Natural antioxidants from brown seaweeds for a sustainable cosmetic

Brown macroalgae have recently been in the focus of many researches due to their composition and the accumulation of specific metabolites with great antioxidant potential. Food, cosmetics, and pharmaceutical industries are constantly working to find natural, non-toxic compounds that can be used in their products. In this study, we evaluated the antioxidant activity of two (methanolic and dichloromethane) different fractions from three brown macroalgae, Dichtyota dichotoma, Dichtyota fasciola, and Halopteris scoparia. Several methods were used for the evaluation of antioxidant activity including the reduction of the radical cation (ABTS), the 2, 2-diphenyl-1-picryl-hydrazyl (DPPH), the Folin–Ciocalteu, and the oxygen radical absorbance capacity (ORAC) assays. Also, total protein content was determined by the Lowry method with slight modifications, while chlorophyll and carotenoid content were determined spectrophotometrically by the Lichtenthaler method. The toxicity of samples was determined using the zebrafish embryotoxicity test up to 96 h of embryonal development. All methanolic fractions showed higher antioxidant activity than the dichloromethane fractions, while H. scoparia methanolic fraction showed the highest activity (IC50 concentration of 1.947 mg/mL). The highest protein value was observed for Halopteris scoparia (20.7%) followed by Dichtyota dichotoma (7.4%) and Dichtyota fasciola (3.3%). Because of their good antioxidant potential, all three researched brown macroalgae have the potential to be used as a source of natural antioxidants in the cosmetic industry.