Tobacco is the dried leaves of the cultivated plant Nicotiana tabacum, a native of North and South America (Nicotiana rustica), and a plant that is a member of the Solanacae (nightshade) family. A wide variety of plants, all native to North America, were either combined with tobacco or contain nicotine-like substances, but the only two that were widely cultivated were Nicotiana tabacum (common tobacco) and Nicotiana rustica (Aztec tobacco; Figure 7.1). The derivation of the word tobacco comes from the West Indian (Caribbean) word tabaco and Spanish tobaco (tobago or tobah), which actually refer to the pipe or tube with which the Indians smoked the plant. The name was then transferred by the Spaniards to the plant itself. Tobacco is widely used in various products that can be smoked, such as cigars, pipes, and cigarettes, or administered through the oral and nasal cavities, such as via snuff or chewing tobacco.
Cigarette smoke contains more than 4,000 chemicals, many of which could potentially contribute to the addictive properties of tobacco. However, the most well known constituent that causes the acute psychopharmacological properties of tobacco is nicotine, and this has been found to be a major component in tobacco smoke that is responsible for nicotine addiction (Box 7.1).
Nicotine derives its name from the botanical name Nicotiana, which in turn was eponymously derived from Jean Nicot de Villemain, the French ambassador to Portugal who introduced tobacco to the French court. Mr. Nicot brought tobacco powder via Portugal to Queen Catherine de Medicis after the death of Portugal’s King Henri II in 1561. Catherine de Medicis appreciated the pleasurable effects of this poudre Américaine (“American powder”). She developed a taste for it, became an enthusiast, and ensured its popularity, first inside and then outside the court.
Figure 7.1 Parts of the Nicotiana tabacum plant: – summit of stem with inflorescence; 2 – corolla split open; 3 – capsule with persistent calyx; 4 – a seed; 5 – section of the same (4 and 5 are greatly enlarged). [Taken with permission from Bentley R, Trimen H. Medicinal Plants: Being descriptions with original figures of the principal plants employed in medicine and an account of the characters, properties, and uses of their parts and products of medicinal value, vol. 3. J & A Churchill, London, 1880, no. 191.]
Nicotine itself was isolated by Posselt and Reimann in 1828. It is a highly toxic alkaloid that is derived from tobacco. It is water-soluble, colorless, and bitter-tasting in the liquid form and is a weak base with pH 8.5. Nicotine is not to be confused with nicotinic acid, which is the fat-soluble vitamin B-3, called niacin,used in the treatment of pellagra, a niacin deficiency syndrome characterized by cutaneous, gastrointestinal, neurologic, and mental symptoms.
Tobacco smoke contains not only nicotine but also carbon monoxide and tar. “Tar” is a generic term for what remains after the moisture and nicotine are removed from tobacco and largely consists of aromatic hydrocarbons, many of which are carcinogens (Table 7.1).