Nicotine and Cotinine Adducts of a Melanin Intermediate Demonstrated by Matrix-Assisted Laser Desorption/Ionization Time-of-Flight Mass Spectrometry

Abstract

Pigmentation is a major factor in the incorporation of many drugs into hair. In an attempt to elucidate potential mechanisms of drug-melanin interaction, melanin was synthesized in vitro in the presence of nicotine, which we have shown to have a substantial interaction with melanin, and cotinine, a primary nicotine metabolite. L-DOPA, a precursor of eumelanin, was oxidized and oligomerized with tyrosinase. Nicotine, cotinine, and/or their deuterated analogues were added to the oligomerization reaction mixture in a 10:1 L-DOPA:drug ratio. A black precipitate formed within 60 min. Aliquots were removed from the incubation mixture at 60, 120, and 360 min. MALDI-TOF MS determinations were carried out on each sample to provide a mean and standard error for the masses of interest. Internal calibration allowed accurate mass measurement of the products. A careful comparison of the spectra of samples prepared both with and without drug indicated the presence of masses corresponding to the protonated drug, melanin oligomers, and nicotine or continine adducts of the monomeric melanin intermediate dopaquinone (DOPAQ). Additional support for the presence of drug-melanin adducts was provided by employing deuterated analogues of nicotine and L-DOPA in the reaction and observing that the masses shifted accordingly. Structures of the adducts were further confirmed by select ion gating and postsource decay analysis.

Candy Flavorings in Tobacco

“…This dual focus is consistent with the emphasis the tobacco industry itself places on the nature and acceptability of emissions in their product development and evaluation (1,2,5,21). This includes industry research on the physical nature of smoke ("smoke chemistry" and appearance) and its acceptability to potential consumers (21,36).…”

“…Nicotine dosage can be carefully controlled by manufacturers to ensure that nicotine dose levels are sufficient for target populations to produce desired effects such as relaxation and mental acuity, while minimizing the risk of producing undesirable effects such as nausea and intoxication (20)(21)(22).…”

“…These constituents serve to optimize the free nicotine levels and subsequent dependence potential (4,20,21,25,27,30,33).…”

“…This includes industry research on the physical nature of smoke ("smoke chemistry" and appearance) and its acceptability to potential consumers (21,36). The physical design characteristics of the tobacco product interact with its chemical composition to influence its function and effect (2,21).…”

“…This includes industry research on the physical nature of smoke ("smoke chemistry" and appearance) and its acceptability to potential consumers (21,36). The physical design characteristics of the tobacco product interact with its chemical composition to influence its function and effect (2,21). For example, the size of the cuttings of the tobacco in cigarettes and non-combusted and non-heated tobacco, its level of acidity (measured as pH), and the presence of other substances interact to influence the release of nicotine from the product (3,21).…”