Microemulsion containing guava leaves essential oil: Enhanced anti-inflammatory, anti-oxidation, anti-tyrosinase activities and skin permeation

In this study, a microemulsion system containing guava leaf essential oil (GLE) was developed to enhance water miscibility, stability and bioactivity. The major chemical components of GLE, d-limonene, and β-caryophyllene, were identified by GC-MS analysis. The microemulsion system consisted of Tween 80 and propylene glycol as the surfactant (S) and co-surfactant (Co–S), respectively, with GLE serving as the oil phase. Three pseudo-ternary phase diagrams were constructed with different S:Co–S ratios (Km) at 2:1, 1:1, and 1:2 to illustrate the microemulsion area. Characterization of GLE contained microemulsions (GLEMEs) was performed using dynamic light scattering (DLS), viscometry, and conductivity measurements. The particle sizes of GLEMEs ranged from 10 to 150 nm. Selected GLEMEs exhibited stable particle sizes for more than 90 days and remained stable over a wide pH range. Additionally, compared to free GLE, these microemulsions demonstrated enhanced anti-tyrosinase and antioxidant activity, as well as improved anti-inflammatory properties. Moreover, microemulsions with high oil content exhibited deeper skin penetration compared to free GLE, while those with high water content accumulated in the upper skin layer.