Methylglyoxal (MG) is recognized as the most reactive glycating agent, generated during glycation and endogenously via carbohydrate, lipid and protein metabolism, especially during the glycolysis pathway [
1,
2]. Whilst the glyoxalase defense system converts the damaging MG into D-lactate via the glyoxalase enzyme complex, elevated tissue and plasma levels of MG are commonly observed in diabetes [
3,
4]. Methylglyoxal hydroimidazolone (MG-H1) is reported to be the most abundant MG-derived AGE modification in vivo leading to protein dysfunction [
5]. The interaction of AGEs with a receptor for AGEs (RAGE) triggers signal transduction by activation of the MAPK pathway, resulting in reactive oxygen species (ROS) overproduction and inflammation [
6]. The glycation reaction of amino acids with MG directly generates ROS, causing damage to cellular protein and DNA [
7‐
10]. In particular, oxidative damage of DNA is associated with the development of several pathologies, including physiological ageing, metabolic syndrome, diabetes, cancer and cardiovascular diseases [
11‐
13].
MG has been recognized as a potential target for intervention and novel pharmacological strategies are being developed to limit its accumulation and minimize its detrimental effects. Of these strategies, the ability for some AGE inhibitors to trap MG has received considerable interest [
14]. The early clinical trials with aminoguanidine (AG) showed great promise as an AGEs inhibitor. However, studies in people with diabetic nephropathy were terminated following safety and efficacy concerns [
15,
16]. Alternatively, studies on AGE inhibitors from natural products show more promise to combat AGE-associated diseases by scavenging free radicals, or by directly trapping MG. In this regard, pyridoxamine, a form of naturally occurring vitamin B
6 and inducer of glyoxalase enzyme expression -isothiocyanates and sulforaphanes found in cruciferous vegetables, have been reported to have some promise [
17,
18]. In particular, anthocyanins, the colourful pigment in various fruits and vegetables reduced ROS generation in human HepG2 cells exposed to a high glucose environment [
19]. This could explain, in part their biological effectiveness as anti-oxidant, anti-carcinogenic, anti-microbial and anti-inflammatory agents and their role in ameliorating hyperglycemia by improving insulin sensitivity via the cAMP-activated protein kinase pathway in diabetic mice [
20‐
23]. A derivative of anthocyanin, cyanidin-3-rutinoside (C3R), maybe particularly important as it delays postprandial glycemia by inhibiting α-glucosidase and pancreatic α-amylase which play an important role in glucose metabolism [
24‐
26]. Most recently, C3R inhibited ribose-, fructose-, glucose- and galactose-induced protein glycation and oxidation in vitro [
27]. Collectively these findings suggest that C3R may prevent MG-induced AGEs formation and oxidative protein and DNA damage which have not been investigated previously.
This study aimed to determine whether C3R inhibited MG-induced protein glycation (formation of AGEs) and oxidation (depletion of thiol groups) in vitro, and reduced MG/lysine-induced DNA damage using a plasmid DNA assay. To investigate possible mechanisms of action, we evaluated the role of C3R in reducing the generation of superoxide anion and hydroxyl radicals as well as direct scavenging of the MG. Due to the complexity of the glycation cascade, in vitro models were used as they enabled identification of the pathways of action.