Identification of nitrophenols as nitrosation products from capsaicin and red chillies

The in vitro nitrosation of sun-dried red chillies (Capsicum annuum) and of its constituents capsaicin and dihydrocapsaicin was studied. The nitrophenols 4-nitroguaiacol, 4,6-dinitroguaiacol, nitrocapsaicin and nitrodihydrocapsaicin were detected as final products, whereas no formation of nitrosamides was observed though this is expected from the amide precursors capsaicin and dihydrocapsaicin. The nitrosation occurs readily with remarkable yields of nitrophenols even at physiological pH and at nitrite concentrations which are within the range of those found in the human stomach. Due to their toxicity, nitrophenols need to be included in total risk assessment through potential endogenous nitrosation of foodstuffs.