Mechanism-Based Pharmacokinetic Model for the Deglycosylation Kinetics of 20(S)-Ginsenosides Rh2.

Aim: The 20(S)-ginsenoside Rh2 (Rh2) is being developed as a new antitumor drug. However, to date, little is known about the kinetics of its deglycosylation metabolite (protopanoxadiol) (PPD) following Rh2 administration. The aim of this work was to 1) simultaneously characterise the pharmacokinetics of Rh2 and PPD following intravenous and oral Rh2 administration, 2) develop and validate a mechanism-based pharmacokinetic model to describe the deglycosylation kinetics and 3) predict the percentage of Rh2 entering the systemic circulation in PPD form. Methods: Plasma samples were collected from rats after the I.V. or P.O. administration of Rh2. The plasma Rh2 and PPD concentrations were determined using HPLC-MS. The transformation from Rh2 to PPD, its absorption, and elimination were integrated into the mechanism based pharmacokinetic model to describe the pharmacokinetics of Rh2 and PPD simultaneously at 10 mg/kg. The concentration data collected following a 20 mg/kg dose of Rh2 was used for model validation. Results: Following Rh2 administration, PPD exhibited high exposure and atypical double peaks. The model described the abnormal kinetics well and was further validated using external data. A total of 11% of the administered Rh2 was predicted to be transformed into PPD and enter the systemic circulation after I.V. administration, and a total of 20% of Rh2 was predicted to be absorbed into the systemic circulation in PPD form after P.O. administration of Rh2. Conclusion: The developed model provides a useful tool to quantitatively study the deglycosylation kinetics of Rh2 and thus, provides a valuable resource for future pharmacokinetic studies of glycosides with similar deglycosylation metabolism.

Theory-based pharmacokinetics and pharmacodynamics of S- and R-warfarin and effects on international normalized ratio: influence of body size, composition and genotype in cardiac surgery patients.

AIMS: The aims of this study are to apply a theory-based mechanistic model to describe the pharmacokinetics (PK) and pharmacodynamics (PD) of S- and R-warfarin. METHODS: Clinical data were obtained from 264 patients. Total concentrations for S- and R-warfarin were measured by ultra-high performance liquid tandem mass spectrometry. Genotypes were measured using pyrosequencing. A sequential population PK parameter with data method was used to describe the international normalized ratio (INR) time course. Data were analyzed with NONMEM. Model evaluation was based on parameter plausibility and prediction-corrected visual predictive checks. RESULTS: Warfarin PK was described using a one-compartment model. CYP2C9 *1/*3 genotype had reduced clearance for S-warfarin, but increased clearance for R-warfarin. The in vitro parameters for the relationship between prothrombin complex activity (PCA) and INR were markedly different (A = 0.560, B = 0.386) from the theory-based values (A = 1, B = 0). There was a small difference between healthy subjects and patients. A sigmoid Emax PD model inhibiting PCA synthesis as a function of S-warfarin concentration predicted INR. Small R-warfarin effects was described by competitive antagonism of S-warfarin inhibition. Patients with VKORC1 AA and CYP4F2 CC or CT genotypes had lower C50 for S-warfarin. CONCLUSION: A theory-based PKPD model describes warfarin concentrations and clinical response. Expected PK and PD genotype effects were confirmed. The role of predicted fat free mass with theory-based allometric scaling of PK parameters was identified. R-warfarin had a minor effect compared with S-warfarin on PCA synthesis. INR is predictable from 1/PCA in vivo.

Hypericum japonicum Thunb. ex Murray: phytochemistry, pharmacology, quality control and pharmacokinetics of an important herbal medicine.

Hypericum japonicum Thunb. ex Murray is mainly distributed throughout Asia, Oceania and North America and is used as an important herbal medicine. H. japonicum contains many valuable secondary metabolites, such as flavonoids, phloroglucinols and xanthones and has hepatoprotective, anti-tumor, antibacterial, antiviral, and antioxidant activities and effects on the cardiovascular system and immunity. Coupled with phytochemical and pharmacological research, a series of analytical methods have been developed to evaluate the quality of H. japonicum based on its bioactive components. A pharmacokinetics study involved the absorption of two main flavonoids of H. japonicum in rats. This review aims to present an up-to-date and comprehensive overview of the phytochemistry, pharmacology, quality control and pharmacokinetics of H. japonicum, which should be useful for the greater development of H. japonicum, especially in the development of new drugs and therapeutics for various diseases.

Pharmacokinetic interactions between 20(S)-ginsenoside Rh2 and the HIV protease inhibitor ritonavir in vitro and in vivo.

AIM: 20(S)-Ginsenoside Rh2 (Rh2) has shown potent inhibition on P-glycoprotein (P-gp), while most HIV protease inhibitors are both substrates and inhibitors of P-gp and CYP3A4. The aim of this study was to investigate the potential pharmacokinetic interactions between Rh2 and the HIV protease inhibitor ritonavir. METHODS: The effects of Rh2 on the cellular accumulation and transepithelial transport of ritonavir were studied in Caco-2 and MDCK-MDR1 cells. Male rats were administered Rh2 (25 or 60 mg/kg, po) or Rh2 (5 mg/kg, iv), followed by ritonavir (25 mg/kg, po). The P-gp inhibitors verapamil (20 mg/kg, po) or GF120918 (5 mg/kg, po) were used as positive controls. The concentrations of ritonavir in plasma, bile, urine, feces and tissue homogenates were analyzed using LC-MS. RESULTS: Rh2 (10 µmol/L) significantly increased the accumulation and inhibited the efflux of ritonavir in Caco-2 and MDCK-MDR1 cells, as verapamil did. But Rh2 did not significantly alter ritonavir accumulation or transport in MDCK-WT cells. Intravenous Rh2 significantly increased the plasma exposure of ritonavir while reducing its excretion in the bile, and oral verapamil or GF120918 also increased plasma exposure of ritonavir but without changing its excretion in the bile. Interestingly, oral Rh2 at both doses did not significantly change the plasma profile of ritonavir. Moreover, oral Rh2 (25 mg/kg) significantly elevated the ritonavir concentration in the hepatic portal vein, and markedly increased its urinary excretion and tissue distribution, which might counteract the elevated absorption of ritonavir. CONCLUSION: Rh2 inhibits the efflux of ritonavir through P-gp in vitro. The effects of Rh2 on ritonavir exposure in vivo depend on the administration route of Rh2: intravenous, but not oral, administration of Rh2 significantly increased the plasma exposure of ritonavir.

[Evaluation of myocardial ischemia rat model based on metabonomic method of small molecule metabolites of plasma and cardiac muscle].

Isoproterenol (ISO)-induced myocardial ischemia animal model has been widely applied to the study of myocardial ischemia and evaluation of drug efficacy. Metabolic profiling of endogenous compounds can make a deep insight into biochemical process of the ISO-induced myocardial ischemia rats. Herein, rats were treated with ISO (2 mg x kg(-1)) for 10 days. After the model was established by measuring myocardial histopathology and plasma creatine kinase, GC/TOF-MS was used to determine endogenous metabolites in plasma and cardiac muscle of rats, and pattern recognition was used to process the data. Results showed that the plasma metabolic profiling of ISO-induced myocardial ischemia rats was significantly different from that of the control, and it had the tendency to the normal state after the discontinue of ISO injection. Besides, the cardiac muscle of rats treated with ISO for 10 days and the normal cardiac muscle could also be separated clearly. The potential biomarkers in plasma and cardiac muscle of model rats had homogeneity and their own specialty. Biochemical metabolic pathway analysis indicated that this myocardial ischemia model was involved in the alternation of energy metabolism, saccharometabolism, lipid metabolism, nucleoside metabolism and amino acid metabolism, and in relationship with oxidative stress. These findings revealed that metabonomics may be a promising tool to evaluate myocardial ischemia rat model induced by ISO and could further extend the study of pharmacodynamic action of drugs at the molecular level.

[Metabonomic phenotype of "formula corresponding to pattern types" based on "qi and yin deficiency pattern" of myocardial ischemia rat model].

In order to explore the scientific connotation of "Fangzhengduiying (formula corresponding to pattern types)", "Qiyinliangxuzheng (Qi and Yin deficiency pattern)" of myocardial ischemia rat model and GC-TOF/MS based metabonomic method were used for comparing the effects of Sheng-mai injection, Salvia injection and propranolol in the present study. After data processing and pattern recognition, Sheng-mai injection showed better efficacy than the other two drugs in accordance with not only visual observation from PLS-DA scores plots but also the number of abnormal endogenous compounds restored to the normal level. Further studies showed that Sheng-mai injection could normalize the level of plasma endothelin-1, the index related to cardiovascular diseases and sleep disorders, which verified the results of metabonomics. Finally, the regulated metabolites and related metabolic pathways were analyzed, and it was supposed that the effects of Sheng-mai injection involved in the alternation of energy metabolism, lipid metabolism, amino acids metabolism, and so on. These findings provided scientific evidence to Shengmai "Fang" used for "Qi and Yin deficiency pattern" correspondingly, indicating that metabonomics has great potential in traditional Chinese medical research, which provides a novel approach and way to modernization of traditional Chinese medicine.

GC-TOF/MS-based metabolomic profiling of estrogen deficiency-induced obesity in ovariectomized rats.

AIM: To explore the alteration of endogenous metabolites and identify potential biomarkers using metabolomic profiling with gas chromatography coupled a time-of-flight mass analyzer (GC/TOF-MS) in a rat model of estrogen-deficiency-induced obesity. METHODS: Twelve female Sprague-Dawley rats six month of age were either sham-operated or ovariectomized (OVX). Rat blood was collected, and serum was analyzed for biomarkers using standard colorimetric methods with commercial assay kits and a metabolomic approach with GC/TOF-MS. The data were analyzed using multivariate statistical techniques. RESULTS: A high body weight and body mass index inversely correlated with serum estradiol (E2) in the OVX rats compared to the sham rats. Estrogen deficiency also significantly increased serum total cholesterol, triglycerides, and low-density lipoprotein cholesterol. Utilizing GC/TOF-MS-based metabolomic analysis and the partial least-squares discriminant analysis, the OVX samples were discriminated from the shams. Elevated levels of cholesterol, glycerol, glucose, arachidonic acid, glutamic acid, glycine, and cystine and reduced alanine levels were observed. Serum glucose metabolism, energy metabolism, lipid metabolism, and amino acid metabolism were involved in estrogen-deficiency-induced obesity in OVX rats. CONCLUSION: The series of potential biomarkers identified in the present study provided fingerprints of rat metabolomic changes during obesity and an overview of multiple metabolic pathways during the progression of obesity involving glucose metabolism, lipid metabolism, and amino acid metabolism.

Differential regulations of blood pressure and perturbed metabolism by total ginsenosides and conventional antihypertensive agents in spontaneously hypertensive rats.

AIM: To investigate the regulatory effects of total ginsenosides and the conventional antihypertensive agents (captopril, amlodipine, terazosin and hydrochlorothiazide) on the blood pressure and perturbed metabolism in spontaneously hypertensive rats (SHRs) and to analyze the cause-effect relationships between high blood pressure and the metabolic disorders of hypertension. METHODS: SHRs were administrated with total ginsenosides or the antihypertensive agents for eight weeks. Systolic blood pressure (SP) was measured every week and low-molecular-weight compounds in blood plasma were quantitatively analyzed using a nontargeted high-throughput metabolomic tool: gas chromatography/time of flight mass spectrometry (GC/TOFMS) . The metabolic patterns were evaluated using principal components analysis and potential markers of hypertension were identified. RESULTS: Total ginsenosides and the antihypertensive agents differentially regulated SP and the metabolic pattern in SHRs. Total ginsenosides caused a progressive and prolonged reduction of SP and markedly normalized the perturbed metabolism with 14 of 27 (51.8%) markers of hypertension which were regulated toward normal. Total ginsenosides also reduced free fatty acids' level toward normal levels. In contrast, captopril, amlodipine and terazosin efficiently depressed SP, but had little effect on metabolic perturbation with only 8 (29.6%), 4 (14.8%), and 4 (14.8%) markers, respectively, which were regulated. CONCLUSION: The metabolic changes persisted when the blood pressure was lowered by the conventional antihypertensive agents, suggesting that hypertension may not be the cause of the metabolic perturbation in SHRs.

[Metabonomic profiling of plasma metabolites in Wistar rats to study the effect of aging by means of GC/TOFMS-based techniques].

The global metabolite profiles of endogenous compounds of Wistar rats from 12 to 20 weeks old were investigated to take deep insight into and get better understanding of the pathogenesis of development and aging. Plasma from Wistar rats at 12, 14, 16, 18, and 20 weeks old were analyzed using GC/TOFMS. Multivariate data analysis was then used to process the metabonomic data which indicated excellent separation between different weeks and showed that the metabolic profiles of the samples changed with age, enabling age-related metabolic trajectories to be visualized. Decreased concentrations of citric acid, cis-aconitic acid, 9-(z)-hexadecenoic acid along with increased levels of hexanedioic acid, alpha-tocopherol, 3-indole propionic acid, etc contributed to the separation. Several major metabolic pathways were identified to be involved in metabolic regulation. This suggests that GC/TOFMS-based metabonomics is a powerful alternative approach to identifying potential biomarkers and investigating the physiological developments of aging and it is important to employ suitable age-match control group in metabonomic study of physiological monitoring, drug safety assessment, and disease diagnosis, etc.

Simultaneous determination of GFA and its active metabolites in human plasma by liquid chromatography electrospray ionization mass spectrometry and its application to pharmacokinetic studies.

A sensitive and rapid liquid chromatography electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed and validated for simultaneous quantification of guanfu base A (GFA) and its metabolites guanfu base I (GFI) and guanfu alcohol-amine (AA) in human plasma with phenoprolamine hydrochloride (DDPH) as the internal standard. The analytes were extracted from human plasma by using liquid-liquid extraction with ethyl acetate and the LC separation was performed on a Diamonsil C(18) analytical column (150 mm x 2.1 mm i.d., 5 microm). The MS acquisition was performed in selected ion monitoring (SIM) mode of positive ions. Analysis was carried out in SIM mode at m/z 430.25 for GFA [M+H](+), m/z 388.25 for GFI [M+H](+), m/z 346.25 for AA [M+H](+) and m/z 344.20 for the IS DDPH [M+H](+). The calibration curves were linear over the range of 50-5000 ng/mL for GFA and 5-1000 ng/mL for GFI and AA, with coefficients of correlation above 0.999. The lower limit of quantification for GFA was 1 ng/mL, while for GFI and AA were both 5 ng/mL. The intra- and inter-day precisions (CV) of analysis were within 9%, and the accuracy ranged from 91% to 108%. The overall recoveries for GFA, GFI and AA were about 94.2%, 87.8% and 80.6%, respectively. The total LC-MS run-time was only 5.5 min. This quantitation method was successfully applied to the simultaneous determination of GFA and its metabolites in human plasma for the metabolic study and pharmacokinetic evaluation.