Some 1,4-naphthoquinone derivatives, such as 2,3,6-trimethyl-1,4-naphthoquinone present in tobacco leaves and 5,8-dihydroxy-1,4-naphthoquinone (naphthazarin), are reported to inhibit both forms of monoamine oxidases, MAO-A and MAO-B, with a reversible mode of action [6,7,8,9], which may specifically explain a certain level of the resistance of tobacco smokers to PD. The gene discussed is MAOB; the disease is Parkinson disease.