Antibacterial and repellent activities of Hypericum perfoliatum (St. John’s Wort) on different bacterial strains and anatomical tissues of Ovine and Bovine species
St. John’s Wort (Hypericum perfoliatum, SJW) is an herbaceous medical plant that grows abundantly and spontaneously in Mediterranean area. Since ancient times, SJW has been used to treat different kind of mental and physical diseases, and for its antiseptic, antinflammatory and antibacterial properties. In this study, we investigated the antibacterial and repellent activities of Hypericum perfoliatum oil on different animal samples in vitro and ex vivo. The inhibitory activity was evaluated on six different bacterial strains: 2 strains of Staphylococcus aureus, 2 strains of Listeria monocytogenes, 1 strain of Salmonella tiphymurium and 1 strain of Escherichia coli O157:H7. Agar gel diffusion technique was used with four different concentrations of the compound. The effect of the oil against the selected strains was evaluated by measuring the halo of inhibition around the discs soaked with Hypericum perfoliatum oil. To establish the repellent activity, different animal samples were brushed once with the oil and kept outdoors for one week. Only Sthaphylococcus aureus was susceptible to Hypericum perfoliatum oil, even at the lowest concentration used. For the other bacterial strains no inhibition was observed. A single application of the oil was effective against different species of insects, unlike untreated samples. The results achieved in this study confirm that Hypericum perfoliatum possesses antibacterial properties only against Gram positive bacteria and a strong repellent activity against insects.