Determination of aristolochic acid in Chinese herbal medicine by capillary electrophoresis with laser-induced fluorescence detection

Magnetic quaternary ammonium polymer bearing porous agarose for selective extraction of Aristolochic acids in the plasma

Aristolochic acids (AAs) naturally occurring in the herbal genus Aristolochia are associated with a high risk of kidney failure, multiple tumors and cancers. However, approaches with high selectivity and rapidity for measuring AAs in biological samples are still inadequate. Inspired by the mechanism of AAs-induced nephrotoxicity, we designed a hybrid magnetic polymer-porous agarose (denoted as MNs@SiO2M@DNV-A), mimicking the effect of basic and aromatic residues of organic anion transporter 1 (OAT1) for efficient enriching aristolochic acid I (AA I) and aristolochic acid II (AA II) in the plasma. The monomers of vinylbenzyl trimethylammonium chloride (VBTAC), N-vinyl-2-pyrrolidinone (NVP) and divinylbenzene (DVB) were employed to construct the polymer layer, which provided a selective adsorption for AAs by multiple interactions. The porous agarose shell contributed to remove interfering proteins in the plasma samples. A magnetic solid-phase extraction (MSPE) based on the proposed composite enhanced the selectivity toward AA I and AA II in the plasma samples. In combination of HPLC analysis, the proposed method was proved to be applicable to fast and specific quantification of AAs in blood samples, which was characterized by a good linearity, high sensitivity, acceptable recovery, excellent repeatability and satisfactory reusability.

Fabrication of a Simple and Efficient HPLC Reduction Column for Online Conversion of Aristolochic Acids to Aristolactams Prior to Sensitive Fluorescence Detection

Aristolochic acids (AAs) are nephrotoxic and carcinogenic nitrophenanthrene carboxylic acids produced naturally by plants from the Aristolochia and Asarum genera, which have been used extensively as herbal medicines. In addition to consuming AA-containing herbal medicinal products, there is emerging evidence that humans are also exposed to AA through the environment. In 2022, the World Health Organization (WHO) called for global action to remove AA exposure sources and to implement preventative measures against the development of AA-associated cancers. Herein, we report the development of a simple and efficient iron powder-packed reduction column that allows online post-column conversion of the nonfluorescing AA to its corresponding strongly fluorescing aristolactam (AL), facilitating the sensitive and selective detection of AA in herbal medicinal products, food grain, arable soil, or groundwater samples by high-performance liquid chromatography with fluorescence detection. Moreover, AL, a group of naturally occurring derivatives of AA that have demonstrated toxicity to cultured bacteria, human cells, and rats, is monitored and quantified simultaneously with AA in one single run without sacrificing sensitivity. In comparison with existing analytical methods for AA measurement, the newly developed method is not only inexpensive and less laborious, but it also offers improved sensitivity. We believe this novel method will find wide application in identifying the presence of AA in food, herbal medicines, and environmental samples, thus assisting in the identification and removal of AA exposure sources.

Generation of a high-affinity DNA aptamer for on-site screening of toxic aristolochic acid I in herbal medicines and botanical products

Aristolochic Acid I (AAI) is an environmental and foodborne toxin found in the Aristolochia and Asarum species of plants that are widespread all over the world. Therefore, there is an urgent need to develop a sensitive and specific biosensor for identifying AAI. Aptamers as a powerful biorecognition element provide the most viable options for solving this problem. In this study, we used library-immobilized SELEX to isolate an AAI-specific aptamer with a K_D value of 86 ± 13 nM. To verify the practicability of the selected aptamer, a label-free colorimetric aptasensor was designed. This aptasensor exhibited a low detection limit of 225 nM. Besides, it had been further applied for the determination of AAI in real samples and the recoveries ranged from 97.9% to 102.4%. In the future, AAI aptamer will provide a promising tool for safety evaluation in various fields of agriculture, food, and medication.

Rapid and robust analysis of aristolochic acid I in Chinese medicinal herbal preparations by surface-enhanced Raman spectroscopy

The use of Chinese herbs containing aristolochic acid can induce the exchange of adenine and thymine in gene mutations and even cause liver cancer. To eliminate the harm of aristolochic acids (AAs) to humans, a rapid and robust method of AAs screening is a prerequisite. In this work, a facile and robust Surface-enhanced Raman spectroscopy (SERS) method was used for the qualitative and quantitative detection of AAs in Chinese medicinal herbal preparations based on the mandelic acid modified Ag nanoparticles SERS substrate. Qualitative and quantitative SERS detection of Aristolochic acid I (AAI) was achieved with a good linear relationship ranging from 0.2 - 120.0 μM and a limit of detection (LOD) of 0.06 μM. The proposed method demonstrates a refined strategy for sensitivity analysis of AAs with the advantages of easy operation, time-saving, high sensitivity, and molecular specificity, making it a preferred platform for the screening of AAI in regular inspections of herbal products and regulatory supervision of the supply chain.

Nitrogen-Rich Tetraphenylethene-Based Luminescent Metal-Organic Framework for Efficient Detection of Carcinogens

The introduction of nitrogen-rich functional groups into a luminescent metal-organic framework (LMOF) can enhance its fluorescent sensing ability. In this work, we designed and synthesized a triazole-containing tetracarboxyl-substituted tetraphenylethene (TPE) ligand, tetrakis[4-(4-carboxyphenyl)(1H-1,2,3-triazol-4,1-diyl)phenyl]ethene (H₄TCPTAPE), featuring a prominent aggregation-induced emission (AIE). A highly porous TPE-based LMOF [Zn₃(TCPTAPE)(H₂O)₂(OH)₂] (1) with large pores was successfully obtained via solvothermal assembly of the H₄TCPTAPE ligand and Zn(II) ions, which showed a high fluorescence quantum yield of 54%. The activated 1 could selectively and sensitively detect aristolochic acid I with a high fluorescence quenching efficiency of 96% and a low detection limit of 1.02 μM, indicating that it has a potential application as a luminescence-based chemical sensor for carcinogens.

Molecularly imprinted ratiometric fluorescent probe for visual and fluorescent determination of aristolochic acid I based on a Schiff-base fluorescent compound

A molecularly imprinted ratiometric fluorescent probe (MIRF probe) was synthesized for the determination of aristolochic acid I (AAI) based on the Schiff-base fluorescent compound N,N'-bis(o-carboxybenzylidene)-p-4,4'-diaminobiphenyl (BDDB). The BDDB was immobilized in the silica nanoparticle (BDDB@SiO₂) as an internal standard material. The blue-emitting BDDB@SiO₂ and the yellow-emitting carbon quantum dots (y-CDs) were wrapped in the molecularly imprinted polymer (MIP) to provide a reliable reference signal at 440 nm and a fluorescent response signal at 530 nm at the excitation wavelength of 365 nm, respectively. In the preparation of the MIP of the MIRF probe, 4-vinylbenzoic acid as the functional monomer and AAI as the template molecule were used. An imprinting factor of 2.25 was obtained. Under the optimum conditions, the fluorescent response signal at 530 nm was quenched gradually by AAI in the range 1.0 to 120.0 μmol/L, while the reference signal at 440 nm remained unchanged. The limit of detection was 0.45 μmol/L, and the fluorescent color of the MIRF probe changed gradually from yellow to green to blue, which illustrated that the developed probe had a specific AAI recognition ability, a good anti-interference ability, and a sensitively visual determination ability. The probe was successfully applied to the AAI determination in traditional Chinese medicine (TCM) Asarum. The results showed that it had satisfactory recoveries (95.5-107.3%) and low relative standard deviations (2.0%). Furthermore, this method has a potential for the onsite naked eye determination of AAI in TCM samples.Graphical abstract.

An Overview on Analytical Methods for Quantitative Determination of Aristolochic Acids

Background:

Aristolochic acids are chemically linked to nitrophenanthrene carboxylic acids which are found in aristolochia plants. These compounds are intrinsically carcinogenic, while they have been used in traditional medicine from a long time ago. Despite the beneficial effects of herbals for treating some diseases, they possess some side effects.

Methods:

Therefore, the development of a sensitive and selective procedure for the determination of these harmful components in various complicated samples is an important task for health systems and drug authorities. In the past years, ultra-pressure liquid chromatography, high performance liquid chromatography and capillary electrophoresis with different detection systems were used for determination of aristolochic acids in various samples.

Results:

In this review, different analytical methods have been discussed in brief and applications of them in diverse samples have been summarized.

Conclusion:

Different approaches are compared from point of sensitivity, selectivity, and extraction efficiency.

Soft-templated mesoporous carbon-modified glassy carbon electrode for sensitive and selective detection of aristolochic acids

In this study, ordered mesoporous carbon (OMC) was synthesized by applying a soft template method, and its mesoporous structure was characterized by scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption-desorption techniques. X-ray diffraction and Raman spectroscopic analyses were conducted to demonstrate the high graphitization and topological defects at the sample surface. An electrochemical sensor based on an OMC-modified glassy carbon electrode (OMC/GCE) was constructed to detect aristolochic acids (AAs) using cyclic voltammetry and linear sweep voltammetry. The dependence of the experimental parameters including solution pH, scan rate, and accumulation time were examined and optimized. Under the optimal conditions, the response of OMC/GCE was linear over wide concentration ranges of AAs (0.6-10 μM and 10-50 μM), with sensitivities of -1.77 and -0.31 μA/μM, respectively. The limit of detection was calculated to be 0.186 μM (at S/N = 3). Furthermore, the proposed OMC/GCE was applied to detect AAs in Asarum sieboldini and the content of AAs was calculated to be 8.9 μg/g with high accuracy and precision. In addition, the modified electrode also exhibited good selectivity, reproducibility, and stability. Therefore, the OMC/GCE can be used as a platform for the determination of AAs.

Developed a novel sensor based on fluorescent graft conjugated polymer for the determination of aristolochic acid in traditional Chinese medicine

A novel fluorescent graft conjugated polymer (poly (2, 5-bis (Polyethylene glycol oxybutyrate)-1, 4-phenylethynylene-alt-1, 4-phenyleneethynylene, PPE-OB-PEG) has been designed and synthesized for the determination of aristolochic acid (AA). The detection conditions and detection characters of PPE-OB-PEG were systematically explored in this work. The fluorescence intensity of PPE-OB-PEG changes with the different concentration of AA. PPE-OB-PEG has a good linear range towards AA from 1.00 × 10^-7 to 8.00 × 10^-5 mol L^-1 and the limit of detection (LOD) is 3.00 × 10^-8 mol L^-1 (S/N = 3). PPE-OB-PEG have been applied to detect AA in traditional Chinese medicine samples and the results are satisfactory. The experimental results show that PPE-OB-PEG can be used as a fluorescence probe for rapid and sensitive detection of AA.

New Dual-Spectroscopic Strategy for the Direct Detection of Aristolochic Acids in Blood and Tissue

Aristolochic acids (AAs) contained in herbal plants are implicated in multiple organ injuries and have a high mutational burden in upper tract urothelial cancers. The currently available techniques for monitoring AAs include LC (liquid chromatography) and LC/MS (mass spectrometry), but the application of these approaches are limited due to the complex sample preparation and derivatization steps. Therefore, there is an urgent need to develop efficient methods for identifying and quantifying AAs. Here, we present a new dual-spectroscopic approach for the direct detection of AAs from blood and tissue samples; the detection of aristolochic acid I (AAI) is performed by surface-enhanced Raman spectroscopy (SERS), and its bioproduct, aristololactam (AAT), is detected by fluorescence spectroscopy based on their distinctive spectral response. Furthermore, a graphene assisted enrichment coupled with a magnetic retrieval strategy was developed to enhance SERS sensitivity toward AAI. Our method was successfully applied to directly determine both AAI and AAT from the blood, liver, and kidney of rats. The potential for real-world application was demonstrated by continuously monitoring AAI and AAT in rat blood and tissues after AAI feeding. The results showed that AAI was gradually metabolized to AAT and transported to different organs. It was found that the metabolism of AAI took place in the kidney, but AAT residue was detected in both liver and kidney, which might be related to long-term toxicity and gene mutation. The proposed dual-spectroscopic strategy is applicable to long-term toxicology research and to the direct diagnosis of AAI-induced organ injury.

Interference-free spectrofluorometric quantification of aristolochic acid I and aristololactam I in five Chinese herbal medicines using chemical derivatization enhancement and second-order calibration methods

A rapid interference-free spectrofluorometric method combined with the excitation-emission matrix fluorescence and the second-order calibration methods based on the alternating penalty trilinear decomposition (APTLD) and the self-weighted alternating trilinear decomposition (SWATLD) algorithms, was proposed for the simultaneous determination of nephrotoxic aristolochic acid I (AA-I) and aristololactam I (AL-I) in five Chinese herbal medicines. The method was based on a chemical derivatization that converts the non-fluorescent AA-I to high-fluorescent AL-I, achieving a high sensitive and simultaneous quantification of the analytes. The variables of the derivatization reaction that conducted by using zinc powder in acetose methanol aqueous solution, were studied and optimized for best quantification results of AA-I and AL-I. The satisfactory results of AA-I and AL-I for the spiked recovery assay were achieved with average recoveries in the range of 100.4-103.8% and RMSEPs <0.78ngmL^-1, which validate the accuracy and reliability of the proposed method. The contents of AA-I and AL-I in five herbal medicines obtained from the proposed method were also in good accordance with those of the validated LC-MS/MS method. In light of high sensitive fluorescence detection, the limits of detection (LODs) of AA-I and AL-I for the proposed method compare favorably with that of the LC-MS/MS method, with the LODs <0.35 and 0.29ngmL^-1, respectively. The proposed strategy based on the APTLD and SWATLD algorithms by virtue of the "second-order advantage", can be considered as an attractive and green alternative for the quantification of AA-I and AL-I in complex herbal medicine matrices without any prior separations and clear-up processes.

Risk assessment of plant food supplements and other herbal products containing aristolochic acids using the margin of exposure (MOE) approach

After the incidences of induction of aristolochic acid nephropathy after consumption of herbal weight loss preparations that accidentally contained aristolochic acids (AAs), several countries defined national restrictions on the presence of AAs in food, including plant food supplements (PFS) and herbal products. This study investigates whether the risks associated with exposure to AAs via PFS and herbal products are at present indeed negligible. Data reported in literature on AA levels in PFS and other herbal products and also obtained from a new series of PFS in the present study were used to calculate the estimated daily intakes (EDIs) and corresponding margins of exposure (MOEs). Available literature data revealed that 206 out of 573 samples were found to contain aristolochic acid I (AAI) and/or aristolochic acid II (AAII). The results obtained from recently collected PFS revealed that both AAI and AAII were detected in three out of 18 analysed PFS at levels up to 594.8 and 235.3 µg g^-1, respectively, being in line with the levels reported in literature. The EDIs resulting from intake of these PFS resulted in MOEs that were generally below 10,000, corroborating the priority for risk management. Although these results refer to PFS collected by targeted sampling strategies, the data reveal that AA-containing PFS are still freely available. When considering that the use of these samples may be limited to shorter periods of time, the EDIs might be lower, but MOE values would still be lower than 10,000 for more than 50% of the AA-containing PFS and herbal products. In conclusion, the presence of AAs in PFS and herbal products even several years after instalment of the legal restrictions still raises concern, especially for people who frequently use the respective PFS and herbal products.

Risk assessment of upper tract urothelial carcinoma related to aristolochic acid

BACKGROUND

Aristolochic acid is a toxin found in plants of the genus Aristolochia, to which humans can be exposed either through certain Chinese herbal medicines or through inadvertent commingling with food crops. Our objective was to estimate cumulative exposures of aristolochic acid associated with increased risk of end-stage renal disease (ESRD), and to conduct a systematic review and meta-analysis on aristolochic acid-induced upper tract urothelial carcinoma (UUC).

METHODS

Using epidemiologic studies on aristolochic acid-related disease from multiple different regions of the world, a systematic review was conducted in which relative risks (RR), HRs, and ORs were derived or extracted directly, and a meta-analysis was conducted. One study was used to estimate a benchmark dose lower confidence limit (BMDL) for aristolochic acid-related ESRD.

RESULTS

Mean values for risk ratios, ORs, RRs, or HRs, of UUC caused by aristolochic acid ranged from 1 to 49. A meta-analysis of these studies resulted in a pooled OR of 5.97 [95% confidence interval (CI), 2.78-12.84] for this aristolochic acid-related cancer. The obtained BMDL for aristolochic acid-related ESRD was 0.42 g cumulative aristolochic acid exposure.

CONCLUSIONS

Aristolochic acid exposure is significantly associated with an increased risk of UUC, and there is a dose-dependent relationship between cumulative aristolochic acid exposure and ESRD risk.

IMPACT

Individuals who use certain Chinese herbal medicines may significantly increase their risk of developing UUC and/or ESRD, as would individuals who are inadvertently exposed to aristolochic acid through commingling of Aristolochia plants with harvested food crops.

Isolation, Characterization and Quantity Determination of Aristolochic Acids, Toxic Compounds in Aristolochia bracteolata L

BACKGROUND

Aristolochic Acids (AAs) are major components of plants in Aristolochia and have been found to be nephrotoxic, carcinogenic and mutagenic. Herein reported are the isolation, identification and quantity determination methods of Aristolochic Acid-I (AA-I) and Aristolochic Acid-II (AA-II) toxic compounds of Aristolochia bracteolata indigenous to Central Sudan and medicinally used in diverse biological functions including analgesic and diuretic effects, treatment of tumors, malaria and/or fevers.

METHODS AND RESULTS

AAs mixture was extracted with methanol from the defatted material of Aristolochia bracteolata whole plant at room temperature and was isolated from the aqueous methanol extract by chloroform. Moreover, Silica-gel column chromatography and Preparative Thin Layer Chromatography (PTLC) using chloroform/methanol gradient mixtures were used to isolate AAs mixtures as a yellow crystalline solid. A preliminary detection of AAs was made by Thin Layer Chromatography (silica-gel, chloroform: methanol (6:1)). The Rf value of the acids mixture was 0.43-0.46. The presence of AAs in plant sample was confirmed by High Performance Liquid Chromatography/Ultraviolet (HPLC/UV) analysis using 1% acetic acid and methanol (40:60) as mobile phase and maximum absorption wave length of 250 nm. Quantitative determination of AA-II (49.03 g/kg) and AA-I (12.98 g/kg) was also achieved by HPLC/UV.

RECOMMENDATION

It is recommended that the use of Aristolochia bracteolata as a medicinal plant should be extremely limited or strictly prohibited. The chromatograms obtained in this study can serve as fingerprints to identify AAs in plant samples.

Recent analytical approaches in quality control of traditional Chinese medicines--a review

Traditional Chinese medicines (TCMs) are gaining more and more attention all over the world, due to their specific theory and long historical clinical practice. But the uncontrollable quality is a bottleneck for its modernization and globalization. This paper reviewed the recent analytical methods in the quality control of TCMs, including screening strategies of bioactive markers from TCMs through biochromatographic methods, the traditional chromatographic methods, DNA methods, as well as the spectroscopic methods, including FT-IR, NIR and NMR. The comprehensive methods, such as fingerprint and multi-component quantification are emphasized; hyphenated techniques, like HPLC-MS, GC-MS, CE-MS, LC-NMR, chemometric methods, and combination of chemical and biological methods, such as biofingerprint, metabolic fingerprint are now more and more widely used in TCMs. In a few word, the analysis and quality control of TCMs are moving towards an integrative and comprehensive direction, in order to better address the inherent holistic nature of TCMs.

Application of metabonomic analytical techniques in the modernization and toxicology research of traditional Chinese medicine

In the recent years, a wide range of metabonomic analytical techniques are widely used in the modern research of traditional Chinese medicine (TCM). At the same time, the international community has attached increasing importance to TCM toxicity problems. Thus, many studies have been implemented to investigate the toxicity mechanisms of TCM. Among these studies, many metabonomic-based methods have been implemented to facilitate TCM toxicity investigation. At present, the most prevailing methods for TCM toxicity research are mainly single analysis techniques using only one analytical means. These techniques include nuclear magnetic resonance (NMR), gas chromatography-mass spectrometry (GC-MS), and liquid chromatography-mass spectrometry (LC-MS), etc.; with these techniques, some favourable outcomes have been gained in the toxic reaction studies of TCM, such as the action target organs assay, the establishment of action pattern, the elucidation of action mechanism and the exploration of action material foundation. However, every analytical technique has its advantages and drawbacks, no existing analytical technique can be versatile. Multi-analysed techniques can partially overcome the shortcomings of single-analysed techniques. Combination of GC-MS and LC-MS metabolic profiling approaches has unravelled the pathological outcomes of aristolochic acid-induced nephrotoxicity, which can not be achieved by single-analysed techniques. It is believed that with the further development of metabonomic analytical techniques, especially multi-analysed techniques, metabonomics will greatly promote TCM toxicity research and be beneficial to the modernization of TCM in terms of extending the application of modern means in the TCM safety assessment, assisting the formulation of TCM safety norms and establishing the international standards indicators.

Simultaneous analysis of glycyrrhizin, paeoniflorin, quercetin, ferulic acid, liquiritin, formononetin, benzoic acid and isoliquiritigenin in the Chinese proprietary medicine Xiao Yao Wan by HPLC

A high performance liquid chromatography coupled with photodiode-array detection method was developed for simultaneous determination of glycyrrhizin, paeoniflorin, benzoic acid, quercetin, ferulic acid, formononetin, liquiritin and isoliquiritigenin in the Chinese proprietary medicine "Xiao Yao Wan" (XYW). The analysis was performed by reverse phase gradient elution, using an aqueous mobile phase (containing 0.1% phosphoric acid) modified by acetonitrile and detection made simultaneously at four wavelengths. The method was validated for accuracy, precision and limits of detection and quantification. Ten batches of XYW obtained from different pharmaceutical companies were analyzed and found to contain different amounts of the eight bioactive markers. This method could be used for quality assessment of this herbal medicine.

Online concentration of aristolochic acid I and II in Chinese medicine preparations by micellar electrokinetic chromatography

In this study, an online concentration method in micellar electrokinetic chromatography (MEKC) applying field-enhanced sample injection (FESI) mode was developed for the detection of aristolochic acids (AAs) in Chinese medicine preparations. AA-I and AA-II were baseline separated with high separation efficiency, and 100-fold enhancement of the detection sensitivity was achieved compared with those obtained from normal capillary zone electrophoresis (CZE) or simple MEKC method. The proposed method was successfully applied for the determination of AAs in Chinese medicine preparations.

A sensitivity enhanced high-performance liquid chromatography fluorescence method for the detection of nephrotoxic and carcinogenic aristolochic acid in herbal medicines

A new, sensitive and selective HPLC method with fluorescence detector (HPLC-FLD) for the determination of nephrotoxic and carcinogenic aristolochic acid (AA) in herbal medicines by using pre-column derivatization with zinc powder in acetic acid is presented. Variables governing the derivatization reaction, such as the amount of zinc powder and acetic acid, as well as the derivatization time were studied and optimized. An extended linear dynamic range over three orders of magnitude was observed for AA-I and AA-II (R(2)>0.9998). Method accuracy at low, medium and high spiked AA levels determined by the percentage mean deviation was below 4.4% and 7.2% for AA-I and AA-II, respectively. The detection limits of 0.39 ng/mL (AA-I) and 0.52 ng/mL (AA-II) were 2 orders of magnitude lower than those obtained from HPLC-MS or CE-ECD analyses, 3-4 orders of magnitude lower than those from HPLC-UV or CE-UV methods. The developed method has been applied for the determination of AA in herbal medicines. Among the tested samples, Guanmutong had the highest AA concentration (2607.0 microg/g AA-I, 711.2 microg/g AA-II). Comparison studies between HPLC-FLD and HPLC-MS/MS demonstrated that the two methods gave similar quantitative results for the selected herb samples.

Assessment of Chinese medicinal herb metabolite profiles by UPLC-MS-based methodology for the detection of aristolochic acids

In this study, aristolochic acid in different herbal medicines containing a mixture of varying herb species was identified through fingerprint pattern similarities. Aristolochic acid I and II are nephrotoxic compounds naturally present in the Aristolochia plant species that are commonly used in Chinese herbal medicines. Twenty-four commercially available herbal formulations were extracted into an aqueous solution and injected into a UPLC-MS system. All the samples were analysed by multiple reaction monitoring (MRM) to check for the presence of aristolochic acids I and II. The same samples were then fingerprinted using two different gradient methods and the chromatograms deconvoluted into retention time (RT) and masses for the chemicals present taking concentration into account. Statistical analysis of this data revealed that samples were highly heterogeneous, and that the main differences between the preparations were concentrations of polar compounds. A model was constructed where the samples could be separated into two groups differentiated by the presence of the two forms of aristolochic acid.

Electrochemical behavior and square wave voltammetric determination of aristolochic acid-I

Electroanalytical procedure for the determination of nephrotoxic aristolochic acid-I in the medicinal plant has been developed in the presence of potential interferences of lead and cadmium by square wave voltametry (SWV). Among the phosphate buffers of pH values at 5.0, 6.1, 6.5 and 7.0, the phosphate buffers of pH 6.1 yielded the most accurate analysis of AA-I in the presence of Pb2+ and Cd2+; Pb2+ was precipitated as Pb(HPO4) and did not appear in the SW voltammogram, while Cd2+ appeared at -0.564 V which was well resolved from AA-I at -0.416 V. When the Ip of AA-I was plotted vs. concentrations between 1.67 x 10(-8) M and 1.67 x 10(-6) M in the presence of Pb2+ and Cd2+, a linear calibration curve was obtained with a slope of 6 x 10(8) nA/M and a correlation coefficient of 0.9999. The present method was applied to determine AA in the dried natural products of Aristolochia contorta Bunge; Total AA in the dried root and the ripe fructus of Aristolochia contorta Bunge were found as 25 +/- 1 microg/g and 85 +/- 3 microg/g, respectively.

Characterization and determination of six aristolochic acids and three aristololactams in medicinal plants and their preparations by high-performance liquid chromatography-photodiode array detection/electrospray ionization mass spectrometry

Aristolochic acid derivatives (AAs) and aristolactam derivatives (ALs) have been characterized by electrospray ionization mass spectrometry, and their fragmentation pathways are proposed. ALs exhibit a single ionization product [M+H]+, whereas AAs show multiple ionization products. By optimizing the chromatographic separation and mass spectrometric parameters, the precursor ions of the derivatives with the best responses were found, and the sensitivities in the determination of the nine derivatives were improved. Based on the investigation of ionization behaviour, a HPLC-DAD/ESI-MS (high-performance liquid chromatography-photodiode array detection/electrospray ionization mass spectrometry) method has been developed for simultaneous analysis of nine derivatives, i.e., AA I, AA II, AA C, AA D, 7-OH AA I, aristolic acid I, AL AII, AL IIIa and AL IVa, in nine medicinal herbs and two preparations. The method appears to be suitable for safety assurance and quality control of commercially available samples with good selectivity and suitable sensitivity.

Optimization of CZE for analysis of phytochemical bioactive compounds

Advantages of CZE such as high efficiency, low cost, short analysis time, and easy implementation result in its wide applications for analysis of phytochemical bioactive compounds (e.g. flavonoids, alkaloids, terpenoids, phenolic acid, saponins, anthraquinones and coumarins). However, several aspects, including sample preparation, separation, and detection have significant effects on CZE analysis. Therefore, optimization of these procedures is necessary for development of the method. In this review, sample preparation such as extraction method and preconcentration, separation factors including buffer type, concentration and pH, additives, voltage and temperature, as well as detection, e.g. direct and indirect UV detection, LIF and MS were discussed for optimization of CZE analysis on phytochemical bioactive compounds. The optimized strategies were also reviewed.