[Tobacco--once a medicinal plant. Does it contain substances with medicinal properties?]

Tobacco and its use was discovered by Christopher Columbus in parallel with the discovery of America. Soon after, tobacco became a known medicinal plant in Europe. Its harmful effects were gradually discovered, especially those of tobacco smoke, and now it is considered a toxic plant. Tobacco leaf has a monograph in German "Hagers Enzyklopädie derArzneistoffe und Drogen", which describes its old, already not valid, medicinal use and clearly shows the toxic effects. Epidemiological studies indicate about 50% lower incidence of Parkinson's disease in smokers than in non-smokers. In turn, studies of the brains of smokers using positron emission tomography showed significantly decreased level of monoamine oxidase B--an enzyme which degrades dopamine--the neurotransmitter which the significant insufficiency of about 80-85%, is responsible for the symptoms of Parkinson's disease. From the tobacco leaves there were isolated MAO-B inhibitors--naphthoquinone--2,3,6-trimethyl-1,4-naphthoquinone and diterpenoid -trans,trans-farnesol, which occur also in tobacco smoke. In the last decade many papers have appeared on the neuroprotective activity of nicotine, the best known component of tobacco. through the effect of this compound on specific nicotinic cholinergic receptors (nAChRs), which interacts with nigrostriatal dopaminergic system as well as the possibility of using nicotine for the treatment of Parkinson's disease and other neurodegenerative diseases. Moreover, tobacco was also found to contain inhibitors of neuronal nitric oxide synthase (nNOS). Tobacco cannot be considered a medicinal plant, but some compounds occurring in that plant may find therapeutic use.