Comparative metabolism of four limonoids in human liver microsomes using ultra-high-performance liquid chromatography coupled with high-resolution LTQ-Orbitrap mass spectrometry

Obacunone, a Promising Phytochemical Triterpenoid: Research Progress on Its Pharmacological Activity and Mechanism

Obacunone, a natural triterpenoid, is an active component of the herbs Dictamnus dasycarpus Turcz. and Phellodendron amurense Rupr, and an indicator of the herbs' quality. Owing to its multiple health benefits, several studies have investigated the multi-targeting potential action mechanisms of obacunone. To summarize recent developments on the pharmacological actions of obacunone and focus on the underlying molecular mechanisms and signaling networks, we searched PubMed, Europe PMC, Wiley Online Library, Web of Science, Google Scholar, Wanfang Medical Network, and China National Knowledge Infrastructure for articles published prior to March 2024. Existing research indicates obacunone has great potential to become a promising therapeutic option against tumors, fibrotic diseases, bone and cholesterol metabolism diseases, and infections of pathogenic microorganisms, among others. The paper contributes to providing up-to-date references for further research and clinical applications of obacunone.

Traditional Uses, Chemical Constituents and Pharmacological Activities of the Toona sinensis Plant

Toona sinensis (A. Juss.) Roem., which is widely distributed in China, is a homologous plant resource of medicine and food. The leaves, seeds, barks, buds and pericarps of T. sinensis can be used as medicine with traditional efficacy. Due to its extensive use in traditional medicine in the ancient world, the T. sinensis plant has significant development potential. In this review, 206 compounds, including triterpenoids (1-133), sesquiterpenoids (134-135), diterpenoids (136-142), sterols (143-147), phenols (148-167), flavonoids (168-186), phenylpropanoids (187-192) and others (193-206), are isolated from the T. sinensis plant. The mass spectrum cracking laws of representative compounds (64, 128, 129, 154-156, 175, 177, 179 and 183) are reviewed, which are conducive to the discovery of novel active substances. Modern pharmacological studies have shown that T. sinensis extracts and their compounds have antidiabetic, antidiabetic nephropathy, antioxidant, anti-inflammatory, antitumor, hepatoprotective, antiviral, antibacterial, immunopotentiation and other biological activities. The traditional uses, chemical constituents, compound cracking laws and pharmacological activities of different parts of T. sinensis are reviewed, laying the foundation for improving the development and utilization of its medicinal value.

Molecular mechanisms of hepatotoxicity induced by compounds occurring in Evodiae Fructus

Evodiae Fructus (EF) is a common herbal medicine with thousands of years of medicinal history in China, which has been demonstrated with many promising pharmacological effects on cancer, cardiovascular diseases and Alzheimer's disease. However, there have been increasing reports of hepatotoxicity associated with EF consumption. Unfortunately, in a long term, many implicit constituents of EF as well as their toxic mechanisms remain poorly understood. Recently, metabolic activation of hepatotoxic compounds of EF to generate reactive metabolites (RMs) has been implicated. Herein, we capture metabolic reactions relevant to hepatotoxicity of these compounds. Initially, catalyzed by the hepatic cytochrome P450 enzymes (CYP450s), the hepatotoxic compounds of EF are oxidized to generate RMs. Subsequently, the highly electrophilic RMs could react with nucleophilic groups contained in biomolecules, such as hepatic proteins, enzymes, and nucleic acids to form conjugates and/or adducts, leading to a sequence of toxicological consequences. In addition, currently proposed biological pathogenesis, including oxidative stress, mitochondrial damage and dysfunction, endoplasmic reticulum (ER) stress, hepatic metabolism disorder, and cell apoptosis are represented. In short, this review updates the knowledge on the pathways of metabolic activation of seven hepatotoxic compounds of EF and provides considerable insights into the relevance of proposed molecular hepatotoxicity mechanisms from a biochemical standpoint, for the purpose of providing a theoretical guideline for the rational application of EF in clinics.

Rapid identification, isolation, and evaluation on anti-neuroinflammatory activity of limonoids derivatives from the root bark of Dictamnus dasycarpus

A total of 49 limonoids derivatives were rapidly identified by UNIFI software and three new limonoids derivatives, named dasycarinone (1, DAS), isodictamdiol C (2) and dasycarinone A (3), along with nineteen known compounds, were isolated from the root bark of Dictamnus dasycarpus, named as "Baixianpi" in Chinese. Their structures were elucidated on the basis of spectroscopic data (UV, IR, HR-ESI-MS, NMR, CD spectra and OR). All the compounds were tested for anti-inflammatory activities by suppressing the nitric oxide (NO) production in lipopolysaccharide (LPS) induced BV-2 cells. DAS exhibited a strong anti-inflammatory activity with IC₅₀ value of 1.8 μM. Nuclear Factor kappa B (NF-κB) luciferase assay and enzyme-linked immune sorbent assay indicated that DAS can suppress the release of inflammatory cytokines such as Tumor Necrosis Factor α (TNF-α), interleukin 6 (IL-6) via inactivating NF-κB signaling pathways. Moreover, we found that anti-inflammatory activities of obacunone-class are better than those of limonin-class by analyzing structure-activity relationship. Our results suggested that obacunone derivatives play an important role on anti-inflammation of Baixianpi. As a representative among them, DAS showed a strong anti-inflammatory activity via suppressing NF-κB signaling pathways.

Krishnolides E-K: New limonoids from the Krishna mangrove Xylocarpus moluccensis

Seven new limonoids, named krishnolides E-K (1-7), including three khayanolides, two mexicanolides, a derivative of trangmolin A, and an andirobin, were isolated from seeds of the Indian Krishna mangrove, Xylocarpus moluccensis. The structures of these limonoids were established by HRESIMS, extensive NMR investigations, and X-ray crystallography. Most notably, the absolute configurations of 1, 5, 6, and 7 were unequivocally determined by single-crystal X-ray diffraction analyses (Cu Kα). Krishnolide F (2) exhibited significant agonistic effects on human pregnane-X-receptor (hPXR) at the concentration of 10.0 μM. Molecular docking revealed that 2 could bind a helix near the region of the Helix 12 of hPXR. Polar contribution could be electrostatic effects from the formation of two stable protein-ligand hydrogen bonds between Gln285/1-OH and His407/1-OH, respectively. This is the first report of agonistic effects of a khayanolide-type limonoid on hPXR.

Traditional uses, phytochemistry, pharmacology, pharmacokinetics and toxicology of the fruit of Tetradium ruticarpum: A review

ETHNOPHARMACOLOGICAL RELEVANCE

The fruit of Tetradium ruticarpum (FTR) known as Tetradii fructus or Evodiae fructus (Wu-Zhu-Yu in Chinese) is a versatile herbal medicine which has been prescribed in Chinese herbal formulas and recognized in Japanese Kampo. FTR has been clinically used to treat various diseases such as headache, vomit, diarrhea, abdominal pain, dysmenorrhea and pelvic inflammation for thousands of years.

AIM OF THE REVIEW

The present paper aimed to provide comprehensive information on the ethnopharmacology, phytochemistry, pharmacology, pharmacokinetics, drug interaction and toxicology of FTR in order to build up a foundation on the mechanism of ethnopharmacological uses as well as to explore the trends and perspectives for further studies.

MATERIALS AND METHODS

This review collected the literatures published prior to July 2020 on the phytochemistry, pharmacology, pharmacokinetics and toxicity of FTR. All relevant information on FTR was gathered from worldwide accepted scientific search engines and databases, including Web of Science, PubMed, Elsevier, ACS, ResearchGate, Google Scholar, and Chinese National Knowledge Infrastructure (CNKI). Information was also obtained from local books, PhD. and MSc. Dissertations as well as from Pharmacopeias.

RESULTS

FTR has been used as an herbal medicine for centuries in East Asia. A total of 165 chemical compounds have been isolated so far and the main chemical compounds of FTR include alkaloids, terpenoids, flavonoids, phenolic acids, steroids, and phenylpropanoids. Crude extracts, processed products (medicinal slices) and pure components of FTR exhibit a wide range of pharmacological activities such as antitumor, anti-inflammatory, antibacterial, anti-obesity, antioxidant, insecticide, regulating central nervous system (CNS) homeostasis, cardiovascular protection. Furthermore, bioactive components isolated from FTR can induce drug interaction and hepatic injury.

CONCLUSIONS

Therapeutic potential of FTR has been demonstrated with the pharmacological effects on cancer, inflammation, cardiovascular diseases, CNS, bacterial infection and obesity. Pharmacological and pharmacokinetic studies of FTR mostly focus on its main active alkaloids. Further in-depth studies on combined medication and processing approaches mechanisms, pharmacological and toxic effects not limited to the alkaloids, and toxic components of FTR should be designed.

Limonin: A Review of Its Pharmacology, Toxicity, and Pharmacokinetics

Limonin is a natural tetracyclic triterpenoid compound, which widely exists in Euodia rutaecarpa (Juss.) Benth., Phellodendron chinense Schneid., and Coptis chinensis Franch. Its extensive pharmacological effects have attracted considerable attention in recent years. However, there is no systematic review focusing on the pharmacology, toxicity, and pharmacokinetics of limonin. Therefore, this review aimed to provide the latest information on the pharmacology, toxicity, and pharmacokinetics of limonin, exploring the therapeutic potential of this compound and looking for ways to improve efficacy and bioavailability. Limonin has a wide spectrum of pharmacological effects, including anti-cancer, anti-inflammatory and analgesic, anti-bacterial and anti-virus, anti-oxidation, liver protection properties. However, limonin has also been shown to lead to hepatotoxicity, renal toxicity, and genetic damage. Moreover, limonin also has complex impacts on hepatic metabolic enzyme. Pharmacokinetic studies have demonstrated that limonin has poor bioavailability, and the reduction, hydrolysis, and methylation are the main metabolic pathways of limonin. We also found that the position and group of the substituents of limonin are key in affecting pharmacological activity and bioavailability. However, some issues still exist, such as the mechanism of antioxidant activity of limonin not being clear. In addition, there are few studies on the toxicity mechanism of limonin, and the effects of limonin concentration on pharmacological effects and toxicity are not clear, and no researchers have reported any ways in which to reduce the toxicity of limonin. Therefore, future research directions include the mechanism of antioxidant activity of limonin, how the concentration of limonin affects pharmacological effects and toxicity, finding ways to reduce the toxicity of limonin, and structural modification of limonin—one of the key methods necessary to enhance pharmacological activity and bioavailability.

Enantioselective metabolism of four chiral triazole fungicides in rat liver microsomes

Triazole fungicides with one or two chiral centers are widely used worldwide. The liver microsomes plays a major role in the metabolism and systemic elimination of chiral pesticides after exposure. In this present work, enantioselective metabolism of four representative chiral triazole fungicides (prothioconazole, flutriafol, triticonazole, and epoxiconazole) in rat liver microsomes (RLM) was investigated using LC-MS/MS. Baseline separation of the four chiral fungicides and prothioconazole-desthio was achieved on Lux-cellulose-1. The results demonstrated that the R-enantiomers of flutriafol and triticonazole were preferentially metabolized with half-life ranged from 17.33 min to 99.00 min. The R,S-epoxiconazole accumulated with a half-life of 173.25 min. There was no stereoselectivity for prothioconazole. However, remarkable stereoselective metabolism was observed for prothioconazole-desthio. The results of enzyme kinetic revealed different affinities between the enantiomers and metabolic enzymes. In addition, homologous modeling and molecular docking results indicated that enantioselectivity were partially to enantiospecific binding affinities with CYP enzymes. This study highlights a new quantitative approach for stereoselective metabolism of chiral agrochemicals and provides more accurate data on risk assessment of triazole fungicides.

Variation in limonin and nomilin content in citrus fruits of eight varieties determined by modified HPLC

The nomilin and limonin content in citrus fruits of different varieties was determined at fruit growth and maturation stages by HPLC. The results showed that the two limonoids can be separated, identified, and quantified in citrus fruits within 10 min by the developed method. The method exhibited good precision, repeatability, stability, and recovery rate. The content of limonin and nomilin in most citrus fruits presented an increasing trend initially, and then decreased during fruit growth and maturation; a peak was observed at the young fruit or fruit expansion stage. The dropped fruits also contained some amount of limonoids, suggesting their industrial application. The variation and cluster analyses results revealed that the orange varieties contained the highest amount of limonoids at the mature stage. The results of this study will enable better use of citrus limonoids.

Biotransformation and Metabolic Profile of Limonin in Rat Liver Microsomes, Bile, and Urine by High-Performance Liquid Chromatography Coupled with Quadrupole Time-of-Flight Mass Spectrometry

Limonin is a triterpenoid in citrus seeds, which has significant biological activities. However, the metabolic profile of limonin has not been fully understood. To expound its metabolism in vivo and in vitro, the metabolites of limonin was studied by rat liver microsomes, urine, and bile. High-performance liquid chromatography/quadrupole time-of-flight mass spectrometry was used for identification. Among the metabolites, the structures of M1 and M3 were confirmed by chemical synthesis and nuclear magnetic resonance spectra analysis. Our results indicated that reduction and hydrolysis were the two major pathways during limonin metabolism in vivo and in vitro. The results from this work are valuable and important for understanding the metabolic process of limonin.

Pharmacokinetics and Pharmacodynamics of Promising Arginase Inhibitors

Up-regulation of arginase activity in several chronic disease conditions, including cancer and hypertension, may suggest new targets for treatment. Recently, the number of new arginase inhibitors with promising therapeutic effects for asthma, cancer, hypertension, diabetes mellitus, and erectile dysfunction has shown a remarkable increase. Arginase inhibitors may be chemical substances, such as boron-based amino acid derivatives, α-difluoromethylornithine (DMFO), and Nω-hydroxy-nor-L-arginine (nor-NOHA) or, of plant origin such as sauchinone, salvianolic acid B (SAB), piceatannol-3-O-β-D-glucopyranoside (PG) and obacunone. Despite their promising therapeutic potential, little is known about pharmacokinetics and pharmacodynamics of some of these agents. Several studies were conducted in different animal species and in vitro systems and reported significant differences in pharmacokinetics and pharmacodynamics of arginase inhibitors. Therefore, extra caution should be considered before extrapolating these studies to human. Physicochemical and pharmacokinetic profiles of some effective arginase inhibitors make it challenging to formulate stable and effective formulation. In this article, existing literature on the pharmacokinetics and pharmacodynamics of arginase inhibitors were reviewed and compared together with emphasis on possible drug interactions and solutions to overcome pharmacokinetics challenges and shortage of arginase inhibitors in clinical practice.

Metabolic profile of Rhizoma coptidis in human plasma determined using ultra-high-performance liquid chromatography coupled with high-resolution mass spectrometry

RATIONALE

Rhizoma coptidis extract and its alkaloids show various pharmacological activities, but its metabolic profile in human plasma has not been thoroughly investigated. In the present research, the metabolism of Rhizoma coptidis at a clinical dose (5 g/60 kg/day) was systematically analyzed to determine its biotransformation processes in human plasma.

METHODS

In this research, the metabolites of Rhizoma coptidis in human plasma after oral administration of Rhizoma coptidis extract at a clinical dose were investigated using ultra-high-performance liquid chromatography (UHPLC) coupled with high-resolution LTQ-Orbitrap mass spectrometry. The structural elucidation of the constituents was confirmed by comparing their retention times (t_R ) and MSⁿ fragments with those of standards and literature reports.

RESULTS

In total, two prototypes and twelve metabolites were detected in human plasma. The two prototypes were confidently identified using reference standards. Of the compounds detected, M7 (berberrubinen-9-O-glucuronide) was the most abundant based on its peak area, which indicates that this compound might be a pharmacokinetic marker for Rhizoma coptidis alkaloids in humans. Based on the metabolites detected in human plasma, a possible metabolic pathway for Rhizoma coptidis in vivo was proposed.

CONCLUSIONS

The results indicated that the alkaloids in Rhizoma coptidis were extensively biotransformed in vivo mainly via conjugation with glucuronic acid (GluA) or sulfuric acid (SulA) to form phase II metabolites, and the GluA metabolites are likely the dominant form in human plasma. To the best of our knowledge, this is the first in vivo evaluation of the metabolic profile of the whole Rhizoma coptidis extract in human plasma, which is essential for determining the chemicals responsible for the pharmacological activities of Rhizoma coptidis in vivo. Moreover, it would be beneficial for us to further systematically study the pharmacokinetic behavior of Rhizoma coptidis in humans.

Metabolic profiling of five flavonoids from Dragon's Blood in human liver microsomes using high-performance liquid chromatography coupled with high resolution mass spectrometry

Although much is known about the pharmacological activities of Dragon's Blood (DB, a traditional Chinese herb), its metabolism in human liver microsomes (HLMs) and the cytochrome P450 (CYP) enzymes has not been studied. This study aims to identify the metabolic profile of five flavonoids (loureirin A, loureirin B, loureirin C, 7,4'-dihydroxyflavone and 5,7,4'-trihydroxyflavanone) from DB in HLMs as well as the CYP enzymes that are involved in the metabolism of them. High-resolution mass spectrometry was used to characterize the structures of their metabolites and 10 cDNA-expressed CYP enzymes (CYP1A2, CYP2A6, CYP2B6, CYP2C8, CYP2C9, CYP2C19, CYP2D6, CYP2E1, CYP3A4 and CYP3A5) were used to verify which isozymes mediate in the metabolism of the metabolites. Totally, 29 metabolites including 10 metabolites of loureirin A, 10 metabolites of loureirin B, 4 metabolites of loureirin C, 2 metabolites of 7,4'-dihydroxyflavone and 3 metabolites of 5,7,4'-trihydroxyflavanone were elucidated and identified on the basis of the high-resolution MSⁿ data. The metabolic profile of the five flavonoids in HLMs involved hydroxylation, oxidation and demethylation. Among them, hydroxylation was the predominant biotransformation of the five flavonoids in HLMs, occurring in combination with other metabolic reactions. Assay with recombinant P450s revealed that CYP2C9 and CYP2C19 played an important role in the hydroxylation of flavonoids in HLMs. To the best of our knowledge, this is the first in vitro evaluation of the metabolic profile of loureirin A, loureirin B, loureirin C, 7,4'-dihydroxyflavone and 5,7,4'-trihydroxyflavanone in HLMs.

The Chemistry and Pharmacology of Citrus Limonoids

Citrus limonoids (CLs) are a group of highly oxygenated terpenoid secondary metabolites found mostly in the seeds, fruits and peel tissues of citrus fruits such as lemons, limes, oranges, pumellos, grapefruits, bergamots, and mandarins. Represented by limonin, the aglycones and glycosides of CLs have shown to display numerous pharmacological activities including anticancer, antimicrobial, antioxidant, antidiabetic and insecticidal among others. In this review, the chemistry and pharmacology of CLs are systematically scrutinised through the use of medicinal chemistry tools and structure-activity relationship approach. Synthetic derivatives and other structurally-related limonoids from other sources are include in the analysis. With the focus on literature in the past decade, the chemical classification of CLs, their physico-chemical properties as drugs, their biosynthesis and enzymatic modifications, possible ways of enhancing their biological activities through structural modifications, their ligand efficiency metrics and systematic graphical radar plot analysis to assess their developability as drugs are among those discussed in detail.

Stereoselective Metabolism of α-, β-, and γ-Hexabromocyclododecanes (HBCDs) by Human Liver Microsomes and CYP3A4

This is the first study investigating the in vitro metabolism of α-, β-, and γ-hexabromocyclododecane (HBCD) stereoisomers in humans and providing semiquantitative metabolism data. Human liver microsomes were incubated with individual racemic mixtures and with individual stereoisomers of α-, β-, and γ-HBCDs, the hydroxylated metabolites formed were analyzed by liquid chromatography-tandem mass spectrometry, and the value of the intrinsic in vitro clearance (Clint,vitro) was calculated. Several mono- and dihydroxylated metabolites of α-, β-, and γ-HBCDs were formed, with mono-OH-HBCDs being the major metabolites. No stereoisomerization of any of the six α-, β-, and γ-HBCD isomers catalyzed by cytochrome P450 (CYP) enzymes occurred. The value of Clint,vitro of α-HBCDs was significantly lower than that of β-HBCDs, which, in turn, was significantly lower than that of γ-HBCDs (p < 0.05). Such differences were explained by the significantly lower values of Clint,vitro of each α-HBCD stereoisomer than those of the β- and γ-HBCD stereoisomers. In addition, significantly lower values of Clint,vitro of the (-) over the (+)α- and β-HBCD stereoisomers, but not γ-HBCDs, were obtained. Our data offer a possible explanation of the enrichment of α-HBCDs over β- and γ-HBCDs on the one hand and, on the other hand, of (-)α-HBCDs over (+)α-HBCDs previously reported in human samples. It also offers information about the mechanism resulting in such enrichments, the stereoisomer-selective metabolism of α-, β-, and γ-HBCDs catalyzed by CYPs with the lack of stereoisomerization.

An Approach to Characterizing the Complicated Sequential Metabolism of Salidroside in Rats

Metabolic study of bioactive compounds that undergo a dynamic and sequential process of metabolism is still a great challenge. Salidroside, one of the most active ingredients of Rhodiola crenulata, can be metabolized in different sites before being absorbed into the systemic blood stream. This study proposed an approach for describing the sequential biotransformation process of salidroside based on comparative analysis. In vitro incubation, in situ closed-loop and in vivo blood sampling were used to determine the relative contribution of each site to the total metabolism of salidroside. The results showed that salidroside was stable in digestive juice, and it was metabolized primarily by the liver and the intestinal flora and to a lesser extent by the gut wall. The sequential metabolism method described in this study could be a general approach to characterizing the metabolic routes in the digestive system for natural products.