An oily liquid substance found in tobacco plants, nicotine is the principal alkaloid of tobacco, constituting about 5% of the plant by weight. Nicotine is found throughout the tobacco plant, but occurs in highest concentrations in the leaves. Common tobacco, Nicotiana tabacum, is native to South America, Mexico, and the West Indies. Wild tobacco, Nicotiana rustica, was cultivated by Native Indians in eastern North America and is presently cultivated in Turkey, India, and several European countries.
In its pure form nicotine is colorless, but when exposed to light or air, it acquires a brown color and gives off a strong tobacco odor. Both nicotine and the genus name for the tobacco plant were named for Jean Nicot, a French ambassador to Portugal, who sent tobacco seeds to Paris in 1550. Crude nicotine was known by 1571, and the compound was first purified in 1828. By 1843, the correct molecular formula had been established and in 1904 it was synthesized in the laboratory.
Nicotine is one of the few liquid alkaloids. Alkaloids are nitrogenous organic compounds that have marked effects on human physiology and nicotine is the primary addictive ingredient that acts as a stimulant and makes tobacco smoking habit forming. Nicotine is currently marketed under a variety of names including Habitrol, Nicoderm, Nicorette, Nicotrol, and ProStep. These preparations are used to help wean smokers from cigarettes through topical or systemic intake of nicotine. The products are manufactured as either chewing gum or transdermal patches.