Chemical and pharmacological evaluation of Hypericum perforatum extracts

AIM: To determine the concentrations of chemical characteristic to extracts of leaves and flowers of Hypericum perforatum (St John's wort) in a number of selected samples and, following chemical characterization, to investiga te the effects of these extracts on several pharmacological properties incl uding effects of the extracts on inhibition of 5-hydroxytryptamine (5-HT) u ptake and on antioxidant properties. METHODS: The samples were analyzed for the presence of characteristic chemicals by high performance liquid chroma tography (HPLC) directly coupled to ultraviolet wavelength absorbance and p ositive or negative mode electrospray mass spectrometric detection. The eff ects of extracts on 5-HT uptake were determined by quantifying H-3-5-HT inc orporation into rat hippocampal prisms. Estimates of effects of extracts on free radical scavenging capacity were made using a dynamic assay based on the ability of compounds to prevent the initiation of a colored reaction pr oduced by the horseradish peroxidase catalyzed formation of hydroxyl free r adicals from hydrogen peroxide using 2,2'-azinobis (3-ethylbenzthiazoline-6 -sulfonic acid) as the color indicator. RESULTS: The chemical profile of a number of extracts were determined and found to differ substantially from e ach other. Inhibition of 5-HT uptake was found to correlate with hyperforin content and free radical scavenging capacity was found to correlate with t he content of several flavonoids including quercetin and hyperoside. CONCLU SION: Standardized extracts of H perforatum varied substantially in the con centration of several characteristic chemicals. The correlation between pha rmacological activity and certain characteristic chemicals found in these e xtracts indicates that the medicinal benefit derived from selected extracts will vary considerably depending on their chemical composition.