Comparative study on the antimicrobial activity of propolis, catechin, quercetin and gallic acid

Propolis, considered one of the most effective natural broad-spectrum antibiotics, which do not induce resistance or destroy the organism's commensal flora, together with catechin, quercetin and gallic acid (at different concentrations), have been tested against Gram positive bacteria Streptococcus pyogenes ATTC 19615, Stapylococcus aureus ATCC 25923 and Gram negative Escherichia coli ATCC 25922 Pseudomonas aeruginosa ATCC 27853, Salmonella enterica ATCC 14028, Shigella flexneri ATTC 12022, as well as the yeast Candida albicans ATTC 10231, using the agar diffusion method. Propolis and the three compounds showed antimicrobial potential at most concentrations. The highest sensitivity to propolis (conc. 0.001-1%) was shown by the Gram-positive bacterial strain S. pyogenes, followed by the Gram-negative bacterium Escherichia coli, while the other species had an equal and reduced reaction. Gallic acid showed high antibacterial activity on S. aureus, P. aeruginosa and S. enterica, and a reduced effect on other bacterial strains. The antibacterial efficiency of 3.0224% quercetin was high against the bacterium S. pyogenes and catechin (2.9028%) proved to be the best antifungal, followed by propolis 1%, and quercetin 3.0224%. At certain concentrations, propolis and the three compounds could supplement gentamicin and ampicillin, as they have shown similar or even higher antibacterial efficacy than conventional drugs.