Chemoenzymatic Synthesis of 4,5-Dihydroxyisoleucine Fragment of α-Amanitin.

The ability of α-amanitin to potently inhibit RNA polymerase II (RNAP II) has elicited further research into its use as a novel payload for antibody-drug conjugates. Despite this promise, the de novo synthesis of α-amanitin is still a major challenge as it possesses an unusual bicyclic octapeptide structure that contains several oxidized amino acids, most notably 4,5-dihydroxy-l-isoleucine. Here, we report a concise chemoenzymatic synthesis of this key amino acid residue, which features two regioselective and diastereoselective enzymatic C-H oxidations on l-isoleucine.

Kidney toxicity and transcriptome analyses of male ICR mice acutely exposed to the mushroom toxin α-amanitin.

Amatoxins are responsible for most fatal mushroom poisoning cases, as it causes both hepatotoxicity and nephrotoxicity. However, studies on amatoxin nephrotoxicity are limited. Here, we investigated nephrotoxicity over 4 days and nephrotoxicity/hepatotoxicity over 14 days in mice. The organ weight ratio, serological indices, and tissue histology results indicated that a nephrotoxicity mouse model was established with two stages: (1) no apparent effects within 24 h; and (2) the appearance of adverse effects, with gradual worsening within 2-14 days. For each stage, the kidney transcriptome revealed patterns of differential mRNA expression and significant pathway changes, and Western blot analysis verified the expression of key proteins. Amanitin-induced nephrotoxicity was directly related to RNA polymerase II because mRNA levels decreased, RNA polymerase II-related pathways were significantly enriched at the transcription level, and RNA polymerase II protein was degraded in the early poisoning stage. In the late stage, nephrotoxicity was more severe than hepatotoxicity. This is likely associated with inflammation because inflammation-related pathways were significantly enriched and NF-κB activation was increased in the kidney.

Biodistribution of radiolabeled alpha-amanitin in mice: An Investigation.

Mushroom poisonings caused by Amanita phalloides are the leading cause of mushroom-related deaths worldwide. Alpha-Amanitin (α-AMA), a toxic substance present in these mushrooms, is responsible for the resulting hepatotoxicity and nephrotoxicity. The objective of our study was to determine the distribution of α-AMA in Balb/c mice by labeling with Iodine-131. Mice were injected with a toxic dose (1.4 mg/kg) of α-AMA labeled with Iodine-131. The mice were sacrificed at the 1st, 2nd, 4th, 8th, 24th, and 48th hours under anesthesia. The organs of the mice were removed, and their biodistribution was assessed in all experiments. The percent injected dose per gram (ID/g %) value for kidney, liver, lung, and heart tissues at 1st hour were 1.59 ± 0.07, 1.25 ± 0.33, 3.67 ± 0.80 and 1.07 ± 0.01 respectively. This study provides insights into the potential long-term effects of α-AMA accumulation in specific organs. Additionally, this study has generated essential data that can be used to demonstrate the impact of antidotes on the biological distribution of α-AMA in future toxicity models.

Wild mushroom poisoning: A case study of amatoxin-containing mushrooms and implications for public health.

Wild mushroom poisoning is a global public health concern, with mushrooms containing amatoxins being the main cause of fatalities. Mushrooms from the genus Amanita and Galerina contain amatoxins. Here we present a case of wild mushroom poisoning that affected three individuals, resulting in two fatalities. Within 10-15 hours after consumption, they experienced symptoms of gastroenteritis such as vomiting, abdominal pain, and diarrhea. One individual sought medical attention promptly and recovered, while the other two sought medical help nearly two or three days after the onset of symptoms, by which time their conditions had already worsened and led to their deaths. The mushrooms were identified belonging to genus Galerina, and laboratory test revealed variations in toxin levels among mushrooms collected from different parts of the decaying stump. The higher levels of α-amanitin, ß-amanitin, and γ-amanitin were detected near the base of the tree stump, but trace levels of α-amanitin were found near the top of the stump, while ß-amanitin and γ-amanitin were undetectable. This case emphasizes the importance of seeking immediate medical attention when experiencing delayed-onset gastrointestinal symptoms, as it may indicate more severe mushroom poisoning, particularly amatoxin poisoning. Timely and appropriate treatment is equally important. Additionally, consuming different units of the mushrooms in the same incident can lead to varying prognoses due to differences in toxin levels.

Colorimetric assay for α-amanitin based on inhibition of carbon dots/AuNPs nanoenzyme activity.

Accidental ingestion of poisonous mushrooms leading to poisoning is a global issue. The most important and lethal toxin causing mushroom poisoning is α-amanitin, with a lethal dose of about 0.1 mg kg-1. Rapid detection of wild mushrooms before consumption or rapid identification of toxins after poisoning can effectively reduce the occurrence of fatalities. This study established a method for detecting α-amanitin using carbon dots/AuNPs nanoenzymes (D-Glu-CDs/AuNPs) with robust peroxidase-like activity. This nanoenzyme was prepared employing glucose carbon dots and sodium citrate as reducing and stabilizing agents, respectively. It could oxidize the substrate TMB (tetramethylbenzidine) to produce blue o-TMB. When α-amanitin specifically bound to the active site of the nanoenzyme, a resultant decrease was observed in catalytic activity and the absorbance value at 652 nm. The regression equation Y = -0.06083x + 0.9643, with an R2 value of 0.996, was obtained. The limit of detection was determined to be 48.03 ng mL-1, and the recoveries in urine ranged from 91.2% to 97.6%. This method enabled the visualization of α-amanitin, and the whole detection process was completed within 20 min. The approach holds promise for the quantitative and qualitative determination of α-amanitin in urine samples.

Unraveling Hematotoxicity of α-Amanitin in Cultured Hematopoietic Cells.

Amanita phalloides poisonings account for the majority of fatal mushroom poisonings. Recently, we identified hematotoxicity as a relevant aspect of Amanita poisonings. In this study, we investigated the effects of the main toxins of Amanita phalloides, α- and ß-amanitin, on hematopoietic cell viability in vitro. Hematopoietic cell lines were exposed to α-amanitin or ß-amanitin for up to 72 h with or without the pan-caspase inhibitor Z-VAD(OH)-FMK, antidotes N-acetylcysteine, silibinin, and benzylpenicillin, and organic anion-transporting polypeptide 1B3 (OATP1B3) inhibitors rifampicin and cyclosporin. Cell viability was established by trypan blue exclusion, annexin V staining, and a MTS assay. Caspase-3/7 activity was determined with Caspase-Glo assay, and cleaved caspase-3 was quantified by Western analysis. Cell number and colony-forming units were quantified after exposure to α-amanitin in primary CD34+ hematopoietic stem cells. In all cell lines, α-amanitin concentration-dependently decreased viability and mitochondrial activity. ß-Amanitin was less toxic, but still significantly reduced viability. α-Amanitin increased caspase-3/7 activity by 2.8-fold and cleaved caspase-3 by 2.3-fold. Z-VAD(OH)-FMK significantly reduced α-amanitin-induced toxicity. In CD34+ stem cells, α-amanitin decreased the number of colonies and cells. The antidotes and OATP1B3 inhibitors did not reverse α-amanitin-induced toxicity. In conclusion, α-amanitin induces apoptosis in hematopoietic cells via a caspase-dependent mechanism.

A Sensitive, Cell-Based Assay for Measuring Low-Level Biological Activity of α-Amanitin.

α-Amanitin is one of the primary toxins produced by the poisonous mushroom genus, Amanita. Because it is odorless and tasteless, it is an important cause of death from the consumption of misidentified mushrooms. To study the thermal stability of α-amanitin, novel cell-based assays were developed to measure the toxin's activity, based on the inhibition of RNA polymerase II by α-amanitin. First, an MTT-formazan cell viability assay was used to measure the biological activity of α-amanitin through the inhibition of cellular activity. This method can detect 10 µg/mL of α-amanitin in a time-dependent manner. Second, a more sensitive quantitative PCR approach was developed to examine its inhibition of viral replication. The new RT-qPCR assay enabled the detection of 100 ng/mL. At this level, α-amanitin still significantly reduced adenovirus transcription. Third, a simpler GFP expression-based assay was developed with an equal sensitivity to the RT-qPCR assay. With this assay, aqueous α-amanitin heated at 90 °C for 16 h or treated in the microwave for 3 min retained its biological activity when tested in HEK293 cells, but a slight reduction was observed when tested in Vero cells. Beyond detecting the activity of α-amanitin, the new method has a potential application for detecting the activity of other toxins that are RNA polymerase inhibitors.

Cannabidiol protects the liver from α-Amanitin-induced apoptosis and oxidative stress through the regulation of Nrf2.

α-Amanitin, the primary lethal toxin of Amanita, specifically targets the liver, causing oxidative stress, hepatocyte apoptosis, and irreversible liver damage. As little as 0.1 mg/kg of α-amanitin can be lethal for humans, and there is currently no effective antidote for α-amanitin poisoning. Cannabidiol is a non-psychoactive natural compound derived from Cannabis sativa that exhibits a wide range of anti-inflammatory, antioxidant, and anti-apoptotic effects. It may play a protective role in preventing liver damage induced by α-amanitin. To investigate the potential protective effects of cannabidiol on α-amanitin-induced hepatocyte apoptosis and oxidative stress, we established α-amanitin exposure models using C57BL/6J mice and L-02 cells in vitro. Our results showed that α-amanitin exposure led to oxidative stress, apoptosis, and DNA damage in both mouse hepatocytes and L-02 cells, resulting in the death of mice. We also found that cannabidiol upregulated the level of Nrf2 and antioxidant enzymes, alleviating apoptosis, and oxidative stress in mouse hepatocytes and L-02 cells and increasing the survival rate of mice. Our findings suggest that cannabidiol has hepatoprotective effects through the regulation of Nrf2 and antioxidant enzymes and may be a potential therapeutic drug for Amanita poisoning.

A label-free electrochemical immunosensor based on decorated cellulose nanofibrous membrane for point-of-care diagnosis of amanitin poisoning via human urine.

α-Amanitin (AMN) is one of the deadliest toxins from mushrooms, present in the deadly mushroom species Amanita phalloides. It is a bicyclic octapeptide and represents up to 40% of the amatoxins in mushrooms, damaging the liver and kidneys. Current methods of detecting amatoxins are time-consuming and require the use of expensive equipment. A novel label-free electrochemical immunosensor was successfully developed for rapid detection of α-amanitin, which was fabricated by immobilization of anti-α-amanitin antibodies onto a functionalized cellulose nanofibrous membrane-modified carbon screen-printed electrode. An oxidation peak of the captured amanitin on the tethered antibodies was observed at 0.45 V. The performance of the nanofibrous membrane on the electrode and necessary fabrication steps were investigated by electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV). Due to its unique structural features and properties such as high specific surface area and microporous structure, the nanofibrous membrane as an immunosensor matrix for antibody tethering improved the electrochemical performance of the immunosensor by more than 3 times compared with cast membranes. Under the optimal conditions, the assembled immunosensor exhibited high sensitivity toward α-amanitin detection in the range of 0.009-2 ng mL-1 with a limit of detection of 8.3 pg mL-1. The results clearly indicate that the fabricated nanofiber-based-immunosensor is suitable for point-of-care detection of lethal α-amanitin in human urine without any pretreatment within 30 min.

Identification of α-amanitin effector proteins in hepatocytes by limited proteolysis-coupled mass spectrometry.

The misuse of poisonous mushrooms containing amatoxins causes acute liver failure (ALF) in patients and is a cause of significant mortality. Although the toxic mechanisms of α-amanitin (α-AMA) and its interactions with RNA polymerase II (RNAP II) have been studied, α-AMA effector proteins that can interact with α-AMA in hepatocytes have not been systematically studied. Limited proteolysis-coupled mass spectrometry (LiP-MS) is an advanced technology that can quickly identify protein-ligand interactions based on global comparative proteomics. This study identified the α-AMA effector proteins found in human hepatocytes, following the detection of conformotypic peptides using LiP-MS coupled with tandem mass tag (TMT) technology. Proteins that are classified into protein processing in the endoplasmic reticulum and the ribosome during the KEGG pathway can be identified through affinity evaluation, according to α-AMA concentration-dependent LiP-MS and LiP-MS in hepatocytes derived from humans and mice, respectively. The possibility of interaction between α-AMA and proteins containing conformotypic peptides was evaluated through molecular docking studies. The results of this study suggest a novel path for α-AMA to induce hepatotoxicity through interactions with various proteins involved in protein synthesis, as well as with RNAP II.

α-amanitin induces autophagy through AMPK-mTOR-ULK1 signaling pathway in hepatocytes.

Amanitin poisoning is one of the most life-threatening mushroom poisonings. α-Amanitin plays a key role in Amanita phalloides intoxication. α-Amanitin shows toxic effects on the liver. However, the mechanism by which α-amanitin induces liver injury has not been elucidated. Autophagy plays a crucial role in maintaining cellular homeostasis and is closely related to the occurrence of a variety of diseases. Studies have shown that autophagy may play an important role in the process of α-amanitin-induced liver injury. However, the mechanism of α-amanitin-induced autophagy remains unclear. Thus, this study aimed to explore the mechanisms of α-amanitin in inducing hepatotoxicity in Sprague Dawley (SD) rats and the normal human liver cell line L02 cells. The SD rats and L02 cells exposed to α-amanitin were observed to determine whether α-amanitin could induce the autophagy of rat liver and L02 cells. The regulatory relationship between autophagy and the AMPK-mTOR-ULK pathway by exposing the autophagy agonist (rapamycin (RAPA)), autophagy inhibitor (3-methylademine (3-MA)), and AMPK inhibitor (compound C) was also explored. Autophagy-related proteins and AMPK-mTOR-ULK pathway-related proteins were detected using Western blot. The results of the study indicated that exposure to different concentrations of α-amanitin led to morphological changes in liver cells and significantly elevated levels of ALT and AST in the serum of SD rats. Additionally, the expression levels of LC3-II, Beclin-1, ATG5, ATG7, AMPK, p-AMPK, mTOR, p-mTOR, and ULK1 were significantly increased in the rat liver. And we found that L02 cells exposed to 0.5 µM α-amanitin for 6 h significantly induced autophagy and activated the AMPK-mTOR-ULK1 pathway. Pretreated with RAPA, 3-MA, and compound C for 1 h, the expression levels of autophagy-related proteins and AMPK-mTOR-ULK pathway-related proteins significantly changed. Our results indicates that autophagy and the AMPK-mTOR-ULK pathway are involved in the process of α-amanitin-induced liver injury. This study may foster the identification of actionable therapeutic targets for A. phalloides intoxication.

Dual-Warhead Conjugate Based on Fibroblast Growth Factor 2 Dimer Loaded with α-Amanitin and Monomethyl Auristatin E Exhibits Superior Cytotoxicity towards Cancer Cells Overproducing Fibroblast Growth Factor Receptor 1.

Targeting fibroblast growth factor receptor 1 (FGFR1) is a promising therapeutic strategy for various cancers associated with alterations in the FGFR1 gene. In this study, we developed a highly cytotoxic bioconjugate based on fibroblast growth factor 2 (FGF2), which is a natural ligand of this receptor, and two potent cytotoxic drugs-α-amanitin and monomethyl auristatin E-with completely independent mechanistic modes of action. Utilizing recombinant DNA technology, we produced an FGF2 N- to C-end dimer that exhibited superior internalization capacity in FGFR1-positive cells. The drugs were site-specifically attached to the targeting protein using SnoopLigase- and evolved sortase A-mediated ligations. The resulting dimeric dual-warhead conjugate selectively binds to the FGFR1 and utilizes receptor-mediated endocytosis to enter the cells. Moreover, our results demonstrate that the developed conjugate exhibits about 10-fold higher cytotoxic potency against FGFR1-positive cell lines than an equimolar mixture of single-warhead conjugates. The diversified mode of action of the dual-warhead conjugate may help to overcome the potential acquired resistance of FGFR1-overproducing cancer cells to single cytotoxic drugs.

Identification of indocyanine green as a STT3B inhibitor against mushroom α-amanitin cytotoxicity.

The "death cap", Amanita phalloides, is the world's most poisonous mushroom, responsible for 90% of mushroom-related fatalities. The most fatal component of the death cap is α-amanitin. Despite its lethal effect, the exact mechanisms of how α-amanitin poisons humans remain unclear, leading to no specific antidote available for treatment. Here we show that STT3B is required for α-amanitin toxicity and its inhibitor, indocyanine green (ICG), can be used as a specific antidote. By combining a genome-wide CRISPR screen with an in silico drug screening and in vivo functional validation, we discover that N-glycan biosynthesis pathway and its key component, STT3B, play a crucial role in α-amanitin toxicity and that ICG is a STT3B inhibitor. Furthermore, we demonstrate that ICG is effective in blocking the toxic effect of α-amanitin in cells, liver organoids, and male mice, resulting in an overall increase in animal survival. Together, by combining a genome-wide CRISPR screen for α-amanitin toxicity with an in silico drug screen and functional validation in vivo, our study highlights ICG as a STT3B inhibitor against the mushroom toxin.

Amatoxin poisoning caused by Galerina sulciceps, a species with no prior record of identification in Japan: a case report.

A 60-year-old man presented with acute gastroenteritis, hypovolemic shock, acute renal failure (BUN/Cr, 56.7/4.24 mg/dl), and aspiration pneumonia. The previous day, he ingested 30 caps of mushrooms of an unknown species. The patient was treated with a massive intravenous infusion, renal replacement therapy, and antimicrobial agents. Late-onset mild liver injury peaked on day 11 (AST/ALT, 62/67 IU/l). Acute renal failure improved once before worsening, with the worst symptoms on day 19 (BUN/Cr, 99/6.61 mg/dl). Thereafter, the patient showed gradual improvement, and renal replacement therapy was discontinued on day 23. His general condition improved fully and he was transferred to another hospital for rehabilitation on day 47. The mushrooms were later identified as Galerina sulciceps by the Basic Local Alignment Search Tool, and toxicologic analysis using liquid chromatography-tandem mass spectrometry revealed an average of 85 ppm α-amanitin and 330 ppm ß-amanitin in the tissue of the mushrooms brought in by the patient's family. Galerina sulciceps is distributed mainly in tropical and subtropical regions of Southeast Asia and had never been identified before in Japan. The heat of fermentation generated by the thick layer of wood chips on the ground or global warming may have contributed to its growth in Japan. Interestingly, our patient did not have liver dysfunction, which is one main and typical amatoxin poisoning symptom. Variation in clinical presentation may be attributed to the different ratios of α-amanitin to ß-amanitin in different mushroom species.

Determination of protein-bound α-amanitin in mouse plasma: A potential new indicator of poisoning with the mushroom toxin α-amanitin.

Approximately 70%∼90% of mushroom poisoning deaths are caused by the class of mushroom toxins known as amatoxins. However, the rapid elimination of amatoxins from plasma within 48 h after mushroom ingestion limits the practical value of plasma amatoxin analysis as a diagnostic indicator of Amanita mushroom poisoning. To increase the positive detection rate and extend the detection window of amatoxin poisoning, we developed a new method to detect protein-bound α-amanitin based on the hypothesis that RNAP II-bound α-amanitin released from the tissue into the plasma could be degraded by trypsin hydrolysis and then detected by conventional liquid chromatography-mass spectrometry (LC‒MS). Toxicokinetic studies on mice intraperitoneally injected with 0.33 mg/kg α-amanitin were conducted to obtain and compare the concentration trends, detection rates, and detection windows of both free α-amanitin and protein-bound α-amanitin. By comparing detection results with and without trypsin hydrolysis in the liver and plasma of α-amanitin-poisoned mice, we verified the credibility of this method and the existence of protein-bound α-amanitin in plasma. Under the optimized trypsin hydrolysis conditions, we obtained a time-dependent trend of protein-bound α-amanitin in mouse plasma at 1-12 days postexposure. In contrast to the short detection window (0-4 h) of free α-amanitin in mouse plasma, the detection window of protein-bound α-amanitin was extended to 10 days postexposure, with a total detection rate of 53.33%, ranging from the limit of detection to 23.94 µg/L. In conclusion, protein-bound α-amanitin had a higher positive detection rate and a longer detection window than free α-amanitin in mice.

[Determination of five amanita peptide toxins in poisonous mushrooms by ultra performance liquid chromatography-quadrupole electrostatic field orbitrap high resolution mass spectrometry].

Food poisoning by toxic mushrooms occurs frequently worldwide. It is one of the most common food poisoning events and the main cause of death. Amanita peptide toxins are the most common lethal toxins in poisonous mushrooms. Presently, a novel method based on ultra performance liquid chromatography-quadrupole electrostatic field orbitrap high resolution mass spectrometry (UPLC-Q/Orbitrap HRMS) was developed for the determination of five amanitapeptide toxins (α-amanitin, ß-amanitin, γ-amanitin, phalloidin, and phallacidin). Because the isotope summit of α-amanitin affects the detection of ß-amanitin, it cannot be distinguished by low resolution mass spectrometry. Therefore, experimental conditions including chromatography and mass spectrometry were explored in detail. The five peptide toxins were extracted from poisonous mushrooms with pure water and filtered through a 0.22 µm teflon microporous membrane. The procedure was rapid, simple, and environmentally friendly. Chromatographic separation was performed on a strong polarity HSS T3 column (100 mm×2.0 mm, 2.1 µm) with gradient elution using acetonitrile and 5 mmol/L ammonium acetate containing 0.1% (v/v) formic acid as mobile phases at a flow rate of 0.3 mL/min. The column temperature was set to 40 ℃. The analytes were ionized using a heating electrospray ionization source and collected in positive ion mode. Full scanning/data-dependent secondary mass spectrometry (Full mass-ddMS2) mode was used for qualitative analysis of the targets within 10 min. The target ion selective scan (Targeted-SIM) mode was used for quantification by external standard calibration. The measured and theoretical values of the exact mass and the MS2 fragment ions of the five compounds were within an error of 5×10-6. Method validation was performed according to the criteria recommended by the Chinese National Standard. All the compounds showed an excellent linear relationship in the range of 1.0-20.0 µg/L. The correlation coefficients (r) ranged from 0.9974 to 0.9989. The limit of detection was 0.006 mg/kg for all five compounds. Recoveries ranged from 81.8% to 102.4%. There was no matrix effect in the blank mushroom sample for the five compounds, and the relative standard deviations ranged from 3.2% to 8.3%. This method provides abundant compound characteristic mass information, such as retention time, exact mass, fragment ions, and other information. The data can be used to identify suspected compounds based on the extracted ion flow diagram and isotope distribution information. Comparison between the actual exact mass and the theoretical exact mass, combined with the fragment ions enables identification of the structures of unknown compounds and collision methods, which can be confirmed in the absence of standard materials. In this study, the isomer of γ-amanitin was identified as amaninamide. The novel method is simple, accurate, specific, and sensitive. The method permits the rapid qualitative and quantitative detection of compound in public health emergency settings and will provide reliable technical support for the rapid screening of such toxic compounds and the structural locking of unknown toxins in the future.

Mechanism and treatment of α-amanitin poisoning.

Amanita poisoning has a high mortality rate. The α-amanitin toxin in Amanita is the main lethal toxin. There is no specific detoxification drug for α-amanitin, and the clinical treatment mainly focuses on symptomatic and supportive therapy. The pathogenesis of α-amanitin mainly includes: α-amanitin can inhibit the activity of RNA polymeraseII in the nucleus, including the inhibition of the largest subunit of RNA polymeraseII, RNApb1, bridge helix, and trigger loop. In addition, α-amanitin acts in vivo through the enterohepatic circulation and transport system. α-Amanitin can cause the cell death. The existing mechanisms of cell damage mainly focus on apoptosis, oxidative stress, and autophagy. In addition to the pathogenic mechanism, α-amanitin also has a role in cancer treatment, which is the focus of current research. The mechanism of action of α-amanitin on the body is still being explored.

Rapid detection of α-amanitin and ß-amanitin in rat plasma by ultra-performance liquid chromatography-tandem mass spectrometry and its application to the toxicokinetic study of Lepiota brunneoincarnata.

PURPOSE: Lepiota brunneoincarnata is a well-known poisonous mushroom and is responsible for fatal mushroom poisoning cases worldwide. α-Amanitin and ß-amanitin are the main amatoxin compounds of Lepiota brunneoincarnata. However, there are no published toxicokinetic studies of Lepiota brunneoincarnata. To study the toxicokinetics of Lepiota brunneoincarnata, we developed an ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method for determination of α-amanitin and ß-amanitin in rat plasma. METHODS: UPLC-MS/MS analyses were performed with a triple quadrupole mass spectrometer in positive-ion mode. The sensitivity of α-amanitin and ß-amanitin detection was increased by inhibiting the production of [M + Na]+ adducts. α-Amanitin and ß-amanitin were separated and quantified on an UPLC octadecyl silyl column in only 2.5 min. RESULTS: The linear ranges were 3.0-3000 ng/mL for α-amanitin and 1.8-1800 ng/mL for ß-amanitin with a correlation coefficient r > 0.99 for both analytes. The lower limit of quantification of 3.0 ng/mL for α-amanitin and 1.8 ng/mL for ß-amanitin was achieved using only 50 µL of rat plasma. The accuracy of α-amanitin and ß-amanitin was between - 9.5 and 7.0% with the precision ranged from 2.2 to 12.5%. The developed method was then applied for Lepiota brunneoincarnata toxicokinetic study after intravenous administration of Lepiota brunneoincarnata extracts. CONCLUSIONS: Establishing UPLC-MS/MS method for quantifying amanitines in rat plasma successfully enabled toxicokinetic study of Lepiota brunneoincarnata extracts.

Investigation of In Vitro and In Vivo Metabolism of α-Amanitin in Rats Using Liquid Chromatography-Quadrupole Time-of-Flight Mass Spectrometric Method.

The purpose of this study is to investigate the difference of in vitro-in vivo correlation of α-amanitin from clearance perspectives as well as to explore the possibility of extra-hepatic metabolism of α-amanitin. First, a liquid chromatography-quadrupole-time-of-flight-mass spectrometric (LC-qTOF-MS) method for α-amanitin in rat plasma was developed and applied to evaluate the in vitro liver microsomal metabolic stability using rat and human liver microsomes and the pharmacokinetics of α-amanitin in rat. The predicted hepatic clearance of α-amanitin in rat liver microsomes was quite low (5.05 mL/min/kg), whereas its in vivo clearance in rat (14.0 mL/min/kg) was close to the borderline between low and moderate clearance. To find out the difference between in vitro and in vivo metabolism, in vitro and in vivo metabolite identification was also conducted. No significant metabolites were identified from the in vivo rat plasma and the major circulating entity in rat plasma was α-amanitin itself. No reactive metabolites such as GSH-adducts were detected either. A glucuronide metabolite was newly identified from the in vitro liver microsomes samples with a trace level. A semi-mass balance study was also conducted to understand the in vivo elimination pathway of α-amanitin and it showed that most α-amanitin was mainly eliminated in urine as intact which implies some unknown transporters in kidney might play a role in the elimination of α-amanitin in rat in vivo. Further studies with transporters in the kidney would be warranted to figure out the in vivo clearance mechanism of α-amanitin.