Protective effect of the seeds of Silybum marianum against advanced glycation end products induced oxidative DNA and protein damage

Diabetes mellitus (DM) is a metabolic syndrome characterized particularly by hyperglycemia which causes diabetes patients to develop microvascular and macrovascular complications such as nephropathy, neuropathy, retinopathy and atherosclerosis. It is stated that the advanced glycation end products (AGE) arisen from high blood-glucose levels takes part in the development of these complications. The non-enzymatic spontaneous reaction of the amino- groups of the proteins with glucose and other reductant sugar is called "glycation". Glycation is the number one cause of the spontaneously occurring damages in physiological systems. Even though glucose is the primary reductant sugar found in body fluids, the phosphoryl byproducts of the carbohydrate metabolism are far more potent glycation agents. Being a strong reductant sugar, fructose causes protein to glycation with 7-9 times more potency compared to glucose. The use of fructose added food and beverages (high fructose corn syrup) have continually been increased (pastry, candies, soda etc.). Since fructose does not interfere with the secretion of insulin and leptin which have effects over appetite suppression, fructose overconsumption is a risk factor for obesity, diabetes and nonalcoholic liver disease. In this thesis, the effect of the ethanol/water (1:1) extract of Silybum marianum seeds on in vitro evolution of free radical scavenging activity was examined. It is known that a significant increase in free-radical production is a result of diabetic complications. For this purpose, total phenolic and flavonoid content, reducing power and ABTS radical cation scavenging activities were investigated. Then, the effects of S. marianum on the proteins modified by the BSA/Fructose system and the antiglycation effects in the prevention of oxidative DNA damage were investigated. Consequently, the total amount of phenolic component of S. marianum was found to be 262,70 ± 13,84 μg gallic acid equivalent (GAE)/mg extract, total flavonoid was found to be 10,50 ± 1,01 μg quercetin equivalent (QUE)/mg extract, ABTS radical cation scavenging activity was found to be % 70.4 and ferric ion reducing power was found. The results suggest that the seeds extract of S. marianum has the potential to be used as an anti-glycating agents with a significant inhibitory effect in preventing the formation of fructosamine, α-dicarbonyl, protein carbonyl and oxidative DNA damage.