Generation of Reactive Oxygen and Nitrogen Species by Interaction of Food Ingredients

Antioxidant compounds, such as polyphenols, are widely contained in food and drink to prevent undesirable oxidation. The FAO/WHO Joint Expert Committee on Food Additives (JECFA) and the Joint FAO/WHO Meeting on Pesticide Residues (JMPR) determine the acceptable daily intake (ADI) based on all available facts at the time of evaluation. JECFA generally sets ADI values based on the lowest relevant no-observed-adverse-effect level (NOAEL) in the most sensitive test species. The ADI values for food additives are commonly derived from NOAEL values in long-term in vivo studies in animals. However, unexpected effects caused by combined reactions may arise, because the ADI is determined for single compounds. There are many ingredients in foods and drinks. In fact, antioxidant compounds are also strong reducing agents. They can act as pro-oxidants under in vitro conditions and in the presence of copper ions. It is necessary that interactions occur in the human body. In this review, we introduced the interaction of antioxidant and pro-oxidant activities using electron spin resonance (ESR) measurements for the increase in reactive oxygen species (ROS) in relation to their structures and interactions with transition metals. The antioxidant activity was assessed with the 1,1-diphenyl-2-picrylhydrazyl (DPPH) assay, and the pro-oxidant effect of phenolic compounds on DNA damage was assessed by measuring 8-hydroxy-2'-deoxyguanosine (8-OHdG), which is effectively formed during oxidative damage. In conclusion, ortho-dihydroxyl groups that can chelate with Cu2+ induce the greatest pro-oxidant activity. Moreover, the interactions between phenolic compounds and copper induced to H2O2 were studied. The obtained results indicated that ROS participated in oxidative stress induced by antioxidant compounds in the presence of Cu2+. Those results indicate that combinations of high concentrations of antioxidants and certain metal ions can generate large amounts of ROS in artificial intestinal juice. Further studies will be needed to evaluate the physiological significance of these findings.