Antibacterial activity of <i>Hypericum perforatum</i> L. (St. John’s wort) extracts against Gram-positive bacteria and characterisation of its secondary metabolites
Özgül Kısa, Lütfiye Öksüz, Hüseyin Servi, Ayhan İbrahim Aysal
Abstract
This study aimed to determine the secondary metabolite profiles and antibacterial activity of H. perforatum L extracts against Gram-positive clinical isolates. The plant materials (Sample A and Sample B) were macerated with n-hexane, ethyl acetate and methanol (MeOH). The antibacterial activitiy of plant extracts and routinely used antibiotics were tested against Gram-positive bacteria. The secondary metabolite profiles of Sample A were determined by LC-Q-TOF-MS. The MIC values for n-hexane and ethyl acetate extracts of Sample A were lower than the susceptibility breakpoints of most broad-spectrum antibiotics (e.g. vancomycin, teicoplanin and linezolid) in a certain proportion of Gram-positive bacteria. The n-hexane extract of Sample A showed good antibacterial activity with MICs lower than the susceptibility breakpoint of teicoplanin in 58% of coagulase-negative staphylococci. The n-hexane and ethyl acetate extracts of Sample A had rich phloroglucinol constituents. The n-hexane and ethyl acetate extracts of Sample A could be alternative antibacterial agents against Gram-positive bacteria.