Enhanced stability, antioxidant capacity and in vivo anti-inflammatory efficacy of glutathione and quercetin via nanoemulsion formulation

Background: Antioxidant and anti-inflammatory effects are increasingly recognized for their pivotal roles in addressing human health challenges. Glutathione (GSH) and quercetin (QC) are natural antioxidants known to protect the immune system, mitigate oxidative stress, and aid in repairing in vivo inflammation. However, their practical application has been limited due to poor stability and susceptibility to oxidation. This study aims to evaluate the feasibility of nanoemulsions (NEs) formulated with saponin, dihexadecyl phosphate, and dioctadecyl dimethylammonium bromide for the encapsulation of GSH or QC, focusing on their physicochemical properties, chemical stability, antioxidant activity, in vitro biocompatibility, and in vivo anti-inflammatory efficacy. Methods: The performance of NEs encapsulating GSH or QC was assessed using dynamic light scattering (DLS), chemical stability tests, encapsulation efficiency measurements, transmission electron microscopy (TEM), cytotoxicity and cell morphology assays, DPPH radical scavenging assays, and a murine skin inflammation assay model. Findings: Incorporating GSH or QC into NEs resulted in an increase in droplet size while maintaining an encapsulation efficiency of approximately 75 %. Encapsulation significantly enhanced the chemical stability and antioxidant capacity of GSH or QC. These NEs demonstrated over 95 % cell viability in HaCaT and HFDPC cells without causing noticeable changes in cell morphology. Furthermore, GSH- or QC-loaded NEs effectively reduced skin erythema, scaling, and epidermal thickening with no significant impact on the drug efficacy. © 2025 Taiwan Institute of Chemical Engineers.