Development, Optimization and Evaluation of Eucalyptus Oil-Based Organogel for Enhanced Topical Antifungal Delivery

Abstract

Background: Topical delivery of essential oils presents formulation challenges because their volatile constituents may be affected by evaporation, while their distribution and release depend on the properties of the delivery vehicle. Organogel offer a structured lipid-based system for incorporating oil-phase ingredients into semisolid formulations. Objective: This study aimed to develop and optimize a eucalyptus oil-based organogel using soy lecithin and beeswax as structuring agents and to evaluate its physicochemical characteristics, in-vitro release behavior and preliminary antifungal activity. Methods: Preliminary formulations were prepared using eucalyptus oil, soy lecithin, beeswax, isopropyl myristate (IPM), ethanol and butylated hydroxytoluene (BHT). A (3^2) factorial design was employed to investigate the effects of soy lecithin (3–7% w/w) and beeswax (1–3% w/w) across nine formulations (F1–F9). The formulations were evaluated for appearance, homogeneity, phase separation, pH, viscosity, spreadability, eucalyptus oil content and in-vitro diffusion. The optimized formulation was further assessed for preliminary antifungal activity. Results: Formulation F5, containing 5% eucalyptus oil, 5% soy lecithin and 2% beeswax, was selected as the optimized batch. It exhibited a pH of 5.56 ± 0.04, viscosity of 9,416 ± 157 cP, spreadability of 16.1 ± 0.3 g·cm/s and eucalyptus oil assay of 98.51%. Cumulative in-vitro diffusion reached 98.06% at 10 h. After six months at 40°C/75% relative humidity, the assay decreased to 94.95%, and cumulative diffusion decreased to 93.94%. Preliminary antifungal testing showed inhibition zones of 29 mm for F5, 28 mm for nystatin and 32 mm for the marketed comparator. Conclusion: The developed Organogel demonstrated promising physicochemical characteristics, in-vitro diffusion behaviour. and antifungal efficacy and topical delivery potential.