Antimicrobial activity of some medicinal plants growing in Serbia and Montenegro

Antimicrobial activity of four medicinal plant species Alnus incana (L.) Moench (leaves, bark, cones), endemic plant species A. viridis (Chaix) DC. (leaves, bark, cones), Cornus mas L. (leaves, flowers) and Cotinus coggygria L. (leaves, flowers) were investigated. According to the literature and our own results, all examined species are rich in polyphenols. Plant material was collected on the mountains of Serbia and Montenegro. Air-dried powdered material was extracted with methanol in Soxhlet for 24h and solvent was evaporated. Dry extracts were used for experiments. A variety of microorganisms [Gram-negative bacteria Escherichia coli (ATCC 25922), Salmonella typhimurium (ATCC 14028), Enterobacter cloacae (ATCC 13883), Pseudomonas aeruginosa (ATCC 27853), P. tolaasii (NCTC 387), Proteus mirabilis (ATCC 14273), and Gram-positive bacteria Staphylococcus aureus (ATCC 25923), S. epidermidis (ATCC 12228), Streptococcus faecalis (ATCC 12952), Bacillus subtilis (ATCC 6051), Micrococcus luteus (ATCC 10240), M. flavus (ATCC 14452), Sarcina lutea (ATCC 10054), Listeria monocytogenes (ATCC 15313) as well as human pathogen fungi Candida albicans] were used in antimicrobial assay. The MIC values were determined using the broth microdilution method in 96-hole plates according to NCCLS [1]. Serial dilutions of the stock solutions of tested extracts in broth medium (Muller-Hinton broth or Sabouraud broth) were prepared in a microtiter plate. The microbial suspensions were added in the microwells at the concentration of 5×10⁵ organisms/mL. MICs were determined as the lowest concentrations preventing visible growth. Streptomycin and nystatin were used as a positive control. Each assay was repeated, independently, two times. Antimicrobial activity was noticed in all examined extract with MIC values ranging from 0.117–0.266mg/mL. The most active were dry extract of cones of A. incana and A. viridis. Antimicrobial activity was not in correlation with the amount of total phenolics.

Reference: 1. NCCLS (2000) Methods for Dilution Antimicrobial Susceptibility Tests for Bacteria That Grow Aerobically; Approved Standard – Fifth Edition. NCCLSocument M7-A5. NCCLS: Wayne, PA, USA.