Influence of Solvents on the Antioxidant Properties of the Birch Outer Bark Extract in Cosmetic Emulsions

Abstract

The goal of this study was to evaluate the influence of birch outer bark (BOB) extraction solvents on the antioxidant properties of the obtained dry extracts, which were added in cosmetic product emulsions. Extracts obtained in ethanol, 2-propanol, 1-butanol and ethyl acetate as well as one purified in ethanol by means of recrystallization were used as antioxidant additives, in 30 and 60 mg·g-1 concentrations, to cosmetic water-in-oil type emulsions. It was found that raw extracts had a considerably higher antioxidant stability than purified ones, because the raw extracts showed a higher phenolic compound content. The highest stability was detected in the cosmetic sample, which had a raw BOB extract obtained in 2-propanol. At the additive concentration of 60 mg·g-1, the protection factor was 20.6 times higher than in the case of a blank sample. Among other solvents used, 2-propanol showed the best solubility for BOB extract phenolic compounds, the content of which reached 3.58 wt% from the oven dry extract. It could be concluded that raw BOB extracts act as an excellent antioxidant additive in cosmetic emulsions.