Studies On Protective Effects Of Natural Antioxidants On DNA Damage And Their Molecular Radiobiology Mechanism

By the analysis techniques of ultra weak chemiluminescence and spectrophotofluorometer, the protective functions against DNA damage of TP(Tea Polyphenols), EGB(Extracts of ginkgo biloba) and EBL(Extracts of bamboo leaf) were studied. The DNA damage was caused by OH from irradiation of 60Co- γ and chemiluminescence system in CuSC>4-Phen-Vc-H2O2-DNA.The results were follows:(1)All of TP,EGB and EBL had effects on clearing away OH and O2- . Comparing this three antioxidants, the order of clearing away both OH' and O2- was TP>EGB>EBL, and their IC50 of TP, EGB and EBL, which scavenging OH was 1.049mg/ml, 1.433mg/ml andl.554mg/ml respectively. At the same time, the ICso of TP, EGB and EBL, which scavenged O2- ,was 3.079ug/ml,3.425ug/ml and 3.593ug/ml respectively.(2)The inhibition rate of relative fluorescence intensity would rise when the concentration of three antioxidants was elevated, and their correlationship was linear. The inhibition rate of relative fluorescence intensity at 1.25mg/ml concentration was 0.902 for TP, 0.821 for EGB and 0.814 for EBL respectively, and the concentration of three antioxidants was approximately 0.5mg/ml when the inhibition rate of relative fluorescence intensity was 50 percent. The results demonstrated the three antioxidants could interact with DNA resemblingly.The inhibition rate of fluorescence intensity, which treated with TP, EGB and EBL respectively, was not saturated when the concentration varied, even above 95 percent. Nevertheless that one treated with Polysaccharide had a saturation character. The results demonstrated the two kinds of substances, which interacted with DNA, had a different mechanism.(3)The three antioxidants could protect DNA from irradiation damage. The three antioxidants at four concentrations (20,40,80, 160ug/ml) had protective functions under 0~20Gy dosage. Meanwhile the protective functions increased while the concentration rose.The protective functions of TP against DNA damage induced by irradiation of 60Co- y were the strongest. The protective functions of EGB were better than those of EBL, but the difference between them was not significant.(4)The three antioxidants were both preventative antioxidant and. chain-breaking antioxidant. The three antioxidants significantly decreased the peak value of chemiluminescence and delayed the back peak value in the kinetic curve of chemiluminescence, simultaneously the value of front peak and the back peak all descended very evidently, and ICso is approximately 0.2ug/ml. The time of the front peak value was barely influenced by these three antioxidants and was approximately 100s, but the time of the back peak varied largely and delayed while the concentration of the antioxidants rose. The concentration, which made the time of the back peak delay doubly, was approximately 0.2ug/ml.The order of inhibition rate of the front and the back peak value was TP, EGB and EBL respectively. The order of the delaying time of the back peak was also TP, EGB and EBL respectively.The effects of scavenging free radical were in accordance with the protective functions against DNA damage induced by irradiation of 60Co- Y and chemiluminescence in CuSO4- Phen-Vc-H2O2-DNA system, namely, TP, the strongest protective function against DNA damage, had the strongest effects on clearing away free radical, EGB the second, and EBL the third.