Effects Of Polyphenols On The Endogenous Formation Of Nitroso Compounds In Simulated Gastric Conditions

Abstract

There is considerable epidemiological evidence supporting a positive association between red and processed meat intake and risk of colorectal cancer. There are several potential mechanism for this positive association, in particular the formation of carcinogenic N-nitroso compounds. Previously, we could show a close relationship between red meat and ATNC (apparent total nitroso compounds) formation. Polyphenols can reduce the formation of N-nitroso compounds in vitro. In this study, we have investigated the protective effect of different polyphenols in a simulated gastric system. The in vitro effect of quercetin, rutin, (-)-epicatechin, rosmarinic acid, ascorbic acid and several plant extracts containing these compounds were tested in an acidic gastric juice environment (bovine serum albumin, haemin and haemoglobin were dissolved in 7mM HCl, pH2.2, 1 mM NaNO2 were added to start the reaction). Different classes nitroso compounds were determined using chemical denitrosation with chemiluminescence detection. This enabled us not only to measure ATNC but also nitrosothiols and iron-nitrosyl (nitrosyl haem) complexes separately to have more information of the mechanism. The highest concentration of ATNC were observed after 20 mins of reaction time, while nitrite concentrations gradually decreased to almost 0 µmol/L. The formation of nitroso compounds were investigated in a simplified stomach environment to simulate high nitrate and high red meat intake with and without the addition of polyphenols. Our results did not show a consistent effect of phenolic compounds on the formation of total nitroso compounds, nitrosothiols or iron-nitrosyl complexes.