Nicotine is a naturally produced alkaloid in the nightshade family of plants (most predominantly in tobacco and Duboisia hopwoodii) and is widely used recreationally as a stimulant and anxiolytic. As a pharmaceutical drug, it is used for smoking cessation to relieve withdrawal symptoms. Nicotine acts as a receptor agonist at most nicotinic acetylcholine receptors (nAChRs), except at two nicotinic receptor subunits (nAChRα9 and nAChRα10) where it acts as a receptor antagonist.
(2'S)-Nicotine-1-oxide, a nicotine metabolite, arises from the liver's metabolism of nicotine via the cytochrome P450 (CYP) isoform CYP2A6. It has been identified in human sperm and semen.
N’-Nitrosonornicotine is a tobacco-specific N-nitrosamine and carcinogen that has been found in unburned tobacco and cigarette smoke.1It induces the formation of DNA adducts in isolated rat nasal mucosa and esophagus. N’-Nitrosonornicotine induces tumor formation in rat esophagus and nasal cavity, mouse lung, forestomach, and trachea, and hamster trachea and forebrain. Urinary levels of N’-nitrosonornicotine are positively correlated with the risk of esophageal cancer in smokers.2 1.Hecht, S.S.Biochemistry, biology, and carcinogenicity of tobacco-specific N-nitrosaminesChem. Res. Toxicol.11(6)559-603(1998) 2.Yuan, J.-M., Knezevich, A.D., Wang, R., et al.Urinary levels of the tobacco-specific carcinogen N’-nitrosonornicotine and its glucuronide are strongly associated with esophageal cancer risk in smokersCarcinogenesis32(9)1366-1371(2011)