Dietary phenolics and betel nut extracts as modifiers of N-nitrosation in rat and man.

Polyphenolic compounds (PPC) isolated from betel nuts and some dietary PPC were examined for their modifying effects on N-nitrosation in vitro and in vivo. The formation of N-nitrosodiethylamine (NDEA) and N-nitrosoproline (NPRO) was either enhanced or inhibited by PPC from betel nuts, depending on (1) the structure of the PPC, (2) the pH of the reaction medium, (3) the relative concentrations of nitrite and PPC, and (4) the nature of the nitrosatable amino compounds. Both catalysis and inhibition of endogenous nitrosation of proline were observed in rats, although to a lesser extent than in vitro. Caffeic and ferulic acids, as well as the PPC-containing beverages tea and coffee, exerted inhibitory effects on endogenous formation of NPRO in two human subjects. These results demonstrate that PPC can modify the yield of endogenously formed N-nitroso compounds, and may thus effect the carcinogen burden in man.