Structural elucidation of koumine metabolites by accurate mass measurements using high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry

Koumine inhibits RANKL-induced ubiquitination and NF-κB activation to prevent ovariectomy and aging-induced bone loss

Osteoporosis (OP) is a bone remodeling disease characterized by an imbalance between bone resorption and formation. Osteoclasts are the primary therapeutic targets for treating bone destruction. Koumine (KM), the most bioactive component in Gelsemium alkaloids, exhibits antitumor, immunosuppressive, anti-inflammatory, and analgesic properties. However, the effects of bone loss have not been well studied. This study conducted in vitro and in vivo verification experiments on KM. The results showed that KM inhibited bone resorption and tartrate-resistant acid phosphatase positive (TRAP+) osteoclasts development by mature osteoclasts in a dose-dependent manner. Moreover, KM prevented OVX-induced OP in vivo and potentially inhibited ubiquitination, a process closely related to various biological activities, including protein interaction, transcription, and transmembrane signal transduction regulation, especially within the nuclear factor-κB (NF-κB) pathway. Previous studies have demonstrated that several proteins ubiquitination promotes osteoclastogenesis, our study indicated that KM inhibits early NF-κB activation and receptor activator of NF-κB ligand induced ubiquitination, a critical factor in osteoclast differentiation. In conclusion, our research suggests that KM holds potential as an effective therapeutic agent for OP.

Toxic Effects of Koumine on the Early-Life Development Stage of Zebrafish

Koumine is one of the most abundant alkaloids found in Gelsemium elegans, and it has a wide range of pharmacological effects including antitumor, anti-inflammatory, analgesic treatment effects, and antianxiety. However, its high toxicity and unclear mechanism of action have greatly limited the medicinal development and use of koumine. We investigated the toxic effects of koumine on the developmental toxicity and behavioral neurotoxicity of zebrafish embryos and larvae. Embryos at 6 h postfertilization (hpf) were exposed to 12.5, 25, 50, 75, and 100 mg/L of koumine until 120 hpf. Koumine affected the hatching and heartbeats of the embryos. The morphological analysis also revealed many abnormalities, such as shortened bodies, yolk sac edemas, tail malformations, and pericardial edemas. To identify the neurotoxicity of koumine, the behavior of the larvae was measured. Koumine at 50 and 100 mg/L affect the escape response. The embryos exhibited uncoordinated muscle contractions along the body axis in response to touch at 36 hpf. More importantly, we found that the neurotoxicity of koumine is mainly caused by influencing the ACh content and the activity of AChE without impairing motor neuron development. A comprehensive analysis shows that a high concentration of koumine has obvious toxic effects on zebrafish, and the safe concentration of koumine for zebrafish should be less than 25 mg/L. These results will be valuable for better understanding the toxicity of koumine and provide new insights into the application of koumine.

A high-resolution mass spectrometric approach to a qualitative and quantitative comparative metabolism of the humantenine-type alkaloid rankinidine

RATIONALE

Rankinidine belongs to the humantenine-type alkaloids isolated from Gelsemium. Currently, the mechanism behind the toxicity differences of rankinidine has not been explained. In this study, our purpose was to elucidate the major in vitro metabolic pathways of rankinidine and to compare the formation of metabolites of rankinidine in human (HLMs), rat (RLMs), goat (GLMs) and pig (PLMs) liver microsomes.

METHODS

This is the first study to compare the in vitro metabolism of rankinidine with high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry (LC/QTOF). The MS/MS data and LC/MS peak area acquired in positive ion mode were used to analyze metabolite structures and compare metabolism.

RESULTS

We identified 11 metabolites (M1-M11) in total and found five main metabolic pathways, consisting of demethylation (M1), reduction (M2), oxidation at different positions (M3-M5), oxidation and reduction (M6-M10) and demethylation and oxidation (M11). The metabolism of rankinidine has qualitative and quantitative species-specific differences in vitro. In PLMs and GLMs, the main metabolic pathway of rankinidine was oxidation. Notably, among the four species, the oxidation ability of rankinidine was highest in pigs and goats, and the demethylation and reduction abilities of rankinidine were highest in humans and rats.

CONCLUSIONS

The interspecific metabolic differences of rankinidine in HLMs, PLMs, GLMs and RLMs were compared and studied for the first time using LC/QTOF. These findings will certainly support future studies of rankinidine metabolism in vivo and will contribute to elucidating the cause of species-specific differences behind Gelsemium toxicity.

Gelsemium elegans Benth: Chemical Components, Pharmacological Effects, and Toxicity Mechanisms

Gelsemium elegans Benth (GEB), also known as heartbreak grass, is a highly poisonous plant belonging to the family Loganiaceae and genus Gelsemium that has broad application prospects in medicine. This article reviews its chemical components, pharmacological effects, toxicity mechanisms, and research progress in clinical applications in recent years. Indole alkaloids are the main active components of GEB and have a variety of pharmacological and biological functions. They have anti-tumor, anti-inflammatory, analgesic, and immunomodulation properties, with the therapeutic dose being close to the toxic dose. Application of small-dose indole alkaloids fails to work effectively, while high-dose usage is prone to poisoning, aggravating the patient’s conditions. Special caution is needed, especially to observe the changes in the disease condition of the patients in clinical practice. In-depth research on the chemical components and mechanisms of GEB is essential to the development of promising lead compounds and lays the foundation for extensive clinical application and safe usage of GEB in the future.

Metabolic profile and tissue distribution of Humantenirine, an oxindole alkaloid from Gelsemium, after oral administration in rats

Humantenirine is an active oxindole alkaloid extracted from Gelsemium elegans Benth (G. elegans). In the present study, the metabolites of humantenirine in liver microsomes were first identified by HPLC/QqTOF-MS. Then, the metabolic profile and tissue distribution after oral administration in rats were further investigated. A total of seven metabolites were identified in vitro, and five metabolites in vitro were found in vivo. Moreover, a Ⅱ-phase metabolite was identified first in vivo. The results indicated that humantenirine could be metabolized widely. The parent drug and its metabolites were distributed widely in various tissues and highly in the liver and pancreas. However, the parent drug and its metabolites had low peak intensities in plasma. The elimination of humantenirine occurred rapidly as well, the most unconverted forms of which were found in the kidney. Metabolic pathways, including demethylation, dehydrogenation, oxidation and glucuronidation, were proposed. The present findings may provide a basis for the study of pharmacokinetic characteristics and will contribute to the evaluation of the pharmacology and toxicity of G. elegans.

Streptozotocin-Induced Hyperglycemia Affects the Pharmacokinetics of Koumine and its Anti-Allodynic Action in a Rat Model of Diabetic Neuropathic Pain

Koumine (KM), the most abundant alkaloid in Gelsemium elegans, has anti-neuropathic, anti-inflammatory, and analgesic activities; thus, it has the potential to be developed as a broad-spectrum analgesic drug. However, factors determining the relationship between analgesic efficacy and the corresponding plasma KM concentration are largely unclear. The pharmacokinetics and pharmacodynamics of KM and their optimization in the context of neuropathic pain have not been reported. We investigated the pharmacokinetics and pharmacodynamics of KM after oral administration in a streptozotocin-induced rat model of diabetic neuropathic pain (DNP) using a population approach. A first-order absorption and elimination pharmacokinetics model best described the plasma KM concentration. This pharmacokinetic model was then linked to a linear pharmacodynamic model with an effect compartment based on the measurement of the mechanical withdrawal threshold. KM was rapidly absorbed (time to maximum plasma concentration: 0.14–0.36 h) with similar values in both DNP and naïve rats, suggesting that DNP did not influence the KM absorption rate. However, the area under the curve (AUC_0–∞) of KM in DNP rats was over 3-fold higher than that in naïve rats. The systemic clearance rate and volume of KM distribution were significantly lower in DNP rats than in naïve rats. Blood glucose value prior to KM treatment was a significant covariate for the systemic clearance rate of KM and baseline value of the threshold. Our results suggest that streptozotocin-induced hyperglycemia is an independent factor for decreased KM elimination and its anti-allodynic effects in a DNP rat model. To the best of our knowledge, this is the first study to investigate the role of DNP in the pharmacokinetics and pharmacokinetics-pharmacodynamics of KM in streptozotocin-induced diabetic rats.

The metabolism of gelsevirine in human, pig, goat and rat liver microsomes

Gelsemium is a small genus of flowering plants from the family Loganiaceae comprising five species, three of which, Gelsemium sempervirens (L.) J. St.‐Hil., G. elegans Benth and G. rankinii Small, are particularly popular. Compared with other alkaloids from G. elegans, gelsemine, gelsevirine and koumine exhibit equally potent anxiolytic effects and low toxicity. Although the pharmacological activities and metabolism of koumine and gelsemine have been reported in previous studies, the species differences of gelsevirine metabolism have not been well studied. In this study, the metabolism of gelsevirine was investigated by using liver microsomes of humans, pigs, goats and rats by means of HPLC‐QqTOF/MS. The results indicated that the metabolism of gelsevirine in liver microsomes had qualitative and quantitative species differences. Based on the results, the possible metabolic pathways of gelsevirine in liver microsomes were proposed. Investigation of the metabolism of gelsevirine will provide a basis for further studies of the in vivo metabolism of this drug.

An integrated strategy toward comprehensive characterization and quantification of multiple components from herbal medicine: An application study in Gelsemium elegans

Objective

To develop a powerful integrated strategy based on liquid chromatography coupled with mass spectrometry (LC-MS) systems for the comprehensive characterization and quantification of multiple components of herbal medicines.

Methods

Firstly, different mobile phase additives, analysis time, and MS acquisition modes were orthogonally tested with liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (LC-QTOF/MS) in order to detect as many components of Gelsemium elegans as possible with high peak intensity. Secondly, several data mining strategies, including database searching, diagnostic ion filtering and neutral loss filtering, were utilized to perform chemical profiling. Subsequently, this study focused on the quantification and validation of the performance of a liquid chromatography-triple mass spectrometry (LC-QqQ/MS) assay based on derivative multiple reaction monitoring (DeMRM).

Results

A total of 147 components from G. elegans were characterized, among them 116 nontarget components were reported for the first time. A sensitive and reproducible LC-QqQ/MS method was successfully developed and validated for the simultaneous relative quantification of 41 components of G. elegans. This LC-QqQ/MS method was then applied to compare the contents of components in the roots, stems and leaves.

Conclusion

The present integrated strategy would significantly contribute to chemical studies on herbal medicine, and its utility could be extended to other research fields, such as metabolomics, quality control, and pharmacokinetics.

Comparative metabolism of gelsenicine in liver microsomes from humans, pigs, goats and rats

RATIONALE

Gelsemium elegans (G. elegans) is highly toxic to humans and rats but has insecticidal and growth-promoting effects on pigs and goats. However, the mechanisms behind the toxicity differences of G. elegans are unclear. Gelsenicine, isolated from G. elegans, has been reported to be a toxic alkaloid.

METHODS

In this study, the in vitro metabolism of gelsenicine was investigated and compared for the first time using human (HLM), pig (PLM), goat (GLM) and rat (RLM) liver microsomes and high-performance liquid chromatography/mass spectrometry (HPLC/MS).

RESULTS

In total, eight metabolites (M1-M8) were identified by using high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (HPLC/QqTOF-MS). Two main metabolic pathways were found in the liver microsomes of the four species: demethylation at the methoxy group on the indole nitrogen (M1) and oxidation at different positions (M2-M8). M8 was identified only in the GLM. The degradation ratio of gelsenicine and the relative percentage of metabolites produced during metabolism were determined by high-performance liquid chromatography/tandem mass spectrometry (HPLC/QqQ-MS/MS). The degradation ratio of gelsenicine in liver microsomes decreased in the following order: PLM ≥ GLM > HLM > RLM. The production of M1 decreased in the order of GLM > PLM > RLM > HLM, the production of M2 was similar among the four species, and the production of M3 was higher in the HLM than in the liver microsomes of the other three species.

CONCLUSIONS

Based on these results, demethylation was speculated to be the main gelsenicine detoxification pathway, providing vital information to better understand the metabolism and toxicity differences of G. elegans among different species.

Orally Administered Koumine Persists Longer in the Plasma of Aged Rats Than That of Adult Rats as Assessed by Ultra-Performance Liquid Chromatography-Tandem Mass Spectrometry

Aging leads to changes in nearly all pharmacokinetic phases. Koumine (KM), an alkaloid derived from Gelsemium elegans Benth., is effective against age-associated chronic diseases, but its dose proportionality following oral administration in aged individuals remains unknown. Herein, we established and validated a simple method that requires low sample volumes to determine KM concentration in rats using ultra-performance liquid chromatography-tandem mass spectrometry. The maximum plasma concentration (C_max) of 7 mg·kg⁻¹ KM was ~12-fold and ~24-fold higher than that of 0.28 mg·kg⁻¹ KM in adult and aged rats, respectively (P < 0.01). Time to reach C_max (T_max) for 7 mg·kg⁻¹ KM was 4-fold longer in aged rats (P < 0.05). The area under the curve (AUC) of 7 mg·kg⁻¹ KM was >17-fold and >43-fold higher than those of 0.28 mg·kg⁻¹ KM in adult and aged rats, respectively (P < 0.01). The half-life (t_1/2) of 7 mg·kg⁻¹ KM was over 4-fold longer than that of 0.28 mg·kg⁻¹ KM in adult rats (P < 0.01). The t_1/2 of 1.4 and 7 mg·kg⁻¹ KM were 1.5~2-fold longer, than that of 0.28 mg·kg⁻¹ KM in aged rats (P < 0.05). The clearance rate of 7 mg·kg⁻¹ KM was significantly lower in aged than in adult rats (P < 0.05). For 7.0 mg·kg⁻¹ KM, the C_max in aged rats was higher than in adult rats during the T_max period (P < 0.05). In aged rats, the AUC for KM was >2.5-fold higher (P < 0.05) and the t_1/2 was >60% longer than in adult rats (P < 0.05). These results help interpret the pharmacokinetics of KM in aging-associated diseases.

Characterization of absorbed and produced constituents in goat plasma urine and faeces from the herbal medicine Gelsemium elegans by using high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry

ETHNOPHARMACOLOGICAL RELEVANCE

Herbal medicine contains hundreds of natural products, and studying their absorption, metabolism, distribution, and elimination presents great challenges. Gelsemium elegans (G. elegans) is a flowering plants in the Loganiaceae family. The plant is known to be toxic and has been used for many years as a traditional Chinese herbal medicine for the treatment of rheumatoid arthritis, neuropathic pain, spasticity, skin ulcers and cancer. It was also used as veterinary drugs for deworming, promoting animal growth, and pesticides. At present, studies on the metabolism of G. elegans have primarily focused on only a few single available reference ingredients, such as koumine, gelsemine and gelsedine.

MATERIAL AND METHODS

The goal of this work is to elucidate the overall metabolism of whole G. elegans powder in goats using high-performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (HPLC/QqTOF-MS).

RESULTS

Analyses of plasma, urine and fecal samples identified or tentatively characterized a total of 44 absorbed natural products and 27 related produced metabolites. Gelsedine-type, sarpagine-type and gelsemine-type alkaloids were the compounds with the highest metabolite formation. In the present study, most natural products identified in G. elegans were metabolized through glucuronidation and oxidation. Hydrogenation, dehydrogenation and demethylation also occurred.

CONCLUSION

To our knowledge, this is the first report of the metabolite profiling of the G. elegans crude extract in goats, which is of great significance for a safer and more rational application of this herbal medicine.

The Metabolism and Disposition of Koumine, Gelsemine and Humantenmine from Gelsemium

BACKGROUND

Gelsemium is a toxic flowering plant of the Gelsemiaceae family. It is used to treat skin diseases in China, and it is an important medicinal and homeopathic plant in North America. Up to now, more than 200 compounds have been isolated and reported from Gelsemium. More than 120 of these are indole alkaloids, including the main components, koumine, gelsemine and humantenmine which produce the pharmacological and toxicological effects of Gelsemium. However, their clinical application their limited by its narrow therapeutic window. Therefore, it is very important to study the metabolism and disposition of indole alkaloids from Gelsemium before their clinical application. This paper reviews all the reports on the metabolism and disposition of alkaloids isolated from Gelsemium at home and abroad.

METHODS

The metabolism and disposition of alkaloids from Gelsemium were searched by the Web of Science, NCBI, PubMed and some Chinese literature databases.

RESULTS

Only koumine, gelsemine and humantenmine have been reported, and few other alkaloids have been described. These studies indicated that the three indole alkaloids are absorbed rapidly, widely distributed in tissues, extensively metabolized and rapidly eliminated. There are species differences in the metabolism of these alkaloids, which is the reason for the differences in their toxicity in animals and humans.

CONCLUSION

This review not only explains the pharmacokinetics of indole alkaloids from Gelsemium but also facilitates further study on their metabolism and mechanism of toxicity.

Characterization of gelsevirine metabolites in rat liver S9 by accurate mass measurements using high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry

RATIONALE

Gelsemium elegans Benth. belongs to the family Loganiaceae and is widely distributed in northern America, east Asia, and southeast Asia. It has attracted wide attention for its diverse biological effects and complex architectures. Gelsevirine is one of the major components in G. elegans. Compared with other alkaloids from G. elegans, gelsevirine exhibits equally potent anxiolytic effects but with less toxicity. However, the metabolism of gelsevirine has not been clearly elucidated.

METHODS

The metabolism of gelsevirine was investigated using liver S9 fractions derived from rat liver homogenates by centrifugation at 9000 g. A rapid and accurate high-performance liquid chromatography/quadrupole-time-of-flight mass spectrometry (HPLC/QqTOF-MS) method was applied to characterize the gelsevirine metabolites.

RESULTS

We discovered a total number of four metabolites of gelsevirine. The metabolic pathways of gelsevirine consisted of hydrogenation, N-demethylenation and oxidation in rat liver S9.

CONCLUSIONS

This is the first study on the metabolism of gelsevirine. We proposed possible metabolic pathways of gelsevirine. These findings may warrant future studies of the in vivo metabolism of gelsemine in animals.

Characterization of N-methylcanadine and N-methylstylopine metabolites in rat liver S9 by high-performance liquid chromatography/quadrupole time-of-flight mass spectrometry

RATIONALE

N-Methylcanadine and N-methylstylopine are two types of isoquinoline alkaloids which are considered to be the main medicinally active constituents of the genus Papaveraceae. However, to date, no metabolism studies of N-methylcanadine and N-methylstylopine have been reported. Therefore, the purpose of the present study was to investigate the in vitro metabolism of these two alkaloids in rat liver S9.

METHODS

N-Methylcanadine or N-methylstylopine was incubated with rat liver S9 for 1 h, and then the incubation mixture was processed with 15% trichloroacetic acid. High-performance liquid chromatography with quadrupole time-of-flight mass spectrometry (HPLC/QqTOF-MS) as a reliable analytical method was used. The structural characterization of these metabolites was performed by the combination of the accurate MS/MS spectra and the known elemental composition.

RESULTS

As a result, a total of four metabolites of N-methylcanadine and five metabolites of N-methylstylopine in rat liver S9 were tentatively identified. The cleavage of the methylenedioxy group of the drugs was the main metabolic pathway of N-methylcanadine and N-methylstylopine.

CONCLUSIONS

The present study is the first in vitro metabolic investigation of N-methylcanadine and N-methylstylopine in rat liver S9 using a reliable HPLC/QqTOF-MS method. The metabolic pathways of N-methylcanadine and N-methylstylopine are tentatively proposed. This work lays the foundation for the in vivo metabolism of the two compounds in animals.