Development of Herbal Mouthwash Powder Using a Self-Nanoemulsifying Drug Delivery System Containing Galangal Extract and Lemongrass Oil for Oral Candidiasis Treatment

<b>Objective:</b> This study aimed to develop and characterize the physicochemical properties of a self-emulsion drug delivery system (SNEDDS) incorporating galangal extract (GE) and lemongrass oil (LGO). Then, to develop mouthwash powders containing GE- and LGO-loaded SNEDDS (GL-mouthwash powder) as a promising alternative for preventing and treating denture stomatitis. <b>Methods:</b> The solubility of GE in various vehicles was determined. Subsequently, pseudo-ternary phase diagrams of the different ingredients, oil (LGO), surfactant (Tween^® 80), and co-surfactant (Propylene glycol) were selected to develop the SNEDDS. Then, SNEDDS containing GE and LGO (GL-SNEDDS) were prepared and characterized. The optimized liquid GL-SNEDDS was transformed into GL-mouthwash powder by absorbing onto mannitol and blending with a sweetener. Subsequently, various evaluations including drug recovery, moisture content, emulsification time, stability, anti-<i>Candida</i> activity, and in vitro cytotoxicity were performed. <b>Results:</b> The developed SNEDDS formulation improved GE and LGO solubility. The optimized GL-SNEDDS exhibited a small droplet size of 148.2 ± 2.1 nm with a polydispersity index of 0.11 ± 0.03 and a zeta potential of 2.14 ± 0.11 mV. In addition, the GL-mouthwash powder demonstrated a high drug recovery of >80% with a low moisture of <10% and exhibited greater physicochemical stability under accelerated conditions. The developed GL-mouthwash powder rapidly formed a stable nanoemulsion within 2 min after reconstitution. Interestingly, GL-mouthwash powder exhibited strong anti-<i>Candida</i> activity with no toxicity to human fibroblast cells, which demonstrated superior biocompatibility relative to existing commercial products. <b>Conclusions:</b> These findings suggest that GL-mouthwash powder has potential as an alternative prevention and treatment of oral <i>Candida</i> infection.