Variation in the Chemical Composition and Biological Activities of Propolis Collected During Two Seasonal Periods in the Zona da Mata Region of Brazil

Abstract

Propolis is a chemically complex bee product whose composition and biological properties are influenced by botanical and environmental factors. This study compared eight propolis samples collected during summer and winter from four apiaries in the Zona da Mata region of Minas Gerais, Brazil. Samples were characterized by physicochemical properties, phenolic and flavonoid content, qualitative chemical profiles by UHPLC-ESI-MS/MS, and electrical impedance, while antioxidant, antibacterial, and cytotoxic activities were evaluated using complementary in vitro assays. Summer-collected samples generally exhibited higher dry extract and total phenolic content and lower wax levels, whereas flavonoid content remained comparatively stable. Differences were also observed in electrical impedance and several antioxidant responses, with total phenolic content strongly and negatively correlated with DPPH IC50 values (ρ = −0.864). All extracts inhibited Staphylococcus aureus, predominantly with MIC (Minimal Inhibitory Concentration) values of 250–500 µg/mL, without detectable bactericidal activity at the concentrations tested. UHPLC-ESI-MS/MS profiling revealed qualitatively similar chemical profiles comprising phenolic and prenylated derivatives, including artepillin C, consistent with a possible contribution from Baccharis dracunculifolia. Notably, the samples from D apiary (D1 and D2) showed pronounced and selective cytotoxicity against MDA-MB-231 cells. Overall, differences in chemical, physicochemical, and biological properties were observed between the two collection periods of regional propolis.