Nicotine is naturally found in the plants belonging to the Solanaceae family. Concentrations high enough to have a pharmacological effect are seen only in the tobacco sub-family, approximately 2% of dry weight and in Duboisia Hopwoodii that has been used by Australian aborigines ( http://en.wikipedia.org/wiki/Duboisia_hopwoodii ). It is also present in the range of 2–7 microgram per kg of various edible plants.
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Karl Fagerström (2014) studied this question.
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