Abstract 1442 "Investigation of Rambutan and its Molecular Components as Inhibitors of DNA Oxidation"

Oxidative damage to DNA is involved in various diseases and this damage is observed primarily at guanine (G) because it is the most easily oxidized base. Rambutan fruit contains a number of antioxidants, including ellagic acid, p-coumaric acid, gallic acid, butylated hydroxytoluene, and corilagin. Here, we examined whether aqueous extracts of rambutan flesh, organic extracts of its peel and other molecules found in rambutan can inhibit the formation of oxidative DNA-protein crosslinks. The flash-quench technique is a photochemical method used for guanine oxidation and it can induce DNA-protein crosslinking. In these experiments, samples containing histone protein and pUC19 DNA were oxidized and the gel shift assay was then used to detect the oxidative DNA-protein crosslinking. In control experiments, there was a significant reduction in intensity for the supercoiled and nicked bands at longer irradiation times, along with the appearance of lower mobility material (crosslinked DNA). In contrast, when the aqueous rambutan extract or its molecular components were present, only a small change was observed in the supercoiled and nicked bands, with minimal amounts of lower mobility material; similar results were seen for ellagic acid and p-coumaric acid. When observing the presence of the organic rambutan-peel extract or the organic molecular component extracts in comparison to that of the aqueous extracts, a slightly stronger intensity was noted in the supercoiled and nicked bands, also displaying minimal amounts of lower mobility material. Transient absorption spectroscopy was utilized to monitor the intermediates formed, and a positive signal was observed at 510nm for a sample containing p-coumaric acid, consistent with the formation of a phenolic radical that would result from reaction of guanine radical with the antioxidant. We would like to thank the following foundations for their support: MSMU-NSF Building Capacities Grant + Research Fellowship John Stauffer Summer Research Program EastonFoundation Loring-Denault Endowed Chair in Chemistry