Molecular modeling of major tobacco alkaloids in mainstream cigarette smoke

Consensus of opinion in literature regarding tobacco research has shown that cigarette smoke can cause irreparable damage to the genetic material, cell injury, and general respiratory landscape. The alkaloid family of tobacco has been implicated is a series of ailments including addiction, mental illnesses, psychological disorders, and cancer. Accordingly, this contribution describes the mechanistic degradation of major tobacco alkaloids including the widely studied nicotine and two other alkaloids which have received little attention in literature. The principal focus is to understand their energetics, their environmental fate, and the formation of intermediates considered harmful to tobacco consumers.

The intermediate components believed to originate from tobacco alkaloids in mainstream cigarette smoke were determined using as gas-chromatography hyphenated to a mass spectrometer fitted with a mass selective detector (MSD) while the energetics of intermediates were conducted using the density functional theory framework (DFT/B3LYP) using the 6-31G basis set.

The density functional theory calculations conducted using B3LYP correlation function established that the scission of the phenyl C-C bond in nicotine and β-nicotyrine, and C-N phenyl bond in 3,5-dimethyl-1-phenylpyrazole were respectively 87.40, 118.24 and 121.38 kcal/mol. The major by-products from the thermal degradation of nicotine, β-nicotyrine and 3,5-dimethyl-1-phenylpyrazole during cigarette smoking are predicted theoretically to be pyridine, 3-methylpyridine, toluene, and benzene. This was found to be consistent with experimental data presented in this work.

Clearly, the value of the bond dissociation energy was found to be dependent on the π-π interactions which plays a primary role in stabilizing the phenyl C-C in nicotine and β-nicotyrine and the phenyl C-N linkages in 3,5-dimethyl-1-phenylpyrazole. This investigation has elucidated the energetics for the formation of free radicals and intermediates considered detrimental to human health in cigarette smoking.Graphical abstractSome molecular alkaloids of tobacco the plant.