A novel pre-column fluorescent derivatization method for the sensitive determination of aristolochic acids in medicinal herbs by high-performance liquid chromatography with fluorescence detection

Rapid and Simultaneous Quantification of Six Aristolochic Acids and Two Lignans in Asari Radix et Rhizoma Using Ultra-Performance Liquid Chromatography-Triple Quadrupole Tandem Mass Spectrometry

Asari Radix et Rhizoma (AR) is a widely-used Chinese herbal medicine containing multiple active lignans and rare nephrotoxic components-aristolochic acids derivatives (AAs). However, the current quality control method carried out by Chinese Pharmacopoeia has defects in trace AAs detection and insufficient marker ingredients, which is unable to comprehensively evaluate the efficacy and safety of AR. To improve the quality control method of AR, a rapid, sensitive, and reliable chromatographic analytic method based on ultra-high-performance liquid chromatography-triple quadrupole tandem mass spectrometry (UHPLC-QqQ-MS) was established for the simultaneous analysis of multiple AAs and lignans in AR samples. Positive electrospray ionization mode with multiple reaction monitoring (MRM) was applied for the detection of the eight analytes. The method showed available linearity (R ² ≥ 0.991), the limit of quantification (2-5 ng/mL), precision (RSD <8.12%), and accuracy (89.78-112.16%). A total of 6 AAs and 2 lignans were quantified for their content in 15 AR samples. The content of AA-IVa, AA-VIIa, and aristololactam I (AL-I) was much higher than the AA-I controlled by pharmacopoeia. Considering the potential toxicity of AAs, AA-IVa, AA-VIIa, and AL-I should also be controlled in AR. A considerable amount of active sesamin was detected in AR, suggesting that it could be added as a quality marker for the quality control of AR. The newly developed analytical method could be applied for the fast evaluation of toxic AA's content and quality during quality control of AR or preparations containing AR.

Preparation of Anti-Aristolochic Acid I Monoclonal Antibody and Development of Chemiluminescent Immunoassay and Carbon Dot-Based Fluoroimmunoassay for Sensitive Detection of Aristolochic Acid I

Aristolochic acid (AA) toxicity has been shown in humans regarding carcinogenesis, nephrotoxicity, and mutagenicity. Monitoring the AA content in drug homologous and healthy foods is necessary for the health of humans. In this study, a monoclonal antibody (mAb) with high sensitivity for aristolochic acid I (AA-I) was prepared. Based on the obtained mAb, a chemiluminescent immunoassay (CLEIA) against AA-I was developed, which showed the 50% decrease in the RLU_max (IC₅₀) value of 1.8 ng/mL and the limit of detection (LOD) of 0.4 ng/mL. Carbon dots with red emission at 620 nm, namely rCDs, were synthesized and employed in conventional indirect competitive enzyme-linked immunosorbent assay (icELISA) to improve the assay sensitivity of a fluoroimmunoassay (FIA). Oxidized 3,3'',5,5''-tetramethylbenzidine dihydrochloride (oxTMB) can quench the emission of the rCDs through the inner-filter effect; therefore, the fluorescence intensity of rCDs can be regulated by the concentration of mAb. As a result, the assay sensitivity of FIA was improved by five-fold compared to CLEIA. A good relationship between the results of the proposed assays and the standard ultra-high performance liquid chromatography-triple quadrupole mass spectrometer (UPLC-QQQ-MS/MS) of real samples indicated good accuracy and practicability of CLEIA and FIA.

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.

Liquid chromatography-tandem mass spectrometry analysis of aristolochic acids in soil samples collected from Serbia: Link to Balkan endemic nephropathy

RATIONALE

Over the past six decades, residents of farming villages in multiple countries of the Balkan peninsula have been suffering from a unique type of chronic renal disease, Balkan endemic nephropathy (BEN). It was speculated that environmental pollution by aristolochic acids (AAs) produced naturally by Aristolochia clematitis L., a weed that grows in the area, was causing the disease. However, the human exposure pathway to this class of phytotoxin remains obscure. Knowledge of the sink and stability of AAs in the environment would assist in the formulation of policy reducing exposure risk.

METHODS

Using our newly developed liquid chromatography/tandem mass spectrometry method of high sensitivity and selectivity, we analysed over 130 soil samples collected from cultivation fields in southern Serbia for the presence of AAs. The environmental stability of AAs was also investigated by incubating soil samples spiked with AAs at various temperatures.

RESULTS

The analysis detected AA-I in over two-fifths of the tested samples at sub-μg/kg to μg/kg levels, with higher concentrations observed in more acidic farmland soil. Furthermore, analysis of soil samples incubated at various temperatures revealed half-lives of over 2 months, indicating that AAs are relatively resistant to degradation.

CONCLUSIONS

Cultivation soil in southern Serbia is being extensively contaminated with AAs released from the decomposition of A. clematitis weeds. Since AAs are resistant to degradation, it is possible that AAs could have been taken up by root absorption and transported to the edible part of food crops. Prolonged exposure to AA-contaminated food grown from polluted soil could be one of the main aetiological mechanisms of BEN observed in the area.

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.

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.

Development of an Eastern blotting technique for the visual detection of aristolochic acids in Aristolochia and Asarum species by using a monoclonal antibody against aristolochic acids I and II

INTRODUCTION

Aristolochic acids (AAs) are naturally occurring nephrotoxicants and human carcinogens. Aristolochic acid I (AA-I) and aristolochic acid II (AA-II) are two important AAs with clear toxicity.

OBJECTIVE

To obtain a monoclonal antibody (MAb) recognising AA-I and AA-II and develop an Eastern blotting technique for the specific visualisation and easy determination of AA-I and AA-II in plant extracts or tissues of Aristolochia and Asarum species.

METHODS

A hybridoma secreting MAb against AAs was prepared by cell fusion with splenocytes derived from a mouse immunised with AA-I-keyhole limpet haemocyanin (KLH) conjugate and the myeloma cell line SP2/0-Ag14. AA-I and AA-II were separated by thin-layer chromatography (TLC) and then blotted onto a positively charged polyethersulphone (PES) membrane using a modified carbodiimide method. The resulting membrane-bound AA-protein conjugates were linked to the newly prepared MAb and then to the secondary antibody labelled with peroxidase. 4-Chloro-1-naphthol was then added as the peroxidase substrate for staining.

RESULTS

MAb 2A10-10B showed a high specificity for AA-I (100%) and AA-II (69.3%) and low cross reactivity (≤ 2.2%) toward analogues that may disrupt detection of AA-I and AA-II in plants. An established Eastern blotting method was applied to the immunohistolocalisation of AA-I and AA-II in dry plant tissues, and this analysis showed that the phelloderm, cortex and phloem of Aristolochia manshuriensis stem may contain higher amounts of total AA-I and AA-II as compared with the pith and xylem.

CONCLUSION

This method was extremely useful for the visual screening of AA-I and AA-II among easily mistaken herbal medicines.

A fluorescence-based analysis of aristolochic acid-derived DNA adducts

Aristolochic acids (AAs), major components of plant extracts from Aristolochia species, form (after metabolic activation) pro-mutagenic DNA adducts in renal tissue. The DNA adducts can be used as biomarkers for studies of AA toxicity. Identification of these adducts is a complicated and time-consuming procedure. We present here a fast, nonisotopic, fluorescence-based assay for the detection of AA-DNA adducts in multiple samples. This approach allows analysis of AA adducts in synthetic DNA with known nucleotide composition and analysis of DNA adducts formed from chemically diverse AAs in vitro. The method can be applied to compare AA-DNA adduct formation in cells and tissues.