Objectives: This study sought to examine the chemical profile, antioxidant, antimicrobial, antibiofilm, and anti-quorum sensing potential of two propolis ethanolic extracts (PEEs) collected from northeast Algeria.
Materials and methods: To achieve the main objectives of this study, multiple in vitro tests were employed. The phenolic and flavonoid contents were analyzed, and the chemical composition of both PEE was determined by high-performance liquid chromatography. The antioxidant properties of the propolis extracts were investigated using six complementary tests. The inhibitory effects of propolis extracts were evaluated against multidrug-resistant (MDR) clinical isolates using agar well diffusion and microdilution methods, whereas their antibiofilm and quorum-sensing disruption effects were determined by spectrophotometric microplate methods.
Results: The results demonstrated that phenolic and flavonoid contents were higher in propolis from the Guelma (PEEG) region (PEEG; 188.50 ± 0.33 μg GAE/mg E, 144.23 ± 1.03 μg QE/mg E), respectively. Interestingly, different components were identified, and cynarin was the major compound detected. The PEEG sample exhibited potential antioxidant effects in scavenging ABTS•+ radicals with minimal inhibitory concentration values equal to 10.46 ± 1.40 µg/mL. Furthermore, the highest antibacterial activity was recorded by PEEG against Gram-positive Staphylococcus aureus MDR1. Similarly, PEEG effectively inhibited the biofilm formation of S. aureus MDR1 and the degradation of biofilm was up to 60%. In addition, quorum sensing disruption revealed that both extracts have a moderate capacity for violacein inhibition by the Chromobacterium violaceum ATCC 12472 strain in a concentration-dependent manner.
Conclusion: These findings indicate that propolis can be regarded as a natural therapeutic agent for health problems associated with MDR bacteria and oxidative stress.
Keywords: Antibacterial; antioxidant; multidrug-resistant; propolis; quorum sensing.