The characterization of st. john's wort (Hypericum perforatum L.) phenolics and the determination of their antioxidant and antimicrobial potentials

In this study the extracts of St.John's Wort (Hypericum Perforatum L.) plant are obtained by using several solvents (ethanol, methanol, sunflower oil, olive oil and water) and the phenolic compound, antioxidant and antimicrobial effects of these extracts have been examined. Phenolic compounds have been determined by using high performance-liquid chromatography based-electronic ionization mass spectrometer (HPLC-DAD-ESI-MSn). The antioxidant potentials of the extracts have been investigated in details by making use of the DPPH and ABTS methods. The antimicrobial effect of the St.John's Wort plant has been explored by the method of agar well diffusion. As a result of the analysis made, 22 fenolic components have been defined. As far as the extracts which have been prepared are concerned; neoclorogenic acid-a compound of clorogenic acid group, epicatechin-a compound of flavan-3-ol group, caffeic acid-a compound of fenolic acid group, hypericin- a compound of naftodiantro and hyperosoid- a compound of flavonoids have been determined as the dominant compounds. During the study it has been observed in general that the number and amount of compounds defined in methanol and ethanol extracts is more than those in the sunflower oil, olive oil and water extracts. The antioxidant capacity analysis results have shown that, the highest content is in methanol extracts whereas the lowest content is in sunflower oil. When the outcomes of the antimicrobial activity analysis is examined; the extracts of Hypericum Perforatum L. which have been prepared with sunflower oil and olive oil did not yield any inhibition effect on Escherichia coli, Staphylococcus aeureus, Pseudomonas aeuroginasa microorganisms where as the extracts that have been prepared with methanol, ethanol and water showed antimicrobial effects. The lowest antimicrobial activity has been observed in the plant extract which was prepared with water. When the entire results are assessed in general, it is seen that the number and amount of compounds is higher in the extracts that are prepared with ethanol and methanol, as well as the antioxidant potential has been fixed relatively higher in comparison to the other extracts. Among the microorganisms which were subject to testing, the highest antimicrobial activity was observed in ethanol and methanol extracts. Key Words: St. John's Wort, Hypericum perfaratum L., phenolic compounds, antioxidant capacity, agar well diffusion method, LC-DAD-ESI-MS/MS