Development of New Indonesian Propolis Extract-Loaded Selfemulsifying: Characterization, Stability and Antibacterial Activity

This study aimed to prepare, characterize, examine the stability and evaluation of the antibacterial activity of Indonesian propolis extract-loaded self-emulsifying (PESE).

Oil, emulsifier, and co-emulsifier were selected as the carrier for the PESE formulation through a propolis-extract solubility test on each carrier, followed by evaluation of the nanoemulsion region in a pseudo ternary phase diagram. Pre-concentrate of PESE was prepared with the addition of 150 mg/mL propolis extract followed by characterization for the transmittance, globule size, zeta potential, thermodynamic stability, robustness to dilution, and accelerated stability. The selected formulation was tested for antibacterial activity using a microdilution method.

The PESE characterization produced a clear nanoemulsion with a globule size ranging from 13 to 45 nm and zeta potential of less than −38 mV. The PESE formulation with a composition of 150 mg/mL propolis extract, 20% castor oil, 40%–70% Kolliphor EL, and 10%–40% polyethylene glycol (PEG) 400 were thermodynamically stable. The PESE formulation with the composition of 20% castor oil, 40% Kolliphor EL, and 40% PEG 400 was the optimum formulation that passed the robustness to dilution evaluation and an accelerated stability test for 3 months. The antibacterial activity test on this formulation indicated improved activity against Escherichia coli and Staphylococcus aureus compared with that of propolis extract.

These studies demonstrated that PESE in optimum formulation could be used as an antibacterial, particularly in E. coli and S. aureus.