Innovative Antimicrobial Nanoemulsion with Controlled Release Properties Based on Melaleuca alternifolia Essential Oil

Abstract

Essential oils (EOs) present limitations such as volatility, low water solubility, and instability, which restrict their direct application in pharmaceutical and cosmetic formulations. This study aimed to develop and characterize a nanoemulsion (NE) based on Melaleuca alternifolia EO, overcoming these challenges. The EO was extracted by hydrodistillation (yield: 3%) and analyzed by gas chromatography-mass spectrometry (GC-MS), identifying terpinen-4-ol (47.49%), γ-terpinene (17.89%), and α-terpinene (9.35%) as major components. The NE was prepared using ultrasound and Tween 80 as a surfactant, resulting in a monomodal distribution with a mean droplet size of 60 nm, confirmed by dynamic light scattering and the Tyndall effect. Stability assessments, including thermal and centrifugation tests, revealed a robust system, with optimal performance at 5-25 °C and controlled release behavior at 50 °C. The NE demonstrated potent antimicrobial activity, with minimum inhibitory concentrations (MIC) as low as 0.0078 μg mL⁻¹. Although not directly compared to the crude EO, the results indicate preserved and possibly enhanced antimicrobial efficacy due to encapsulation. These findings suggest that the nanoemulsion is a promising platform for pharmacosmetic applications, enabling EO delivery at low concentrations while improving physicochemical stability and biological performance.

Keywords:
tea tree; nanoemulsions; gas chromatography; antimicrobial activity; ultrasound