Background: Nagasari (Mesua ferrea L.) has antibacterial activity against Bacillus subtilis because it contains active compounds such as phenol, flavonoid, tannin, and terpenoid. However, these secondary metabolites have poor absorption in the body. Nanoemulsion can increase the absorption and solubility of drugs in the body because of the smaller particle size. The purpose of this study was to determine the effect of variations in the concentration of co-surfactant PEG 400 on the stability and physical properties of nanoemulsion of ethanol extract of Nagasari (Mesua ferrea L) and to determine the antibacterial activity against Bacillus subtilis.

Methodology: The nanoemulsions was carried out using the emulsification method with a sonicator. The nanoemulsion was formulated into 3 formulas with varying concentration of PEG 400 1%, 3%, 5%. Furthermore, the physical properties and solubility test are organoleptic, pH, type of emulsion, percent transmittance, particle size, zeta potential and freeze thaw. The selected formula which is formula I, was tested for antibacterial activity against Bacillus subtilis by disc diffusion method. The data obtained were analyzed statistically.

Results: The results showed that the lower concentration of PEG 400, the higher the pH value and a decrease in the negative zeta potential value. Formula I nanoemulsion of ethanol extract of Nagasari leaves (Mesua ferrea L.) was chosen for antibacterial activity test because the potential zeta value was closest to the required range with an average bacterial inhibition of 19.15 mm compared to the ethanol extract of Nagasari leaf which produced an average of diameter of the inhibition zone was 15.8 mm.

Conclusion: Variations in the concentration of co-surfactant PEG 400 did not affect the stability and physical properties but did affect the zeta potential value and pH value. Formula I nanoemulsion of ethanol extract of Nagasari leaves (Mesua ferrea L.) was selected as an antibacterial activity test producing 19.15 mm of antibacterial inhibition zone diameter against Bacillus subtilis.

Keywords: Nanoemulsion, Nagasari leaves, PEG 400, Bacillus subtilis