Isoferulic acid prevents methylglyoxal-induced protein glycation and DNA damage by free radical scavenging activity

BACKGROUND Isoferulic acid (IFA), a naturally occurring cinnamic acid derivative, is a main active ingredient of the rhizoma of Cimicifuga dahurica. It has been shown various pharmacological activities. The aim of the study was to investigate the effect of IFA against MG-induced protein glycation and oxidative DNA damage. Free radical scavenging activity and the MGO-trapping abilities of IFA were also investigated. METHODS The fluorescent MG-derived AGEs and non-fluorescent N(ε)-(carboxymethyl) lysine (N(ε)-CML) was measured using a spectrofluorometer and an enzyme linked immunosorbant assay (ELISA). Protein carbonyl content was used to detect protein oxidation. Gel electrophoresis was used to determine DNA damage. Superoxide anion radicals and hydroxyl radicals were determined using cytochrome c reduction assay and thiobarbituric acid reactive 2-deoxy-D-ribose oxidation products, respectively. The MG-trapping capacity was performed by HPLC. RESULTS IFA (1.25-5 mM) inhibited the formation of fluorescent MG-derived AGEs, and N(ε)-CML, and protein carbonyl in bovine serum albumin. In addition, IFA (0.1-1 mM) also prevented MG/lysine-mediated oxidative DNA damage in the presence and absence of copper ion. The protective ability of IFA was directly correlated to inhibition of hydroxyl and superoxide anion radical generation during the reaction of MG and lysine. Most notably, IFA had no the directly trapping ability to MG. CONCLUSIONS The present results highlighted that free radical scavenging activity, but not the MG-trapping ability, is the mechanism of IFA for preventing MG-induced protein glycation and DNA damage.