Metabolite profiling and identification of triptolide in rats

Antitumor mechanisms and future clinical applications of the natural product triptolide

Triptolide (TPL) is a compound sourced from Tripterygium wilfordii Hook. F., a traditional Chinese medicinal herb recognized for its impressive anti-inflammatory, anti-angiogenic, immunosuppressive, and antitumor qualities. Notwithstanding its favorable attributes, the precise mechanism through which TPL influences tumor cells remains enigmatic. Its toxicity and limited water solubility significantly impede the clinical application of TPL. We offer a comprehensive overview of recent research endeavors aimed at unraveling the antitumor mechanism of TPL in this review. Additionally, we briefly discuss current strategies to effectively manage the challenges associated with TPL in future clinical applications. By compiling this information, we aim to enhance the understanding of the underlying mechanisms involved in TPL and identify potential avenues for further advancement in antitumor therapy.

Metabolic Activation of the Toxic Natural Products From Herbal and Dietary Supplements Leading to Toxicities

Currently, herbal and dietary supplements have been widely applied to prevent and treat various diseases. However, the potential toxicities and adverse reactions of herbal and dietary supplements have been increasingly reported, and have gradually attracted widespread attention from clinical pharmacists and physicians. Metabolic activation of specific natural products from herbal and dietary supplements is mediated by hepatic cytochrome P450 or intestinal bacteria, and generates chemical reactive/toxic metabolites that bind to cellular reduced glutathione or macromolecules, and form reactive metabolites-glutathione/protein/DNA adducts, and these protein/DNA adducts can result in toxicities. The present review focuses on the relation between metabolic activation and toxicities of natural products, and provides updated, comprehensive and critical comment on the toxic mechanisms of reactive metabolites. The key inductive role of metabolic activation in toxicity is highlighted, and frequently toxic functional groups of toxic natural products were summarized. The biotransformation of drug cytochrome P450 or intestinal bacteria involved in metabolic activation were clarified, the reactive metabolites-protein adducts were selected as biomarkers for predicting toxicity. And finally, further perspectives between metabolic activation and toxicities of natural products from herbal and dietary supplements are discussed, to provide a reference for the reasonable and safe usage of herbal and dietary supplements.

Comprehensive Metabolomic Analysis Reveals Dynamic Metabolic Reprogramming in Hep3B Cells with Aflatoxin B1 Exposure

Hepatitis B virus (HBV) infection and aflatoxin B1 (AFB1) exposure have been recognized as independent risk factors for the occurrence and development of hepatocellular carcinoma (HCC), but their combined impacts and the potential metabolic mechanisms remain poorly characterized. Here, a comprehensive non-targeted metabolomic study was performed following AFB1 exposed to Hep3B cells at two different doses: 16 μM and 32 μM. The metabolites were identified and quantified by an ultra-performance liquid chromatography-mass spectrometry (UPLC-MS)-based strategy. A total of 2679 metabolites were identified, and 392 differential metabolites were quantified among three groups. Pathway analysis indicated that dynamic metabolic reprogramming was induced by AFB1 and various pathways changed significantly, including purine and pyrimidine metabolism, hexosamine pathway and sialylation, fatty acid synthesis and oxidation, glycerophospholipid metabolism, tricarboxylic acid (TCA) cycle, glycolysis, and amino acid metabolism. To the best of our knowledge, the alteration of purine and pyrimidine metabolism and decrease of hexosamine pathways and sialylation with AFB1 exposure have not been reported. The results indicated that our metabolomic strategy is powerful to investigate the metabolome change of any stimulates due to its high sensitivity, high resolution, rapid separation, and good metabolome coverage. Besides, these findings provide an overview of the metabolic mechanisms of the AFB1 combined with HBV and new insight into the toxicological mechanism of AFB1. Thus, targeting these metabolic pathways may be an approach to prevent carcinogen-induced cancer, and these findings may provide potential drug targets for therapeutic intervention.

What dominates the changeable pharmacokinetics of natural sesquiterpene lactones and diterpene lactones: a review focusing on absorption and metabolism

Sesquiterpene lactones (STLs) and diterpene lactones (DTLs) are two groups of common phytochemicals with similar structures. It's frequently reported that both exhibit changeable pharmacokinetics (PK) in vivo, especially the unstable absorption and extensive metabolism. However, the recognition of their PK characteristics is still scattered. In this review, representative STLs (atractylenolides, alantolactone, costunolide, artemisinin, etc.) and DTLs (ginkgolides, andrographolide, diosbulbins, triptolide, etc.) as typical cases are discussed in detail. We show how the differences of treatment regimens and subjects alter the PK of STLs and DTLs, with emphasis on the effects from absorption and metabolism. These compounds tend to be quite permeable in intestinal epithelium, but gastrointestinal pH and efflux transporters (represented by P-glycoprotein) have great impact and result in the unstable absorption. As the only characteristic functional moiety, the metabolic behavior of lactone ring is not dominant. The α, β-unsaturated lactone moiety has the strongest metabolic activity. While with the increase of low-activity saturated lactone moieties, the metabolism is led by other groups more easily. The phase I (oxidation, reduction and hydrolysis reaction) and II metabolism (conjugation reaction) are both extensive. CYP450s, mainly CYP3A4, are largely involved in biotransformation. However, only UGTs (UGT1A3, UGT1A4, UGT2B4 and UGT2B7) has been mentioned in studies about phase II metabolic enzymes. Our work offers a beneficial reference for promoting the safety evaluation and maximizing the utilization of STLs and DTLs.

Structure-Based Reactivity Profiles of Reactive Metabolites with Glutathione

Therapeutic agents can be transformed into reactive metabolites under the action of various metabolic enzymes in vivo and then covalently combine with biological macromolecules (such as protein or DNA), resulting in increasing toxicity. The screening of reactive metabolites in drug discovery and development stages and monitoring of biotransformation in post-market drugs has become an important research field. Generally, reactive metabolites are electrophilic and can be captured by small nucleophiles. Glutathione (GSH) is a small peptide composed of three amino acids (i.e., glutamic acid, cysteine, and glycine). It has a thiol group which can react with electrophilic groups of reactive metabolic intermediates (such as benzoquinone, N-acetyl-p-benzoquinoneimine, and Michael acceptor) to form a stable binding conjugate. This paper aims to provide a review on structure-based reactivity profiles of reactive metabolites with GSH. Furthermore, this review also reveals the relationship between drugs' molecular structures and reactive metabolic toxicity from the perspective of metabolism, giving a reference for drug design and development.

Transforming of Triptolide into Characteristic Metabolites by the Gut Microbiota

The importance of the gut microbiota in drug metabolism, especially in that of nonabsorbable drugs, has become known. The aim of this study was to explore the metabolites of triptolide by the gut microbiota. With high-performance liquid chromatography coupled with tandem mass spectrometry and ion trap time-of-flight multistage mass spectrometry (LC-MS/MS and LC/MSn-IT-TOF), four metabolites of triptolide (M1, M2, M3, and M4) were found in the intestinal contents of rats. M1 and M2, were isomeric monocarbonyl-hydroxyl-substituted metabolites with molecular weights of 390. M3 and M4 were isomeric dehydrogenated metabolites with molecular weights of 356. Among the four metabolites, the dehydrogenated metabolites (M3 and M4) were reported in the gut microbiota for the first time. The metabolic behaviors of triptolide in the gut microbiota and liver microsomes of rats were further compared. The monocarbonyl-hydroxyl-substituted metabolites (M1 and M2) were generated in both systems, and another monohydroxylated metabolite (M5) was found only in the liver microsomes. The combined results suggested that the metabolism of triptolide in the gut microbiota was specific, with two characteristic, dehydrogenated metabolites. This investigation might provide a theoretical basis for the elucidation of the metabolism mechanism of triptolide and guide its proper application in clinical administration.

Rapid identification of "mad honey" from Tripterygium wilfordii Hook. f. and Macleaya cordata (Willd) R. Br using UHPLC/Q-TOF-MS

Cases of honey poisoning have been reported widely, meaning there is a need for methods that detect "mad honey" or honey contaminated with plant-derived toxins to protect human health. In this study, we compared whole flower extracts and honey from Tripterygium wilfordii Hook. f. (TwHf) and Macleaya cordata (Willd) R. Br (McRB) using QuEChERS (quick, easy, cheap, effective, rugged, and safe) and ultra-high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (UHPLC/Q-TOF-MS). The results revealed several compounds common to whole flowers and honey samples. Triptolide and protopine were selected as potential markers for identifying "mad honeys" from these plants. The developed method can easily detect different honey varieties that were spiked with 5% TwHf and McRB honey samples. Additionally, 90 commercial honey samples were analyzed and determined as free from contamination. The method described in this report could be useful for studies on honey from other poisonous nectar and pollen plants.

Preclinical Pharmacokinetics of Triptolide: A Potential Antitumor Drug

Background:

Triptolide, a bioactive component in Tripterygium wilfordii extracts, possess strong antiproliferative activity on all 60-National Cancer Institute (NCI) cancer cell lines. However, the widespread use of triptolide in the clinical practice is greatly limited for its multi-organ toxicity and narrow therapeutic window. All the toxic characteristics of triptolide are associated with the pharmacokinetics especially its distribution and accumulation in the target organ.

Methods:

The literature review was done using PubMed search, SciFinder and Google Scholar databases with specific keywords such as triptolide, pharmacokinetics, drug-drug interaction, transporters, metabolism, modification to collect the related full-length articles and abstracts from 2000 to 2018.

Results:

Oral triptolide is rapidly and highly absorbed. Grapefruit juice affects oral absorption, increasing the area under the concentration-time curve (AUC) by 153 % and the maximum concentration (Cmax) by 141 %. The AUC and the Cmax are not dose proportional. Triptolide distributes into the liver, heart, spleen, lung and kidney. Biotransformation of triptolide in rats includes hydroxylation, sulfate, glucuronide, N-acetylcysteine (NAC) and Glutathione (GSH) conjugation and combinations of these pathways. Less than 4 % of triptolide was recovered from the feces, bile and urine within 24 h. After repeating dosage, triptolide was eliminated quickly without accumulation in vivo. As a substrate of P-glycoprotein (P-gp) and CYP3A4, triptolide could have clinically significant pharmacokinetic interactions with those proteins substrates/inhibitors.

Conclusion:

The findings of this review confirm the importance of pharmacokinetic character for understanding the pharmacology and toxicology of triptolide.

Identification of hepatotoxic and nephrotoxic potential markers of triptolide in mice with delayed-type hypersensitivity

Triptolide (TP) is the crucial active ingredient of Tripterygium glycoside tablets and has been shown to have a significant therapeutic effect on delayed-type hypersensitivity (DTH)-related diseases. However, due to its potential hepatotoxicity and nephrotoxicity, adverse reactions have often been observed in long-term treatment regimens. Therefore, it is meaningful to find metabolic markers for toxicity for early diagnosis. In this study, a feasible strategy using HPLC-HRMS method combined with multivariate statistical analysis to discover toxic potential markers of TP was developed. TP was used to treat a DTH mouse model at a therapeutic dose (45μg/kg) and toxic dose (900 μg/kg). The metabolic profiles of the liver, kidney and plasma were characterized by HPLC-Q/TOF MS. Significant differences in the metabolite profiles of the liver, kidney and plasma existed between the toxic and therapeutically dosed mice. Forty-six metabolites were identified and 27 of them may be related to toxicity based on a structure-toxicity prediction model. Using OPLS-DA analysis, the metabolite profiles between the two dose groups could be well distinguished. It was found that 18, 4 and 4 metabolic markers were altered in the liver, kidney and plasma, respectively; 15, 4 and 3 of these metabolic markers were predicted to be toxic. Two toxic markers detected both in mouse plasma and human liver microsomes following incubation with TP showed great potential as early diagnosis markers for TP hepatotoxicity and nephrotoxicity.

CYP3A4 inducer and inhibitor strongly affect the pharmacokinetics of triptolide and its derivative in rats

Triptolide is the most active ingredient of Tripterygium wilfordii Hook F, which is used to treat rheumatoid arthritis. (5R)-5-Hydroxytriptolide is a hydroxylation derivative of triptolide with a reduced toxicity. To investigate the metabolic enzymes of the two compounds and the drug-drug interactions with enzyme inducers or inhibitors, a series of in vitro and in vivo experiments were conducted. In vitro studies using recombinant human cytochrome P450 enzyme demonstrated that cytochrome P450 3A4 (CYP3A4) was predominant in the metabolism of triptolide and (5R)-5-hydroxytriptolide, accounting for 94.2% and 64.2% of the metabolism, respectively. Pharmacokinetics studies were conducted in male SD rats following administration of triptolide or (5R)-5-hydroxytriptolide (0.4 mg/kg, po). The plasma exposure to triptolide and (5R)-5-hydroxytriptolide in the rats was significantly increased when co-administered with the CYP3a inhibitor ritonavir (30 mg/kg, po) with the values of AUC_0-∞ (area under the plasma concentration-time curve from time zero extrapolated to infinity) being increased by 6.84 and 1.83 times, respectively. When pretreated with the CYP3a inducer dexamethasone (50 mg·kg^-1·d^-1, for 3 d), the AUC_0-∞ values of triptolide and (5R)-5-hydroxytriptolide were decreased by 85.4% and 91.4%, respectively. These results suggest that both triptolide and (5R)-5-hydroxytriptolide are sensitive substrates of CYP3a. Because of their narrow therapeutic windows, clinical drug-drug interaction studies should be carried out to ensure their clinical medication safety and efficacy.

NMR-based Metabolomic Techniques Identify the Toxicity of Emodin in HepG2 Cells

Emodin is a natural anthraquinone derivative that is present in various herbal preparations. The pharmacological effects of emodin include anticancer, hepatoprotective, anti-inflammatory, antioxidant and even antimicrobial activities. However, emodin also has been reported to induce hepatotoxicity, nephrotoxicity, genotoxicity and reproductive toxicity. The mechanism of emodin's adverse effects is complicated and currently not well understood. This study aimed to establish a cell metabonomic method to investigate the toxicity of emodin and explore its potential mechanism and relevant targets. In the present study, metabonomic profiles of cell extracts and cell culture media obtained using the ¹H NMR technique were used to assess emodin toxicity in HepG2 cells. Multivariate statistical analyses such as partial least squares-discriminant analysis (PLS-DA) and orthogonal partial least squares-discriminant analysis (OPLS-DA) were used to characterize the metabolites that differed between the control and emodin groups. The results indicated that emodin resulted in differences in 33 metabolites, including acetate, arginine, aspartate, creatine, isoleucine, leucine and histidine in the cell extract samples and 23 metabolites, including alanine, formate, glutamate, succinate and isoleucine, in the cell culture media samples. Approximately 8 pathways associated with these metabolites were disrupted in the emodin groups. These results demonstrated the potential for using cell metabonomics approaches to clarify the toxicological effects of emodin, the underlying mechanisms and potential biomarkers. Our findings may help with the development of novel strategies to discover targets for drug toxicity, elucidate the changes in regulatory signal networks and explore its potential mechanism of action.

Glycyrrhetinic Acid Accelerates the Clearance of Triptolide through P-gp In Vitro

Triptolide (TP) is an active ingredient isolated from Tripterygium wilfordii Hook. f. (TWHF), which is a traditional herbal medicine widely used for the treatment of rheumatoid arthritis and autoimmune disease in the clinic. However, its adverse reactions of hepatotoxicity and nephrotoxicity have been frequently reported which limited its clinical application. The aim of this study was to investigate the mechanism of glycyrrhetinic acid (GA) effecting on the elimination of TP in HK-2 cells and the role of the efflux transporters of P-gp and multidrug resistance-associated proteins (MRPs) in this process. An ultra performance liquid chromatography-electrospray ionization-mass spectrometry (UPLC-ESI-MS) analytical method was established to determine the intracellular concentration of TP. In order to study the role of efflux transporters of P-gp and MRPs in GA impacting on the accumulation of TP, the inhibitors of efflux transporters (P-gp: verapamil; MRPs: MK571) were used in this study. The results showed that GA could enhance the elimination of TP and reduce the TP accumulation in HK-2 cells. Verapamil and MK571 could increase the intracellular concentration of TP; in addition, GA co-incubation with verapamil significantly increased the TP cellular concentration compared with the control group. In conclusion, GA could reduce the accumulation of TP in HK-2 cells, which was related to P-gp. This is probably one of the mechanisms that TP combined with GA to detoxify its toxicity. Copyright © 2017 John Wiley & Sons, Ltd.

Absorption and Metabolism Characteristics of Triptolide as Determined by a Sensitive and Reliable LC-MS/MS Method

In this research, a sensitive and reliable LC-MS/MS method was developed and applied to determine the concentration of triptolide in rat plasma, microsomes, and cell incubation media. The absolute oral bioavailability of triptolide is 63.9% at a dose of 1 mg·kg⁻¹. In vitro, the bidirectional transport of triptolide across Caco-2 cells was studied. A markedly higher transport of triptolide across Caco-2 cells was observed in the basolateral-to-apical direction and was abrogated in the presence of the P-gp inhibitor, verapamil. The result indicated that P-gp might be involved in the absorption of triptolide in intestinal. The metabolic stability was also investigated using human liver microsome incubation systems in vitro. In HLMs, incubations with an initial triptolide concentration of 1 μM resulted in an 82.4% loss of substrate over 60 min, and the t_1/2 was 38 min, which indicated that triptolide was easily metabolized in human liver microsomes. In conclusion, the absolute oral bioavailability of triptolide in plasma, transport across Caco-2 cell monolayers, and metabolic stability in human liver microsomes were systematically investigated by using a sensitive and reliable LC-MS/MS method.

Structural identification of neopanaxadiol metabolites in rats by ultraperformance liquid chromatography/quadrupole-time-of-flight mass spectrometry

RATIONALE

Neopanaxadiol (NPD) is one of the major ginsenosides in Panax ginseng C. A. Meyer (Araliaceae) that has been suggested to be a drug candidate against Alzheimer's disease. However, few data are available regarding its metabolism in rats.

METHODS

In this study, a method of ultraperformance liquid chromatography/quadrupole-time-of-flight mass spectrometry (UPLC/QTOFMS) was developed to identify major metabolites of NPD in the stomach, intestine, urine and feces of rats, with the aim of determining the main metabolic pathways of NPD in rats after oral administration.

RESULTS

UPLC/QTOFMS revealed two metabolites in the stomach of rats, one metabolite in the intestine and two metabolites in feces. One metabolite, named M2, was isolated and purified from rats feces, which was identified as (20S,22S)-dammar-22,25-epoxy-3β,12β,20-triol based on extensive NMR spectroscopy and mass spectrometry data. The main metabolites of NPD in rats were the products of epoxidation, dehydrogenation and hydroxylation. NPD was predominantly metabolized by 20,22-double-bond epoxidation and rearrangement to yield an expoxidation product (M2).

CONCLUSIONS

Based on the profiles of the metabolites, possible metabolic pathways of NPD in rats were proposed for the first time. This study provides new and available information on the metabolism of NPD, which is indispensable for further research on metabolic pathways of dammarane ginsengenins in vivo.

Excretion of [3H]triptolide and its metabolites in rats after oral administration

AIM

To investigate the routes of elimination and excretion for triptolide recovered in rats.

METHODS

After a single oral administration of [(3)H]triptolide (0.8 mg/kg, 100 μCi/kg) in Sprague Dawley rats, urine and fecal samples were collected for 168 h. To study biliary excretion, bile samples were collected for 24 h through bile duct cannulation. Radioactivity was measured using a liquid scintillation analyzer, and excretion pathway analysis was performed using an HPLC/on-line radioactivity detector.

RESULTS

The total radioactivity recovered from the urine and feces of rats without bile duct ligation ranged from 86.6%-89.1%. Most of the radioactivity (68.6%-72.0%) was recovered in the feces within 72 h after oral administration, while the radioactivity recovered in the urine and bile was 17.1%-18.0% and 39.0%-39.4%, respectively. The HPLC/on-line radiochromatographic analysis revealed that most of the drug-related radioactivity was in the form of metabolites. In addition, significant gender differences in the quantity of these metabolites were found: monohydroxytriptolide sulfates were the major metabolites detected in the urine, feces, and bile of female rats, while only traces of these metabolites were found in male rats.

CONCLUSION

Radiolabeled triptolide is mainly secreted in bile and eliminated in feces. The absorbed radioactivity is primarily eliminated in the form of metabolites, and significant gender differences are observed in the quantity of recovered metabolites, which are likely caused by the gender-specific expression of sulfotransferases.