Bioactive potencial of green propolis extracts obtained under different extraction conditions

Green propolis is characterized by its high content of phenolic compounds and flavonoids, which are responsible for its antioxidant and antimicrobial activities and make it a promising natural product for applications in the food, pharmaceutical, and biomaterials fields. However, the extraction efficiency of these compounds depends on the processing conditions. This study investigated the effects of hydroethanolic extraction protocols and propolis-to-solvent ratio on the recovery of bioactive compounds and the antioxidant and antimicrobial activities of green propolis extracts. Extractions were performed with 80% (v/v) ethanol under three conditions: conventional extraction (50 °C, 30 min), ultrasound-assisted extraction (500 W, 20 min) followed by shaker agitation (30 °C, 120 rpm, 24 h), and shaker extraction (30 °C, 120 rpm, 24 h), using propolis:solvent ratios of 1:3 and 1:35 (w/v). Total phenolic and flavonoid contents, antioxidant activity (DPPH and FRAP assays), and antimicrobial activity against Staphylococcus aureus were evaluated. At the 1:3 propolis:solvent ratio, conventional extraction yielded the highest total phenolic content (310 ± 8 mg GAE/g dry extract), differing significantly only from shaker extraction (258 ± 10 mg GAE/g dry extract; p < 0.05), whereas ultrasound-assisted extraction showed an intermediate value. At the 1:35 (propolis:solvent) ratio, no significant differences were observed among extraction protocols regarding total phenolic and flavonoid contents (40 ± 1.2 mg EQ/g db) or antioxidant activity (450 ± 16 mg ET/g by FRAP; or 255 mg ET/g by DPPH). All extracts inhibited the growth of Staphylococcus aureus, with inhibition zones ranging from 17.1 to 19.1 mm and no significant differences among extraction protocols. Although total phenolic content was influenced by the extraction protocol at the higher propolis concentration, antioxidant and antimicrobial activities remained comparable under all evaluated conditions. Overall, conventional extraction at a 1:3 (propolis:solvent) ratio provided the highest phenolic recovery while reducing processing time from 24 h to only 30 min, representing an efficient and practical strategy for producing bioactive green propolis extracts.