Determination of active ingredients of Rhododendron dauricum L. by capillary electrophoresis with electrochemical detection

Chemistry, biosynthesis, and theranostics of antioxidant flavonoids and polyphenolics of genus Rhododendron: an overview

The genus Rhododendron is an ancient and most widely distributed genus of the family Ericaceae consisting of evergreen plant species that have been utilized as traditional medicine since a very long time for the treatment of various ailments including pain, asthma, inflammation, cold, and acute bronchitis. The chemistry of polyphenolics isolated from a number of species of the genus Rhododendron has been investigated. During the currently designed study, an in-depth study on the phytochemistry, natural distribution, biosynthesis, and pharmacological properties including their potential capability as free radical scavengers has been conducted. This work provides structural characteristics of phenolic compounds isolated from the species of Rhododendron with remarkable antioxidant potential. In addition, biosynthesis and theranostic study have also been encompassed with the aims to furnish a wide platform of valuable information for designing of new drug entities. The detailed information including names, structural features, origins, classification, biosynthetic pathways, theranostics, and pharmacological effects of about 171 phenolics and flavonoids isolated from the 36 plant species of the genus Rhododendron with the antioxidant potential has been covered in this manuscript. This study demonstrated that species of Rhododendron genus have excellent antioxidant activities and great potential as a source for natural health products. This comprehensive review might serve as a foundation for more investigation into the Rhododendron genus.

Bioactive Flavonoids: A Comprehensive Review on Pharmacokinetics and Analytical Aspects

Flavonoids are a diversified group of natural substances which were discovered to provide a variety of health benefits in human beings. Vegetables, fruits, wine and tea are the primary flavonoid dietary sources for humans and as the flavonoids are so closely connected to human dietary items and health, it is vital to explore the structural-activity connection. The arrangement, replacement of functional groups, and total number of hydroxyl groups around flavonoid's nucleus structure affect their biological activity, metabolism, and bioavailability. Various flavonoids have been proven to have hepatoprotective properties, that help in the prevention of coronary heart disease. Similarly, these flavonoids also possess anticancer, and anti-inflammatory activities. Flavonoids have been found to have a functional and structural link with their enzyme inhibitory action, that appears to have antiviral effect through acting as antioxidants, damaging cell membranes, blocking enzymes, activating mechanisms of host self-defense, and limiting virus penetration and attaching to cells. Identification, characterization, isolation, and biological role of flavonoids, as well as their uses on health advantages, are all major topics in research and development currently. This review represents a summary of various sources of flavonoids, class, subclass, their chemical structures, biological activities, the pharmacokinetics of flavonoids and various analytical, bioanalytical and electrochemical methods for determination of flavonoids from different matrices.

Simple Portable Voltammetric Sensor Using Anodized Screen-Printed Graphene Electrode for the Quantitative Analysis of p-Hydroxybenzoic Acid in Cosmetics

Screen-printed graphene electrodes (SPGEs) have become a potential option in electrochemical applications because of their outstanding properties and disposable approach to miniaturize the electrodes for onsite analysis. Herein, the detection of para-hydroxybenzoic acid (PHBA) in cosmetics using the anodized SPGE has been pioneered and reported. The simple anodization of the SPGE surface was operated by anodic pretreatment at a constant potential on SPGE. The surface morphologies and electrochemical behaviors of anodized SPGEs in different anodization electrolytes were examined. Using anodized SPGE in a phosphate-buffered solution, a nontoxic solution, the sensitivity of PHBA detection was significantly improved compared with pristine SPGE owing to the increase of the polar oxygen-containing functional group during the anodization. The anodized SPGE could detect a PHBA down to 0.073 μmol/L. Finally, the developed anodized SPGE presented high ability and feasibility for PHBA detection in cosmetics. Furthermore, a facile electrode preparation step with a nontoxic solution can present high reproducibility and compatibility with a portable potentiostat for onsite PHBA detection during manufacturing.

A Complete Study of Farrerol Metabolites Produced in Vivo and in Vitro

Although farrerol, a characteristically bioactive constituent of Rhododendron dauricum L., exhibits extensive biological and pharmacological activities (e.g., anti-oxidant, anti-immunogenic, and anti-angiogenic) as well as a high drug development potential, its metabolism remains underexplored. Herein, we employed ultra-high performance liquid chromatography/quadrupole time-of-flight mass spectrometry coupled with multiple data post-processing techniques to rapidly identify farrerol metabolites produced in vivo (in rat blood, bile, urine and feces) and in vitro (in rat liver microsomes). As a result, 42 in vivo metabolites and 15 in vitro metabolites were detected, and farrerol shown to mainly undergo oxidation, reduction, (de)methylation, glucose conjugation, glucuronide conjugation, sulfate conjugation, N-acetylation and N-acetylcysteine conjugation. Thus, this work elaborates the metabolic pathways of farrerol and reveals the potential pharmacodynamics forms of farrerol.

Magnetic molecularly imprinted polymers doped with graphene oxide for the selective recognition and extraction of four flavonoids from Rhododendron species

Herein, a novel magnetic molecularly imprinted polymer doped with reticular graphene oxide (Fe₃O₄@SiO₂-GO@MIPs) was synthesized for the selective recognition and extraction of 4 flavonoids (farrerol, taxifolin, kaempferol, and hyperin) from Rhododendrons species. The Fe₃O₄@SiO₂-GO@MIPs with lamellar membranes showed outstanding adsorption capacity. The 3D cavities complementary to the "shape" of farrerol were "imprinted" on the polymer framework after removal of farrerol template. Competitive binding assays showed that the polymer has a higher selectivity for farrerol compared with other analogues and references. The Fe₃O₄@SiO₂-GO@MIPs as solid-phase extraction adsorbents combined with liquid chromatography-tandem quadrupole mass spectrometry (LC-MS/MS) was used for selective determination of four flavonoids from Rhododendrons samples. The limits of detection (LOD) were 0.07, 0.08, 0.06, and 0.08 μg L^-1 for farrerol, taxifolin, kaempferol, and hyperin, respectively. These results suggest that the prepared Fe₃O₄@SiO₂-GO@MIPs have the potential applicability to extract, purify, and enrich flavonoids from herbs, supplements, and other natural products.

Identification of Chinese Herbs Using a Sequencing-Free Nanostructured Electrochemical DNA Biosensor

Due to the nearly identical phenotypes and chemical constituents, it is often very challenging to accurately differentiate diverse species of a Chinese herbal genus. Although technologies including DNA barcoding have been introduced to help address this problem, they are generally time-consuming and require expensive sequencing. Herein, we present a simple sequencing-free electrochemical biosensor, which enables easy differentiation between two closely related Fritillaria species. To improve its differentiation capability using trace amounts of DNA sample available from herbal extracts, a stepwise electrochemical deposition of reduced graphene oxide (RGO) and gold nanoparticles (AuNPs) was adopted to engineer a synergistic nanostructured sensing interface. By using such a nanofeatured electrochemical DNA (E-DNA) biosensor, two Chinese herbal species of Fritillaria (F. thunbergii and F. cirrhosa) were successfully discriminated at the DNA level, because a fragment of 16-mer sequence at the spacer region of the 5S-rRNA only exists in F. thunbergii. This E-DNA sensor was capable of identifying the target sequence in the range from 100 fM to 10 nM, and a detection limit as low as 11.7 fM (S/N = 3) was obtained. Importantly, this sensor was applied to detect the unique fragment of the PCR products amplified from F. thunbergii and F. cirrhosa, respectively. We anticipate that such a direct, sequencing-free sensing mode will ultimately pave the way towards a new generation of herb-identification strategies.

The antioxidative potential of farrerol occurs via the activation of Nrf2 mediated HO-1 signaling in RAW 264.7 cells

Farrerol, (S)-2,3-dihydro-5,7-dihydroxy-2-(4-hydroxyphenyl)-6,8-dimethyl-4-benzopyrone, isolated from rhododendron, has been shown to have antioxidative potential, but the molecular mechanism underlying this activity remains unclear. The inducible expression of heme oxygenase-1 (HO-1), a potent antioxidative and cytoprotective enzyme, is known to play an important role in cytoprotection in a variety of pathological models. In this study, we evaluated the antioxidative potential of farrerol against oxidative damage and investigated its antioxidative mechanism in RAW 264.7 cells. The molecular mechanism underlying the cytoprotective function of farrerol was determined by analyzing intracellular signaling pathways, transcriptional activation and the inhibitory effect of HO-1 on ROS production. Farrerol induced antioxidant enzymes mRNA expression, HO-1 protein expression and nuclear translocation of NF-E2-related factor 2 in RAW 264.7 macrophage cells. Farrerol down-regulated the expression of the Keap1 protein and the thiol reducing agents attenuated farrerol-induced HO-1 expression. Further investigation utilizing Western blotting and specific inhibitors of Akt, p38, JNK and ERK demonstrated that Akt, p38, and ERK axis of signaling pathway mediates HO-1 expression. Moreover, tert-butyl hydroperoxide (t-BHP)-induced oxidative damage was ameliorated by farrerol treatment in a dose-dependent manner, which was abolished by Akt, p38, ERK and HO-1 inhibitors (Snpp). It is hence likely that farrerol inactivated KEAP-1 or activated the Akt, p38 and ERK to facilitate the release of Nrf2 from Keap1 and subsequent reduced the intracellular production of reactive oxygen species via the induction of HO-1 expression. These results support the central role of HO-1 in the cytoprotective effect of farrerol.

Quality control of traditional Chinese medicines: a review

Traditional Chinese medicines (TCMs) are in great demand all over the world, especially in the developing world, for primary health care due to their superior merits such as low cost, minimal side effects, better cultural acceptability, and compatibility with humans. However, Chinese medicines consist of several herbs which may contain tens, hundreds, or even thousands of constituents. How these constituents interact with each other, and what the special active ones are, may be the biggest bottleneck for the modernization and globalization of TCMs. Valid methods to evaluate the quality of TCMs are therefore essential and should be promoted and be developed further through advanced separation and chromatography techniques. This paper reviews the strategies used to control the quality of TCMs in a progressive perspective, from selecting single or several ingredients as the evaluation marker, to using different kinds of chromatography fingerprint methods. In summary, the analysis and quality control of TCMs are developing in a more effective and comprehensive manner to better address the inherent holistic nature of TCMs.

Phytochemicals and Biological Activities of Poisonous Genera of Ericaceae in China

The family Ericaceae is comprised of about 70 genera of which about 20 are found throughout China. Of these Ledum, Rhododendron, Enkianthus, Pieris, Craibiodendron, Gaultheria, Vaccinium, and Leucothoe are regarded as poisonous. Many species of these poisonous genera are used as Chinese herbal medicines for the treatment of, for example, inflammation, asthma, and coughs. Modern research has demonstrated that the toxic ingredients of these poisonous genera are chiefly tetracyclic diterpenes, which have adverse effects on the digestive, cardiovascular and nervous systems. Because various species of these poisonous genera also have medicinal functions, extensive studies of these plants have led to the identification of many kinds of compound. This paper compiles 306 compounds from the eight poisonous genera, reported in 141 references.

Farrerol regulates antimicrobial peptide expression and reduces Staphylococcus aureus internalization into bovine mammary epithelial cells

Mastitis, defined as inflammation of the mammary gland, is an infectious disease with a major economic influence on dairy industry. Staphylococcus aureus is a common gram-positive pathogen that frequently causes subclinical, chronic infection of the mammary gland in dairy cows. Farrerol, a traditional Chinese medicine isolated from rhododendron, has been shown to have anti-bacterial activity. However, the effect of farrerol on S. aureus infection in mammary epithelium has not been studied in detail. The aim of this study was to investigate the effect of farrerol on the invasion of bovine mammary epithelial cells (bMEC) by S. aureus. The expression of antimicrobial peptide genes by bMEC were assessed in the presence or absence of S. aureus infection. Our results demonstrated that farrerol (4-16 μg/ml) reduced > 55% the internalization of S. aureus into bMEC. We also found that farrerol was able to down-regulate the mRNA expression of tracheal antimicrobial peptide (TAP) and bovine neutrophil β-defensin 5 (BNBD5) in bMEC infected with S. aureus. The Nitric oxide (NO) production of bMEC after S. aureus stimulation was decreased by farrerol treatment. Furthermore, farrerol treatment suppressed S. aureus-induced NF-κB activation in bMEC. These results demonstrated that farrerol modulated TAP and BNBD5 gene expression in mammary gland, enhances bMEC defense against S. aureus infection and could be useful in protection against bovine mastitis.

Different effects of farrerol on an OVA-induced allergic asthma and LPS-induced acute lung injury

Background

Farrerol, isolated from rhododendron, has been shown to have the anti-bacterial activity, but no details on the anti-inflammatory activity. We further evaluated the effects of this compound in two experimental models of lung diseases.

Methodology/Principal Findings

For the asthma model, female BALB/c mice were challenged with ovalbumin (OVA), and then treated daily with farrerol (20 and 40 mg/kg, ip) as a therapeutic treatment from day 22 to day 26 post immunization. To induce acute lung injury, female BALB/c mice were injected intranasally with LPS and treated with farrerol (20 and 40 mg/kg, i.p.) 1 h prior to LPS stimulation. Inflammation in the two different models was determined using ELISA, histology, real-time PCR and western blot. Farrerol significantly regulated the phenotype challenged by OVA, like cell number, Th1 and Th2 cytokines levels in the BALF, the OVA-specific IgE level in the serum, goblet cell hyperplasia in the airway, airway hyperresponsiveness to inhaled methacholine and mRNA expression of chemokines and their receptors. Furthermore, farrerol markedly attenuated the activation of phosphorylation of Akt and nuclear factor-κB (NF-κB) subunit p65 both in vivo and in vitro. However, farrerol has no effect on the acute lung injury model.

Conclusion/Significance

Our finding demonstrates that the distinct anti-inflammatory effect of farrerol in the treatment of asthma acts by inhibiting the PI3K and NF-κB pathway.

Mechanism and conformational studies of farrerol binding to bovine serum albumin by spectroscopic methods

The mechanism and conformational changes of farrerol binding to bovine serum albumin (BSA) were studied by spectroscopic methods including fluorescence quenching technique, UV-vis absorption, circular dichroism (CD) spectroscopy and Fourier transform infrared (FT-IR) spectroscopy under simulative physiological conditions. The results of fluorescence titration revealed that farrerol could strongly quench the intrinsic fluorescence of BSA through a static quenching procedure. The thermodynamic parameters enthalpy change and entropy change for the binding were calculated to be -29.92 kJ mol(-1) and 5.06 J mol(-1) K(-1) according to the van't Hoff equation, which suggested that the both hydrophobic interactions and hydrogen bonds play major role in the binding of farrerol to BSA. The binding distance r deduced from the efficiency of energy transfer was 3.11 nm for farrerol-BSA system. The displacement experiments of site markers and the results of fluorescence anisotropy showed that warfarin and farrerol shared a common binding site I corresponding to the subdomain IIA of BSA. Furthermore, the studies of synchronous fluorescence, CD and FT-IR spectroscopy showed that the binding of farrerol to BSA induced conformational changes in BSA.

Involvement of estrogen receptor-β in farrerol inhibition of rat thoracic aorta vascular smooth muscle cell proliferation

AIM

To investigate the effect of farrerol, a major active component isolated from a traditional Chinese herb "man-shan-hong" (the dried leaves of Rhododendron dauricum L) on fetal bovine serum (FBS)-induced proliferation of cultured vascular smooth muscle cells (VSMCs) of rat thoracic aorta.

METHODS

VSMCs proliferation, DNA synthesis and cell cycle progression were studied using the MTT assay, bromodeoxyuridine (BrdU) incorporation and flow cytometry, respectively. The mRNA levels of cell cycle proteins were quantified using real-time RT-PCR, and the phosphorylation of ERK1/2 was determined using Western blotting. Reporter gene and receptor binding assays were employed to study the interaction between farrerol and estrogen receptors (ERs).

RESULTS

Farrerol (0.3-10 μmol/L) inhibited VSMC proliferation and DNA synthesis induced by 5% FBS in a concentration-dependent manner. The effects were associated with G(1) cell cycle arrest, down-regulation of cell cycle proteins and reduction in FBS-induced ERK1/2 phosphorylation. Using a reporter gene, it was found that farrerol (3 μmol/L) induced 2.1-fold transcription of ER. In receptor binding assays, farrerol inhibited the binding of [(3)H]estradiol for ERα and ERβ with IC(50) values of 57 μmol/L and 2.7 μmol/L, respectively, implying that farrerol had a higher affinity for ERβ. Finally, the inhibition of VSMC proliferation by farrerol (3 μmol/L) was abolished by the specific ERβ antagonist PHTPP (5 μmol/L).

CONCLUSION

Farrerol acts as a functional phytoestrogen to inhibit FBS-induced VSMC proliferation, mainly via interaction with ERβ, which may be helpful in the treatment of cardiovascular diseases related to abnormal VSMCs proliferation.

Binding analysis of farrerol to lysozyme by spectroscopic methods

Binding of farrerol to lysozyme (LYSO) was investigated at 302, 313 and 318 K at pH 7.4 using spectrophotometric techniques such as fluorescence emission, circular dichroism (CD) and UV absorption. The data obtained from fluorescence quenching experiments showed that farrerol was bound to LYSO and the affinity was enhanced by the addition of farrerol. When the concentration ratio of farrerol to LYSO was higher than 5.4, both the binding constant and the binding stoichiometry went up. Based on the thermodynamic parameters evaluated from the van't Hoff equation, the enthalpy change (deltaH degrees ) and entropy change (deltaS degrees ) were derived to be negative values. They indicated that both van der Waals forces and hydrogen bonds are the major interactions between farrerol and LYSO. A value of 2.67 nm for the average distance r between farrerol (acceptor) and tryptophan residues (Trp) of LYSO (donor) was derived from the fluorescence resonance energy transfer. Besides, the change in the conformation of LYSO was observed, being caused by the interaction with farrerol.

Determination of active components in Cynanchum chinense R. Br. by capillary electrophoresis

A method for the determination of 7-O-alpha-l-rhamnopyranosyl-kaempferol-3-O-beta-d-glucopyranoside (GL) and 7-O-alpha-l-rhamnopyranosyl-kaempferol-3-O-alpha-l-rhamnopyranoside (RH) in the traditional Chinese herb Cynanchum chinense R. Br. by capillary electrophoresis has been developed. With botate buffer (30 mmol/L, pH 9.50) as running buffer and an applied voltage of 20 kV, the compounds were completely separated within 6 min and detected at UV 254 nm. The correlation coefficients of the calibration curves for GL and RH were 0.9990 and 0.9992, respectively, over the concentration ranges (15.0-1000.0 and 12.0-1000.0 microg/mL), and the recoveries were from 91.4 to 107.1%.

Application of reverse-flow micellar electrokinetic chromatography for the simultaneous determination of flavonols and terpene trilactones in Ginkgo biloba dosage forms

A reverse-flow micellar electrokinetic chromatographic (RF-MEKC) method was developed for the simultaneous qualitative determination of 10 components consisting of the flavonol glycosides, rutin and quercitrin, the flavonol aglycones, isorhamnetin, kaempferol and quercetin, the terpene trilactones, ginkgolides A, B, C and J and the sesquiterpene, bilobalide. This method was used to fingerprint Ginkgo biloba solid oral dosage forms and validated for the quantitation of the marker compounds, rutin and quercetin in some commercial products. In addition to the usual variables, the influence of some essential background electrolyte (BGE) components such as sodium dodecyl sulphate (SDS) and <beta>-cyclodextrin concentrations were investigated. A polyimide fused-silica square capillary column (75 microm I.D. x 360 microm O.D.) with a total length of 60.0 cm and effective length of 45.0 cm was used for the separation. The final BGE consisted of 20 mM phosphoric acid, 40 mM SDS and 12 mM <beta>-cyclodextrin (pH 2.2) using reverse polarity with a voltage of -17.5 kV. Samples were injected electrokinetically at -5 kV for 3 s for the qualitative analysis and hydrodynamically at 20 mbar for 0.6 s for the quantitative assay. The total run time was 22 min and the limits of detection were 3.13 microg/ml and 1.88 microg/ml for rutin and quercetin, respectively. Fingerprint profiles of the solid oral dosage forms and the results of the quantitative analysis indicated that there were major discrepancies in the marker content between products and illustrates the value of this method for use as a procedure to assess product quality of commercially available Ginkgo biloba products.

Determination of three bile acids in artificial Calculus Bovis and its medicinal preparations by micellar electrokinetic capillary electrophoresis

A micellar electrokinetic capillary electrophoresis (MEKCE) method for the determination of cholic acid (CA), hyodeoxycholic acid (HDCA) and chenodeoxycholic acid (CDCA) in artificial Calculus Bovis and its four medicinal preparations is described. The buffer solution consisted of 40 mM disodic phosphate and 40 mM sodium dodecylsulfate (SDS) adjusted to pH 9.0. UV detection was set to 200 nm. Under optimum conditions, the analytes were baseline separated within 11min. The linear calibration range was 12.1-970 microgml(-1) for CA and 18.8-950 microgml(-1) for HDCA and CDCA, respectively. It was found that overall recoveries were within the range of 98-102%, and R.S.D.s were less than 5% for the analytes. This method, due to its convenience, high accuracy and good reproducibility can be employed in quality control of artificial Calculus Bovis and its medicinal preparations.

Analytical separation and detection methods for flavonoids

Flavonoids receive considerable attention in the literature, specifically because of their biological and physiological importance. This review focuses on separation and detection methods for flavonoids and their application to plants, food, drinks and biological fluids. The topics that will be discussed are sample treatment, column liquid chromatography (LC), but also methods such as gas chromatography (GC), capillary electrophoresis (CE) and thin-layer chromatography (TLC), various detection methods and structural characterization. Because of the increasing interest in structure elucidation of flavonoids, special attention will be devoted to the use of tandem-mass spectrometric (MS/MS) techniques for the characterization of several important sub-classes, and to the potential of combined diode-array UV (DAD UV), tandem-MS and nuclear magnetic resonance (NMR) detection for unambiguous identification. Emphasis will be on recent developments and trends.

Determination of active ingredients of Ilex Purpurea Hassk and its medicinal preparations by capillary electrophoresis with electrochemical detection

A method based on capillary electrophoresis with electrochemical detection has been developed for the separation and determination of isovanillic acid, gentisic acid, kaempferol, quercetin, caffeic acid and protocatechuic acid in Ilex Purpurea Hassk and its medicinal preparations for the first time. The effects of working electrode potential, pH and concentration of running buffer, separation voltage and injection time on CE-ED were investigated. Under the optimum conditions, the analytes could be separated in a 50 mmoll(-1) borate buffer (pH 9.0) within 21 min. A 300 microm diameter carbon disk electrode has a good response at +0.95 V (versus SCE) for all analytes. The response was linear over three orders of magnitude with detection limits (S/N=3) ranging from 3 x 10(-8) to 2 x 10(-7)gml(-1) for the analytes. The method has been successfully applied to the analysis of real sample, with satisfactory results.

Fast and simultaneous detection of prominent natural antioxidants using analytical microsystems for capillary electrophoresis with a glassy carbon electrode: A new gateway to food environments

This paper examines for the first time the analytical possibilities of fast and simultaneous detection of prominent natural antioxidants including examples of flavonoids and vitamins using a CE microchip with electrochemical detection (ED). Unpinched injection conditions, zone electrophoretic separation and amperometric detection were carefully assayed and optimised. Analysis involved the zone electrophoretic separation of arbutin, (+)-catechin and ascorbic acid in less than 4 min using a borate buffer (pH 9.0, 50 mM), employing 2 kV as the separation voltage and +1.0 V as the detection potential. In addition, the separation of different 'couples' of natural antioxidants of food significance including (+)-catechin and ascorbic acid, (+)-catechin and rutin, as well as arbutin and phlorizdin is proposed. To demonstrate the potential and future role of CE microsystems, analytical possibilities and a new route in the raw sample analysis are presented. The preliminary results obtained allow the proposal of CE-ED microchips as a real gateway to microanalysis in foods.

Differentiation of Swertia Mussotii Franch from Artemisiae Capillaris Herba by capillary electrophoresis with electrochemical detection

A high-performance capillary electrophoresis (CE) with electrochemical detection (ED) method is developed for differentiation of Swertia Mussotii Franch from Artemisiae Capillaris Herba in this work. Swertia Mussotii Franch contains a great deal of swertiamarin and mangiferin that are not present in Artemisiae Capillaris Herba, whereas Artemisiae Capillaris Herba consists of abundant chlorogentic acid. Therefore, determining their swertiamarin, mangiferin and chlorogentic acid contents can differentiate these two crude herbs. Operated in a wall-jet configuration, a 300 microm diameter carbon-disk electrode was used as the working electrode, which exhibits good response at +1000 mV (versus SCE) for the three analytes. With a separation voltage of 14 kV, the three analytes were separated within 14 min in a 52 cm length capillary in 50 mmol/l borax buffer (pH 9.2). The system was demonstrated good stability and reproducibility with an R.S.D. of less than 5% for both migration time and peak current. This method was successfully used to analyze and identify the crude herbs with satisfactory assay results.

Recent advances in analysis of Chinese medical plants and traditional medicines

Chinese herbal medicine is gaining increasing popularity worldwide for health promotion and adjuvant therapy. Thus, selective and efficient analytical methods are required not only for quality assurance but also for authentication of the plant material. Applications of both chromatographic and electrophoretic techniques to the analysis of medicinal plants and Chinese traditional medicine preparations over the last 3 years are outlined in this review. The role of chemical fingerprinting is highlighted and a brief survey of determination of toxic components, natural and synthetic adulterants is also included. Moreover, different sample pretreatment and extraction methods are discussed.

Determination of liquiritigenin and isoliquiritigenin in Glycyrrhiza uralensis and its medicinal preparations by capillary electrophoresis with electrochemical detection

A simple, reliable, reproducible and sensitive method, based on capillary electrophoresis with electrochemical detection (ED), for the determination of liquiritigenin and isoliquiritigenin in Glycyrrhiza uralensis and its medicinal preparations was described. Operated in a wall-jet configuration, a 300 microm diameter carbon-disk electrode was used as the working electrode, which exhibits good responses at + 1000 mV (versus SCE) for the two analytes. Under the optimum conditions, the analytes were base-line separated within 8 min, and excellent linearity was obtained in the concentration range from 5.0 x 10(-4) to 1.0 x 10(-6) mol/l. The detection limit (S/N = 3) was 4.7 x 10(-7) and 2.9 x 10(-7) mol/l for liquiritigenin and isoliquiritigenin, respectively. This work provides a useful method for the analysis of traditional Chinese medicines.

Amperometric and voltammetric detection for capillary electrophoresis

The focus of this article is amperometric and voltammetric detection coupled with capillary electrophoresis. Fundamental concepts and progress in the field of capillary electrophoresis with electrochemical detection (CEEC) that have occurred within the past three years, including new methodologies and unique applications, are highlighted. This review contains 95 references.