Microwave-Assisted Extraction (MAE) of Propolis from Tetragonula biroi (Philippine Kiwot Bee) Hives

Propolis is a resinous substance known for its bioactive compounds, such as phenolics and flavonoids, which exhibit antioxidant, antibacterial, and anti-inflammatory benefits. While it can be harvested from sources globally, it can also be derived from the native stingless Philippine kiwot bees. This study used microwave-assisted extraction (MAE) using ethanol, changing the solvent-to-sample ratio (5 mL/g, 10 mL/g, and 15 mL/g), solvent concentration (35% v/v, 65% v/v, and 95% v/v), and extraction time (60 s, 180 s, and 300 s), to determine their effects on the yield and phenolic and flavonoid contents. The extracted propolis was concentrated using rotary evaporator and freeze-dried. Phenolic content was determined through the Folin–Ciocalteu method, while flavonoid content was identified through aluminum chloride complex formation in methanol solution. Interactions between solvent-to-sample ratio and solvent concentration significantly affected yield, while extraction time did not. Results show that using MAE with ethanol as a solvent successfully extracted propolis. Lower solvent-to-sample ratios with increasing solvent concentration resulted in higher yields. Conversely, high solvent concentrations with increasing solvent-to-sample ratio decreases yield. The highest yield (0.144 g/g) was obtained with 5 mL/g solvent-to-sample ratio, 95% v/v solvent concentration, and 300 s extraction time. Phenolic and flavonoid contents of the propolis produced using the parameters resulting in the highest yield were determined to be 142.660 mg GAE/g propolis and 65.900 mg QE/g propolis, comparable to propolis extracted using traditional methods. Effects of extraction parameters were determined, which can further optimize the quantity and quality of propolis.