Site-specific Natural Isotopic Fractionation of hydrogen and carbon in nicotine, glycerol and vanillin was studied by NMR spectroscopy (SNIF-NMR) in order to point out specific mechanistic and environmental effects. Several products (cellulose, sugars, acids, nicotine) isolated from tobacco leaves present related carbon and nitrogen fractionation profiles. In nicotine, it is possible to measure eleven site-specific isotope ratios (D/H)iwhich give useful information about the climate of the region of production. The origin of glycerol in fermented beverages can be determined by2H and13C-NMR, and the botanical origin of triglycerides can also be checked in the same way.