Development of propolis extract-loaded nanoparticles with chitosan and hyaluronic acid for improving solubility and stability

Propolis extract (PE) is a natural polyphenol with various biological activities; however, its application is limited due to low solubility and instability. To overcome these drawbacks, we encapsulated PE in nanoparticles (PE-loaded nanoparticles, PE-NP) using chitosan (CS) and hyaluronic acid (HA) as wall materials. We examined the physicochemical characteristics (size, polydispersity index, zeta potential, and entrapment efficiency) of PE-NP prepared with the various ratios of CS to HA and core to the wall material, and confirmed the optimal ratio for the formulation of PE-NP as 4:7 and 1:2, respectively. In addition, PE-NP significantly increased the solubility of PE by 2.43-fold compared to that of free PE (p < 0.05). Moreover, the retention rate of total flavonoid content (TFC) in PE-NP was significantly higher than that in free PE after the heat treatment (90 °C) for 24 h (p < 0.05). Furthermore, PE-NP showed significantly higher retention rates of TFC and DPPH radical scavenging effects than free PE after storage for 4 weeks at 30 and 50 °C (p < 0.05). In conclusion, these findings suggest that PE-NP may be a promising approach to enhance the solubility and stability of PE and could provide helpful information for expanding the application of PE.