LC–MS/MS determination and comparative pharmacokinetics of strychnine, brucine and their metabolites in rat plasma after intragastric administration of each monomer and the total alkaloids from Semen Strychni

Peroxodicarbonate - a renaissance of an electrochemically generated green oxidizer

The direct anodic conversion of alkali carbonates in aqueous media provides access to peroxodicarbonate, which is a safe to use and green oxidizer. Although first reports date back around 150 years, its low concentrations and limited thermal stability have consigned this reagent to oblivion. Boron-doped diamond anodes, novel electrolyser concepts for heat dissipation, and the mixed cation trick allow record breaking peroxodicarbonate concentrations >900 mM. The electrochemical generation of peroxodicarbonate was already demonstrated on a pilot scale. The inherent safety is ensured by the limited stability of the peroxodicarbonate solution, which decomposes under ambient conditions to oxygen and facilitates subsequent downstream processing. This peroxide has, in particular at higher concentrations, an unusual reactivity and seems to be an ideal reagent when peroxo-equivalents in combination with alkaline base are required. The conversions with peroxodicarbonate include the Dakin reaction, epoxidation, oxidation of amines (aliphatic and aromatic) and sulfur compounds, deborolative hydroxylation reactions, and many more. Since the base equivalents also represent the makeup chemical for pulping plants, peroxodicarbonate is an ideal reagent for the selective degradation of lignin to vanillin. Moreover, peroxodicarbonate can be used as a halogen-free bleaching agent. The emerging electrogeneration and use of this green platform oxidizer are surveyed for the first time.

Synthesis of Aromatic N-Oxides Using Electrochemically Generated Peroxodicarbonate

Electrochemically generated green platform oxidizers like peroxodicarbonate (PODIC) constitute a game-changing technology in terms of sustainable chemistry while serving as an alternative counterreaction in the electrochemical hydrogen evolution. Peroxodicarbonate avoids the storage and shipping of concentrated hydrogen peroxide solution. We herein disclose an efficient method for the N-oxidation of quinolines, pyridines, and complex tertiary amines. The use of phenoyloxy succinimide (POSI) is the decisive factor for obtaining N-oxides (28 examples) in isolated yields of up to 98%.

Ultra-sensitive fluorescent detection of strychnine based on carbon dot self-assembled gold nanocage sensing probe

The ultra-sensitive detection of strychnine is crucial to provide powerful evidence in strychnine poisoning cases. In this study, a novel fluorescent carbon dots (CDs) self-assembled gold nanocage (AuNCs) composite is synthesized for the ultra-sensitive detection of strychnine using molecularly imprinted polymer sensing technology (MIPs-CDs@AuNCs). With strong loading and delivery capability of AuNCs, the CDs could be loaded into AuNCs, where the anisotropy of CDs could significantly decrease and the fluorescence of the MIPs-CDs@AuNCs probe gained lower relative standard deviation (RSD). Moreover, the fluorescence response of MIPs-CDs@AuNCs to target strychnine was observed to be more significant than MIPs-CDs without gold nanocages. Under optimal conditions, the developed MIPs-CDs@AuNCs fluorescence strategy showed good linear relationship at the concentration of strychnine from 3 ng mL-1 to 200 ng mL-1 with the limit of detection as low as 1 ng mL-1. Besides, real blood samples were analyzed without complex pre-preparation procedure to investigate the performance of the proposed molecularly imprinted fluorescence probe, and satisfactory results were obtained with absolute deviations between -1.16 ng mL-1 and 1.28 ng mL-1, which exhibited a great potential for the detection of strychnine in health care work.

A Combination of In Silico ADMET Prediction, In Vivo Toxicity Evaluation, and Potential Mechanism Exploration of Brucine and Brucine N-oxide-A Comparative Study

Brucine (BRU) and brucine N-oxide (BNO) are prominent, bioactive, and toxic alkaloids in crude and processed Semen Strychni. Studies have demonstrated that BRU and BNO possess comprehensive pharmacological activities, such as anti-inflammatory and analgesic. In this context, a comparative study of BRU and BNO was performed by combination analysis of in silico ADMET prediction, in vivo toxicity evaluation, and potential action mechanism exploration. ADMET prediction showed that BRU and BNO might induce liver injury, and BRU may have a stronger hepatoxic effect. The prediction was experimentally verified using the zebrafish model. The BRU-induced hepatotoxicity of zebrafish larvae had a dose-response relationship. The mechanism of BRU-induced hepatotoxicity might relate to phosphorylation, kinase activity, and signal transduction. By comparison, signal transduction and gap junctions might involve BNO-induced hepatotoxicity. Our results provided a better understanding of BRU- and BNO-induced hepatotoxicity. We also built a foundation to elucidate the material base of the hepatotoxicity of traditional Chinese medicine Semen Strychni.

The safety of Chinese medicine: A systematic review of endogenous substances and exogenous residues

BACKGROUND

Safety and toxicity have become major challenges in the internationalization of Chinese medicine. Inspite of its wide application, security problems of Chinese medicine still occur from time to time, raising widespread concerns about its safety. Most of the studies either only partially discussed the intrinsic toxicities or extrinsic harmful residues in Chinese medicine, or briefly described detoxification and attenuation methods. It is necessary to systematically discuss Chinese medicine's extrinsic and intrinsic toxic components and corresponding toxicity detoxification or detection methods as a whole.

PURPOSE

This review comprehensively summarizes various toxic components in Chinese medicine from intrinsic and extrinsic. Then the corresponding methods for detoxification or detection of toxicity are highlighted. It is expected to provide a reference for safeguards for developing and using Chinese medicine.

METHODS

A literature search was conducted in the databases, including PubMed, Web of Science,Wan-fang database, and the China National Knowledge Infrastructure (CNKI). Keywords used were safety, toxicity, intrinsic toxicities, extrinsic harmful residues, alkaloids, terpene and macrolides, saponins, toxic proteins, toxic crystals, minerals, heavy metals, pesticides, mycotoxins, sulfur dioxide, detoxification, detection, processing (Paozhi), compatibility (Peiwu), Chinese medicine, etc., and combinations of these keywords. All selected articles were from 2006 to 2022, and each was assessed critically for our exclusion criteria. Studies describe the classification of toxic components of Chinese medicine, the toxic effects and mechanisms of Chinese medicine, and the corresponding methods for detoxification or detection of toxicity.

RESULTS

The toxic components of Chinese medicines can be classified as intrinsic toxicities and extrinsic harmful residues. Firstly, we summarized the intrinsic toxicities of Chinese medicine, the adverse effects and toxicity mechanisms caused by these components. Next, we focused on the detoxification or attenuation methods for intrinsic toxicities of Chinese medicine. The other main part discussed the latest progress in analytical strategies for exogenous hazardous substances, including heavy metals, pesticides, and mycotoxins. Beyond reviewing mainstream instrumental methods, we also introduced the emerging biochip, biosensor and immuno-based techniques.

CONCLUSION

In this review, we provide an overall assessment of the recent progress in endogenous toxins and exogenous hazardous substances concerning Chinese medicine, which is expected to render deeper insights into the safety of Chinese medicine.

Study on the Potential Mechanism of Semen Strychni against Myasthenia Gravis Based on Network Pharmacology and Molecular Docking with Experimental Verification

Background

Semen Strychni (SS) is an effective Chinese medicine formula for treating myasthenia gravis (MG) in clinics. Nonetheless, its molecular mechanism is largely unknown.

Objective

Using network pharmacology, molecular docking, and experimental validation, we aim to identify the therapeutic effect of SS on MG and its underlying mechanism.

Methods

The main ingredients of SS and their targets and potential disease targets for MG were extracted from public databases. The protein-protein interaction (PPI) network was constructed using the STRING 11.0 database, and Cytoscape was used to identify the hub targets. In addition, Gene Ontology (GO) and the Kyoto Encyclopedia of Genes and Genomes (KEGG) were used to identify molecular biological processes and signaling pathways. Then, AutoDock Via conducted molecular docking. The experimental autoimmune myasthenia gravis (EAMG) model in female Lewis rats, quantitative real-time polymerase chain reaction (qRT-PCR), Western blot, and enzyme-linked immunosorbent assay (ELISA) were performed to confirm the effect and mechanism of SS on MG.

Results

The following active compounds and hub targets were identified by screening and analyzing: isobrucine, vomicine, (S)-stylopine, strychnine, brucine-N-oxide, brucine and AKT1, MAPK1, MAPK14, CHRM1, ACHE, and CHRNA4. KEGG enrichment analyses indicated that the cholinergic synapse and neuroactive ligand-receptor interaction signaling pathway may be necessary. The results of molecular docking revealed that the main active ingredients bind well to the hub targets. In vivo experiments proved that SS could improve the weight loss and Lennon scores in the EAMG model. Experiments in molecular biology showed that SS could treat MG by affecting the cholinergic synapse through the respective antibody, receptor, and key enzymes in the cholinergic pathway.

Conclusion

This study provided a preliminary overview of the active constituents, primary targets, and potential pathways of SS against MG. SS ameliorated EAMG by regulating the cholinergic synaptic junction.

CYP3A1 metabolism-based neurotoxicity of strychnine in rat

Strychnine is one of the main bioactive and toxic constituents of Semen Strychni. In the present study, the neurotoxic effects of strychnine, and the role of individual differences in metabolism on susceptibility to neurotoxicity of strychnine were investigated. The acute toxicity was observed by a single dose of strychnine (2.92 mg/kg, i.g.) in rats, the epileptic stages of rats were scored according to Racine's scale. The neurotoxicity of strychnine was evaluated by the levels of ROS, MDA, SOD and GSH in hippocampus, striatum, and cortex tissues measurements and histopathological analysis. The concentrations of strychnine in the plasma, hippocampus, striatum, and cortex tissues were determined using high performance liquid chromatography tandem mass spectrometry (LC-MS/MS). The expressions of the cytochrome P450, which is the most critical protein family involved in drugs metabolism, were detected by proteomics. The mechanism of susceptibility to neurotoxicity of strychnine was elucidated by correlation analysis among above indicators. The results indicated that striatum and cortex were the main toxic targets of strychnine, and the CYP3A1 might be a susceptible biomarker to neurotoxicity of strychnine. These results provide valuable insights into the neurotoxic susceptibility of strychnine that will aid in the rational clinical use of strychnine (possibly including Semen Strychni).

SZAP exerts analgesic effects on rheumatalgia in CIA rats by suppressing pain hyperalgesia and inhibiting TRPV1 and P2X3

ETHNOPHARMACOLOGICAL RELEVANCE

ShexiangZhuifeng Analgesic Plaster (SZAP) is a traditional Chinese medicine and transdermal formulation composed of many Chinese herbs and active compounds. SZAP was recently approved by the China Food and Drug Administration for the treatment of pain associated with osteoarticular diseases and is preferred by most rheumatoid arthritis patients in China. However, its mechanism has not been elucidated in detail.

AIM OF THE STUDY

We sought to determine the analgesic effect of SZAP in collagen-induced arthritis (CIA) rats and explore the underlying mechanisms of pain transmission, such as via the TRPV1 and P2X3 receptors.

METHODS

After CIA was established, rats were treated with SZAP for 7 days. Paw thickness, arthritis score, and haematoxylin and eosin staining were used to evaluate the effectiveness of SZAP. Paw withdrawal threshold (PWT) and tail-flick latency (TFL) were used to estimate the analgesic effect of SZAP. The levels of PGE₂, BK, 5-HT, SP, and CGRP in the serum and synovium were determined using ELISA kits, and ATP in the synovium was measured using HPLC. The expression of TRPV1 and P2X3 in the DRG was detected using western blotting and immunofluorescence. TRPV1 and P2X3 agonists were further used to determine the analgesic effects of SZAP on CIA rats based on PWT and TFL.

RESULTS

SZAP not only significantly ameliorated arthritis scores and paw thickness by improving the pathological damage of synovial joints, but also remarkably alleviated pain in CIA rats. Further, treatment with SZAP significantly reduced peripheral 5-HT, PGE₂ BK, SP, CGRP, and ATP. Additionally, the expression of TRPV1 and P2X3 in the DRG was markedly downregulated by SZAP. Interestingly, the analgesic effect of SZAP was weakened (reduction of PWT and TFL) when TRPV1 and P2X3 were activated by capsaicin or α,β-meATP, respectively.

CONCLUSION

SZAP ameliorates rheumatalgia by suppressing hyperalgesia and pain transmission through the inhibition of TRPV1 and P2X3 in the DRG of CIA rats.

Ion-Pair Compounds of Strychnine for Enhancing Skin Permeability: Influencing the Transdermal Processes In Vitro Based on Molecular Simulation

This research aimed to explore how Strychnine (Str) ion-pair compounds affect the in vitro transdermal process. In order to prevent the influence of different functional groups on skin permeation, seven homologous fatty acids were selected to form ion-pair compounds with Str. The in vitro permeation fluxes of the Str ion-pair compounds were 2.2 to 8.4 times that of Str, and Str-C₁₀ had the highest permeation fluxes of 42.79 ± 19.86 µg/cm²/h. The hydrogen bond of the Str ion-pair compounds was also confirmed by Fourier Transform Infrared (FTIR) Spectroscopy, Nuclear Magnetic Resonance (NMR) Spectroscopy and molecular simulation. In the process of molecular simulation, the intercellular lipid and the viable skin were represented by ceramide, cholesterol and free fatty acid of equal molar ratios and water, respectively. It was found by the binding energy curve that the Str ion-pair compounds had better compatibility with the intercellular lipid and water than Str, which indicated that the affinity of Str ion-pair compounds and skin was better than that of Str and skin. Therefore, it was concluded that Str ion-pair compounds can be distributed from the vehicle to the intercellular lipid and viable skin more easily than Str. These findings broadened our knowledge about how Str ion-pair compounds affect the transdermal process.

Isoliquiritigenin Alleviates Semen Strychni-Induced Neurotoxicity by Restoring the Metabolic Pathway of Neurotransmitters in Rats

Acute neurotoxicity of Semen Strychni can result in sudden death in epilepsy. The detoxification method and mechanism of Semen Strychni acute poisoning have not been clarified. This experiment focused on the mechanism of Semen Strychni neurotoxicity and the alleviation effects of isoliquiritigenin. The rats were intraperitoneally injected with Semen Strychni extract (125 mg/kg), followed by oral administration of isoliquiritigenin (50 mg/kg) for 7 days. FJ-B staining was used to evaluate the degree of injury on hippocampus neurons. The concentration of monoamines, amino acids, and choline neurotransmitters, the Dopamine (DA) and 5-hydroxytryptamine (5-HT) metabolic pathway in the hippocampus, cerebellum, striatum, prefrontal cortex, hypothalamus, serum, and plasma were detected by LC-MS/MS. The expression of neurotransmitter metabolic enzymes [catechol-O-methyl transferase (COMT) and monoamine oxidase (MAO)] and neurotransmitter receptors [glutamate N-methyl-D-aspartic acid receptors (NMDARs) and gamma-aminobutyric acid type A receptor (GABRs)] were, respectively determined using ELISA and qRT-PCR. The results indicated that Semen Strychni induced neuronal degeneration in the hippocampal CA1 region. Meanwhile, Semen Strychni inhibited the mRNA expression of NMDAR1, NMDAR2A, NMDAR2B, GABRa1, GABRb2 and reduced the level of MAO, which disrupted the DA and 5-HT metabolic pathway. However, isoliquiritigenin reversed these effects. In summary, isoliquiritigenin showed alleviation effects on Semen Strychni-induced neurotoxicity, which could be attributed to restoring neurotransmitters metabolic pathway, most likely through the activation of NMDA receptors.

Core-shell magnetic zeolite imidazolate framework-8 as adsorbent for magnetic solid phase extraction of brucine and strychnine from human urine

Core-shell magnetic zeolite imidazolate framework-8 (Fe3O4@PAA@ZIF-8) was successfully synthesized and first employed as adsorbent of magnetic solid-phase extraction (MSPE) for the determination of brucine and strychnine in human urine sample coupled with high performance liquid chromatography. The as-prepared Fe3O4@PAA@ZIF-8 was characterized by transmission electron microscopy, Fourier-transform infrared spectrometry, X-ray diffraction, vibrating sample magnetometer and zeta potential analysis. Main parameters affecting the MSPE efficiency, including amount of adsorbent, sample solution pH, extraction time, ionic strength, desorption solvent, desorption time and desorption volume were further optimized. Under the optimized conditions, the proposed method provided good linearity (5.0-1000.0 μg L-1) with determination coefficients between 1.0000 and 0.9998, low limits of detection in the range of 1.1-1.2 μg L-1, and excellent reproducibility with relative standard deviations of less than 7.7%. The intra-day and inter-day precision were 1.5-3.2% and 2.1-7.2%, respectively. Satisfactory spiked recoveries were between97.2% and 115.4% with the relative standard deviations less than 6.3%. The results demonstrated that Fe3O4@PAA@ZIF-8 composite was a promising magnetic adsorbent for the preconcentration of brucine and strychnine in human urine sample.

Chronotoxicity of Semen Strychni is associated with circadian metabolism and transport in mice

OBJECTIVES

We aimed to determine the circadian responses of mice to Semen Strychni and to investigate the role of pharmacokinetics in generating chronotoxicity.

METHODS

Total extract of Semen Strychni was administered by oral gavage to wild-type (WT) and Bmal1-/- (a circadian clock-deficient model) mice at different circadian time points for toxicity (including survival) and pharmacokinetic characterization. Nephrotoxicity and neurotoxicity were evaluated by measuring plasma creatinine and creatine kinase BB (CK-BB), respectively. Drug metabolism and transport assays were performed using liver/intestine microsomes and everted gut sacs, respectively.

KEY FINDINGS

Semen Strychni nephrotoxicity and neurotoxicity as well as animal survival displayed significant circadian rhythms (the highest level of toxicity was observed at ZT18 and the lowest level at ZT2 to ZT6). According to pharmacokinetic experiments, herb dosing at ZT18 generated higher plasma concentrations (and systemic exposure) of strychnine and brucine (two toxic constituents) compared with ZT6 dosing. This was accompanied by reduced formation of both dihydroxystrychnine and strychnine glucuronide (two strychnine metabolites) at ZT18. Bmal1 ablation sensitized mice to Semen Strychni-induced toxicity (with increased levels of plasma creatinine and CK-BB) and abolished the time dependency of toxicity. Metabolism of Semen Strychni (strychnine and brucine) in the liver and intestine microsomes of WT mice was more extensive at ZT6 than at ZT18. These time differences in hepatic and intestinal metabolism were lost in Bmal1-/- mice. Additionally, the intestinal efflux transport of Semen Strychni (strychnine and brucine) was more extensive at ZT6 than ZT18 in WT mice. However, the time-varying transport difference was abolished in Bmal1-/- mice.

CONCLUSIONS

Circadian responses of mice to Semen Strychni are associated with time-varying efflux transport and metabolism regulated by the circadian clock (Bmal1). Our findings may have implications for optimizing phytotherapy with Semen Strychni via timed delivery.

Determination of 8 Endogenous Alkaloid Components inBoletusUsing Ultrahigh-Performance Liquid Chromatography Combined with Quadrupole-Time of Flight Mass Spectrometry

A ultrahigh performance liquid chromatography coupled with quadrupole-time of flight mass spectrometry (UPLC-Q-TOF/MS) method was developed for simultaneous determination of 8 endogenous alkaloid compounds inBoletus.Boletussamples were extracted by 50% (V/V) methanol-water solution, then separated by CORTECS UPLC HILIC column using a binary solvent system by gradient elution. The analytes were determined by Q-TOF/MS in TOF MS and information dependent acquisition (IDA)-MS/MS mode. The results showed that mass accuracy error of the 8 endogenous alkaloids were lower than 5.0 × 10−6, good linear relationship was got in range of 0.2–500 μg/L, and correlation coefficient was higher than 0.9990. The limit of detection was in the range of 0.002–0.100 mg/kg and the limit of quantification was in the range of 0.004–0.200 mg/kg. Recovery of the method was in range of 80.1%–101.5% with spike levels of 0.004–2.00 mg/kg, relative standard deviations were lower than 10%. The method was simple, specific, and reliable. It could be used for the rapid screening and quantitative analysis of 8 endogenous alkaloids inBoletus.

A simple, cost-effective and rapid method for simultaneous determination of Strychnos nux-vomica alkaloids in blood and Ayurvedic medicines based on ultrasound-assisted dispersive liquid-liquid microextraction-thin-layer chromatography-image analysis

A simple, rapid, cost-effective and green analytical method is developed based on ultrasound-assisted dispersive liquid-liquid microextraction (US-DLLME) coupled to thin-layer chromatography (TLC)-image analysis for the simultaneous determination of two major alkaloids of Strychnos nux-vomica L i.e., strychnine and brucine. The method is composed of three steps, namely (i) US-DLLME by injecting a mixture of 100-μL chloroform (extraction solvent) and 1-mL methanol (disperser solvent) in 5 mL of aqueous sample, followed by ultrasonication and centrifugation, (ii) TLC of 20 μL of sedimented phase with methanol: ammonia (100:1.5, v/v) as the mobile phase and visualization under ultraviolet radiation (254 nm) and (iii) photography of TLC plate and quantification of spots by image analysis using freely available imageJ software (National Institute of Health, Bethesda, MD, USA). The limit of detection and limit of quantification for both alkaloids were found to be in the range of 0.12-0.15 and 0.36-0.48 μg/spot, respectively. The method was found to be linear in the range of 0.5-5 μg/spot with correlation coefficient (R2) of 0.995 and 0.997 for strychnine and brucine, respectively. The developed method was successfully applied for the determination of strychnine and brucine in Ayurvedic formulations and blood samples. The method does not require any sophisticated instrument and handling skills and can be adopted for rapid analysis of strychnine and brucine in forensic toxicological laboratories.

Study on Absorption Mechanism and Tissue Distribution of Fucoidan

Fucoidan exhibits several pharmacological activities and is characterized by high safety and the absence of toxic side effects. However, the absorption of fucoidan is not well-characterized. In the present study, fucoidan were labeled with fluorescein isothiocyanate (FITC) and their ability to traverse a monolayer of Caco-2 cells was examined. The apparent permeability coefficients (Papp × 10⁻⁶) of FITC-labeled fucoidan (FITC-fucoidan) were 26.23, 20.15, 17.93, 16.11 cm/sec, respectively, at the concentration of 10 μg/mL at 0.5, 1, 1.5 and 2 h. The absorption of FITC-fucoidan was suppressed by inhibitors of clathrin-mediated endocytosis, chlorpromazine, NH₄Cl, and Dynasore; the inhibition rates were 84.24%, 74.61%, and 63.94%, respectively. This finding suggested that clathrin-mediated endocytosis was involved in fucoidan transport. Finally, tissue distribution of FITC-fucoidan was studied in vivo after injection of 50 mg/kg body weight into the tail vein of mice. The results showed that FITC-fucoidan targeted kidney and liver, reaching concentrations of 1092.31 and 284.27 μg/g respectively after 0.5 h. In summary, the present work identified the mechanism of absorption of fucoidan and documented its tissue distribution, providing a theoretical basis for the future development of fucoidan applications.

Prophylactic Neuroprotection of Total Glucosides of Paeoniae Radix Alba against Semen Strychni-Induced Neurotoxicity in Rats: Suppressing Oxidative Stress and Reducing the Absorption of Toxic Components

Strychnos alkaloids (SAs) are the main toxic constituents in Semen Strychni, a traditional Chinese medicine, which is known for its fatal neurotoxicity. Hence, the present study was carried out to evaluate the neurotoxicity induced by SAs and the pre-protective effects of the total glucosides of Paeoniae Radix Alba (TGP). An SA brain damage model was firstly established. The neurotoxicity induced by SAs and the pre-protective effects of TGP were confirmed by physical and behavioral testing, biochemical assay, and histological examination. Then, a liquid chromatography-tandem mass spectrometry method was developed and validated to investigate the time-course change and distribution of strychnine and brucine (two main SAs) in the brain after oral SA administration with or without TGP pretreatment. Biochemical analysis results indicated that TGP could ameliorate the oxidative stress status caused by SAs. Time-course change and distribution studies demonstrated that strychnine and brucine were rapidly absorbed into the brain, peaked early at 0.5 h, and were mainly located in the hippocampus and cerebellum. TGP showed a pre-protective effect against neurotoxicity by reducing the absorption of toxic alkaloids into the brain. These findings could provide beneficial information in facilitating future studies of Semen Strychni neurotoxicity and developing herbal medicines to alleviate neurotoxicity in the clinic.

Toxicokinetics of strychnine and brucine after the oral administration of Biqi capsule to rats by RRLC-MS/MS

Biqi capsule is a well-known traditional Chinese medicine formula that has been widely applied for the clinical treatment of such diseases as rheumatoid arthritis, scapulohumeral periarthritis and cervical spondylopathy. However, there is concern regarding the toxicity of Biqi capsule owing to its active ingredients, strychnine and brucine. To investigate the toxicokinetics of strychnine and brucine after oral administration of Biqi capsule to rats, a sensitive and simple rapid-resolution liquid chromatography/tandem mass spectrometry method was developed to determine the levels of strychnine and brucine in rat plasma. Chromatographic separation was performed on a Capcell Pak C₁₈ MG II (3.0 μm, 2.0 × 35 mm) column by gradient elution with acetonitrile and 0.2% formic acid as the mobile phase. The method was validated over the range of 0.25-250 ng/mL for strychnine and 0.025-25 ng/mL for brucine. The intra- and inter-day accuracies of strychnine and brucine in rat plasma were 100.3-106.6 and 90.75-106.1% respectively, and the precisions were within 14.2%. The established method was successfully applied to the toxicokinetic study of strychnine and brucine after single and multiple oral administration of Biqi capsule to male and female rats at 0.4, 0.8 and 1.6 g/kg doses. The results showed different toxicokinetic characteristics in the different groups.

An analytical strategy to investigate Semen Strychni nephrotoxicity based on simultaneous HILIC-ESI-MS/MS detection of Semen Strychni alkaloids, tyrosine and tyramine in HEK 293t cell lysates

A Previous metabolomics study has demonstrated that tyrosine metabolism might be disrupted by treating with Semen Strychni on the cell nephrotoxicity model. To investigate the relationship between Semen Strychni alkaloids (SAs) and endogenous tyrosine, tyramine under the nephrotoxicity condition, an HILIC-ESI-MS/MS based analytical strategy was applied in this study. Based on the established Semen Strychni nephrotoxicity cell model, strychnine and brucine were identified and screened as the main SAs by an HPLC-Q Exactive hybrid quadrupole Orbitrap mass system. Then, a sensitive HILIC-ESI-MS/MS method was developed to simultaneously monitor strychnine, brucine, tyrosine and tyramine in cell lysate. The analytes were separated by a Shiseido CAPCELL CORE PC (150mm×2.1mm, 2.7μm) HILIC column in an acetonitrile/0.1% formic acid gradient system. All the calibration curves were linear with regression coefficients above 0.9924. The absolute recoveries were more than 80.5% and the matrix effects were between 91.6%-107.0%. With the developed method, analytes were successfully determined in cell lysates. Decreased levels of tyrosine and tyramine were observed only in combination with increased levels of SAs, indicating that the disturbance of tyrosine metabolism might be induced by the accumulation of SAs in kidney cell after exposure of Semen Strychni. The HILIC-ESI-MS/MS based analytical strategy is a useful tool to reveal the relationships between the toxic herb components and the endogenous metabolite profiling in the toxicity investigation of herb medicines.