N-Nitrosonornicotine (NNN) is formed by synthetic or biological N-nitrosation of the tobacco alkaloid nornicotine. Following metabolic activation of NNN, DNA and protein adducts are formed releasing 4-hydroxy-1-(3-pyridyl)-1-butanone (HPB), an actual biomarker to differentiate between tobacco smokers and passive smokers. NNN and HPB can be prepared in a new one-step reaction by N-nitrosation of the nicotinoid myosmine which has been found not only in tobacco but also in nut products. The reaction was tested also in human gastric juice. The formation rate of NNN and HPB depends on the pH value in the reaction solutions. This is important under the aspect of myosmine uptake by humans from other biological sources and subsequent biological activation. The new reaction pathway indicates that human exposure to nicotinoid nitrosation products seems to be not restricted exclusively to tobacco.