Phytocosmetic Emulsion Containing Extract of Morus nigra L. (Moraceae): Development, Stability Study, Antioxidant and Antibacterial Activities

Morus nigra L. is a species popularly known in the Northeast of Brazil as “amora miúra”. This species is a source of flavonoids with antioxidant activity. Antioxidants play an important role in the preservation of cosmetic formulations, and they neutralize free radicals. The objective of this study was to develop a topical emulsion containing leaf extract of Morus nigra L., as well as to evaluate the stability, antioxidant and antibacterial activities of the formulations. A crude hydroalcoholic (70%) extract of M. nigra leaves (MnCE) was submitted to high-performance liquid chromatography with diode-array detection (HPLC–DAD) analysis and incorporated into an anionic base emulsion. Antioxidant activity was evaluated according to the DPPH (2,2-diphenyl-1-picrylhydrazyl) method, and the stability of the formulation was assessed for 90 days, submitting the emulsion to storage at 4, 20, and 37 °C. Microdilution techniques evaluated the antibacterial activity and a challenge test assessed the microbiological stability. Analysis by HPLC–DAD identified the flavonoids rutin and isoquercetin in the M. nigra extract. The emulsion and plant extract presented antioxidant activity, and the stability of the emulsion was preserved in terms of pH value and viscosity—which did not show significant changes, except for the spreadability, which was affected by the temperature. The antioxidant activity did not change significantly, except for the sample under 4 °C, which showed a considerable decrease in activity. The crude hydroalcoholic extract and formulation showed antimicrobial activity and the emulsion was considered stable in terms of organoleptic, physicochemical, and microbiological properties.