Objective & Background: Emergence and spreading of antimicrobial resistance is one of the serious
challenges of modern medicine. Many microorganisms acquired various resistance mechanisms, including mutations
of the antimicrobial targets, adoption of resistance genes coding for enzymes degrading or modifying the antimicrobial
molecules, protecting or modifying the antimicrobial targets, or coding for efflux systems that pumps
the antimicrobials out of the cells. The spectrum and quantity of medically important microbial strains resistant to
antimicrobials are steadily increasing. Nowadays, the antimicrobial resistance poses a real threat of the postantibiotic
era, and increases mortality and morbidity of infected patients, as well as the cost of health care expenses.
Conclusion: The effort of current pharmaceutical research is to search for new classes of active compounds with
better antimicrobial activity and different target sites than antimicrobial drugs in current use. Alkaloids, essential
oils and phenolic compounds such as tannins, phenolic acids and flavonoids are important groups of plants secondary
metabolites that are not essential for plant survival but are significant for their defense, especially against microbial
pathogens. Several studies investigated and approved their antimicrobial effects also in human medicine.
These compounds are promising alternative natural antibacterial, antiviral and antifungal agents.