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The use of proton NMR spectroscopy allows the analysis of complex multi-component mixtures such as plant extracts by simultaneous quantification of all proton-bearing compounds and consequently all relevant substance classes. Since the spectra obtained are too complicated to be analysed visually, the classification of spectra was carried out using multivariate statistical methods. The spectroscopic data of various extracts of St. John's wort (Hypericum perforatum) samples derived from 4 different accessions extracted with 6 distinct solvents were chemometrically evaluated and calibrated using the partial least square (PLS) algorithm. In a first approach, we found a consistent correlation for the spectroscopic pattern of the extracts and the corresponding IC (50) values derived from non-selective binding to opioid receptors. Consequently, the multivariate data analysis was used to predict the pharmacological efficacy of further St. John's wort extracts on the basis of their proton NMR spectra. In a second approach a PLS 2 model was used to predict the biological activity for eight St. John's wort extracts based on two pharmacological data sets: (i) non-selective binding to opioid receptors and (ii) antagonist effect at corticotrophin-releasing factor type 1 (CRF (1)) receptors. The PLS 2 model confirmed the useful application of the presented approach to assess the quality of medicinal herbs and extracts by spectroscopic analysis derived from bioactivity-related quality parameters.

Various locations in Switzerland were screened for Petasites hybridus plants with high petasin and low pyrrolizidine alkaloid content. The mean petasin content of the various populations ranged from 7.4 to 15.3 mg/g dry weight in rhizomes and from 3.3 to 11.4 mg/g dry weight in leaves. Mean pyrrolizidine alkaloid content in rhizomes ranged from 5 to 90 ppm whereas leaves contained between 0.02 to 1.50 ppm. These results suggest that leaves might be a preferable source for harvesting compared to the underground organ due to the finding of high petasin contents and consistently lower amounts of toxic pyrrolizidine alkaloids.

In vitro and in vivo studies suggest that extracts of St John's wort (Hypericum perforatum, L .; SJWE) interact with various drugs, by enhancing their elimination, due to induction of intestinal and hepatic cytochrome P450 3A4 (CYP3A4) and P-glycoprotein (P-gp), the gene product of multidrug resistance gene 1 (MDR1/ABCB1). The aim of our study was to identify the major constituents responsible for this induction and their relative importance. Therefore, plant extracts were investigated that vary in these constituents with respect to their effect on mRNA expression of MDR1/CYP3A4. First, different pure constituents of Hypericum perforatum L . were investigated. Secondly, diverse SJWE with different concentrations of hyperforin, quercitrin and hypericin were investigated. The concentrations of hyperforin, hypericin, and quercitrin in the plant extracts were determined by HPLC, and an "artificial extract" containing the same mixture of these constituents was investigated. Different plant extracts, pure constituents or "artificial extracts" were applied to the human colon carcinoma-derived cell line (LS180) and the induction of MDR1 and CYP3A4 expression was analyzed by quantitative RT-PCR. MDR1 and CYP3A4 mRNA expression were both induced by single constituents of SJW such as hypericin and hyperforin in a concentration of 10 microM. Additionally, CYP3A4 mRNA expression was induced by quercitrin. SJW extracts containing hyperforin induced significantly MDR1 mRNA expression, whereas no CYP3A4 induction was observed after treatment with any of the investigated SJWE. These effects could be mimicked by "artificial extracts" containing the same compositions of hyperforin, hypericin and quercitrin as the plant extracts.

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