PRODUCTS OF OXIDIZED L-ASCORBIC ACID DAMAGE ACELLULAR DNA

L-ascorbic acid can be pro-oxidant and anti-oxidant in different reaction. This study aims to test the effects about products of oxidized L-ascorbic acid on acellular Dna. Measurement: acellular Dna, nuclear Dna fixed on slides, are used in our experiment. There are four groups and one negative. negative control is sham-treated with buffer(ph 7.2 and aa/ h2o2/fenton free). Experimental groups are treated separately with 0.06 mM L-ascorbic acid (aa) alone(exposed in air), 0.06 mM L-ascorbic acid (aa) alone(no exposure in air), 1.2 mM hydrogen peroxide (h2o2) alone, and a mixture of final concentration of 0.03 mM L-ascorbic acid and 0. 6 mM hydrogen peroxide (aa+ h2o2). Each experimental group consists of 4 slides and each slide is treated for 4 hours at 4 ℃ in a dark place. The Dna damage is quantified by alkaline Comet assay. The comet images are analysed by Comet a1.0 software. Differences among groups are compared with SPSS 11.0. Results: Dna singlestrand breakage is found to be treatment-dependent in the following sequence: aa+ h2o2> aa(oxidized) > h2o2, aa(without oxidization) and Control. Conclusion: acellular Dna can tolerate the low concentration h2o2, but is sensitive to free radical. The results indicate that aa expose in air and mixture of aa and h2o2 can produce •oh and L-dehydroascorbate (Dha), •oh can damage Dna.