Pharmacokinetics, absolute bioavailability, and tissue distribution of WJ-14, a novel N-methyl-d-aspartate receptor antagonist, in rats by liquid chromatography-tandem mass spectrometry.

To circumvent the limitations of current antidepressants, WJ-14, a novel N-methyl-d-aspartate receptor antagonist, was synthesized and demonstrated to have remarkable efficiency in the treatment of depression. To illustrate the pharmacokinetics, absolute bioavailability, and tissue distribution of WJ-14 in rats, a rapid and sensitive liquid chromatography-tandem mass spectrometry-based analytical method was developed and validated for the separation and detection of WJ-14 in both plasma and tissue samples. After oral administration, WJ-14 was rapidly absorbed into the blood with time to reach the maximum plasma concentration (Tmax ) within 0.28 h and quickly eliminated with clearance (Cl) exceeding 6.80 L/h/kg and elimination half-life (t1/2 ) within 2.69 h. No obvious accumulation was found with mean residencetime (MRT) within 4.10 h. Tissue distribution revealed that WJ-14 was extensively distributed in the main tissues of rats, and massive amounts of WJ-14 were distributed in the liver. Extensive distribution and quick elimination led to extremely low absolute bioavailability of WJ-14 (1.91% of 8.33 mg/kg and 3.30% of 24.99 mg/kg). WJ-14 was detected in the brain only 0.083 h after oral administration, which is crucial for a rapid-onset antidepressant candidate. In addition, WJ-14 likely exhibited a non-linear pharmacokinetic process at dosages of 8.33 and 24.99 mg/kg. The findings may provide valuable information for subsequent studies on WJ-14.

Absorption, tissue distribution, and excretion of glycycoumarin, a major bioactive coumarin from Chinese licorice (Glycyrrhiza uralensis Fisch).

Licorice (Glycyrrhiza uralensis Fisch) is a natural plant resource widely used as a food and herbal medication in China. Glycycoumarin (GCM) is a major coumarin in licorice that possesses several biological activities. However, little is known about its pharmacokinetic profile. The present study aimed to describe the oral absorption, tissue distribution, and excretion of GCM in rats. Free (parent drug) and/or total (parent drug plus the glucuronidated metabolite) GCM in biological samples was quantified before and after the hydrolysis reaction with ß-glucuronidase using a reliable LC-MS/MS method. The results indicated that GCM was rapidly absorbed and transformed into its conjugated metabolites after administration. Free GCM plasma concentrations after i. v. (10 mg/kg) administration quickly decreased with an average t1/2,λz of 0.71 h, whereas the total GCM concentration reduced slowly with a t1/2, λz of 2.46 h. The area under the curve of glucuronidated metabolites was approximately four-times higher than that of free GCM. Presumably, because of hepatic and/or intestinal tract first-pass metabolism, GCM exhibited a poor bioavailability of 9.22%, as estimated from its total plasma concentration. Additionally, GCM was distributed rapidly and widely in various tissues except the brain. The liver had the highest concentration; further, GCM was promptly eliminated from test tissues after intraperitoneal (20 mg/kg) administration, but only a small amount of GCM was excreted via bile and urine. Overall, GCM is absorbed and rapidly transformed into its conjugated metabolites with low bioavailability; further, it is distributed in various tissues, except the brain. These pharmacokinetic results are helpful for better understanding the characteristics and pharmacological effects of GCM.

Pharmacological Activities and Pharmacokinetics of Glycycoumarin.

Glycycoumarin is a representative coumarin compound with significant pharmacological activities isolated from Glycyrrhiza uralensis Fisch., Fabaceae. Studies have shown that glycycoumarin has many biological activities, such as anti-tumor, liver protection, antispasmodic, antibacterial, and antivirus. However, the poor solubility of glycycoumarin in water and the accompanying reactions of the phase I (hydroxylation) and II (glucuronidation) metabolism limit its druggability, which manifests as low absorption in the body after oral administration and low free drug concentration, ultimately leading to low bioavailability. Therefore, a comprehensive review of the pharmacological effects and pharmacokinetics of glycycoumarin is presented to provide a reference for further research and application as a therapeutic agent. Supplementary Information: The online version contains supplementary material available at 10.1007/s43450-022-00342-x.

Development and validation of an LC-MS/MS method for detection of glycyrol in rat plasma and its application to a pharmacokinetic study.

Licorice (Glycyrrhiza uralensis) is one of the most popular edible and medicinal plants and is widely used in Asia. Glycyrol (GC) is a major coumarin present in licorice that exhibits various biological activities. We aimed to develop a highly sensitive and rapid liquid chromatography coupled with mass spectrometry method for the quantitative determination analysis of GC in rat plasma. GC showed linear calibration ranges of 1-100 and 50-2,000 ng/ml with correlation coefficients >0.99. The average extraction recovery ranged from 113.26 to 114.84%, and the relative standard deviation of internal standard normalized matrix factors ranged from 6.36 to 9.46%. The intra-day and inter-day precisions of GC were <15%, and the accuracy ranged from 95.31 to 112.72%. Pharmacokinetic studies showed that GC was distributed in the body with a volume of distribution of 9.06 L/kg, and the initial plasma concentration was 3275.11 ng/ml. The area under the plasma concentration vs. time curve was 479.25 ng h/ml. It was rapidly eliminated with a terminal elimination half-life of 1.47 h and a clearance rate of 4.24 L/h/kg. The pharmacokinetic results can help us to better understand the pharmacological effects of GC in the body.

Pharmacokinetic and pharmacodynamic analysis of cefoperazone/sulbactam for the treatment of pediatric sepsis by Monte Carlo simulation.

Pediatric sepsis syndrome is one of the most common reasons for pediatric intensive care unit hospitalization (PICU). Cefoperazone/sulbactam is a time-dependent beta-lactamase inhibitor combination which has been widely used in the treatment of sepsis. But the pharmacokinetic (PK) and pharmacodynamic (PD) data of cefoperazone/sulbactam are unknown in children with sepsis. The present work aimed to determine whether the usual dosing regimens of cefoperazone/sulbactam (1 hour infusion, 50 mg kg-1, every 12 hours) were suitable for these patients in PICU. A total of fourteen patients were enrolled and the PK parameters were estimated by non-compartmental analysis using WinNonlin software. The t1/2 and AUC0-12 of cefoperazone and sulbactam were 3.60 and 1.77 h, and 900.97 and 67.68 h µg mL-1, respectively. The Vd and CL of cefoperazone and sulbactam were 1.65 L and 5.16 L, and 17.41 mL min-1 and 122.62 mL min-1, respectively. The probability of target attainments (PTAs) of cefoperazone at different minimum inhibitory concentrations (MICs) based on the percentage time that concentrations exceed the minimum inhibitory concentration (% T > MIC) value were performed by Monte Carlo simulation and PTA was >90% at MICs ≤16 µg mL-1. The PK/PD profile of dosing regimens tested will assist in selecting the appropriate cefoperazone/sulbactam regimens for these patients. At a target of 80% T > MIC, the usual dosing regimens can provide good coverage for pathogens with MICs of ≤32 µg mL-1. The ratio between cefoperazone and sulbactam at 1 : 1 may be more suitable in pediatric sepsis. Individual dose and therapeutic drug monitoring in clinical practice will help achieve the best therapeutic effect while minimizing toxicity.

Herb-Drug Interaction Between Xiyanping Injection and Lopinavir/Ritonavir, Two Agents Used in COVID-19 Pharmacotherapy.

The global epidemic outbreak of the coronavirus disease 2019 (COVID-19), which exhibits high infectivity, resulted in thousands of deaths due to the lack of specific drugs. Certain traditional Chinese medicines (TCMs), such as Xiyanping injection (XYPI), have exhibited remarkable benefits against COVID-19. Although TCM combined with Western medicine is considered an effective approach for the treatment of COVID-19, the combination may result in potential herb-drug interactions in the clinical setting. The present study aims to verify the effect of XYPI on the oral pharmacokinetics of lopinavir (LPV)/ritonavir (RTV) using an in vivo rat model and in vitro incubation model of human liver microsomes. After being pretreated with an intravenous dose of XYPI (52.5 mg/kg) for one day and for seven consecutive days, the rats received an oral dose of LPV/RTV (42:10.5 mg/kg). Except for the t1/2 of LPV is significantly prolonged from 4.66 to 7.18 h (p < 0.05) after seven consecutive days pretreatment, the pretreatment resulted in only a slight change in the other pharmacokinetic parameters of LPV. However, the pharmacokinetic parameters of RTV were significantly changed after pretreatment with XYPI, particularly in treatment for seven consecutive days, the AUC0-∞ of RTV was significantly shifted from 0.69 to 2.72 h µg/mL (p < 0.05) and the CL exhibited a tendency to decrease from 2.71 L/h to 0.94 L/h (p < 0.05), and the t1/2 of RTV prolonged from 3.70 to 5.51 h (p < 0.05), in comparison with the corresponding parameters in untreated rats. After administration of XYPI, the expression of Cyp3a1 protein was no significant changed in rats. The in vitro incubation study showed XYPI noncompetitively inhibited human CYP3A4 with an apparent Ki value of 0.54 mg/ml in a time-dependent manner. Our study demonstrated that XYPI affects the pharmacokinetics of LPV/RTV by inhibiting CYP3A4 activity. On the basis of this data, patients and clinicians can take precautions to avoid potential drug-interaction risks in COVID-19 treatment.

Absorption, Metabolism, and Excretion of Cajaninstilbene Acid.

Cajaninstilbene acid (CSA), an active stilbene isolated from the leaves of pigeon pea (Cajanus cajan), exhibits several bioactivities. To develop CSA as a potential nutraceutical and provide pharmacokinetic foundations for its further in vivo bioactivity studies, this study aims to explore its absorption, metabolism, and excretion systematically. Human colon adenocarcinoma (Caco-2) cell monolayers were utilized to investigate the CSA transport mechanism. CSA metabolites were identified in rat biological samples and quantified to explore their excretion routes. CSA exhibited a high permeability and was transported across Caco-2 monolayers mainly by passive transport via the transcellular process. Four new CSA metabolites were found in vivo, namely, CSA-2-COO-glucuronide, 6,12-dihydroxy CSA, 3-hydroxy-5-methoxystilbene-3-O-glucuronide, and 6-hydroxy CSA-3-O-glucuronide, in addition to our previously reported metabolite CSA-3-O-glucuronide. These metabolites were mainly excreted in bile. Our results indicate that metabolism but not absorption is the major barrier limiting the oral bioavailability of CSA.

Glycyrol exerts potent therapeutic effect on lung cancer via directly inactivating T-LAK cell-originated protein kinase.

Molecular targeted therapy for non-small cell lung cancer (NSCLC) has demonstrated promising outcomes. T-lymphokine-activated killer cell-originated protein kinase (TOPK) is found overexpressed in many cancer types such as NSCLC, and is considered to be an effective target for lung cancer treatment. In the present study, we found that glycyrol (GC), a representative coumarin compound isolated from licorice, was highly effective against several human NSCLC cell lines in vitro, and significantly suppressed tumor growth in vivo. Mechanistically, we demonstrated that GC can strongly bind to the TOPK protein and inhibited its kinase activity, leading to the activation of apoptotic signaling pathways. The findings of the present study suggest that GC is a novel promising TOPK inhibitor and this compound deserves to be further investigated for its potential anti-NSCLC activity.

Pharmacokinetics of Nuciferine and N-Nornuciferine, Two Major Alkaloids From Nelumbo nucifera Leaves, in Rat Plasma and the Brain.

The leaf of the lotus (Nelumbo nucifera) is a natural plant resource used as both food and herbal medicine (He-Ye) in China. Alkaloids are considered the major bioactive compound of the herb and exhibit various biological activities, including anti-hyperlipidemia, anti-obesity, anti-inflammatory, and anti-hyperuricemic effects. Nuciferine (NF) and N-nuciferine (N-NF) are two major alkaloids found in the herb. In the present work, the plasma and brain pharmacokinetics of the two compounds were investigated after oral and intravenous (i.v.) administration of a lotus leaf alkaloid fraction to SD rats via ultra-performance liquid chromatography coupled with photodiode array detection and brain microdialysis. After oral administration (50 mg/kg), the two compounds NF and N-NF were rapidly absorbed into the blood and reached a mean maximum concentration (Cmax) of 1.71 µg/mL at 0.9 h and 0.57 µg/mL at 1.65 h, respectively. After i.v. administration (10 mg/kg), NF and N-NF were found to have a relatively wide volume of distribution (Vd, λz, 9.48 and 15.17 L/kg, respectively) and slow elimination half-life (t1/2, λz, 2.09 and 3.84 h, respectively). The oral bioavailability of NF and N-NF was estimated as 58.13% and 79.91%, respectively. After i.v. dosing (20 mg/kg), the two compounds rapidly crossed the blood-brain barrier and reached their Cmax (in unbound form): 0.32 and 0.16 µg/mL at 0.89 and 1.22 h, respectively. Both alkaloids had widespread distribution in the brain, with Vd, λz/F-values of 19.78 L/kg and 16.17 L/kg, respectively. The mean t1/2, λz values of NF and N-NF in the brain were 1.24 and 1.39 h, respectively. These results can help us to better understand the characteristics and neuro-pharmacological effects of the lotus alkaloid fraction.

Glycycoumarin protects mice against acetaminophen-induced liver injury predominantly via activating sustained autophagy.

BACKGROUND AND PURPOSE: Acetaminophen-induced acute liver injury (AILI) is the most frequent cause of acute liver failure in developed countries. Given the significant limitations associated with N-acetyl cysteine, the only antidote used to treat AILI, the development of novel therapeutic approaches that can offer a wide range of therapeutic time-windows is clearly needed. Glycycoumarin (GCM), a natural coumarin purified from liquorice, has been previously demonstrated to possess potent hepatoprotective effects. In the present study, we aimed to investigate the therapeutic potential of GCM against AILI. EXPERIMENTAL APPROACH: Acetaminophen (300 mg·kg-1 ) was administered to male C57BL/6 mice, with and without GCM. Serum transaminases, haematoxylin and eosin staining and Western blot were used to assess hepatic damage. KEY RESULTS: GCM (50 mg·kg-1 ) was highly effective against acetaminophen-induced hepatotoxicity. Moreover, GCM was superior to N-acetyl cysteine, in terms of the dosage and the therapeutic time-windows. Further mechanistic investigations revealed that the therapeutic action of GCM was not a result of inhibition of acetaminophen metabolic activation or associated with Nrf2. Instead, the protective effect of GCM appeared to be predominantly dependent on sustained activation of autophagy, which attenuated acetaminophen-induced mitochondrial oxidative stress and JNK activation. CONCLUSIONS AND IMPLICATIONS: Collectively, our results indicate that GCM alleviated acetaminophen-induced oxidative stress through activating autophagy, thereby protecting against AILI. Our findings suggest that GCM has potential as a novel therapeutic agent for treating AILI.

Glycycoumarin Sensitizes Liver Cancer Cells to ABT-737 by Targeting De Novo Lipogenesis and TOPK-Survivin Axis.

Glycycoumarin (GCM) is a representative of bioactive coumarin compounds isolated from licorice, an edible and medicinal plant widely used for treating various diseases including liver diseases. The purpose of the present study is to examine the possibility of GCM as a sensitizer to improve the efficacy of BH3 mimetic ABT-737 against liver cancer. Three liver cancer cell lines (HepG2, Huh-7 and SMMC-7721) were used to evaluate the in vitro combinatory effect of ABT-737/GCM. HepG2 xenograft model was employed to assess the in vivo efficacy of ABT-737/GCM combination. Results showed that GCM was able to significantly sensitize liver cancer cells to ABT-737 in both in vitro and in vivo models. The enhanced efficacy by the combination of ABT-737 and GCM was attributed to the inactivation of T-LAK cell-originated protein kinase (TOPK)-survivin axis and inhibition of de novo lipogenesis. Our findings have identified induction of TOPK-survivin axis as a novel mechanism rendering cancer cells resistant to ABT-737. In addition, ABT-737-induced platelet toxicity was attenuated by the combination. The findings of the present study implicate that bioactive coumarin compound GCM holds great potential to be used as a novel chemo-enhancer to improve the efficacy of BH3 mimetic-based therapy.

Inhibitory effects of Danhong Injection and its major constituents on human cytochrome P450 enzymes in vitro.

Danhong Injection (DHI) as a Chinese patent medicine is mainly used to treat ischemic encephalopathy and coronary heart disease in combination with other chemotherapy. However, the information on DHI's potential drug interactions is limited. The goal of this work was to examine the potential P450-mediated metabolism drug interaction arising from DHI and its active components. The results showed that DHI inhibited CYP2C19, CYP2D6, CYP3A4, CYP2E1 and CYP2C9 with IC50 values of 1.26, 1.42, 1.63, 1.10 and 1.67% (v/v), respectively. Danshensu and rosmarinic acid inhibited CYP2E1 and CYP2C9 with IC50 values of 36.63 and 75.76 µm, and 34.42 and 76.89 µm, respectively. Salvianolic acid A and B inhibited CYP2D6, CYP2E1 and CYP2C9 with IC50 values of 33.79, 21.64 and 31.94 µm, and 45.47, 13.52 and 24.15 µm, respectively. The study provides some useful information for safe and effective use of DHI in clinical practice.

The effect of lycopene on cytochrome P450 isoenzymes and P-glycoprotein by using human liver microsomes and Caco-2 cell monolayer model.

Lycopene is widely used as a dietary supplement. However, the effects of lycopene on cytochrome P450 (CYP) enzymes or P-glycoprotein (P-gp) are not comprehensive. The present study was performed to investigate the effects of lycopene on the CYP enzymes and P-gp activity. A cocktail method was used to evaluate the activities of CYP3A4, CYP2C9, CYP2C19, CYP2D6 and CYP2E1. Caco-2 cell monolayer model was carried out to assay lycopene on P-gp activity. The results indicated that lycopene had a moderate inhibitory effect on CYP2E1, with IC50 value of 43.65 µM, whereas no inhibitory effects on CYP3A4, CYP2C19, CYP2D6 and CYP2E1, with IC50 values all over 100 µM. In addition, lycopene showed almost no inhibitory effect on rhodamine-123 efflux and uptake (p > .05), indicated no effects on P-gp activity. In conclusion, there should be required attention when lycopene are coadministered with other drugs that are metabolised by CYP2E1.

Ganoderic Acid A Metabolites and Their Metabolic Kinetics.

Ganoderic acid A (GAA), a representative active triterpenoid from Ganoderma lucidum, has been reported to exhibit antinociceptive, antioxidative, cytotoxic, hepatoprotective and anticancer activities. The present study aims (1) to identify GAA metabolites, in vivo by analyzing the bile, plasma and urine after intravenous administration to rats (20 mg/kg), and in vitro by incubating with rat liver microsomes (RLMs) and human liver microsomes (HLMs); (2) to investigate the metabolic kinetics of main GAA metabolites. Using HPLC-DAD-MS/MS techniques, a total of 37 metabolites were tentatively characterized from in vivo samples based on their fragmentation behaviors. The metabolites detected in in vitro samples were similar to those found in vivo. GAA underwent extensive phase I and II metabolism. The main metabolic soft spots of GAA were 3, 7, 11, 15, 23-carbonyl groups (or hydroxyl groups) and 12, 20, 28 (29)-carbon atoms. Ganoderic acid C2 (GAC2) and 7ß,15-dihydroxy-3,11,23-trioxo-lanost-26-oic acid were two main reduction metabolites of GAA, and their kinetics followed classical hyperbolic kinetics. The specific isoenzyme responsible for the biotransformation of the two metabolites in RLMs and HLMs was CYP3A. This is the first report on the comprehensive metabolism of GAA, as well as the metabolic kinetics of its main metabolites.

Lotus leaf alkaloid fraction can strongly inhibit CYP2D6 isoenzyme activity.

ETHNOPHARMACOLOGICAL RELEVANCE: The Chinese herbal medicine He-Ye, the leaves of the lotus (Nelumbo nucifera) plant, is traditionally used in China for the treatment of sunstroke, thirst, diarrhea, and fever. Currently, the leaf is used not only as an herbal tea to reduce lipid level and control body weight, but also as a major ingredient in some lipid-lowering Chinese patented medicines. Our previous study demonstrated that the alkaloid fraction (AF) of the herb has a strong inhibitory effect on CYP2D6 isoenzyme activity in vitro. The present study aims to further verify this activity using the in vivo rat model and to explore the inhibitory mechanism on CYP2D6 using human liver microsomes (HLMs). MATERIALS AND METHODS: After a continuous 7-d oral dose of AF (50mg/kg) or a vehicle, Sprague Dawley rats received a single intravenous dose of dextromethorphan or metoprolol. Blood samples were collected at various time points, and the plasma concentrations of the relevant metabolites dextrorphan and hydroxymetoprolol were assayed by LC-MS/MS for evaluating the effect of AF on their pharmacokinetics and CYP2D6 activity. Dextromethorphan as a probe at different concentrations was incubated with HLMs in an incubation buffer system, in the presence or absence of AF at different concentrations. After incubation, the produced metabolite was assayed. RESULTS: After being pretreated with AF in rats, the plasma concentrations of dextrorphan and hydroxymetoprolol significantly decreased, with Cmax going from 79.44 to 29.96 and 151.18 to 83.39hng/mL (P<0.05), AUCall from 167.27 to 62.25 and 347.68 to 223.24hng/mL (P<0.05), and AUCinf from 183.39 to 84.76 and 350.59 to 234.57hng/mL (P<0.05), respectively, in comparison with those of untreated rats. The t1/2 of hydroxymetoprolol significantly increased from 1.14 to 1.99h (P<0.05). The in vitro incubation test showed that AF competitively inhibited the CYP2D6, with apparent Ki value of 0.64µg/mL. CONCLUSIONS: AF can strongly inhibit the activity of CYP2D6 enzyme, as confirmed by in vivo and in vitro models. Possible drug interactions may occur between AF and other medications metabolized by CYP2D6. Thus, caution should be paid when the lotus leaf and its preparations are concurrently administered with conventional medicines.

The Effect of Vinpocetine on Human Cytochrome P450 Isoenzymes by Using a Cocktail Method.

Vinpocetine is a derivative of the alkaloid vincamine, which had been prescribed for chronic cerebral vascular ischemia and acute ischemic stroke or used as a dietary supplement for its several different mechanisms of biological activities. However, information on the cytochrome P450 (CYP) enzyme-mediated drug metabolism has not been previously studied. The present study was performed to investigate the effects of vinpocetine on CYPs activity, and cocktail method was used, respectively. To evaluate the effects of vinpocetine on the activity of human CYP3A4, CYP2C9, CYP2C19, CYP2D6, and CYP2E1, human liver microsomes were utilized to incubate with the mixed CYPs probe substrates and the target components. The results indicate that vinpocetine exhibited weak inhibitory effect on the CYP2C9, where the IC50 value is 68.96 µM, whereas the IC50 values for CYP3A4, CYP2C19, CYP2D6, and CYP2E1 were all over range of 100 µM, which showed that vinpocetine had no apparent inhibitory effects on these CYPs. In conclusion, the results indicated that drugs metabolized by CYP2C9 coadministrated with vinpocetine may require attention or dose adjustment.

Metabolism profiles of nuciferine in rats using ultrafast liquid chromatography with tandem mass spectrometry.

Nuciferine (NF) is one of the main aporphine alkaloids existing in the traditional Chinese medicine Folium Nelumbinis (lotus leaves). Modern pharmacological studies have demonstrated that NF has a broad spectrum of bioactivities, such as anti-HIV and anti-hyperlipidemic effects, and has been recommended as a leading compound for new drug development. However, the metabolites and biotransformation pathway of NF in vivo have not yet been comprehensively investigated. The present study was performed to identify the metabolites of NF for exploring in vivo fates. Rat plasma and urine samples were collected after oral administration and prepared by liquid-liquid extraction with ethyl acetate. A method based on ultrafast liquid chromatography with tandem mass spectrometry was applied to identify the metabolites. Q1 (first quadrupole) full scan combined with a multiple reaction monitoring (MRM) survey scan were used for the detection of metabolites. MRM-information-dependent acquisition of enhanced product ions was used for the structural identification of detected metabolites. A total of 10 metabolites were identified, including phase I (demethylation, oxidation and dehydrogenation) and phase II (glucuronidation, sulfation and glutathione) biotransformation products. Demethylation is the main metabolic pathway of NF in the body. These results can help in improving understanding of the disposition and pharmacological mechanism of NF in the body. Copyright © 2016 John Wiley & Sons, Ltd.

Identification and characterization of potent CYP2D6 inhibitors in lotus leaves.

ETHNOPHARMACOLOGICAL RELEVANCE: The herb of lotus (Nelumbo nucifera) leaves is a commonly used traditional Chinese herbal medicine that is utilized for the treatment of sunstroke, to assuage thirst, and to cure both diarrhea and fever in China. Modern pharmacological studies have demonstrated that the herb exhibits various pharmacological effects, such as anti-hyperlipidemia, anti-obesity, anti-oxidant, anti-HIV, anti-microbial, and anti-hypoglycemic activities. Currently, the herb is becoming more popular in China as a "tea drink" or as a main ingredient of some herbal formulations, which implies that the herb and/or its products are now more likely to be concurrently administered with conventional medicines for losing body weight and reducing blood lipids. However, its potential inhibitory effect on human cytochrome P450 (CYP) has not been systemically investigated to date. The present study was performed to assess the potential inhibitory effects of lotus leaf alcoholic extract (LAE), its major fractions, and its main compounds on five CYP isoenzymes (CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4) in vitro. MATERIAL AND METHODS: Five probe substrates were incubated with human liver microsomes in the presence or absence of the LAE, the alkaloid fraction (AF), the flavonoid fraction (FF), or the individual aporphine alkaloids, namely, nuciferine (NF), N-nornuciferine (N-NF), and 2-hydroxy-1-methoxyaporphine (HMA). After the incubation, the relative metabolites of the substrates were analyzed using LC-MS/MS. RESULTS: The results showed that the LAE strongly inhibited CYP2D6 with an IC50 value of 12.05µg/mL and weakly inhibited other isoenzymes. In addition, FF was found to weakly inhibit CYP2D6, whereas AF exerted a markedly higher inhibitory effect on CYP2D6 activity with an IC50 value of 0.96µg/mL. The three aporphine alkaloids isolated from the AF (NF, N-NF, and HMA) significantly inhibited CYP2D6 with IC50 values of 3.78, 3.76, and 3.15µM, respectively. Their Lineweaver-Burk plots and Dixon plots showed that NF, N-NF, and HMA competitively inhibited CYP2D6 activity with Ki values of 1.88, 2.34, and 1.56µM, respectively. CONCLUSION: The study revealed that the alkaloid compounds in lotus leaves exert a potent inhibitory effect on CYP2D6 isoenzyme. The possible drug interactions of the leaves and their preparations with conventional medicines should thus be taken into account.

Different pharmacokinetics of the two structurally similar dammarane sapogenins, protopanaxatriol and protopanaxadiol, in rats.

Dammarane Sapogenins (DS), with main ingredients of protopanaxatriol (PPT, 33%) and protopanaxadiol (PPD, 16%), is an alkaline hydrolyzed product of ginsenosides and had significant activities in improving learning and memory and decreasing chemotherapy-induced myelosuppression. In the present study, the pharmacokinetics and oral bioavailabilities of PPT and PPD were investigated when a single dose of DS was administrated orally (75 mg/kg) and intravenously (i.v., 30 mg/kg) to rats. Their in vitro stabilities in the GI tract were also investigated. PPT and PPD concentrations were measured by LC-MS. The results showed that PPT was eliminated rapidly from the body with an average t1/2, λz value of 0.80 h and CL of 4.27 l/h/kg after i.v. administration, while PPD was eliminated relatively slowly with a t1/2, λz of 6.25 h and CL of 0.98l/h/kg. After oral administration, both PPD and PPT could be absorbed into the body, but their systemic exposures were quite different. PPT was absorbed into the body quickly, with a Tmax of 0.58 h and a Cmax of 0.13 µg/ml, while PPD was absorbed relatively slowly with a Tmax of 1.82 h and a Cmax of 1.04 µg/ml. The absolute bioavailabilities of PPT and PPD were estimated as 3.69% and 48.12%, respectively. The stability test found that PPT was instable in the stomach with 40% degradation after 4h incubation at 37°C, both in pH1.2 buffer and in the stomach content solution. The instability in the stomach might be one of the reasons for PPT's poor bioavailability.