Evaluation of Antimicrobial Activity of Some Medicinal Plants on Human Standard Bacteria and Candida albicans

Abstract

Background: Continuous and indiscriminate use of chemical drugs causes resistance to microorganisms, which in turn weakens the effect of drugs. This adverse event is associated with an increased number of drugs used by patients and the tendency to use compounds with newer and stronger formulations. Furthermore, the essential oils of several plants contain a significant inhibitory effect on pathogenic microorganisms. Objectives: Hence, the current study intended to evaluate the antimicrobial activity of some medicinal plants on some standard human pathogenic bacteria and Candida albicans fungi isolated from women. Methods: Leaves of Cichorium intybus L., Hypericum perforatum L., Lavandula angustifolia, Thymus vulgaris L., and Taxus baccata L. were collected and analyzed in the botanical laboratory of the University of Zabol. Then, the ethanolic extract was prepared using 40 g of dried leaves in 400 cc of ethanol. Standard bacteria and fungi were obtained from the center for genetic and biological resources of Iran. To determine the activity of free radical trapping, diphenylpicryl hydrazyl was used, and then the antimicrobial effects were investigated by diffusion method in Müller-Hinton agar medium using 6 mm paper disks according to the Bauer and Kirby instructions. Statistical calculations were administered using Statistx Ver10. Mean comparisons were performed using the LSD at the 1% level, and Excel was also used to draw the shapes. Results: The diameter of the inhibitory zone of plant extracts against standard bacteria and clinical fungi of Candida albicans at a dilution of 100 ppm was analyzed, which revealed different effects (P < 0.01). Taxus baccata L., with a 15 mm diameter growth zone, showed the highest effect on inhibiting the growth of Bacillus cereus and Pseudomonas aeruginosa. Hypericum perforatum L. with a diameter of 15 mm was found as the most useful plant in inhibiting Shigella dysentery., with a diameter of 10 mm, was the most useful plant in inhibiting the growth of Escherichia coli. The Taxus baccata L., with a maximum growth inhibition zone diameter (20 mm), has been the most effective plant against Candida albicans. Conclusions: Considering the side effects of chemical drugs and antibiotics as well as the significant effect of medicinal plant extracts used in this study, the Taxus baccata L. was the most useful plant on inhibiting Candida albicans, Bacillus cereus, and Pseudomonas aeruginosa. Moreover, Hypericum perforatum L. was found as the most useful plant to control the growth of Escherichia coli.