Enhanced Extraction of Bioactive Compounds from Brazilian Brown Propolis: Employing Pressurized Liquid Extraction in a Semicontinuous Flow-Through System

This study investigated the influence of ethanol concentration (0–80%), temperature (60–120 °C), and pH (2–12) on the extraction efficiency of bioactive compounds from Brazilian brown propolis using pressurized liquid extraction (PLE) in a semicontinuous flow system. Unlike previous studies that mainly focus on batch PLE systems or single-variable optimization, this work integrates a semicontinuous flow-through PLE system with pH modulation and response surface methodology to enhance extraction efficiency and process sustainability. The results showed that the maximum total phenolic content (144.55 ± 8.73 mg GAE g–1) was obtained with 0% ethanol, 90 °C, and pH 7, while the highest flavonoid yield (56.01 ± 3.37 mg CE g–1) was achieved with 80% ethanol, 120 °C, and pH 12. High temperatures and alkaline pH conditions promoted the formation of Maillard reaction products, altering the colorimetric properties of the extracts, reducing luminosity, and increasing chroma values. The antioxidant activity, evaluated using the DPPH and ferric-reducing antioxidant power assays, reached a maximum of 304.82 ± 0.40 and 385.37 ± 18.88 μmol TEAC g–1, respectively, under conditions of 40% ethanol, 90 °C, and pH 2. These results indicate that PLE can be optimized to extract distinct classes of bioactive compounds selectively while minimizing thermal degradation. In conclusion, extraction at 90 °C and pH 7 was ideal for phenolic recovery, while higher temperatures (120 °C) and alkaline pH (12) favored flavonoid extraction. Overall, this study demonstrates that semicontinuous PLE is an efficient and sustainable approach for recovering bioactive compounds from brown propolis, offering reduced solvent consumption, improved process control, and strong potential for industrial scalability in food, pharmaceutical, and cosmetic applications.