Determination of photoprotective properties of flavonols against UV-radiation induced skin damage
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Flavonols constitute a class of polyphenolic compounds, which are known to protect a number of plant species from UV-radiation induced damage. Flavonols have received much interest because of the beneficial role of polyphenols in chemoprevention. The overall goal of this study was to investigate the sun screening properties of flavonols. We had 5 objectives to accomplish our goal: developing an analytical method to measure UV radiation-induced damage to DNA; determining the ability of flavonols to protect against UV radiation-induced damage to an artificial skin mimic; determining the UVA and aqueous stability properties of a range of flavonols; determine the decomposition products of the stability studies; general trend of flavonol photochemistry using a prototype compound 3-hydroxyflavone. Objective 1: To develop an analytical method to quantify direct UV radiation-induced DNA damage. The quantitative analysis of DNA lesion was achieved by validating a simple and robust analytical method based on HPLC-APCI-MS/MS technology to quantify cyclobutane pyrimidine dimers involving two thymines, the major DNA lesions produced in human skin when exposed to UV radiation. Objective 2: To use the analytical method for thymine dimer damage to determine the ability of three flavonols (quercetin, kaempferol and galangin) to protect EpiDerm™, an artificial skin mimic, against UV radiation-induced thymine dimer formation. We found that all three flavonols (4nmol/cm2) protected EpiDerm™ against UVB radiation-induced DNA damage. The levels of thymine dimer formation from UVA radiation were below the limit of quantification of our method. Objective 3: To determine the stability of a series of flavonols (galangin, kaempferol, quercetin and myricetin) to UVA radiation and aqueous media. The stability of flavonols was achieved by monitoring the levels of a range of flavonols remaining over time to UVA radiation and aqueous media by using HPLC-UV detection. We determined that stability of the flavonols was inversely related to the number of hydroxyl groups on the B-ring. Objective 4: To determine the decomposition products of the stability studies. This was accomplished by using HPLC-MS/MS and we determined that the flavonols (galangin, kaempferol, quercetin and myricetin) mainly decomposed to depside and its hydrolysis products in both systems and produced additional aldehyde products in the UVA experiment. Objective 5: To study the general trend of flavonol photochemistry using a prototype compound 3-hydroxyflavone. In order to identify whether there exists a general trend of photodecomposition of flavonols, we chose to investigate decomposition of 3-OH-F.
DegreeMaster of Science (M.Sc.)
DepartmentPharmacy and Nutrition
SupervisorKrol, Edward S.
CommitteeBadea, Ildiko; El-Aneed, Anas; Alcorn, Jane
Copyright DateOctober 2012
cyclobutane thymine dimer