Influence of Phytochemical Profile on Antibacterial Activity of Different Medicinal Plants Against Gram-Positive and Gram-Negative Bacteria

Nettle (Urtica dioica), basil (Ocimum basilicum), thyme (Thymus serphyllium), costmary (Chrysanthemum balsamita) and yarrow (Achillea millefolium) are used worldwide as aromatic herbs and medicinal plants. The alcoholic macerates of these plants were prepared and their chemical composition was investigated by spectrophotometric methods and HPLC chromatography with photodiode array detection. Alcoholic extracts were tested also in vitro against 5 pathogenic bacterial strains: 2 Gram-positive (Staphyloccocus aureus and Bacillus cereus) and 3 Gram-negative (Escherichia coli, Pseudomonas aeruginosa and Salmonella typhimurium). Minimum inhibitory concentrations for the extracts against all the microorganisms were determined by serial dilutions method. All the extracts demonstrated antibacterial activity against Gram-positive bacteria and partially against Gram-negative bacteria. In addition, nettle extract possessed the highest polyphenolic and flavonoid content. The results obtained indicated that these plants represent a potential source of natural antibacterial substances and can be used for the production of natural antibacterial formulations.