Determination of naphthodianthrones and phloroglucinols from Hypericum perforatum extracts by liquid chromatography/tandem mass spectrometry

UPLC-MS-Based Metabolomics Profiling and Chemometric Analysis for Hypericum sinaicum Boiss and the Endophytic Aspergillus foetidus in Comparison to Hypericum perforatum L

One of the endangered plant species in Saint Catherine protectorate is Hypericum sinaicum Boiss which is endemic to Egypt, Jordan, and Saudi Arabia. The fungus-host relationship can assist in the investigation of bioactive compounds produced by H. sinaicum paving the way for economic and medicinal implications. Therefore, a comprehensive metabolic approach via MS and chemical analysis was used to track and compare metabolites from H. sinaicum and Aspergillus foetidus var. pallidus, the endophytic fungus, with Hypericum perforatum. Metabolomics analysis revealed the presence of 25 metabolites distributed among samples and the discovery of new chemotaxonomic compounds, i. e., phloroglucinols and xanthones, allowing the discrimination between species. A. foetidus extract is considered a reliable source of furohyperforin and naphthodianthrone derivatives. In conclusion, using A. foetidus as an in vitro technique for producing potential phytoconstituents was cost effective, having easier optimization conditions and faster growth with fewer contamination rates than other in vitro methods.

Phytochemical profiling of several Hypericum species identified using genetic markers

In the present study, we performed phytochemical profiling of several under-exploited Hypericum representatives taxonomically belonging to the sections Ascyreia, Androsaemum, Inodora, Hypericum, Coridium, Myriandra, and Adenosepalum. The authenticity of the starting plant material was confirmed using the nuclear ribosomal internal transcribed spacer as a molecular marker, DNA content and chromosome number. Phenolic constituents were analyzed using high-performance liquid chromatography to complement species-specific metabolic profiles. In several Hypericum representatives, the pharmacologically important compounds, including naphthodianthrones; phloroglucinol derivatives; chlorogenic acid; and some classes of flavonoids, particularly the flavonols rutin and hyperoside, flavanol catechin, and flavanones naringenin and naringin, were reported for the first time. Comparative multivariate analysis of chemometric data for seedlings cultured in vitro and acclimated to the outdoor conditions revealed a strong genetically predetermined interspecific variability in phenolic compound content. In addition to hypericins, which are the most abundant chemomarkers for the genus Hypericum, rarely employed phenolic metabolites, including phloroglucinol derivatives, chlorogenic acid, catechin, naringenin, naringin, and kaempferol-3-O-glucoside, were shown to be useful for discriminating between closely related species. Given the increasing interest in natural products of the genus Hypericum, knowledge of the spectrum of phenolic compounds in shoot cultures is a prerequisite for future biotechnological applications. In addition, phytochemical profiling should be considered as an additional part of the integrated plant authentication system, which predominantly relies upon genetic markers.

Optimized and Validated HPLC Analysis of St. John's Wort Extract and Final Products by Simultaneous Determination of Major Ingredients

Aim of this work was to develop a validated high performance liquid chromatography method for the analysis of extracts and final products of St. John's wort, according to international guidelines for bioanalytical method validation. Chromatographic separation was performed on a C18 column with a combination of gradient and isocratic steps; the mobile phase composed of ammonium acetate solution (pH 4.5; 10 mM), acetonitrile and methanol. Quantification and method validation was performed using extract spiked with external reference standards of chlorogenic acid, rutin, hyperoside, isoquercitrin, quercetin and hypericin. Validation study revealed that trans-chlorogenic acid is partially transformed into its cis-isomer during analysis. The method showed good linearity, precision and accuracy. Hyperforin was completely unstable. All other ingredients were stable at -18°C and after three freeze-thaw cycles, while stability of most ingredients was limited at room temperature and 4 - 8°C; quercetin was the most unstable one. The major ingredients of methanolic extracts, infusions and final products of Hypericum perforatum were completely resolved and quantified. Beyond its potential usefulness in the analysis of St. John's wort products, this study addresses the issue of validation from the perspective of the field of bioanalysis and reveals the wealth of critical information which can be derived.

Phytochemical characterization,in vitroandin silicoapproaches for threeHypericumspecies

Members of theHypericumgenus are spread throughout the world and have a long history of use in traditional systems of medicines.

Quality control of Hypericum perforatum L. analytical challenges and recent progress

Objectives

The most widely applied qualitative and quantitative analytical methods in the quality control of Hypericum perforatum extracts will be reviewed, including routine analytical tools and most modern approaches.

Key findings

Biologically active components of H. perforatum are chemically diverse; therefore, different chromatographic and detection methods are required for the comprehensive analysis of St. John's wort extracts. Naphthodianthrones, phloroglucinols and flavonoids are the most widely analysed metabolites of this plant. For routine quality control, detection of major compounds belonging to these groups seems to be sufficient; however, closer characterization requires the detection of minor compounds as well.

Conclusions

TLC and HPTLC are basic methods in the routine analysis, whereas HPLC-DAD is the most widely applied method for quantitative analysis due to its versatility. LC-MS is gaining importance in pharmacokinetic studies due to its sensitivity. Modern approaches, such as DNA barcoding, NIRS and NMR metabolomics, may offer new possibilities for the more detailed characterization of secondary metabolite profile of H. perforatum extracts.

Negative ion electrospray high-resolution tandem mass spectrometry of polyphenols

Representative compounds with a 1,3-dihydroxybenzene substructure belonging to different important polyphenol classes (stilbenes, flavones, isoflavones, flavonols, flavanones, flavanols, phloroglucinols, anthraquinones and bisanthraquinones) were investigated based on detailed high-resolution tandem mass spectrometry measurements with an Orbitrap system under negative ion electrospray conditions. The mass spectral behaviour of these compound classes was compared among each other not only with respect to previously described losses of CO, CH2 CO and C3 O2 but also concerning the loss of CO2 and successive specific fragmentations. Furthermore, some unusual fragmentations such as the loss of a methyl radical during mass spectral decomposition are discussed. The obtained results demonstrate both similarities and differences in their mass spectral fragmentation under MS(n) conditions, allowing a characterization of the corresponding compound type. Copyright © 2015 John Wiley & Sons, Ltd.

Isolation and purification of series bioactive components from Hypericum perforatum L. by counter-current chromatography

Counter-current chromatography (CCC) combined with pre-separation by ultrasonic solvent extraction was successively used for the separation of series bioactive compounds from the crude extract of Hypericum perforatum L. The petroleum ether extract was separated by the solvent system of n-heptane-methanol-acetonitrile (1.5:0.5:0.5, v/v) and n-heptane-methanol (1.5:1, v/v) in gradient elution, yielding a phloroglucinol compound, hyperforin with HPLC purity over 98%. The ethyl acetate extract was separated by using the solvent system composed of hexane-ethyl acetate-methanol-water (1:1:1:1 and 1:3:1:3, v/v) in gradient through both reverse phase and normal phase elution mode, yielding a naphthodianthrone compound, hypericin with HPLC purity about 95%. The n-butanol extract was separated with the solvent system composed of n-butanol-ethyl acetate-water (1:4:5 and 1.5:3.5:5, v/v) in elution and back-extrusion mode, yielding two of flavones, rutin and hyperoside, with HPLC purity over 95%. HPLC-MS, reference sample and UV spectrum were selectively used in separation to search for target compounds from HPLC-DAD profiles of different sub-extracts. The structures of isolated compounds were further identified by ESI-MS, ¹HNMR and ¹³CNMR.

A Semiquantitative FIA-ESI-MS Method for the Rapid Screening of Hypericum perforatum Crude Extracts

A method based on FIA-ESI-MS has been developed to profile the major constituents of Hypericum perforatum extracts. The objective was to obtain simultaneous semi-quantitative data on hypericin, chlorogenic acid, rutin, quercitrin, quercetin and hyperforin contents for a high-throughput screening of the raw plant material. The principal drawback of FIA-ESI analysis of complex mixtures involves ion suppression effects: the ionization of some components of the mixture can be severely suppressed by ionization of others. The results show that this problem can be alleviated using a new approach to generate calibration curves.

Quantitative analysis of the major constituents of St John's wort with HPLC-ESI-MS

A method was developed to profile the major constituents of St John's wort extracts using highperformance liquid chromatography-electrospray mass spectrometry (HPLC-ESI-MS). The objective was to simultaneously separate, identify and quantify hyperforin, hypericin, pseudohypericin, rutin, hyperoside, isoquercetrin, quercitrin and chlorogenic acid using HPLC-MS. Quantification was performed using an external standardisation method with reference standards. The method consisted of two protocols: one for the analysis of flavonoids and glycosides and the other for the analysis of the more lipophilic hypericins and hyperforin. Both protocols used a reverse phase Luna phenyl hexyl column. The separation of the flavonoids and glycosides was achieved within 35 min and that of the hypericins and hyperforin within 9 min. The linear response range in ESI-MS was established for each compound and all had linear regression coefficient values greater than 0.97. Both protocols proved to be very specific for the constituents analysed. MS analysis showed no other signals within the analyte peaks. The method was robust and applicable to alcoholic tinctures, tablet/capsule extracts in various solvents and herb extracts. The method was applied to evaluate the phytopharmaceutical quality of St John's wort preparations available in the UK in order to test the method and investigate if they contain at least the main constituents and at what concentrations.

Hypericins as potential leads for new therapeutics

70 years have passed since the first isolation of the naphthodianthrones hypericin and pseudohypericin from Hypericum perforatum L. Today, they continue to be one of the most promising group of polyphenols, as they fascinate with their physical, chemical and important biological properties which derive from their unique chemical structure. Hypericins and their derivatives have been extensively studied mainly for their antitumor, antiviral and antidepressant properties. Notably, hypericin is one of the most potent naturally occurring photodynamic agents. It is able to generate the superoxide anion and a high quantum yield of singlet oxygen that are considered to be primarily responsible for its biological effects. The prooxidant photodynamic properties of hypericin have been exploited for the photodynamic therapy of cancer (PDT), as hypericin, in combination with light, very effectively induces apoptosis and/or necrosis of cancer cells. The mechanism by which these activities are expressed continues to be a main topic of discussion, but according to scientific data, different modes of action (generation of ROS & singlet oxygen species, antiangiogenesis, immune responces) and multiple molecular pathways (intrinsic/extrinsic apoptotic pathway, ERK inhibition) possibly interrelating are implicated. The aim of this review is to analyse the most recent advances (from 2005 and thereof) in the chemistry and biological activities (in vitro and in vivo) of the pure naphthodianthrones, hypericin and pseudohypericin from H. perforatum. Extracts from H. perforatum were not considered, nor pharmakokinetic or clinical data. Computerised literature searches were performed using the Medline (PubMed), ChemSciFinder and Scirus Library databases. No language restrictions were imposed.

Dereplication of bioactive constituents of the genus hypericum using LC-(+,-)-ESI-MS and LC-PDA techniques: Hypericum triquterifolium as a case study

Utilizing liquid chromatography-electro spray ionization-mass spectrometry (LC-(+,-)-ESI-MS) and liquid chromatography-photodiode array detection (LC-PDA) techniques, a dereplication strategy for the analysis of the secondary metabolites constituents of the genus Hypericum has been developed. From the crude methanolic extract of the aerial parts of H. triquetrifolium (leaves, stems, and flowers) and on the basis of their UV-profiles, chromatographic retention times and (+,-)-ESI-MS (TIC and SIM) mass spectral data, seven known (1-7) compounds were dereplicated fairly rapidly. The compounds were classified into three structural classes: phloroglucinols: hyperfirin and adhyperfirin; naphthodianthrones: hypericin, pseudo-hypericin, proto-hypericin, and protopseudo-hypericin; and the flavonoid rutin.

Rapid and efficient purification of naphthodianthrones from St. John's wort extract by using liquid-liquid extraction and SEC

Hypericin and pseudohypericin, the main naphthodianthrones present in Hypericum species are among the most promising natural products, but the research concerning their biological activities is hindered by their low content in the plant. In this paper a method for the rapid isolation of hypericin and pseudohypericin from Hypericum perforatum hydro-alcoholic dried extracts has been developed. Briefly, the method consists of a partition of the extract between organic and aqueous layers and further purification of the richest extract in naphthodianthrones with Sephadex LH-20 column chromatography. A final separation of hypericin from pseudohypericin was achieved using Sephadex LH-60 column chromatography. All partitions were carried out in triplicate and monitored by LC-MS and NMR analyses. The best results were obtained by successive extraction with n-hexane, Et(2)O and EtOAc. A three-step fractionation resulted in 98% content in total naphthodianthrones. To the best of our knowledge this is the first report on the separation of hypericin from pseudohypericin using size exclusion chromatography.

The main components of St John's Wort inhibit low-density lipoprotein atherogenic modification: A beneficial “side effect” of an OTC antidepressant drug?

Hypericin and pseudohypericin are polycyclic-phenolic structurally related compounds found in Hypericum perforatum L. (St John's wort). As hypericin has been found to bind to LDL one may assume that it can act as antioxidant of LDL lipid oxidation, a property which is of prophylactic/therapeutic interest regarding atherogenesis as LDL oxidation may play a pivotal role in the onset of atherosclerosis. Therefore, in the present paper hypericin, pseudohypericin and hyperforin, an other structurally unrelated constituent in St John's wort were tested in their ability to inhibit LDL oxidation. LDL was isolated by ultracentrifugation and oxidation was initiated either by transition metal ions (copper), tyrosyl radical (myeloperoxidase/hydrogen peroxide/tyrosine) or by endothelial cells (HUVEC). LDL modification was monitored by conjugated diene and malondialdehyde formation. The data show that all compounds (hypericin, pseudohypericin and hyperforin) at doses as low as 2.5 micromol/l are potent antioxidants in the LDL oxidation systems used. The results indicate that the derivatives found in Hypericum perforatum have possible antiatherogenic potential.

Identification of the major constituents of Hypericum perforatum by LC/SPE/NMR and/or LC/MS

The newly established hyphenated instrumentation of LC/DAD/SPE/NMR and LC/UV/(ESI)MS techniques have been applied for separation and structure verification of the major known constituents present in Greek Hypericum perforatum extracts. The chromatographic separation was performed on a C18 column. Acetonitrile-water was used as a mobile phase. For the on-line NMR detection, the analytes eluted from column were trapped one by one onto separate SPE cartridges, and hereafter transported into the NMR flow-cell. LC/DAD/SPE/NMR and LC/UV/MS allowed the characterization of constituents of Greek H. perforatum, mainly naphtodianthrones (hypericin, pseudohypericin, protohypericin, protopseudohypericin), phloroglucinols (hyperforin, adhyperforin), flavonoids (quercetin, quercitrin, isoquercitrin, hyperoside, astilbin, miquelianin, I3,II8-biapigenin) and phenolic acids (chlorogenic acid, 3-O-coumaroylquinic acid). Two phloroglucinols (hyperfirin and adhyperfirin) were detected for the first time, which have been previously reported to be precursors in the biosynthesis of hyperforin and adhyperforin.

Simultaneous determination of benzophenones and gentisein in Hypericum annulatum Moris by high-performance liquid chromatography

The content of the benzophenones, hypericophenonoside, neoannulatophenonoside, annulatophenonoside, annulatophenone, acetylannulatophenonoside and the xanthone derivative gentisein have been determined in aerial parts, leaves, flowers and stems of Hypericum annulatum Moris. Extraction of samples with methanol by magnetic stirring at room temperature allowed a good recovery of analytes (from 90.70% for gentisein to 103.81% for annulatophenonoside) and the precision of the entire procedure was < 6.05%. The subsequent HPLC separation and quantification was achieved using a Hypersil ODS C18 column and UV detection at 290 nm. The mobile phase comprised methanol and 20 mm potassium dihydrogen phosphate (adjusted to a pH of 3.19 with o-phosphoric acid), and gradient elution mode was applied. The detection limits were 0.03, 0.02 and 0.001 microg/mL for hypericophenonoside, acetylannulatophenonoside and gentisein, respectively. The total amounts of the phenolic compounds assayed ranged from 10.92 mg/g in stems to 82.86 mg/g in leaves. Hypericophenonoside was the dominant benzophenone present in the majority of the plant samples, being present in amounts between 7.54 +/- 0.25 mg/g in stems and 64.22 +/- 2.44 mg/g in leaves. Hypericophenonoside accounted for up to 77.50% of the components found in the leaves, whereas annulatophenonoside (6.29 +/- 0.15 mg/g) and acetylannulatophenonoside (8.95 +/- 0.09 mg/g) were detected in much lower quantities. In contrast to leaves, flowers showed a tendency towards higher contents of gentisein (9.35 +/- 0.07 mg/g) and neoannulatophenonoside (4.72 +/- 0.04 mg/g) than the other parts assayed.

Optimization of the assay of naphthodianthrones in dry St John’s wort extract by reversed-phase liquid chromatography

An optimization procedure for the reversed-phase liquid chromatography (RPLC) assay of naphthodianthrones in St John's wort extract from the European Pharmacopoeia project is described. The results obtained from two screening designs showed that light exposure, recommended in the monograph as sample pretreatment, does not permit one to obtain a reproducible quantification of the main ingredients. Improvement of the method robustness implies the need to overcome the problem of light exposure, to subsequently quantify protonaphthodianthrones and to perform the separation on octadecyl (ODS)-bonded phase at optimized flow rate. The method robustness was checked by using a bifurcation sequential approach investigating the influence of 13 factors. The eluent recommended in the monograph is a ternary mixture of methanol, phosphate buffer and ethyl acetate. For the sake of simplicity, the phosphate buffer was substituted by an acetate buffer. The best composition of the ternary mixture was determined by a combined design including three mixture variables and the temperature as an independent variable. Chromatographic parameters were modelled in terms of analysis time, resolution and asymmetry. Desirability functions permit one to cope with these parameters and to determine the best compromise. The naphthodianthrones were separated on a conventional endcapped octadecyl silica gel column eluted by a ternary mobile phase at 40 degrees C in 10 min.

A high-performance liquid chromatography with electrochemical detection for the determination of total hypericin in extracts of St. John's Wort

An HPLC method for the quantitation of hypericin using a new and sensitive amperometric detection is presented. Hypericin was eluted isocratically using a mobile phase consisting of ammonium acetate, methanol and acetonitrile. The oxidation was carried out with a glassy carbon electrode at a potential of + 1.1 V vs. an Ag-AgCl-KCl reference electrode. Under the conditions described, hypericin was separated at a retention time (Rt) of 12 min. Linearity was obtained over the range 0.035-1.30 microg/mL (r = 0.9994). The limit of detection was determined to be 0.010 ng on-column for hypericin. The method was applied to the determination of total hypericin (hypericin, pseudohypericin, protohypericin and protopseudohypericin) in extracts of St. John's wort using hypericin as an external standard. The protoforms were converted into hypericin and pseudohypericin by subjecting the sample to artificial light prior to chromatographic analysis. For the evaluation of total hypericin, the peak areas of pseudohypericin (Rt 3.7 min) and hypericin (Rt 12.0 min) were combined. The relative standard deviation in analysing samples containing Hypericum ranged from 2.5 to 5.4%.

Development and evaluation of methods for determination of naphthodianthrones and flavonoids in St. John's wort

Several major constituents in St. John's wort were determined for a homogenized plant sample. Three extraction techniques were evaluated: Soxhlet extraction, pressurized-fluid extraction (PFE), and sonication extraction. Levels of nine constituents (chlorogenic acid, rutin, hyperoside, isoquercitrin, quercitrin, quercetin, amentoflavone, pseudohypericin, and hypericin) were measured using liquid chromatography with ultraviolet/visible absorbance, mass spectrometric, and fluorescence detection. Levels of total naphthodianthrones determined by liquid chromatography (LC) with absorbance detection at 590 nm were compared with levels determined by direct spectrophotometry at the same wavelength. Additionally, the methods described in this paper were applied to several brands of St. John's wort finished products.

Mass spectral characterization of phloroglucinol derivatives hyperforin and adhyperforin

Active phloroglucinol constituents of Hypericum perforatum (St. John's wort) extracts, hyperforin and adhyperforin, have been studied following ion activation using tandem mass spectrometry (MS/MS) and complemented by accurate mass measurements. These two compounds were readily analyzed as protonated and deprotonated molecules with electrospray ionization. MS/MS and MS3 data from a quadrupole-linear ion trap tandem mass spectrometer were employed to elucidate fragmentation pathways. Fourier transform ion cyclotron resonance measurements afforded excellent mass accuracies for the confirmation of elemental formulae of product ions formed via infrared multiphoton dissociation and sustained off-resonance irradiation collision-induced dissociation. Fragmentation schemes have been devised for the dissociation of hyperforin and adhyperforin in negative and positive ion modes. This information is expected to be especially valuable for the characterization of related compounds, such as degradation products, metabolites and novel synthetic analogs of hyperforin.

Prediction of herb-drug metabolic interactions: a simulation study

In vitro and in vivo studies have indicated that the induction or inhibition of cytochrome P450 (CYP) is one of the major mechanisms for some clinically important pharmacokinetic herb-drug interactions. An attempt was made to simulate the effects of herbal preparation with single or multiple CYP-inhibiting constituents on the area of the plasma concentration-time curve (AUC) of coadministered drug that was either a low clearance drug by intravenous (i.v.) injection or a high clearance drug by oral route. Our simulation studies indicated that the expected increase (Rc) in the AUC of the coadministered drug by inhibiting herbal constituent(s) was dependent on the route of administration. For low clearance drug by i.v. injection, Rc was generally determined by inhibition constant (Ki), unbound inhibitor concentration ([I]), hepatic fraction (fh), number of inhibitory herbal constituents (n) and metabolic pathway fraction in hepatic metabolism (fm), while Rc for a high clearance drug by oral route, Rc was determined by Ki, [I], n and fm. By varying these parameters, Rc changed accordingly. It appeared likely to predict a herb-drug metabolic interaction, if the inhibiting herbal constituents could be quantitatively determined. However, many herb- and drug-related factors may cause difficulties with the prediction, and thus in vivo animal and human studies are always necessary.

Liquid chromatography-mass spectrometry studies of St. John's wort methanol extraction: active constituents and their transformation

The influence of light and solution pH on the stability behavior of phloroglucinols (hyperforin and adhyperforin) and naphthodianthrones (hypericin, pseudohypericin, protohypericin and protopseudohypericin) extracted with methanol from St. John's wort powder (Hypericum perforatum L.) were studied using liquid chromatography-mass spectrometry (LC-MS). When exposed to light, hyperforin and adhyperforin in this extract solution degraded rapidly, particularly at pH 7, where within 12h complete transformation was observed. Contrastingly, when protected from light, the solutions regardless of pH, underwent minimal transformation after 36h. Under light and neutral pH conditions, phloroglucinols and naphthodianthrones had different stability behaviors, which were attributed to the different oxidation mechanisms. Four experiments performed on naphthodianthrones exhibited serious transformation at acidic pHs. One hyperforin transformation product was studied using LC-MS. The molecular structure was proposed on the basis of ion fragmentation patterns obtained from MS/MS studies.

Development of a high-performance liquid chromatographic method with electrochemical detection for the determination of hyperforin

An HPLC method with electrochemical detection for the determination of hyperforin extracts without using additional sample precleaning has been developed and validated. The hyperforin solutions were separated isocratically using a mobile phase consisting of 10% ammonium acetate buffer (0.5 M, pH 3.7)-MeOH-acetonitrile (10:40:50, v/v) at a flow rate of 0.8 mL/min. Hyperforin was detected amperometrically with a glassy carbon electrode at a potential of +1.1 V versus Ag/AgCl/3 M potassium chloride reference electrode. Under these conditions, a plot of integrated peak area versus concentration of hyperforin was found to be linear over the range of 0.054-5.4 microg/mL, with a relative standard deviation of 2.2-8.6%. The limit of detection was 0.050 ng on column. The determination of the hyperforin content in a commercially available St. John's Wort preparation exhibited a mean content of 1.56 mg. Recovery experiments led to a mean recovery rate of 97 +/- 5.8%. The proposed method is not time-consuming, sensitive and reproducible and is therefore suitable for routine analysis of hyperforin in herbal medicinal products.

Characterization of supercritical fluid extracts of St. John’s Wort (Hypericum perforatum L.) by HPLC–MS and GC–MS

Supercritical fluid extracts (carbon dioxide without modifiers) of St. John's Wort (Hypericum perforatum L., Clusiaceae) were analyzed by GC-MS, HPLC-DAD and HPLC-DAD-MS. Besides the dominating phloroglucinols hyperforin (36.5 +/- 1.1%) and adhyperforin (4.6 +/- 0.1%), the extracts mainly contained alkanes (predominantly nonacosane), fatty acids and wax esters. The apolar components tended to accumulate in a waxy phase resting a top of the hyperforin-enriched phase. No components of higher polarity like naphthodianthrones were found. A set of hyperforin oxidation products was detected and tentatively assigned using HPLC-MS.

Determination of Hyperforin in Mouse Brain by High-Performance Liquid Chromatography/Tandem Mass Spectrometry

Hyperforin is one of the essential active ingredients of St. John's wort extract, which is used as an antidepressant for mild to moderately severe depressions. In vitro and in vivo data as well as several clinical studies and meta analyses have confirmed the pharmacological effect of treatment with hyperforin-containing preparations. However, little is known about the brain availability of hyperforin until now. Accordingly, a highly sensitive and selective LC/MS method for this purpose was developed and validated. This method proved suitable for the determination of hyperforin in mouse brain, after oral administration of hyperforin sodium salt and St. John's wort extract. This method involves liquid-liquid extraction of hyperforin with ethyl acetate followed by separation with rapid reversed-phase high-performance liquid chromatography and tandem mass spectrometry detection using electrospray ionization. Excellent linearity was obtained for the entire calibration range from 0.25 to 10 ng/mL (corresponding to 2.5-100 ng/g brain tissue concentration, calculated with the factor derived from sample processing) with an average coefficient of correlation of 0.9992. The recovery of hyperforin from mouse brain homogenates was between 71.4 and 75.3% with a relative standard deviation of less than 3%. Validation assays for the lower limit of quantitation yielded an accuracy of 5.8%. Intraday accuracy and precision for the developed method were between 4.6 and 10.6% and 4.3-8.4%, respectively, while the interday parameters varied between 6.7 and 12.2% for accuracy and 2.0-5.0% for precision. After the method validation, hyperforin brain levels in mice, treated with 15 mg/kg hyperforin (either as the sodium salt or as 5% St. John's wort extract), were investigated. The average concentration of hyperforin found for the sodium salt group was 28.8+/-10.1 ng/g of brain (n = 8), which was somewhat higher than the hyperforin concentration of 15.8+/-10.9 ng/g of brain (n = 8), determined in the extract-treated group. This method is robust, selective, and highly sensitive and represents an appropriate tool to further prove the occurrence and distribution of hyperforin in mouse brain.

Fast high-performance liquid chromatographic analysis of naphthodianthrones and phloroglucinols from Hypericum perforatum extracts

Hypericum perforatum L. (St. John's Wort) has been used in modern medicine for treatments of depression and neuralgic disorders. An HPLC method with photodiode array detection for the rapid determination of the major active compounds, naphthodianthrones and phloroglucinols, has been developed. The method permits the determination of hypericin, protohypericin, pseudohypericin, protopseudohypericin, hyperforin and adhyperforin in an extract in less than 5 min. Good linearity over the range 0.5-200 microg/mL for hyperforin and 0.02-100 microg/mL for hypericin was observed. Intra-assay accuracy and precision varied from 0.1 to 17% within these ranges. Lower levels of quantitative determination were 2 microg/mL for hyperforin and 0.5 microg/mL for hypericin, while detection limits were 0.1 and 0.02 microg/mL, respectively.

Use of an on-line, precolumn photochemical reactor in high-performance liquid chromatography of naphthodianthrones in Hypericum perforatum preparations

A method has been developed for the determination of naphthodianthrones in Hypericum perforatum L. extracts and phytopharmaceutical preparations by high-performance liquid chromatography combined with on-line, precolumn photochemical conversion followed by photodiode-array detection. The chromatographic separation was performed on a C18 column under isocratic reversed-phase conditions. An on-line, precolumn photochemical reactor equipped with a knitted PTFE reaction coil around a visible light source was used in order to transform the light sensitive naphthodianthrones, protohypericin and protopseudohypericin, very easily into the non-protoforms, hypericin and pseudohypericin, respectively. Two UV chromatograms (photochemical reactor "on" and "off") were compared and were quite useful in characterizing the sample. Validation studies demonstrated that this HPLC method is simple, rapid, reliable and reproducible. The time-consumptive manual irradiation of the samples is omitted by this automated on-line irradiation step. The developed method was successfully applied to the quality control of Hypericum perforatum L. extracts and its phytopharmaceutical preparations.