Screening of in vitro antimicrobial and antioxidant activity of nine Hypericum species from the Balkans

The in vitro antimicrobial and antioxidant activities of the crude methanol extracts of nine Hypericum species (H. barbatum Jacq., H. hirsutum L., H. linarioides Bosse, H. maculatum Crantz, H. olympicum L., H. perforatum L., H. richeri Vill., H. rumeliacum Boiss. and H. tetrapterum Fries) growing spontaneously in the Balkans were screened using a disk diffusion assay against a panel of standardized bacteria and fungi and a phosphomolybdenum method, respectively. The most active extract against all microbial strains was that of Hypericum hirsutum (collected at Vranjska Banja, South Serbia), which showed remarkable antimicrobial activity at a dose of 5 μg per disk and a diameter of growth inhibition zone reaching values more than two times larger than that of standard antibiotics. The antimicrobial activity of H. barbatum, H. hirsutum, H. olympicum, H. richeri and H. tetrapterum has not hitherto been published. All the extracts possess a very broad spectrum of strong antimicrobial activity. All the investigated species, except H. perforatum, have been tested for the first time in an antioxidant capacity assay. The results are correlated and discussed with respect to the until now known constituents of the investigated species.