Development of Forsythia Essential Oil Microemulsions: Effects of Surfactants on Stability and Antibacterial Activity

This study developed a stable Forsythia essential oil (FEO) microemulsion (FEO-ME) using a self-microemulsifying drug delivery system (SMEDDS). The FEO-ME effectively reduced the volatility of essential oil and inhibited bioactive component degradation. By constructing pseudoternary phase diagrams, the optimal formulation was identified, utilizing the surfactant EL-40 and cosurfactant ethanol. The resulting microemulsion exhibited an average droplet size of 21.58 nm and an encapsulation efficiency of 85.6%. FEO-ME demonstrated excellent storage stability over 15 days, with minimal changes in droplet size and polydispersity index (PDI), ensuring long-term reliability. Additionally, antibacterial tests revealed enhanced efficacy against Escherichia coli compared to raw FEO. These findings highlight the potential of FEO-ME to enhance the bioactivity, stability, and applicability of essential oils with promising applications in food preservation, pharmaceuticals, and other industries.