title: Microbiological assessment of the ultraviolet screening effect of sunscreen preparations.
abstract: The purpose of this study was the development of a microbiological method for the assessment of the ultraviolet (UV) screening effect of sunscreen preparations and determination of their sun protection factor. The method is based on the lethal effect of UV radiation on Escherichia coli (E. coli ) and the protective ability of sunscreens. The time of UV exposure required for the reduction of the E. coli viable count by 90% (decimal reduction time, DRT) was used as the photoprotection assessment parameter. The method was tested by assessing the effect of selected experimental variables on the DRT. The suitability of the method as a quality control tool for sunscreen preparations was then checked by assessing the influence of selected formulation variables on the photoprotective effect of a series of o/w emulsion formulations with different compositions. The method proved valid for detecting changes in the photoprotective effect of a market sunscreen product as a result of modifying experimental conditions. It also proved valid for ranking market sunscreen products according to their UV screening effect. Equally important, the method could successfully detect changes in the photoprotective effect of sunscreen test formulations as a function of the concentration and type of the sunscreen agents.
authors.affiliation: Department of Pharmaceutics, University of Alexandria, El-Khartoum Square, Azarita, Alexandria 21521, Egypt.
authors.forename: Yasmine
authors.initials: Y
authors.lastname: Gomaa
authors.forename: Elsayed
authors.initials: E
authors.lastname: Aboulmagd
authors.forename: Nabila A
authors.initials: NA
authors.lastname: Boraei
authors.forename: Inas A
authors.initials: IA
authors.lastname: Darwish
authors.forename: Labiba K
authors.initials: LK
authors.lastname: El-Khordagui
mesh_terms: D001562:Benzimidazoles / Q000494:pharmacology; D001577:Benzophenones / Q000494:pharmacology; D004353:Drug Evaluation, Preclinical / Q000379:methods; D004926:Escherichia coli / Q000254:growth & development / Q000528:radiation effects*; D015203:Reproducibility of Results; D013451:Sulfonic Acids / Q000494:pharmacology; D013473:Sunscreening Agents / Q000494:pharmacology*; D014025:Titanium / Q000494:pharmacology; D014466:Ultraviolet Rays / Q000009:adverse effects*
chemical_list: D001562:Benzimidazoles; D001577:Benzophenones; D013451:Sulfonic Acids; D013473:Sunscreening Agents; C009495:titanium dioxide; C005290:oxybenzone; C499767:ensulizole; D014025:Titanium