Antioxidant and Antimicrobial Potential of Romanian Propolis Extract Combinations: Linking Chemical Composition with Biological Activity

Background/Objectives: Propolis is a chemically complex product whose antimicrobial activity varies with geographical origin and composition. This study evaluated the chemical, antioxidant, and antimicrobial properties of five Romanian propolis ethanolic extracts (PEEs) and their combinations, focusing on antimicrobial interactions and chemical-biological relationships.

Methods

Five PEEs were evaluated individually, as ten binary combinations, and as one five-extract mixture. Antioxidant activity and 20 phenolic compounds were determined. Antimicrobial activity against 16 strains was assessed using agar diffusion and broth microdilution assays. Extract interactions were evaluated using the fractional inhibitory concentration index (FICI). Principal Component Analysis (PCA), Spearman correlation, and Partial Least Squares (PLS) regression investigated chemical-biological relationships.