An. Wijewickreme et Dd. Kitts, MODULATION OF METAL-INDUCED GENOTOXICITY BY MAILLARD REACTION-PRODUCTS ISOLATED FROM COFFEE, Food and chemical toxicology, 36(7), 1998, pp. 543
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.