Modifying Effects of Polyphenols and Other Constituents of Beer on the Formation of N-Nitroso Compounds. B. Pignatelli, R. Scriban, G. Descotes, and H. Bartsch. J. Am. Soc. Brew. Chem. 42:0018, 1984.

Effects of cysteine, phenolic acids, cinnamic acids, and of lyophilized malt and beer samples varying in their total content of polyphenolic compounds on the formation of N-nitroso compounds in vitro and in vivo were examined. N-Nitrosoproline (NPRO) and N-nitrosomorpholine were formed in vitro from the respective amines after 15 min, and NPRO excreted in 24-hr urine of rats dosed with proline and nitrite was measured in the presence and in the absence of modifiers. N-Nitrosation of proline was inhibited by cysteine, phenolic acids, and cinnamic acids; that of proline and morpholine was inhibited by beer constituents in vitro. The inhibitory effects were concentration dependent and were most pronounced at pH <4. Formation of NPRO in rats was inhibited by beer and malt samples in a manner similar to that observed in vitro. Although individual compounds in beer and malt and their relative contributions remain to be identified, the inhibition of N-nitrosation seems to be attributable to several compounds, including polyphenolic compounds, sulfhydryl compounds (eg, cysteine), and vitamin C.

Keywords: Beer, Cinnamic acids, Cysteine, Endogenous nitrosation, Malt, N-Nitroso compounds, Phenolic acids, Polyphenols