Microparticles of greenish-brown propolis extract: phytochemical, physicochemical characterisation and in vitro dissolution profile

Abstract

The low solubility of propolis in water and its limited bioavailability reduce the effectiveness of bioactive compounds, demonstrating the necessity of techniques that can overcome these limitations. Spray-drying is a promising approach to overcoming these challenges. In this study, microparticulate systems containing greenish-brown propolis extract were produced and characterised. The following analyses were performed: antioxidant activity; total phenol and flavonoid content; UV–Vis and FTIR spectroscopy; thermal analysis; scanning electron microscopy (SEM); and in vitro dissolution tests. The extracts and microparticles exhibited a total flavonoid content of 5.15% and 1.13%, respectively (equivalent to quercetin), and a total phenol content of 14.16% and 4.81% (equivalent to gallic acid). Antioxidant activity was assessed using the IC₅₀ method, yielding values of 13.77 µg.cm −3 for the propolis extract and 60.80 µg.cm −3 for the propolis microparticles. UV–Vis and FTIR analyses confirmed the encapsulation of the phenolic compounds, while thermal analysis demonstrated the thermal protection provided by the excipients. In vitro dissolution tests showed that the microparticulate system released an average of 66% of flavonoids in different dissolution media over 240 min, highlighting their low solubility in water. These results suggest that adding pharmacotechnical adjuvants could enhance the dissolution of active compounds, thereby expanding the therapeutic potential of encapsulated brown-green propolis in pharmaceutical and nutraceutical applications. Schematic representation of the polymer-drug conjugate and its time-dependent and dissolution medium-dependent mechanism in greenish-brown propolis microparticles