substrates used in the natural synthetic pathway performed in the tobacco plant and the substrates most used in synthesis. Another approach measures the carbon-14 content which also differs between natural and laboratory-based tobacco. These methods remain to be fully evaluated and validated using a wide range of samples. Natural occurrence Nicotine is a secondary metabolite produced in a variety of plants in the family Solanaceae, most notably in tobacco Nicotiana tabacum, where it can be found at high concentrations of 0.5 to 7.5%. Nicotine is also found in the leaves of other tobacco species, such as Nicotiana rustica (in amounts of 2–14%). Nicotine production is strongly induced in response to wounding as part of a jasmonate-dependent reaction. Specialist insects on tobacco, such as the tobacco hornworm (Manduca sexta), have a number of adaptations to the detoxification and even adaptive re-purposing of nicotine. Nicotine is also found at low concentrations in the nectar of tobacco plants, where it may promote outcrossing by affecting the behavior of hummingbird pollinators. Nicotine occurs in smaller amounts (varying from 2–7 μg/kg, or 20–70 millionths of a percent wet weight) in other Solanaceaeous plants, including some crop species such as potatoes, tomatoes, eggplant, and peppers, as well as non-crop species such as Duboisia hopwoodii. The amounts of nicotine in tomatoes lowers substantially as the fruit ripens. A 1999 report found "In some papers it is suggested that the contribution of dietary nicotine intake is significant when compared with exposure to ETS [environmental tobacco smoke] or by active smoking of small numbers of cigarettes. Others consider the dietary intake to be negligible unless inordinately large amounts of specific vegetables are consumed." The amount of nicotine eaten per day is roughly around 1.4 and 2.25 μg/day at the 95th percentile. These numbers may be low due to insufficient food intake data. The concentrations of nicotine in vegetables are difficult to measure accurately, since they are very low (parts per billion range). History, society and culture Nicotine was originally isolated from the tobacco plant in 1828 by chemists Wilhelm Heinrich Posselt and Karl Ludwig Reimann from Germany, who believed it was a poison. Its chemical empirical formula was described by Melsens in 1843, its structure was discovered by Adolf Pinner and Richard Wolffenstein in 1893, and it was first synthesized by Amé Pictet and A. Rotschy in 1904. Nicotine is named after the tobacco plant Nicotiana tabacum, which in