Development and Antioxidant Efficacy of Corosolic Acid Nanoemulsion Using Tremella fuciformis Polysaccharides as a Natural Emulsifier

Corosolic acid (CA), a potent natural triterpenoid with significant bioactivity, is limited by its poor aqueous solubility and low bioavailability, which restrict its practical applications in functional foods and nutraceuticals. To address these challenges, this study developed a novel, clean-label oil-in-water (O/W) nanoemulsion (Corosolic Acid-Loaded Nanoemulsion, CA-NE) using Tremella fuciformis polysaccharide (TFP) as a natural and functional aqueous phase. The formulation was systematically optimized through solubility studies, compatibility tests, and pseudo-ternary phase diagram analysis, ensuring the production of an effective and stable nanoemulsion. The resulting CA-NE exhibited favorable characteristics, including a small Z-average size of 14.96 ± 0.72 nm, a low polydispersity index (PDI) of 0.100, a ζ-potential of -11.08 ± 3.99 mV, and a high loading capacity of 14.25 mg/g. In vitro release studies revealed a sustained-release profile, supporting its potential for controlled CA delivery. Notably, the CA-NE demonstrated significantly enhanced in vitro antioxidant activity compared to free CA, as evidenced by 2,2-Diphenyl-1-picrylhydrazyl (DPPH) radical scavenging and ferric reducing antioxidant power (FRAP) assays, indicating a significant enhancement beyond the additive effect of its individual components, which suggests a potential synergistic interaction between CA and TFP. Additionally, the nanoemulsion exhibited robust stability under various stress conditions, such as centrifugation, heat, varying pH levels, and long-term storage, confirming its potential for commercial application. This work presents a stable, natural ingredient-based nano-delivery system that not only enhances CA's solubility and bioavailability but also improves its antioxidant efficacy, offering a promising strategy for incorporating lipophilic bioactive compounds into functional foods and nutraceuticals.