, having an unpleasant, pungent, and acrid odour of stale, burnt tobacco. It gradually becomes brown in contact with the air, and is inflammable. In very dilute, aqueous solution, it has a sharp, burning, and persistent taste. It is extremely poisonous, nearly sixteen times more so than coniine. The free base is laevorotatory, the salts dextrorotatory. Its aqueous solution is alkaline, and turns red litmus blue, but does not redden phenol phthalein. Specific gravity, 1.01. Boiling-point, 240° to 242°. It remains liquid at -10°, and volatilises readily and without decomposition in a current of steam. Applied to paper it leaves an oily stain, which gradually disappears. Concentrated sulphuric and nitric acids produce no colour in the cold. Five decimils (0.5 milliliters) of nicotine warmed with 15 decimils (1.5 milliliters) of water should give no turbidity (absence of coniine). It should also remain clear when mixed with twice its volume of ether. Potassium hydroxide separates it from its aqueous solution. Bromine added to a dilute aqueous solution forms a yellow flocculent precipitate. Chlorine colours it brown to blood-red. It is precipitated by most of the usual alkaloidal reagents. On adding an ethereal solution of iodine to an ethereal solution of nicotine, a brownish-red resinous precipitate falls; this gradually becomes crystalline, while from the supernatant liquid translucent ruby-red crystals with a blue opalescence separate. Oxidation with chromic acid mixture yields nicotinic acid, and this, when distilled with lime, yields pyridine.
Freely soluble in water, alcohol, ether, petroleum ether, terpenes, or the fixed oils.
Action and Uses.—Nicotine first stimulates nerve cells and then paralyses them. It, therefore, at first raises blood pressure and later diminishes it. The paralysing action also results in a quicker heart, dilated bronchioles, and more active peristalsis, the latter from depression of the inhibitory fibres of the sympathetic. Nicotine is rarely used in medicine; it has been recommended for use in tetanus and as an antidote in strychnine poisoning. Nicotine salicylate (Eudermol) is employed as a parasiticide. It occurs in white or yellowish-white crystals, or as a crystalline powder, with a faint empyreumatic odour. It is soluble in water and in alcohol, but is used chiefly in the form of ointment (1 per cent.), prepared with lard, soft paraffin, or hydrous wool fat, for scabies and sycosis. Preparations of nicotine are largely employed in horticulture as insecticides, usually by vaporisation. In using these, precautions should be taken against absorption by contact with the skin. It is an extremely poisonous substance, and large doses may prove fatal within a few minutes, the symptoms being those of sudden paralysis of the central nervous system, including the respiratory centre. In cases of poisoning by nicotine the stomach should be evacuated, and repeated doses of tannic acid given. The patient must be kept warm in bed, and the medulla kept active by such stimulants as caffeine, atropine, and strychnine; but if there are signs of respiratory failure artificial respiration with oxygen must be resorted to immediately.
Dose.—¼ to 3 centimils (0.0025 to 0.03 milliliters) (1/24 to ½ minim).
C18H26N2O12, 2H2O = 498.26.
Nicotine tartrate or bitartrate, C10H14N2(C4H6O6)2, 2H2O, may be prepared by dissolving 10 of nicotine in an alcoholic solution of 18.5 of tartaric acid, and shaking out with ether; on evaporating the ether, nicotine tartrate separates out as an oil. It may be crystallised from absolute alcohol containing ether. It occurs in tufts of colourless or reddish-white crystals.
Soluble in water.
Action and Uses.—Nicotine tartrate has the properties described under Nicotine.
Dose.—1 to 3 milligrams (1/64 to 1/20 grain).