Stable Oil-in-Water Nanoemulsions Stabilized by Polygonatum sewerzowii Extract: A Plant-Derived Alternative to Synthetic Surfactants

Growing demand for clean-label ingredients has intensified the search for sustainable plant-derived emulsifiers capable of replacing synthetic surfactants in nanoformulations. In this study, the emulsifying potential of crude Polygonatum sewerzowii extract (PSE), obtained by optimized ultrasonic-assisted extraction, was evaluated for the preparation of oil-in-water nanoemulsions. PSE exhibited effective emulsifying properties and successfully produced stable nanoemulsions with droplet sizes of 191.7 ± 4.1 nm; PDI = 0.034 ± 0.023. The formulations remained physically stable during 30 days of storage with minimal changes in droplet size and reduced the sunflower oil–water interfacial tension to 12.30 ± 0.44 mN/m at a concentration of 1% (w/w). Chemical characterization revealed that the extract contained 2.8 ± 0.05% saponins, 11.2 ± 0.37% phenolic compounds, 13.1 ± 0.24% proteins, 62.5 ± 0.12% carbohydrates, and 6.2 ± 0.52% ash, whose combined presence is likely responsible for the observed emulsifying behavior. Nanoemulsions prepared with 5% sunflower oil and 1% PSE exhibited satisfactory short-term physical stability during the investigated 30-day storage period, although changes in PDI, ζ-potential, and conductivity were observed at 25 °C. These findings identify P. sewerzowii extract as a promising plant-derived emulsifier for oil-in-water nanoemulsion systems. However, further studies addressing long-term stability, safety, biocompatibility, and application-specific performance are required before its suitability for food, cosmetic, or pharmaceutical applications can be established.