Influence of extracting solvents on phenolic composition and radical scavenging activity of selected South–West Nigerian bee-propolis

Propolis is a bee product made from various plant sources which is used traditionally as medicine in some climes due to its potential pharmaceutical importance. Propolis has been reported to be an efficient protective agent for use as a natural antioxidant and antibacterial additive in food systems. This study investigates the phenolic composition and antioxidant activity of selected Nigerian propolis samples from Ondo and Ekiti States. Propolis samples were collected and prepared by defatting with n-hexane followed by successive extraction using solvents of varying polarities (ethyl acetate, acetone, ethanol and water). Total phenolic compounds (TPC) and total flavonoid contents (TFC) were quantified by Folin-Ciocalteu, and AlCl₃ colorimetric methods respectively. Antioxidant activity was assessed using the 1,1-diphenyl-2-picrylhydrazyl (DPPH). The highest extraction yield was obtained by acetone. Aqueous extracts of Ondo and Ekiti propolis samples exhibited the highest TPC content (65.12 ± 0.27 and 30.82 ± 0.08 mg gallic acid equivalent/g of defatted propolis sample, respectively), while acetone extracts of both propolis samples recorded the highest TFC content (345.33 ± 0.96 and 322.19 ± 3.04 mg quercetin equivalent/g of defatted propolis samples). The extracts of Ondo and Ekiti propolis obtained by acetone showed the highest anti-radical action against 1,1-diphenyl-2-picryl hydrazyl (DPPH) radicals (77.18% and 54.57% inhibition at 20 µg/mL). This study provides insights into the influence of solvent polarity on phenolic composition, flavonoid content, and antiradical scavenging activity of some Nigerian propolis, highlighting the importance of geographical origin and extraction methods. Further research is needed to elucidate specific bioactive compounds and mechanisms of action for propolis-based health products and pharmaceutical formulations.