Brown seaweeds, due to their wide range of bioactive compounds, have a high ability to inhibit free radicals and protect against ultraviolet rays. In the present study, the ethyl acetate fraction (EF) was isolated from the Padina boergesenii brown seaweed. Antioxidant activity (by the DPPH scavenging activity method) and cytotoxicity against UVB-induced cytotoxicity in HaCaT human keratinocytes were evaluated. Then, this fraction was used as a bio-filter in the formulation of sunscreen, and the physical properties and stability were investigated. The results showed that the EF could inhibit DPPH radical scavenging (54 ± 1%) and cell viability of HaCaT keratinocytes exposed to UVB irradiation (81.2 ± 0.1%). The results of the stability study of the cream formulated with EF showed that at temperatures 4 °C and 25 °C it has high stability; and at 40 °C on the 28th day, a slight decrease in its stability was observed. The pH and Sun Protection Factor of the cream formulated with EF were reported at 5.8 and 20.55, respectively. Also, the DPPH scavenging activity of the cream was not altered for 28 days of storage at temperatures of 4-40 °C. According to our results, it was proved that the sunscreen formulated with EF of P. boergesenii brown seaweed has promising properties and characteristics that can create a new opportunity for the development of cosmetics and skin care products.
Keywords: brown seaweed; cosmetics; marine natural products; polyphenol compounds; sunscreen cream.