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Nicotine occurs throughout the tobacco plant and especially in the leaves. Nicotine alkaloids are also found in the leaves of the coca plant. Nicotine constitutes 0.3 to 5% of the tobacco plant by dry weight, with biosynthesis taking place in the roots and accumulating in the leaves.
Nicotine is one of the few liquid alkaloids. In its pure state it is a colorless, odourless liquid with an oily consistency, but when exposed to light or air, it acquires a brown colour and gives off a strong odour of tobacco. Nicotine’s chemical formula is C10H14N2.
Nicotine is the addictive ingredient in the tobacco used in cigarettes, cigars, and snuff. In its psychoactive effects, nicotine is a unique substance with a biphasic effect; when inhaled in short puffs it has a stimulant effect, but when smoked in deep drags it can have a tranquilizing effect. This is why smoking can feel invigorating at some times and can seem to block stressful stimuli at others.
Nicotine is also an addictive drug, though, and smokers characteristically display a strong tendency to relapse after having successfully stopped smoking for a time. When ingested in larger doses, nicotine is a highly toxic poison that causes vomiting and nausea, headaches, stomach pains, and, in severe cases, convulsions, paralysis, and death.
Nicotine is commercially obtained from tobacco scraps and is used as an insecticide and as a veterinary vermifuge. Nitric acid or other oxidizing agents convert it to nicotinic acid, or niacin, which is used as a food supplement.
It is potent neurotoxin with particular specificity to insects; therefore nicotine was widely used as an insecticide in the past and currently nicotine derivatives such as imidacloprid continue to be widely used.
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