MODULATION OF METAL-INDUCED GENOTOXICITY BY MAILLARD REACTION-PRODUCTS ISOLATED FROM COFFEE

PM2 bacteriophage DNA was exposed to non-dialysable Maillard reaction products (MRPs) isolated from brewed (Br), boiled (Bo) and instant (I) coffee brew extracts in a Fe2+ catalysed Fenton reaction at four pH c onditions (i.e. 7.5, 4.0, 3.2, 2.6). MRPs were incubated with DNA eith er directly with Fe2+, or following a short preincubation period condu cted with Fe2+ in an atmosphere of oxygen or argon. Damage to supercoi led DNA resulting in strand scissions as characterized by both nicked circular and linear forms were found to occur either with coffee MRPs or Fe2+ alone, in a dose-dependent manner at all pH conditions tested. At low MRP concentrations, damage to DNA with respect to Fe2+ was low ered only when MRPs were preincubated with Fe2+ in argon or oxygen bef ore incubating with DNA. The addition of MRPs and Fe2+ to DNA without preincubation; had no effects in protecting DNA damage. This finding s howed that a preincubation step is necessary for MRPs to chelate in or der to mitigate the Fenton reaction. In contrast, the protective effec ts against Fe2+-induced DNA breakage by MRPs were lost at high coffee MRP concentrations, irrespective of the incubation method used. Increa singly higher concentrations of MRPs in combination with Fe2+ actually enhanced the breakage of DNA with respect to the control. These resul ts indicate that MRPs at high concentrations do not improve Fe2+ ion c helation, but rather accelarate the DNA breakage by possibly changing the redox state of the transition element. (C) 1998 Elsevier Science L td. All rights reserved.