Developing resistance to several antibiotics has a crucial importance. For this reason, researchers are trying to discover alternative methods or agents. More recent studies focused on the potential antimicrobial properties of hypericin. In this study, antibacterial activity of hypericin was tested against Pseudomonas aeruginosa ATCC 27853, Enterococcus faecalis ATCC 19433, Escherichia coli ATCC 25922, Staphylococcus aureus ATCC 29213, Staphylococcus epidermidis ATCC 12228, and Klebsiella pneumoniae ATCC 700603 by broth macro-dilution method. The study was designed in two different conditions: exposure to daylight and non exposure to daylight (in the dark). 64 mg/mL concentration of hypericin inhibited the growth of S. aureus ATCC 29213and S. epidermidis ATCC 12228, without light. Conversely, there was no inhibition of hypericin in the range of concentration investigated for other bacteria. Positive or negative effect of daylight has not been observed. Perhaps, the usage of a different wavelength of light or the investigation of antibacterial activity at higher concentrations of hypericin may lead to different results. From our study, hypericin causes inhibition of growth of some bacteria through mechanisms different from photo-oxidation. Mechanisms between hypericin and bacterial enzymes, receptors and wall components should be investigated in further studies.
Key words: Hypericin, Hypericum perforatum L, broth macrodilution method, antibacterial activity
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