THE INHIBITORY EFFECTS OF COFFEE ON RADICAL-MEDIATED OXIDATION AND MUTAGENICITY

Hydrogen peroxide (H2O2) has been implicated as a major contributor to coffee mutagenicity and genotoxicity in vitro. We have used three ass ays to show the gradual formation of H2O2 in freshly prepared roasted ground coffee and in instant coffees over time reaching levels of 400- 450 mu M after a l-h incubation period. Formation of H2O2 occurs throu gh an auto-oxidation process where polyphenolics, in the presence of t ransition metals, reduce atmospheric oxygen. However, because of these polyphenolics, coffee also possesses in vitro antioxidant activity as shown by its capacity to inhibit lipid peroxidation in Fenton-catalys ed hydroxylation reactions. The pro- and antioxidative effects of coff ee are also reflected in its mutagenic and antimutagenic activity in t he Ames test. Coffee is directly mutagenic in strains TA100 and TA102 due to H2O2 formation. However, coffee is also an antioxidant and anti mutagen. This beverage exerts a strong protective effect against the m utagenicity and cytotoxicity induced by the oxidant t-butylhydroperoxi de (t-BOOH). Thus, coffee, like many antioxidants, exhibits dual effec ts in vitro which are highly dependent upon parameters such as dose, a tmospheric oxygen, transition metals as well as the biological and che mical endpoints used for measurement. Consequently, the data obtained on the pro- and antioxidant properties of foods and beverages from in vitro bioassays must be interpreted with caution and the results are n ot easily extrapolated in vivo to assess the impact on human health.