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

Abstract

Growing demand for clean-label ingredients has intensified the search for sustainable plantderived 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.