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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 liquidto-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. [ABSTRACT FROM AUTHOR]

The impact of solvent polarity on the kinetics, reducing capacity, antioxidant activity, and mineral composition of black locust (Robinia pseudoacacia) flowers extracts obtained by ultrasound-assisted extraction was investigated. The DPPH assay and the Folin-Ciocalteu method were applied to define the antioxidant activity and reducing capacity of the extracts, respectively. The mineral content was defined using the ICP-OES method. Ponomaryov and non-stationary diffusion models were used for modeling the extraction of antioxidants. The obtained results showed that antioxidant activity, phenolic and mineral contents of the extracts were varied significantly depending on the solvent polarity. The highest reducing capacity (3.78 g gallic acid equivalent per 100 g dry weight) had the 50% (v/v) methanol extract, while the strongest antioxidant activity (IC50 = 0.3381 mg/mL) was found in the 50% (v/v) ethanol extract. HPLC analysis showed that water as a solvent had the highest extraction capacity for vanillic acid and catechin hydrate. ICP-OES analysis confirmed that the black locust flower extracts are rich in macroelements (Ca, Na, Mg, K) with low content of heavy metals (Pb, Cd). The 50% (v/v) ethanol extract had the highest amount of macroelements, predominantly potassium (10.49 g/kg). The prepared extracts due to good antioxidant activity, high phenolic and mineral content, and low heavy metal contents can be considered useful for further human uses. [ABSTRACT FROM AUTHOR]