Antimicrobial activity of royal jelly, honey, and their mixture
As antimicrobial drugs destroy microorganisms or stop their growth, they are used to treat infections. Due to the increasing resistance of infectious agents to antimicrobial drugs, there is a need to find new natural products with antimicrobial properties. Natural products such as bee products honey, propolis, pollen, bee bread, and royal jelly are important products with numerous different active biological features, antimicrobial and antiviral among them. The aim of this study was to investigate the antimicrobial effect of royal jelly, honey, and the mixture of honey and royal jelly on gram-positive and gram-negative bacteria, spore bacteria, and the fungus Candida albicans. Royal jelly and honey were collected in Lithuanian apiaries. The antimicrobial activity of royal jelly, honey, and honey-royal jelly mixture (9% solution) was determined using the ‘well’ method of diffusion into agar. Reference cultures of gram-positive and gram-negative bacteria, spore bacteria, and the fungus Candida albicans were used in the study. Royal jelly was found to be the most effective against Staphylococcus epidermidis and Enterococcus faecalis. Royal jelly had the strongest antibacterial effect on Enterococcus faecalis, honey on Listeria monocytogenes and Staphylococcus aureus, and the mixture of honey-royal jelly on S. epidermidis. Royal jelly, honey, and honey-royal jelly solutions were not antibacterial against Proteus vulgaris. Royal jelly, honey, and honey-royal jelly had a weak effect on Escherichia coli, Klebsiella pneumoniae, and Pseudomonas aeruginosa. Royal jelly had no effect on Bacillus subtilis, Bacillus cereus, and Candida albicans, and the antibacterial effect of honey and honey-royal jelly mixture was weak. Royal jelly, honey, honey-royal jelly mixture had the strongest effect on gram-positive bacteria. A weaker antimicrobial effect was observed against gram-negative bacteria, spore bacteria, and C. albicans. Royal jelly had no effect on P. vulgaris, and honey-royal jelly mixture had similar antimicrobial activity to honey.