Simultaneous characterization of pyrrolizidine alkaloids and N-oxides in Gynura segetum by liquid chromatography/ion trap mass spectrometry

Rapid chemical characterization and pharmacological mechanism of Fining Granules in the treatment of chronic bronchitis based on UHPLC-Q-exactive orbitrap mass spectrometer and network pharmacology

Background

Senecio cannabifolius Less. is a perennial herb belonging to the Compositae family that has been used in traditional medicine as an antitussive and expectorant for treating chronic bronchitis and acute respiratory infections. Traditionally, Feining Granules are prepared from water extracts of the raw plant material. However, the chemical composition and pharmacological mechanisms of Feining Granules have not been thoroughly investigated.

Methods

A systematic strategy for the rapid detection and identification of the constituents of Feining Granules was developed using ultrahigh-performance liquid chromatography-quadrupole-exactive orbitrap mass spectrometry (MS) with parallel reaction monitoring.

Results

Overall, 162 compounds, including flavonoids, alkaloids, organic acids, and others, were identified unambiguously and tentatively by comparing the retention times and MS fragmentation with reference standards and literature data. Ninety-nine of these were reported for the first time to the best of our knowledge. Network pharmacology suggests that Feining Granules can be used to treat chronic bronchitis as they contain active components associated with the ALB, VEGFA, and SRC target genes influenced by HIF-1, VEGF, and other signaling pathways.

Conclusion

These results provide information that can help understand the effective substances of S. cannabifolius Less. and improve quality control.

Investigation of Gynura segetum root extract (GSrE) induced hepatotoxicity based on metabolomic signatures and microbial community profiling in rats

In recent years, many reports focus on the hepatotoxicity of Gynura segetum root extract (GSrE), but the interaction between GSrE and the gut microbiota is still unclear. This study investigated the mechanism of GSrE-induced hepatotoxicity of different doses and exposure durations by combining metabolomics and gut microbiota analysis. SD rats were divided into 3 groups: blank, low-dose (7.5 g/kg), and high-dose (15 g/kg) groups. Urine and feces samples were collected on day 0, day 10, and day 21. Metabolomics based on gas chromatography-mass spectrometry (GC-MS) was carried out to identify metabolites and metabolic pathways. 16S rDNA gene sequencing was applied to investigate the composition of gut microbiota before and after GSrE-induced hepatotoxicity. Finally, a correlation analysis of metabolites and gut microbiota was performed. Differential metabolites in urine and feces involved amino acids, carbohydrates, lipids, organic acids, and short chain fatty acids. Among them, L-valine, L-proline, DL-arabinose, pentanoic acid, D-allose, and D-glucose in urine and D-lactic acid and glycerol in fecal metabolites depended on the exposure of time and dose. In addition, 16S rDNA sequencing analysis revealed that GSrE-induced hepatotoxicity significantly altered the composition of gut microbiota, namely, f_Muribaculaceae_Unclassified, Lactobacillus, Bacteroides, Lachnospiraceae_NK4A136_group, f_Ruminococcaceae_Unclassified, Prevotellaceae_Ga6A1_group, and Escherichia-Shigella. The correlation analysis between gut microbiota and differential metabolites showed the crosstalk between the gut microbiota and metabolism in host involving energy, lipid, and amino acid metabolisms. In summary, our findings revealed that peripheral metabolism and gut microbiota disorders were time- and dose-related and the correlation between gut microbiota and metabolites in GSrE-induced hepatotoxicity.

Current Knowledge Regarding Pharmacological Profile and Chemical Constituents of Gynura procumbens

Gynura procumbens (Lour.) Merr. is a well-known plant used in the folkloric medicine in tropical Asian countries. The plant is prevalently employed by traditional healers in the treatment of diabetes, cancer, hypertension, inflammation, fever and skin disorders. Several scientific studies reported that, Gynura procumbens possesses considerable therapeutic value for the development of emerging treatment options. The diverse pharmacological effects of this plant are attributed to its vast phytoconstituent content. Different chemical classes including alkaloids, flavonoids, phenolics, steroids, proteins and polysaccharides have been isolated from this plant. In this review, we tried to explore the different aspects of Gynura procumbens as an established medicinal plant. The data gathered here give an indication that the plant Gynura procumbens is a good natural source of chemical compounds with different types of pharmacological actions and these chemical compounds can be used as model for the development of de novo therapeutic agents.

Comprehensive insights into the formation of metabolites of the ghrelin mimetics capromorelin, macimorelin and tabimorelin as potential markers for doping control purposes

Analytical methods to determine the potential misuse of the ghrelin mimetics capromorelin (CP-424,391), macimorelin (macrilen, EP-01572) and tabimorelin (NN703) in sports were developed. Therefore, different extraction strategies, i.e. solid-phase extraction, protein precipitation, as well as a "dilute-and-inject" approach, from urine and EDTA-plasma were assessed and comprehensive in vitro/in vivo experiments were conducted, enabling the identification of reliable target analytes by means of high resolution mass spectrometry. The drugs' biotransformation led to the preliminary identification of 51 metabolites of capromorelin, 12 metabolites of macimorelin and 13 metabolites of tabimorelin. Seven major metabolites detected in rat urine samples collected post-administration of 0.5-1.0 mg of a single oral dose underwent in-depth characterization, facilitating their implementation into future confirmatory test methods. In particular, two macimorelin metabolites exhibiting considerable abundances in post-administration rat urine samples were detected, which might contribute to an improved sensitivity, specificity, and detection window in case of human sports drug testing programs. Further, the intact drugs were implemented into World Anti-Doping Agency-compliant initial testing (limits of detection 0.02-0.60 ng/ml) and confirmation procedures (limits of identification 0.18-0.89 ng/ml) for human urine and blood matrices. The obtained results allow extension of the test spectrum of doping agents in multitarget screening assays for growth hormone-releasing factors from human urine.

Detection of pyrrolizidine alkaloids in jamu available on the Indonesian market and accompanying safety assessment for human consumption

The occurrence and accompanying risks of pyrrolizidine alkaloids (PAs) in Indonesian jamu were evaluated. PAs were detected in 34 out of 35 jamu containing PA-producing botanicals, in the range of 12.3-235,376 μg/kg. A total PA level of 5.9-3,421 μg/kg was found in 17 out of 23 jamu made of non-PA-producing botanicals pointing to contamination with PA-producing plants. Short-time consumption of jamu is unlikely to result in acute toxic effects, although one sample would exceed an intake of 10 μg PA/kg bw/day which may cause hepatic veno-occlusive disease (HVOD) in humans. The risk assessment for the genotoxic and carcinogenic potential of PAs revealed Margin of Exposure (MOE) values below 10,000 for 27 out of all samples analysed (46.6%), indicating a priority for risk management when assuming daily lifelong consumption. Assuming consumption for two weeks every year during a lifetime, and using Haber's rule, 13 out of 35 jamu samples containing PA-producing botanicals (37%) still pose a priority, while the jamu consisting of non-PA-producing botanicals would be of low priority (MOE>10,000). This study provides data that can support risk management actions in Indonesia to minimize the potential health risk for jamu consumers due to the occurrence of toxic PAs in these products.

Using LC Retention Times in Organic Structure Determination: Drug Metabolite Identification

Background:

There is a continued need for improvements in the efficiency of metabolite structure elucidation.

Objective:

We propose to take LC Retention Time (RT) into consideration during the process of structure determination.

Methods:

Herein, we develop a simple methodology that employs a Chromatographic Hydrophobicity Index (CHI) framework for standardizing LC conditions and introduce and utilize the concept of a pre-dictable CHI change upon Phase 1 biotransformation (CHIbt). Through the analysis of literature exam-ples, we offer a Quantitative Structure-Retention Relationship (QSRR) for several types of biotransfor-mation (especially hydroxylation) using physicochemical properties (clogP, hydrogen bonding).

Results:

The CHI system for retention indexing is shown to be practical and simple to implement. A da-tabase of CHIbt values has been created from re-incubation of 3 compounds and from analysis of an addi-tional 17 datasets from the literature. Application of this database is illustrated.

Conclusion:

In our experience, this simple methodology allows complementing the discovery efforts that saves resources for in-depth characterization using NMR.

Pyrrolizidine Alkaloids: Biosynthesis, Biological Activities and Occurrence in Crop Plants

Pyrrolizidine alkaloids (PAs) are heterocyclic secondary metabolites with a typical pyrrolizidine motif predominantly produced by plants as defense chemicals against herbivores. They display a wide structural diversity and occur in a vast number of species with novel structures and occurrences continuously being discovered. These alkaloids exhibit strong hepatotoxic, genotoxic, cytotoxic, tumorigenic, and neurotoxic activities, and thereby pose a serious threat to the health of humans since they are known contaminants of foods including grain, milk, honey, and eggs, as well as plant derived pharmaceuticals and food supplements. Livestock and fodder can be affected due to PA-containing plants on pastures and fields. Despite their importance as toxic contaminants of agricultural products, there is limited knowledge about their biosynthesis. While the intermediates were well defined by feeding experiments, only one enzyme involved in PA biosynthesis has been characterized so far, the homospermidine synthase catalyzing the first committed step in PA biosynthesis. This review gives an overview about structural diversity of PAs, biosynthetic pathways of necine base, and necic acid formation and how PA accumulation is regulated. Furthermore, we discuss their role in plant ecology and their modes of toxicity towards humans and animals. Finally, several examples of PA-producing crop plants are discussed.

Multiple heart-cutting two dimensional liquid chromatography quadrupole time-of-flight mass spectrometry of pyrrolizidine alkaloids

Pyrrolizidine alkaloids (PAs) and their and the corresponding N-oxides (PAs-ox) are genotoxic plant metabolites which can be present as unwanted contaminants in food products of herbal origin like tea and food supplements. PAs and PAs-ox come in a wide variety of molecular structures including many structural isomers. For toxicity assessment it is important to determine the composition of a sample and to resolve all isomeric PAs and PAs-ox, which is currently not possible in one liquid or gas chromatographic (LC or GC) run. In this study an online two dimensional liquid chromatography quadrupole time-of-flight mass spectrometry (2D-LC QToF-MS) method was developed to resolve isomeric PAs and PAs-ox. After comprehensive column and mobile phase selection a polar endcapped C₁₈ column was used at pH 3 in the first dimension, and a cross-linked C₁₈ column at pH 10 in the second dimension. Injection solvents, column IDs, flow rates and temperatures were carefully optimized. The method with column selection valve switching described in this study was able to resolve and visualize 20 individual PAs/PAs-ox (6 sets of isomers) in one 2D-LC QToF-MS run. Moreover, it was shown that all isomeric PAs/PAs-ox could be unambiguously annotated. The method was shown to be applicable for the determination and quantification of isomeric PAs/PAs-ox in plant extracts and could be easily extended to include other PAs and PAs-ox.

Mass-spectrometry-directed analysis and purification of pyrrolizidine alkaloid cis/trans isomers in Gynura japonica

Pyrrolizidine alkaloids are highly hepatotoxic natural chemicals that produce irreversible chronic and acute hepatotoxic effects on human beings. Purification of large amounts of pyrrolizidine alkaloids is necessary for toxicity studies. In this study, an efficient method for targeted analysis and purification of pyrrolizidine alkaloid cis/trans isomers from herbal materials was developed for the first time. Targeted analysis of the hepatotoxic pyrrolizidine alkaloids was performed by liquid chromatography with tandem mass spectrometry (precursor ion scan and daughter ion scan), and the purification of pyrrolizidine alkaloids was achieved with a mass-directed auto purification system. The extraction and preparative liquid chromatography conditions were optimized. The developed method was applied to analysis of Gynura japonica (Thunb.) Juel., a herbal medicine traditionally used for detumescence and relieving pain but is potentially hepatotoxic as it contains pyrrolizidine alkaloids. Twelve pyrrolizidine alkaloids (six cis/trans isomer pairs) were identified with reference compounds or characterized by liquid chromatography with tandem mass spectrometry, and five individual pyrrolizidine alkaloids, including (E)-seneciphylline, seneciphylline, integerrimine, senecionine, and seneciphyllinine, were prepared from G. japonica roots with high efficiency. The results of this work provide a new technique for the preparation of large amounts of pyrrolizidine alkaloid reference substances, which will also benefit toxicological studies of pyrrolizidine alkaloids and treatments for pyrrolizidine alkaloid-induced toxicity.

Investigation of targeted pyrrolizidine alkaloids in traditional Chinese medicines and selected herbal teas sourced in Ireland using LC-ESI-MS/MS

Publications linking hepatotoxicity to the use of herbal preparations are escalating. Herbal teas, traditional Chinese medicines (TCMs) and dietary supplements have been shown to contain pyrrolizidine alkaloids (PAs). Acute PA toxicosis of the liver can result in sinusoidal-obstruction syndrome, also known as veno-occlusive disease (VOD). This paper describes a sensitive and robust method for the detection of targeted PAs and their N-oxides (PANOs) in herbal products (selected herbal teas and TCMs) sourced within Ireland. The sample preparation includes a simple acidic extraction with clean-up via solid-phase extraction (SPE). Sample extracts were accurately analysed by using LC-ESI-MS/MS applying for the first time a pentafluorophenyl (PFP) core-shell column to the chromatographic separation of PAs and PANOs. The method was validated for selectivity, taking into consideration matrix effects, specificity, linearity, precision and trueness. Limits of detection (LOD) and limits of quantitation (LOQ) were quantified for all PAs and PANOs ranging from 0.4 to 1.9 µg kg⁻¹ and from 1.3 to 6.3 µg kg⁻¹, respectively. In this study 10 PAs and four PANOs were targeted because they are commercially available as reference standards. Therefore, this study can only report the levels of these PAs and PANOs analysed in the herbal teas and TCMs. The results reported represent the minimum levels of PAs and PANOs present in the samples analysed; commercially available herbal teas (n = 18) and TCMs (n = 54). A total of 50% herbal teas and 78% Chinese medicines tested positive for one or more PAs and/or PANOs included within this study, ranging from 10 to 1733 and from 13 to 3668 µg kg⁻¹, respectively.

Simultaneous investigation of sesquiterpenes, pyrrolizidine alkaloids and N-oxides in Butterbur (Petasites hybridus) with an offline 2D-combination of HPLC-UV and LC-MMI-ToF-MS

With the worldwide rapid increasing interest in the use of natural products as dietary supplements, medical remedies and functional foods, it has been accepted that omitting the plant constituents with potential adverse effects was a huge fault of the past. Several countries developed regulations to limit the consumption of such products in the markets. Among these natural products, butterbur (Petasites) has been used for years as herbal supplement for its anti-spasmodic and anti-inflammatory effects. However, its hepatotoxic alkaloid content limits the direct usage. In this study, investigation of sesquiterpenes and pyrrolizidine alkaloids (PAs) together with their N-oxide forms has been conducted with an offline 2D-combination using high-performance liquid chromatography with UV detection (HPLC-UV) and liquid chromatography - multi mode ionization - time-of-flight mass spectrometry (LC-MMI-ToF-MS) for plant screening. The content has been qualitatively investigated to provide information on the constituents of the plant rhizomes extracted using ethanol. Besides the reported hepatotoxic and medically bio-active plant constituents, a strategy has been suggested for estimating the retention order and retention times with respect to calculated logD (distribution coefficient) and hydrophobicity distributions on C18 reversed-phase column when all standard compounds are not available in laboratory. In this sense, the influence of calculated logD and hydrophobicity distributions on retention time has been clarified via available PA and PA-N-oxide standards. The ethanolic extract of Petasites hybridus has been used for examination of the strategy in a real-sample model. Additionally, the advantages of the developed HPLC-UV and LC-MMI-ToF-MS combination have been discussed with respect to the presented results.

Investigation of the Volatile Constituents of Different Gynura Species from Two Chinese Origins by SPME/GC-MS

GC-MS analyses of the volatile constituents obtained by solid phase microextraction (SPME) of two Gynura species, i.e. G. divaricata and G. bicolor, collected from Nanjing and Nanping areas in the east of China, enabled the identification of more than 50 different components. Generally, a higher contents of sesquiterpene compounds such as β-caryophyllene, α-caryophyllene and α-copaene were found in G. bicolor than in G. divaricata, regardless of their origin. Qualitatively, the detected major volatiles of G. bicolor and G. divaricata originating from Nanjing were the same, i.e. β-caryophyllene, α-caryophyllene, α-copaene, α-pinene and β-pinene. The volatile profile of a third species, G. medica, also originating from Nanjing was different with sesquiterpenes γ-cadinene, β-caryophyllene, elixene and monoterpene limonene as the major components. The volatile profiles of G. bicolor and G. divaricata originating from Nanping were more diverse. For both species β-caryophyllene, α-copaene and limonene were the major volatiles, but G. bicolor also produced α-caryophyllene and carvone as major constituents, whereas for G. divariata o-cymene was detected. Overall, these results indicate that the biosynthesis of volatiles by Gynura species is not only species related, but is also possibly influenced by the local environmental conditions of growth.

Characteristic ion clusters as determinants for the identification of pyrrolizidine alkaloid N-oxides in pyrrolizidine alkaloid-containing natural products using HPLC-MS analysis

Pyrrolizidine alkaloid (PA)-containing plants are widely distributed in the world. PAs are hepatotoxic, affecting livestock and humans. PA N-oxides are often present together with PAs in plants and also exhibit hepatotoxicity but with less potency. HPLC-MS is generally used to analyze PA-containing herbs, although PA references are unavailable in most cases. However, to date, without reference standards, HPLC-MS methodology cannot distinguish PA N-oxides from PAs because they both produce the same characteristic ions in mass spectra. In the present study, the mass spectra of 10 PA N-oxides and the corresponding PAs were systemically investigated using HPLC-MS to define the characteristic mass fragment ions specific to PAs and PA N-oxides. Mass spectra of toxic retronecine-type PA N-oxides exhibited two characteristic ion clusters at m/z 118-120 and 136-138. These ion clusters were produced by three unique fragmentation pathways of PA N-oxides and were not found in their corresponding PAs. Similarly, the nontoxic platynecine-type PA N-oxides also fragmented via three similar pathways to form two characteristic ion clusters at m/z 120-122 and 138-140. Further application of using these characteristic ion clusters allowed successful and rapid identification of PAs and PA N-oxides in two PA-containing herbal plants. Our results demonstrated, for the first time, that these characteristic ion clusters are unique determinants to discriminate PA N-oxides from PAs even without the availability of reference samples. Our findings provide a novel and specific method to differentiate PA N-oxides from PAs in PA-containing natural products, which is crucial for the assessment of their intoxication.

Hepatic sinusoidal obstruction syndrome associated with consumption of Gynura segetum

BACKGROUND & AIMS

One major cause of hepatic sinusoidal obstruction syndrome (HSOS) is the intake of pyrrolizidine alkaloid (PA)-containing products. Over 8000 PA-induced HSOS cases have been reported worldwide and at least 51 among them were suspected to be attributed to exposure to the Chinese medicine 'Tusanqi'. PA-induced hepatotoxicity involves cytochrome P450-mediated metabolic activation of PAs to electrophilic pyrrolic metabolites which react with macromolecules, such as proteins. However, no studies have found such protein adduction in HSOS patients. We report one HSOS case confirmed by liver biopsy, where the patient claimed taking 'Tusanqi' as self-medication.

METHODS

The herb was analyzed by HPLC-MS, and its induced hepatotoxicity in rats was assessed by monitoring the alteration of serum ALT level and liver morphology. Blood pyrrole-protein adducts were determined by UPLC-MS.

RESULTS

The herb the patient consumed was identified as Gynura segetum, an erroneous substitute of non-PA-containing Sedum aizoon, called 'Tusanqi'. Hepatotoxic PAs senecionine and seneciphylline were detected in G. segetum. In the PA-exposed patient, serum pyrrole-protein adducts were detected by a newly developed analytical approach. The animal study showed a good correlation of liver injury with the ingestion of G. segetum.

CONCLUSIONS

For the first time, serum pyrrole-protein adducts were unequivocally detected in a PA-induced HSOS patient, and such adducts show a potential to be developed as a biomarker for the assessment of PA-induced HSOS. Similar to the well-known case of aristolochic acid-poisoning, the observed HSOS was confirmed to arise from the consumption of PA-containing G. segetum, an erroneous substitute of non-PA-containing S. aizoon.

A high-sensitivity UPLC-MS/MS method for simultaneous determination and confirmation of triptolide in zebrafish embryos

A high-sensitivity ultra-performance liquid-chromatography (UPLC) coupled with tandem mass spectrometric method was developed for simultaneous quantification and confirmation of triptolide in both zebrafish embryos and the aqueous-exposure solution on a tandem quadrupole mass spectrometer (TQ-MS). This was achieved by performing quantification using the multiple reaction monitoring (MRM) acquisition with simultaneous characterization of the MRM peak using product ion confirmation (PIC) acquisition as it elutes from the chromatographic system. Separation was achieved on a 1.7 µm C(18) UPLC column using 0.1% formic acid water-acetonitrile mobile phase with a cycle time of 6 min. The linear range of 0.115-360 ng/mL, and lower limits of detection of 0.02 ng/mL and quantification of 0.064 ng/mL were established. This method was successfully applied to determine the time course of triptolide absorption by zebrafish embryos and the amount of triptolide remaining in the culture medium after administration of two triptolide dosages at three time points. This coupled MRM with PIC approach could provide both qualitative and quantitative results without the need for repetitive analyses. This resulted in the reduction of further confirmative experiments and analytical time, and ultimately increased laboratory productivity.

A new approach for simultaneous screening and quantification of toxic pyrrolizidine alkaloids in some potential pyrrolizidine alkaloid-containing plants by using ultra performance liquid chromatography-tandem quadrupole mass spectrometry

A rapid, but sensitive and selective method for simultaneous screening and quantification of toxic pyrrolizidine alkaloids (PAs) by ultra performance liquid-chromatography (UPLC) coupled with tandem mass spectrometry (MS/MS) on a tandem quadrupole mass spectrometer (TQ-MS) is described. This was accomplished by incorporating the precursor ion scan (PIS) acquisition and multiple reaction monitoring (MRM) acquisition in the same UPLC-MS/MS run. Notably, the developed PIS approach for detecting two pairs of characteristic product ions at m/z 120/138 or 168/150, allowed specific identification of toxic retronecine and otonecine types PAs. This PIS method is highly sensitive with over 10-fold sensitivity improvement upon previously published LC-MS method. Moreover, this new approach is suitable for high sample throughput and was applied to the screening and quantifying toxic PAs in 22 samples collected from seven Parasenecio species and four Senecio species. In addition, coupling the MRM with PIS approach generated quantitative results equivalent to those obtained by conventional MRM-only approach. This coupled MRM with PIS approach could provide both qualitative and quantitative results without the need of repetitive analyses.