Abstract
BackgroundMethylglyoxal (MG) is a highly reactive dicarbonyl precursor for the formation of advanced glycation end products (AGEs) associated with age-related diseases, including diabetes and its complications. Clitoria ternatea L. flower has been reported to possess antioxidant and antiglycating properties. Evidence indicates that the extract of Clitoria ternatea L. flower inhibits fructose-induced protein glycation and oxidative damage to bovine serum albumin (BSA). However, there is no evidence to support the inhibitory effect of CTE against MG-mediated protein glycation and oxidative damage to protein and DNA. Therefore, the aim of the present study was to investigate whether C. ternatea flower extract (CTE) prevents MG-induced protein glycation and oxidative DNA damage.MethodsThe formation of fluorescent AGEs in BSA was evaluated using spectrofluorometer. The protein carbonyl and thiol group content were used for detecting protein oxidation. DNA strand breakage in a glycation model comprising of MG, lysine and Cu2+ or a free radical generator 2,2′-azobis(2-methylpropionamidine) dihydrochloride (AAPH) systems was investigated using gel electrophoresis. Generation of superoxide anions and hydroxyl radicals in the MG/lysine system was assessed by the cytochrome c reduction assay and thiobarbituric acid reactive substances assay, respectively. High performance liquid chromatography (HPLC) was used to measure the MG-trapping ability.ResultsIn the BSA/MG system, CTE (0.25–1 mg/mL) significantly inhibited the formation of fluorescent AGEs and protein oxidation by reducing protein carbonyl content as well as preventing the protein thiol depletion. The concentration of CTE at 0.125–1 mg/mL prevented oxidative DNA cleavage in MG/lysine and AAPH systems associated with the inhibition of superoxide anion and hydroxyl radical formation. It also directly trapped MG in a concentration-dependent manner, ranging from 15 to 43%.ConclusionsThe study findings suggest that the direct carbonyl trapping ability and the free radical scavenging activity of CTE are the underlying mechanisms responsible for the prevention of protein glycation and oxidative DNA damage.
Highlights
Methylglyoxal (MG) is a highly reactive dicarbonyl precursor for the formation of advanced glycation end products (AGEs) associated with age-related diseases, including diabetes and its complications
The effect of C. ternatea flower extract (CTE) on the formation of fluorescent AGEs bovine serum albumin (BSA) incubation with MG caused a 4.5-fold increase in the formation of fluorescent AGEs when compared to BSA alone and this different was statistically significant (Fig. 1)
The addition of AG reduced the level of protein carbonyl content which was a similar amount as BSA alone
Summary
Methylglyoxal (MG) is a highly reactive dicarbonyl precursor for the formation of advanced glycation end products (AGEs) associated with age-related diseases, including diabetes and its complications. Evidence indicates that the extract of Clitoria ternatea L. flower inhibits fructose-induced protein glycation and oxidative damage to bovine serum albumin (BSA). Non-enzymatic crosslinking of MG with lysine or arginine residues of proteins during AGE formation contributes to ROS generation including superoxide anions and hydroxyl radicals [11]. These highly toxic compounds trigger oxidative modification and subsequent damage to cellular components such as proteins [12] and DNA [13, 14]. Finding yielded by recent studies in this field indicate that ROSmediated oxidative damage contributes to the pathogenesis associated with numerous chronic diseases such as cancer, atherosclerosis and cardiovascular disease [15]
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