Simultaneous Determination and Risk Assessment of Pyrrolizidine Alkaloids in Artemisia capillaris Thunb. by UPLC-MS/MS Together with Chemometrics

Mass spectrometric analysis strategies for pyrrolizidine alkaloids

Pyrrolizidine alkaloids (PAs) in food and natural preparations have received widespread attention due to their hepatotoxicity, genotoxicity, and embryotoxicity. Mass spectrometry (MS), as a high resolution, high sensitive, and high throughput detection tool, has been the most commonly used technique for the determination of PAs. The continuous advancement of new technologies, methods, and strategies in the field of MS has contributed to the improvement of the analytical efficiency and methodological enhancement of PAs. This paper provides an overview of the structure, toxicity properties and commonly employed analytical methods, focusing on the concepts, advances, and novel techniques and applications of MS-based methods for the analysis of PAs. Additionally, the remaining challenges, future perspectives, and trends for PA detection are discussed. This review provides a reference for toxicological studies of PAs, content monitoring, and the establishment of quality control and safety standards for herbal and food products.

Profiling of pyrrolizidine alkaloids using a retronecine-based untargeted metabolomics approach coupled to the quantitation of the retronecine-core in medicinal plants using UHPLC-QTOF

Pyrrolizidine alkaloids (PA) are secondary metabolites of high toxicological relevance. Several PA quantitative methodologies were developed based on a limited number of certified standards, including time consuming solid phase extraction (SPE) purification steps. Herein, we shed light on the variability of PA in herbal extracts and propose a quantification methodology based on ultra-high-performance liquid chromatography high-resolution mass spectrometry (UHPLC-HRMS) for the evaluation of the total PA content as retronecine-equivalents (RE) directly from crude matrices. Particularly in the focus of the investigation were Alkanna spp. (Boraginaceae), which possess a wide range of pharmaceutical properties. In addition, a comparative PA screening of crude and SPE enriched extracts was performed and PA-containing plants from Fabaceae and Compositae families were included to demonstrate universal applicability. In total, 105 PA were identified using HRMS^e experiments, specific MS/MS fragmentation PA patterns, a customized in-house library and literature data. Among them, 18 glycosidic PA derivatives were reported for the first time in literature. Using a hierarchical clustering approach, PA distribution in herbal extracts was shown to be family-dependent and significantly different among species. This was further supported by the results of the total PA concentrations, obtained using a retronecine/heliotridine/internal standard-based targeted UHPLC-HRMS quantification method, which varied from 8.64 ± 0.08-3096.28 ± 273.72 μg RE/g extract dry weight in shoots extracts of Alkanna spp. and leaves extracts of Crotalaria retusa L. respectively. Worth mentioning is that the procedure allowed to quantify PA in Alkanna spp. If the procedure based on 35 specific PA recommended by European regulations had been used, results would have been equal to zero for the four species since none were observed in Alkanna spp. Finally, by combining the RE results with the corresponding dereplication results, a customized correction factor for each extract (ranging from 2.12 to 2.48) was assessed leading to a more accurate estimate of the PA content regardless of the molecular weight of each PA. The present methodology will facilitate PA quantification directly from crude extracts and avoid the underestimation the real PA content due to limited availabilty of authentic reference compounds in botanical extracts used in phytomedicines or food supplements/cosmetics.

Combined Hepatotoxicity and Toxicity Mechanism of Intermedine and Lycopsamine

Pyrrolizidine alkaloids (PAs) are common constituents of plants and have serious hepatotoxicity. Intermedine (Im) and lycopsamine (La) are two monoesters of PAs that frequently coexist in the PA-containing plants (e.g., comfrey and tea). The present study aimed to explore the combined hepatotoxicity and toxicity mechanism of the Im and La mixture. In vitro, the combined cytotoxicity of the Im and La mixture on human hepatocytes (HepD) was examined by CCK-8, colony formation, wound healing, and Annexin V/PI staining assays. The combination of Im and La inhibited the ability of HepD cells to proliferate, colonize, and migrate and induced hepatocytes apoptosis in a dose-dependent manner. In addition to significantly causing a burst of intracellular reactive oxygen species (ROS), mitochondrial apoptosis, and endoplasmic reticulum (ER) stress, the Im and La mixture can also cause an increase in intracellular Ca2+, triggering the PERK/eIF2α/ATF4/CHOP apoptosis pathway. This study provided the first direct evidence that the combined PAs induced hepatotoxicity through ER-mediated apoptosis. These results supplemented the basic toxicity data for the combined PAs and provided a new perspective for the risk assessment of combined PA toxicity.

Hepatotoxicity of Pyrrolizidine Alkaloid Compound Intermedine: Comparison with Other Pyrrolizidine Alkaloids and Its Toxicological Mechanism

Pyrrolizidine alkaloids (PAs) are common secondary plant compounds with hepatotoxicity. The consumption of herbal medicines and herbal teas containing PAs is one of the main causes of hepatic sinusoidal obstruction syndrome (HSOS), a potentially life-threatening condition. The present study aimed to reveal the mechanism underlying the cytotoxicity of intermedine (Im), the main PA in Comfrey. We evaluated the toxicity of the retronecine-type PAs with different structures to cell lines derived from mammalian tissues, including primary mouse hepatocytes, human hepatocytes (HepD), mouse hepatoma-22 (H₂₂) and human hepatocellular carcinoma (HepG2) cells. The cytotoxicity of Im to hepatocyte was evaluated by using cell counting kit-8 assay, colony formation experiment, wound healing assay and dead/live fluorescence imaging. In vitro characterization showed that these PAs were cytotoxic and induced cell apoptosis in a dose-dependent manner. We also demonstrated that Im induced cell apoptosis by generating excessive reactive oxygen species (ROS), changing the mitochondrial membrane potential and releasing cytochrome c (Cyt c) before activating the caspase-3 pathway. Importantly, we directly observed the destruction of the cell mitochondrial structure after Im treatment through transmission electron microscopy (TEM). This study provided the first direct evidence of Im inducing hepatotoxicity through mitochondria-mediated apoptosis. These results supplemented the basic toxicity data of PAs and facilitated the comprehensive and systematic evaluation of the toxicity caused by PA compounds.

Pyrrolizidine alkaloids in tea, herbal tea and iced tea beverages- survey and transfer rates

The transfer rate of 37 pyrrolizidine alkaloids (PA) found in ten naturally contaminated teas and herbal teas to their brews was studied in detail. Mixed herbal, peppermint, red bush, senna, black tea and green tea infusions were prepared according to the ISO guide and vendor's instructions, respectively, and parameters like herb-to-water ratio, steeping time and multiple extractions studied. In general, a transfer rate of 38-100% (median 95%) for brews following vendor's instructions was determined. The total concentration range of PA in these ten samples was 154-2412 ng/g (median 422 ng/g) in the herb and for single analytes 0.1-170 ng/g. Seven of the 37 PA occurred unexpectedly; these were tentatively identified and quantified by liquid chromatography-high resolution mass spectrometry (LC-HR-MS), since their contributions to total PA-content matter. Additionally, 46 iced tea beverages were analysed for their PA-load, determined to be in the range 0-631 ng/L (median 40 ng/L). The applied solid-phase extraction (SPE) clean-up turned out to be capable of separating PA in the free base pyrrolizidine alkaloids (PAFB) and their N-oxides (PANO) in a two-step elution, which was a valuable tool to support identification of unexpected PA. Further, atropine was found in 50% of the ten tea herb samples (range: 1-4 ng/g) and in 13% of the iced tea beverage samples (range: 2-65 ng/L).

Analysis of pyrrolizidine alkaloids in Eupatorium fortunei Turcz. and their in vitro neurotoxicity

This study was to analyze the pyrrolizidine alkaloids (PAs) in Eupatorium fortunei herbs and its derived finished products with a view to evaluating their effects on the proliferation and oligodendrogenesis of neural progenitor cells (NPCs). Using a LC-MS/MS method with 32 PAs reference standards, 8 PAs including intermedine, intermedine N-oxide, lycopsamine, lycopsamine N-oxide, retronecine, seneciphylline and senkirkine and 7-acetylintermedine N-oxide were identified with intermedine N-oxide and lycopsamine N-oxide being most abundant. The total PA amounts were found to vary from 0.18 to 61.81 μg/g in 30 batches of herbs and from 0.86 to 36.96 μg/g in 4 commercial finished products, respectively. Risk assessments indicated that the short-term intake seemed unlikely lead to acute toxic effects but the chronic use warranted cautions. Using NPCs derived from mouse induced pluripotent stem cells as an in vitro testing model, intermedine, intermedine N-oxide and lycopsamine N-oxide appeared to decrease cell viability at 30 μM whereas intermedine N-oxide inhibited oligodendrogenesis of NPCs at 10 μM. The present results suggested that the PAs in the majority of E. fortunei herbs and the derived products not only resulted in their exposure far exceeding the acceptable intake limit (i. e. 1.0 μg PA per day for adults) in herbal medicinal products recommended by the European Medicines Agency but also induced neurotoxicity to NPCs in vitro.

The invasive butterbur contaminates stream and seepage water in groundwater wells with toxic pyrrolizidine alkaloids

Pyrrolizidine alkaloids (PAs) are persistent mutagenic and carcinogenic compounds produced by many common plant species. Health authorities recommend minimising human exposure via food and medicinal products to ensure consumer health and safety. However, there is little awareness that PAs can contaminate water resources. Therefore, no regulations exist to limit PAs in drinking water. This study measured a PA base concentration of ~ 70 ng/L in stream water adjacent to an invasive PA-producing plant Petasites hybridus (Asteraceae). After intense rain the PA concentration increased tenfold. In addition, PAs measured up to 230 ng/L in seepage water from groundwater wells. The dominant PAs in both water types corresponded to the most abundant PAs in the plants (senkirkine, senecionine, senecionine N-oxide). The study presents the first discovery of persistent plant toxins in well water and their associated risks. In addition, it for the first time reports monocrotaline and monocrotaline N-oxide in Petasites sp.

Quantitative Analysis of Six Phenolic Acids in Artemisia capillaris (Yinchen) by HPLC-DAD and Their Transformation Pathways in Decoction Preparation Process

We aimed to establish a quantitative analysis method of six constituents (5-caffeoylquinic acid, 3-caffeoylquinic acid, 4-caffeoylquinic acid, 1,3-dicaffeoylquinic acid, 3,4-dicaffeoylquinic acid, and 4,5-dicaffeoylquinic acid) in Artemisia capillaris (Yinchen) and its decoction by using HPLC coupled with DAD. Besides, the transformation paths of the six constituents were analyzed in decoction preparation processing. The analytical method was fully validated in terms of linearity, sensitivity, precision, repeatability, and recovery and applied to assess the transformation trend and quantitative analysis of the six constituents in Yinchen decoction. The contents of six constituents varied greatly in Yinchen herb and Yinchen decoction, and there were inextricable internal relationships between them. Presumably 3-caffeoylquinic acid was isomerized to generate 5-caffeoylquinic acid and 4-caffeoylquinic acid. Similarly, 1,3-dicaffeoylquinic acid and 3,4-dicaffeoylquinic acid were produced by isomerization of 4,5-dicaffeoylquinic acid. In conclusion, this study provides a chemical basis for quality control of Yinchen decoction, and the changes of selected markers in decoction could give us some novel perspectives to study the relationship between substances and drug efficacy.