Study of the Contents of Analogues of Aristolochic Acid in Houttuynia cordata by Ultra-High Performance Liquid Chromatography Tandem Mass Spectrometry

Microbial contribution to 14 biogenic amines accumulation in refrigerated raw and deep-fried hairtails (Trichiurus lepturus)

Biogenic amines (BAs) produced by microbial decarboxylation of amino acids are crucial toxic nitrogenous compounds in fish. An optimized ultra-high performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method with simple pretreatment was established to detect 14 BAs in both raw (control check, CK) and deep-fried (DF) hairtails. This method exhibited a good linear relationship with average recoveries of 73.3-120.0 % and relative standard deviations of 2.5-10.0 %, respectively. The total BAs in CK and DF hairtails decreased sharply to 338.2 and 25.3 mg/kg on the 9th day, respectively. Four BAs, including cadaverine (CAD), histamine (HIS), tyramine (TYR), and putrescine (PUT) accounted for 92.5-99.9 % of total BAs were selected as the dominant BAs. Bacterial analysis showed that the abundance of DF was relatively low. Further correlation analysis proved that Vibrio had a significant (p < 0.05) positive correlation with total BAs and could be the main BA-producing bacterium in DF hairtail. This work provides new evidence of the accumulation of BAs in refrigerated hairtail.

Development and Application of a Comprehensive Nontargeted Screening Strategy for Aristolochic Acid Analogues

Aristolochic acid analogs (AAAs) are naturally occurring carcinogenic and toxic compounds that pose a safety threat to pharmaceuticals and the environment. It is challenging to screen AAAs due to their lack of characteristic mass spectral fragmentation and their presence of structural diversity. A comprehensive nontargeted screening strategy was proposed by taking into account diverse factors and incorporating various self-developed techniques, and a Python3-based toolkit called AAAs_finder was developed for its implementation. The main procedures consist of virtual structure and ultraviolet and visible (UV) spectra database creation, exact mass and UV spectra-based suspect data extraction, tandem mass spectra (MS/MS) anthropomorphic interpretation, and multicondition retention time (RT) prediction-based candidate structures ranking. To initially assess screening feasibility, eight hypothetical unknown samples were subjected to nontargeted screening using the AAAs_finder toolkit and two other advanced tools. The results showed that the former successfully identified all, while the latter two only managed to identify two and three, respectively, indicating that our strategy was more feasible. After that, the strategy was carefully evaluated for false positives and false negatives, instrument dependence, reproducibility, and sensitivity. After the evaluation, the strategy was successfully applied to the screening of AAAs in real samples, such as herbal medicine, spiked soil, and water. Overall, this study proposed a nontargeted screening strategy and toolkit independent of characteristic mass spectral fragmentation and able to overcome challenges posed by structural diversity for the AAAs screening, which is also valuable for other classes of compounds.

Detection and Removal of Aristolochic Acid in Natural Plants, Pharmaceuticals, and Environmental and Biological Samples: A Review

Aristolochic acids (AAs) are a toxic substance present in certain natural plants. Direct human exposure to these plants containing AAs leads to a severe and irreversible condition known as aristolochic acid nephropathy (AAN). Additionally, AAs accumulation in the food chain through environmental mediators can trigger Balkan endemic nephropathy (BEN), an environmental variant of AAN. This paper presents a concise overview of the oncogenic pathways associated with AAs and explores the various routes of environmental exposure to AAs. The detection and removal of AAs in natural plants, drugs, and environmental and biological samples were classified and summarized, and the advantages and disadvantages of the various methods were analyzed. It is hoped that this review can provide effective insights into the detection and removal of AAs in the future.

In vitro nephrotoxicity and quantitative UPLC-MS analysis of three aristololactams in Houttuynia cordata

Three analogues of aristololactam Ⅰ (AL Ⅰ), AL AⅡ, AL FⅠ and AL BⅡ, had been isolated from Houttuynia cordata, a commonly used medicinal and edible plant with heat-removing and toxin-removing functions. Considering the significant nephrotoxicity of AL Ⅰ, this study evaluated the toxicity of these three aristololactams (ALs) on human proximal tubular epithelial cells (HK-2) by MTT assay, ROS assay, ELISA tests and cytologic morphology observation. Furthermore, the distribution of the three ALs in H. cordata were investigated by UPLC-MSⁿ recognition and quantitation in SIM mode, so as to estimate primarily the safety of the plant. The results showed that all the three ALs in H. cordata had comparative cytotoxicity as AL I with the IC₅₀ values from 3.88 μM to 20.63 μM, caused high levels of cellular levels of reactive oxygen species (ROS) in HK-2 cells, exhibited the potential to cause renal fibrosis by remarkably increasing the levels of transforming growth factor-β (TGF-β1) and fibronectin (FN), and induced fibrous changes in morphology of HK-2 cells. The contents of the three ALs varied significantly in 30 batches of H. cordata from different regions and parts. Overall, the aerial part contained much more ALs (3.20 - 108.19 μg/g) than the underground part (0.95 - 11.66 μg/g), and flowers had the highest contents. Besides, no ALs were detected in the water extract of any part of H. cordata. This work revealed that the aristololactams in H. cordata had similar in vitro nephrotoxicity as AL Ⅰ and were mainly distributed in the aerial part of the plant.

Determination of Isoflavones in Radix puerariae from Different Origins by Ultra-High Performance Liquid Chromatography Based on Optimal Pretreatment Method

A new method for simultaneous determination of puerarin, daidzin, daidzein and genistein in Radix puerariae by ultra-high performance liquid chromatography was established. The target analytes were extracted from Radix puerariae by 70% ethylene glycol with the assistance of ultrasonication, purified by the absorption of N-propyl ethylenediamine (PSA), and separated on a Supersil ODS column (4.6 mm × 250 mm × 2.5 μm). Gradient elution in 12 min was performed with the mobile phase 0.1% formic acid(A)-acetonitrile(B). The column temperature was 25 °C and the flow rate was 1 mL/min. The detection wavelength of the four target analytes was 250 nm. The limits of detection (LODs) of puerarin, daidzin, daidzein and genistein were 0.086 mg/L, 0.020 mg/L, 0.027 mg/L and 0.037 mg/L, respectively, and limits of quantitation (LOQs) were 0.29 mg/L, 0.065 mg/L, 0.090 mg/L and 0.12 mg/L, respectively. The recovery of the four substances ranged from 90.5% to 109.6%, and the relative standard deviation (n = 6) was less than 7.7%. With the established methods, puerarin, daidzin, daidzein and genistein in Radix puerariae from 11 origins were determined. The contents of the four compounds varied with the origin and variety. It provides basic data and technical means for quality control and regulation of Radix puerariae.

Progress and prediction of multicomponent quantification in complex systems with practical LC-UV methods

Complex systems exist widely, including medicines from natural products, functional foods, and biological samples. The biological activity of complex systems is often the result of the synergistic effect of multiple components. In the quality evaluation of complex samples, multicomponent quantitative analysis (MCQA) is usually needed. To overcome the difficulty in obtaining standard products, scholars have proposed achieving MCQA through the "single standard to determine multiple components (SSDMC)" approach. This method has been used in the determination of multicomponent content in natural source drugs and the analysis of impurities in chemical drugs and has been included in the Chinese Pharmacopoeia. Depending on a convenient (ultra) high-performance liquid chromatography method, how can the repeatability and robustness of the MCQA method be improved? How can the chromatography conditions be optimized to improve the number of quantitative components? How can computer software technology be introduced to improve the efficiency of multicomponent analysis (MCA)? These are the key problems that remain to be solved in practical MCQA. First, this review article summarizes the calculation methods of relative correction factors in the SSDMC approach in the past five years, as well as the method robustness and accuracy evaluation. Second, it also summarizes methods to improve peak capacity and quantitative accuracy in MCA, including column selection and two-dimensional chromatographic analysis technology. Finally, computer software technologies for predicting chromatographic conditions and analytical parameters are introduced, which provides an idea for intelligent method development in MCA. This paper aims to provide methodological ideas for the improvement of complex system analysis, especially MCQA.