Pro-oxidative effects of melanoidin–copper complexes on isolated and cellular DNA

Abstract

High molecular weight Maillard reaction products (melanoidins) are described to possess metal-chelating properties. Whereas in food systems, this ability contributes to antioxidant properties, the consequences on biological systems are not quite clear. The study was aimed to evaluate the implication of metal complexation by melanoidins on DNA damage. Melanoidins prepared with D-glucose and diVerent L-amino acids under water-free reaction conditions were charged with cupric ions. The eVect on isolated DNA was investigated by the PM2 assay and on cellular systems in the human colon carcinoma cell line HCT-116 by alkaline unwinding. Independent of the amino acid composition, pure melanoidins (MW >14 kDa) did not cause signiWcant DNA damage. By charging melanoidins with Cu 2+ ions, a considerable DNA strand breaking activity was detectable, which was again ampliWed in an oxidative milieu (addition of hydrogen peroxide). Since Cu 2+ normally does not provoke the formation of reactive oxygen species (ROS) via Fenton-type reaction, the results obtained have to be attributed to reducing properties of melanoidins. Thus, in melanoidin-copper complexes redox cycling may take place leading to Cu + which subsequently undergoes Fenton-type and Haber-Weiss reactions. As a consequence, ROS are formed, which may explain the generation of DNA strand breaks.

Systematic Studies on the Antioxidant Capacity and Volatile Compound Profile of Yellow Mealworm Larvae (T. molitor L.) under Different Drying Regimes

“…However, in multi-throughput, these methods are not suitable for quality assessment of individual antioxidants in complex food/feed samples [50]. The variety of molecules reactive towards ABTS • , DPPH • or the FCR ranges from polyphenols, thiols (GSH), vitamin derivatives (L-ascorbic acid, NADH, retinoic acid, tocopherols/trolox), proteins and amino acids (tyrosine, tryptophan, cysteine), nucleotide bases (guanine), aldehydes from lipid oxidation to reductones, heterocycles and melanoidins from the Maillard reaction cascade [26,[82][83][84]. Instrumental setups such as online couplings of liquid chromatography and post-column derivatization with either ABTS •+ or DPPH • (online HPLC-UV/Vis TEAC or DPPH methods) combined with HPLC-ESI-ToF-MS [85,86] offer the possibility to unravel the molecular identity of potent mealworm larvae antioxidants and furthermore to assess changes in their specific antioxidant activity as a result of drying, which is of utmost importance from both insect processing as well as nutritive perspective.…”

Antioxidant and genoprotective effects of spent coffee extracts in human cells

“…Maillard reaction may have prooxidant activity under certain conditions such as high doses or in the presence of metal ions (Azam, et al 2003;Caemmerer et al, 2012;Zheng et al, 2008). Therefore, due to the fact that oxidative stress can be induced by prooxidant agents, either through the formation of ROS or the inhibition of antioxidant systems (Yordi et al, 2012), the possible induction of ROS by the spent coffee extracts was evaluated.…”

Utilization of vinasses as soil amendment: consequences and perspectives

“…These compounds inhibit enzymes that break down proteins (Ibarz et al 2008 ) and are genotoxic by forming complex melanoidin-metals (e.g. Cu), which can affect DNA strands (Cämmerer et al 2012 ). Other compounds in vinasse that might inhibit methanogens are polyphenols at 50–1000 mg L −1 (Arimi et al 2014 ).…”