SUMMARY
Black locust flowers are the source of a significant amount of antioxidants that can be useful against free radicals formed on the skin after the environmental factors. Having in mind these facts, the ultrasound-assisted extraction of antioxidants from plant materials was previously developed. The aim of this study was to prepare a topical formulation based on the extract of black locust flowers. The extract enriched with antioxidants was prepared using the ultrasound-assisted extraction using 60% (v/v) ethanol at 60 °C and a liquid-to-solid ratio of 10 mL/g for 30 min. The two topical formulations in the form of o/w emulsion at different concentrations of the extract (1% and 2%) were prepared by a hot-hot emulsification process. The product quality was estimated and concluded that the emulsion is white in the semi-solid state. The formulations can have adequate application properties due to their present ingredients, which do not leave a greasy film on the skin. The pH value of the prepared formulations was according to the allowed range for the application to the skin. The proper choice of ingredients enabled the achievement of satisfactory formulation stability. The formulations can be microbiologically safe to use for human purposes. A better antimicrobial activity against the investigated microorganism strains showed the formulation with higher content of the extract so it can be selected as an adequate for further analysis.