Screening of differential components of Gegenqinlian decoction and their comparative pharmacokinetics in normal and pyrexia rats using UHPLC-FT-ICR-MS and UHPLC-MS/MS.

UHPLC combined with Fourier-transform ion cyclotron resonance MS metabonomic approach was employed to screen the differential components between normal rats and yeast-induced pyrexia rats after an oral administration of Gegenqinlian decoction (GQLD). Nine compounds, namely puerarin, daidzein, baicalin, wogonoside, wogonin, berberine, palmatine, jateorhizine, and coptisine, were identified as differential components in the plasma. A rapid, sensitive, selective, and accurate UHPLC-MS method was developed and fully validated for the simultaneous determination of the screened components in rat plasma after an oral administration of GQLD. The values for the limit of quantification ranged from 0.025 to 5.0 ng/mL. The inter- and intra-day precision of all analytes was ≤10.7%, with an accuracy of ≤10.5%. Good extraction recovery and matrix effects were also obtained. The method was successfully applied to a comparative pharmacokinetic study of GQLD in normal and pyrexia rats. The results showed that the pharmacokinetic behavior of the analytes was changed in pyrexia rats compared to normal rats. These results could provide beneficial guidance for clinical applications of GQLD.

Binding interaction of protoberberine alkaloids against acetylcholinesterase (AChE) using molecular dynamics simulations and QM/MM calculations.

Acetylcholinesterase (AChE) plays a vital role in Alzheimer's disease (AD), which is one of the most common causes of dementia. Discovering new effective inhibitors against AChE activity is seen to be one of the effective approaches to reduce the suffering from AD. Protoberberine alkaloids isolated from natural resources have previously been reported as potent AChE inhibitors. In order to gain insights into how these alkaloids could inhibit AChE, berberine, palmatine, and cyclanoline were selected to investigate in terms of binding orientation and their key interactions with AChE using molecular docking and molecular dynamics simulations and quantum chemical calculations. The results revealed that the molecular dynamics structures of palmatine and berberine indicated that their equilibrated structures did not occupy the gorge but they slightly moved away from the catalytic site (CAS). For cyclanoline, the binding mode was quite different from those of donepezil and the other protoberberine alkaloids: it preferred to stay deeper in the CAS site. Interaction energies and residual interaction energies confirmed that the key interactions for palmatine and berberine were π-π interactions with Trp286 and Tyr341 and H-bond interactions with Tyr124. Cyclanoline formed π-π interactions with Trp86 and H-bonds to the amino acids in the CAS site. The results suggested the importance of aromaticity in the core structure and the flexibility of the core structure or the substituents in order to fit into the narrow gorge. The HOMO, LUMO, bioavailability, drug-likeness and pharmacokinetics were also predicted. The results obtained will be useful for further AD drug development.

Pharmacokinetic study of three different formulations of l-tetrahydropalmatine in brain tissues of rats.

l-Tetrahydropalmatine (l-THP), an active alkaloid compound isolated from Rhizoma Corydalis-yanhusuo, has been reported to possess biological activity for treating cocaine use. To enhance both oral bioavailability and brain penetration, three formulations of l-THP suspension, mixture of l-THP-puerarin and self-microemulsifying drug delivery systems (SMEDDS) were prepared. A sensitive and reliable ultra-high-performance liquid chromatography with tandem mass spectrometry method was developed and validated for the simultaneous determination of l-THP and its active metabolite l-isocorypalmine (l-ICP) in rat brain. Diazepam was used as the internal standard. The chromatographic separation was achieved on a Bonshell ASB C18 column at 30°C using acetonitrile-aqueous formic acid as mobile phase in gradient mode. The linearity was validated over the concentration ranges of 4.00-2,500 ng/ml for l-THP and 0.400-500 ng/ml for l-ICP. Full method validation was within the acceptance limits. The method was successfully used to determine the pharmacokinetics of two analytes following oral administration of these three formulations to rats. A significant difference was observed in the main pharmacokinetic parameters between SMEDDS and the suspension, and a 3.25- and 2.97-fold increase in the relative bioavailability of l-THP and l-ICP, respectively, was observed with the SMEDDS compared with the suspension formulation. It was concluded that SMEDDS enhanced the absorption of l-THP and l-ICP and delayed their release in brain.

Pharmacokinetic Effects of l-Tetrahydropalmatine on Ketamine in Rat Plasma by Ultraperformance Liquid Chromatography Tandem Mass Spectrometry.

Male Sprague-Dawley rats (n = 18) were randomly divided into three groups: a saline group (20 mL/kg by gavage), a ketamine (KET) group (100 mg/kg by gavage), and a KET (the same routes and doses) combined with levo-tetrahydropalmatine (l-THP; 40 mg/kg by gavage) group (n = 6). Blood samples were acquired at different time points after drug administration. A simple and sensitive ultraperformance liquid chromatography tandem mass spectrometry (UPLC-MS/MS) method was established to determine the concentrations of KET and its metabolite, norketamine (NK), in rat plasma. Chromatographic separation was achieved using a BEH C18 column (2.1 mm × 50 mm, 1.7 µm) with chlorpheniramine maleate (Chlor-Trimeton) as an internal standard (IS). The initial mobile phase consisted of acetonitrile-water with 0.1% methanoic acid (80 : 20, v/v). The multiple reaction monitoring (MRM) modes of m/z 238.1→m/z 179.1 for KET, m/z 224.1→m/z 207.1 for NK, and m/z 275→m/z 230 for Chlor-Trimeton (IS) were utilized to conduct a quantitative analysis. Calibration curves of KET and NK in rat plasma demonstrated good linearity in the range of 2.5-500 ng/mL (r > 0.9994), and the lower limit of quantification (LLOQ) was 2.5 ng/mL for both. Moreover, the intra- and interday precision relative standard deviation (RSD) of KET and NK were less than 4.31% and 6.53%, respectively. The accuracies (relative error) of KET and NK were below -1.41% and -6.07%, respectively. The extraction recoveries of KET and NK were more than 81.23 ± 3.45% and 80.42 ± 4.57%, respectively. This sensitive, rapid, and selective UPLC-MS/MS method was successfully applied to study the pharmacokinetic effects of l-THP on KET after gastric gavage. The results demonstrated that l-THP could increase the bioavailability of KET and promote the metabolism of KET. The results showed that l-THP has pharmacokinetics effects on KET in rat plasma.

UPLC-MS/MS simultaneous determination of seven active ingredients of Yaobitong capsule in rat plasma and its integrated pharmacokinetic application.

A reliable and sensitive UPLC-MS/MS method was first established and validated for the simultaneous determination of seven active ingredients of Yaobitong capsule in rat plasma: ginsenoside Rg1, ginsenoside Rb1, osthole, tetrahydropalmatine, paeoniflorin, albiflorin, and ferulic acid. And this method was further applied for the integrated pharmacokinetic study of Yaobitong capsule in rats after oral administration. Plasma samples (100 µL) were precipitated with 300 µL of methanol using carbamazepine as internal standard. Chromatographic separation was achieved using an Aquity UPLC BEH C18 column (100 × 2.1 mm, 1.7 µm), with the mobile phase consisting of 0.1% formic acid and acetonitrile. The method was validated using a good linear relationship (r ≥ 0.991), and the lower limit of quantification of the analytes ranged from 0.5 to 40 ng/mL. In the integrated pharmacokinetic study, the weight coefficient was calculated by the ratio of AUC0-∞ of each component to the total AUC0-∞ of the seven active ingredients. The integrated pharmacokinetic parameters Cmax , Tmax , and t1/2 were 81.54 ± 9.62 ng/mL, 1.00 ± 0.21 h, and 3.26 ± 1.14 h, respectively. The integration of pharmacokinetic parameters showed a shorter t1/2 because of fully considering the contribution of the characteristics of each active ingredient to the overall pharmacokinetics.

Palmatine: A review of pharmacological properties and pharmacokinetics.

The aim of this review is to collect together the results of the numerous studies over the last two decades on the pharmacological properties of palmatine published in scientific databases like Scopus and PubMed, which are scattered across different publications. Palmatine, an isoquinoline alkaloid from the class of protoberberines, is a yellow compound present in the extracts from different representatives of Berberidaceae, Papaveraceae, Ranunculaceae, and Menispermaceae. It has been extensively used in traditional medicine of Asia in the treatment of jaundice, liver-related diseases, hypertension, inflammation, and dysentery. New findings describe its possible applications in the treatment of civilization diseases like central nervous system-related problems. This review intends to let this alkaloid come out from the shade of a more frequently described alkaloid: berberine. The toxicity, pharmacokinetics, and biological activities of this protoberberine alkaloid will be developed in this work.

Pharmacokinetics and tissue distribution of four major bioactive components in rats after oral administration of Xianglian pill.

Xianglian pill, a TCM prescription, consists of Rhizome Coptidis and Radix Aucklandiae, and has been used to treat gastrointestinal disease for many years. Berberine, jatrorrhizin, coptisine and palmatine are four representative alkaloids in Xianglian pill. Knowing that the drug disposal process in vivo is closely related to the toxicity and efficacy of a drug, it is important to classify the disposal properties of these alkaloids. In this study, the pharmacokinetics and tissue distribution of the four alkaloids were investigated. The analytical samples were analyzed using a validated HPLC-MS/MS method. The results showed that the four alkaloids could be slowly absorbed. The Cmax values of berberine, jatrorrhizin, coptisine and palmatine were 11.420, 2.287, 2.584 and 3.102 ng/ml, respectively. Subsequently, the tissue distribution studies showed that they were quickly distributed to various tissues with rich blood flow in the body.

Palmatine: A review of its pharmacology, toxicity and pharmacokinetics.

Palmatine is a natural isoquinoline alkaloid and has been widely used in pharmaceutical field. The purpose of this review is to provide the latest and comprehensive information on the pharmacology, toxicity and pharmacokinetics of palmatine in the past, to explore the therapeutic potential of this compound and look for ways to reduce toxicity. Information on palmatine was collected from the internet database PubMed, Elsevier, ResearchGate, Web of Science, Wiley Online Library and Europe PMC using a combination of keywords including "pharmacology", "toxicology", "pharmacokinetics". All studies of this genus were included in this review until March 2019. Palmatine has a wide spectrum of pharmacological effects, including anti-cancer, anti-oxidation, anti-inflammatory, neuroprotection, anti-bacterial, anti-viral and regulating blood lipids. However, palmatine has obvious DNA toxicity, and has a complex effect on metabolic enzymes in the liver. Pharmacokinetic studies have demonstrated that glucuronidation and sulfation are the main metabolic pathways of palmatine. Palmatine can be used in many diseases. Future research directions include: how the concentration of palmatine affects pharmacological effects and toxicity; the mechanism of synergy between palmatine and other protoberberine alkaloid; Structural modification of palmatine is one of the key methods to enhance pharmacological activity and reduce activity.

A review on analytical methods for natural berberine alkaloids.

Berberine alkaloids, a group of protoberberine alkaloids under the classification of isoquinoline alkaloids, include berberine, coptisine, palmatine, columbamine, dehydrocorydaline, jatrorrhizine, and epiberberine from natural sources. Studies have shown that berberine alkaloids have various pharmacological functions, such as antibacterial, antiviral, blood pressure-lowering, hypoglycaemic, antiarrhythmia, and anticancer effects. Therefore, it is worthwhile to develop analytical methods to investigate the pharmacokinetics and activity mechanisms of berberine alkaloids and to study berberine alkaloids more comprehensively. Current analytical methods for berberine alkaloids include liquid chromatography, thin-layer chromatography, ultraviolet spectroscopy, capillary electrophoresis, and gas chromatography. The most widely used detection method is mass spectrometry. In order to provide a systematic and comprehensive summary and to serve as a reference for the future pharmacokinetics studies and analysis of berberine alkaloids, analytical methods for natural berberine alkaloids that have been used in the past ten years are reviewed here.

Simultaneous determination of eight bioactive components in rat plasma after oral administration of Yan-Ke-Ning-Tablet by liquid chromatography coupled with Q-Exactive Orbitrap tandem mass spectrometry.

A rapid, sensitive and reliable quantitative method based on ultra-high performance liquid chromatography coupled with Q-Exactive Orbitrap tandem mass spectrometry was developed for simultaneous determination of berberine, berberrubine, palmatine, jatrorrhizine, columbamine, baicalin, baicalein and wogonin in rat plasma after oral administration with Yan-Ke-Ning-Tablet (YKNT). After precipitation with acetonitrile, the plasma samples were separated on a reverse-phase C18 column with 1 mm ammonium acetate containing 0.2% acetic acid-acetonitrile as mobile phase. Calibration curves showed good linearity (r > 0.9983) over the tested concentration ranges of 0.5-200 ng/mL for berberine, berberrubine, palmatine, jatrorrhizine and columbamine, and 1-300 ng/mL for baicalin, baicalein and wogonin. The precision (relative standard deviation) at three different concentration levels was <12.15% and the accuracy (relative error) ranged from -8.24 to 10.85%. No matrix effects were observed with matrix effect value ranging from 89.23 to 107.68%. The extraction recovery was in the range of 82.34-92.31%. The validated assay was further successfully applied to the pharmacokinetic study of these components after oral administration of YKNT. The present study provides the pharmacokinetic profiles of major bioactive components found in YKNT, and provides valuable information regarding the chemical components that were absorbed into plasma, which will be helpful for understanding the therapeutic effects of YKNT.

Biotransformation and tissue distribution of protopine and allocryptopine and effects of Plume Poppy Total Alkaloid on liver drug-metabolizing enzymes.

In this study, the biotransformation in the plasma, urine and feces of rats following oral administration of protopine (PRO) and allocryptopine (ALL)were explored using HPLC-QqTOF MS. An HPLC-MS/MS method for the determination of tissues was developed and applied to the tissue distribution study in rats following intragastric administration of Plume Poppy Total Alkaloid for 3 weeks. A total of ten PRO metabolites and ten ALL metabolites were characterized in rats in vivo. Among these metabolites, six PRO metabolites and five ALL metabolites were reported for the first time. The predicated metabolic pathways including ring cleavage, demethylation following ring cleavage, and glucuronidation were proposed. The low-concentration residue of PRO and ALL in various tissues was detected at 24 h and 48 h after dosing, which indicated that both compounds could be widely distributed in tissues and exist as low levels of residue. The activities of erythromycin N-demethylase, aminopyrine N-demethylase and NAD (P)H quinone oxidoreductase in female rats can be induced post-dose, but these activities were inhibited in male rats. The proposed biotransformation and residues of PRO and ALL and their effects on enzymes may provide a basis for clarifying the metabolism and interpreting pharmacokinetics.

[Pharmacokinetics and oral bioavailability of palmatine and jatrorrhizine in Huangteng in rats].

In this study, the total alkaloids of Huangteng were given to the rats by the methods of intragastric administration and tail vein. After the concentration changes of palmatine and jatrorrhizine in the plasma of rats were determined by RP-HPLC, pharmacokinetic parameters and oral bioavailability were calculated by 3P97 software. After the rats were pre-treated with total alkaloid 60 mg•kg⁻¹ by the methods of intragastric administration and tail vein, the main pharmacokinetic parameters were determined as follows： in the intragastric administration group, the Cmax of palmatine and jatrorrhizine were (0.91±0.06), (0.70±0.08) mg•L⁻¹; tmax of palmatine and jatrorrhizine were (35.24±0.83), (47.76±1.24) min; t1/2 of palmatine and jatrorrhizine were (187.03±1.53), (105.64±16.99) min, AUC of palmatine and jatrorrhizine were (280.30±18.69), (144.36±1.06) mg•min•L⁻¹; in the intravenous injection group, the t1/2 of palmatine and jatrorrhizine were (172.18±12.38), (147.26±1.82) min; AUC of palmatine and jatrorrhizine were (2 553.14±214.91), (328.83±10.81) mg•min•L⁻¹. The oral bioavailability of palmatine was 10.98% and jatrorrhizine was 43.90%.

Elucidation of Compatibility Interactions of Traditional Chinese Medicines: In Vitro Absorptions Across Caco-2 Monolayer of Coptidis Rhizoma and Euodiae Fructus in Zuojin and Fanzuojin Formulas as A Case.

Traditional Chinese medicines are often combined as formulae and interact with each other. As for Coptidis Rhizoma (CR) and Euodiae Fructus (EF), the most classical compatibilities were Zuojin (ZJF) and Fanzuojin formulas (FZJF) with reverse mixture ratios and opposite effects. To compare in vitro absorption interactions between CR and EF, bidirectional transports across Caco-2 cell monolayer of extracts of two formulas and equivalent single herbs were studied. Eighteen alkaloids from CR and EF were determined by liquid chromatography coupled to tandem mass spectrometry. Parameter apparent permeability coefficient (Papp ) and efflux rate (ER) values showed that most alkaloids were well or moderately absorbed and six quaternary protoberberine alkaloids from CR had obvious efflux. ZJF compatibilities reduced both Papp BL→AP and ER values of three indole alkaloids, and increased ER values of two quinolone alkaloids from EF. FZJF compatibilities obviously affected the bidirectional Papp values of CR alkaloids, weakened ERs of five protoberberines from CR and enlarged ERs of two quinolones from EF. Conclusions were drawn that different compatibility ratios of CR and EF led to different interactions on the in vitro absorption of alkaloids. The results may provide a good reference for interaction studies on the compatibilities of traditional Chinese medicines. Copyright © 2017 John Wiley & Sons, Ltd.

Pharmacokinetics and Safety Assessment of l-Tetrahydropalmatine in Cocaine Users: A Randomized, Double-Blind, Placebo-Controlled Study.

Cocaine use disorder (CUD) remains a significant public health challenge. l-Tetrahydropalmatine (l-THP), a well-tolerated and nonaddictive compound, shows promise for the management of CUD. Its pharmacologic profile includes blockade at dopamine and other monoamine receptors and attenuation of cocaine self-administration, reinstatement, and rewarding properties in rats. This study evaluated the safety of l-THP in human cocaine users and its influence on the safety and pharmacokinetics (PK) of cocaine. Twenty-four cocaine-using adult men were randomized to receive l-THP (30 mg twice a day orally) or placebo double-blind for 4 days, with an intranasal cocaine (40 mg) challenge on the fourth day. Safety and tolerability were evaluated using vital signs, ECG, clinical laboratory tests, and standardized self-report instruments. Peripheral venous blood was collected periodically and later assayed for l-THP and cocaine using highly sensitive and specific ultraperformance liquid chromatography-fluorescence detection (UPLC-FLD) methods. Twenty subjects completed the study, of whom 19 provided complete PK data. The short 3.5-day course of l-THP was safe and well tolerated and did not affect cocaine's PK or its acute cardiovascular effects. The cocaine AUC0→∞ was 211.5 and 261.4 h·ng/mL, and the Cmax was 83.3 and 104.5 ng/mL for the l-THP and placebo groups, respectively. In addition there were no significant differences in the number of side effects reported in each group (l-THP group 22 [48%], placebo group 24 [52%]) or vital signs including, heart rate, blood pressure, complete blood count, or ECG. These findings suggest that oral THP has promise for further development as a treatment for CUD.

Pharmacokinetics, tissue distribution, and excretion studies of l-isocorypalmine using ultra high performance liquid chromatography with tandem mass spectrometry.

l-Isocorypalmine is a newly identified metabolite of l-tetrahydropalmatine with a unique dual pharmacological profile as a partial dopamine receptor 1 agonist and dopamine receptor 2 antagonist properties for treating cocaine use disorder. The purpose of this study was to explore the pharmacokinetic profiles, tissue distribution, and excretion of l-isocorypalmine in Sprague-Dawley rats. A sensitive and reliable ultra high performance liquid chromatography with tandem mass spectrometry method was developed and validated for determination of l-isocorypalmine in biological samples. The biological samples were extracted by liquid-liquid extraction and separated on a Bonshell ASB C18 column (2.1 × 100 mm, 2.7 µm, Agela) with gradient mobile phase at the flow rate of 0.2 mL/min. The detection was performed by positive electrospray ionization with multiple reaction monitoring mode. Satisfactory linearity, precision, accuracy, extraction recovery, and acceptable matrix effect were achieved. The quantitative method was successfully applied to the pharmacokinetics, tissue distribution, and excretion study of l-isocorypalmine. The results showed that l-isocorypalmine was rapidly distributed, and eliminated from rat plasma and manifested linear dynamics in a dose range of 7.5-15 mg/kg. In addition, the results would be helpful for further clinical reference of l-isocorypalmine as a potential candidate drug for the treatment of cocaine addiction.

Development and validation of a high performance liquid chromatography quantification method of levo-tetrahydropalmatine and its metabolites in plasma and brain tissues: application to a pharmacokinetic study.

Levo-tetrahydropalmatine (l-THP) is an alkaloid isolated from Chinese medicinal herbs of the Corydalis and Stephania genera. It has been used in China for more than 40 years mainly as an analgesic with sedative/hypnotic effects. Despite its extensive use, its metabolism has not been quantitatively studied, nor there a sensitive reliable bioanalytical method for its quantification simultaneously with its metabolites. As such, the objective of this study was to develop and validate a sensitive and selective HPLC method for simultaneous quantification of l-THP and its desmethyl metabolites l-corydalmine (l-CD) and l-corypalmine (l-CP) in rat plasma and brain tissues. Rat plasma and brain samples were processed by liquid-liquid extraction using ethyl acetate. Chromatographic separation was achieved on a reversed-phase Symmetry® C18 column (4.6 × 150 mm, 5 µm) at 25°C. The mobile phase consisted of acetonitrile-methanol-10 mm ammonium phosphate (pH 3) (10:30:60, v/v) and was used at a flow rate of 0.8 mL/min. The column eluent was monitored at excitation and emission wavelengths of 230 and 315 nm, respectively. The calibration curves were linear over the concentration range of 1-10,000 ng/mL. The intra- and interday reproducibility studies demonstrated accuracy and precision within the acceptance criteria of bioanalytical guidelines. The validated HPLC method was successfully applied to analyze samples from a pharmacokinetic study of l-THP in rats. Taken together, the developed method can be applied for bioanalysis of l-THP and its metabolites in rodents and potentially can be transferred for bioanalysis of human samples.

Simultaneous determination of l-tetrahydropalmatine and its active metabolites in rat plasma by a sensitive ultra-high-performance liquid chromatography with tandem mass spectrometry method and its application in a pharmacokinetic study.

A sensitive and reliable ultra-high-performance liquid chromatography with tandem mass spectrometry (UHPLC-MS/MS) method was developed and validated for simultaneous determination of l-tetrahydropalmatine (l-THP) and its active metabolites l-isocorypalmine (l-ICP) and L-corydalmine (l-CD) in rat plasma. The analytes were extracted by liquid-liquid extraction and separated on a Bonshell ASB C18 column (2.1 × 100 mm; 2.7 µm; Agela) using acetonitrile-formic acid aqueous as mobile phase at a flow rate of 0.2 mL/min in gradient mode. The method was validated over the concentration range of 4.00-2500 ng/mL for l-THP, 0.400-250 ng/mL for l-ICP and 1.00-625 ng/mL for l-CD. Intra- and inter-day accuracy and precision were within the acceptable limits of <15% at all concentrations. Correlation coefficients (r) for the calibration curves were >0.99 for all analytes. The quantitative method was successfully applied for simultaneous determination of l-THP and its active metabolites in a pharmacokinetic study after oral administration with l-THP at a dose of 15 mg/kg to rats.

Simultaneous Determination of Multiple Components in Guanjiekang in Rat Plasma via the UPLC-MS/MS Method and Its Application in Pharmacokinetic Study.

Guanjiekang (GJK) that is formed by five medicinal herbs including Astragali Radix, Aconiti Lateralis Radix Praeparaia, Glycyrrhizae Radix et Rhizoma, Corydalis Rhizoma and Paeoniae Radix Alba was used for the treatment of rheumatoid arthritis (RA). However, the pharmacokinetic (PK) profile of active components in GJK remains unclear. This study aims to evaluate the pharmacokinetic behavior of seven representative active constituents in GJK (i.e., benzoylhypaconine, benzoylmesaconine, paeoniflorin, tetrahydropalmatine, calycosin-7-glucoside, formononetin and isoliquiritigenin) after oral administration of GJK in rats. A rapid, sensitive and reliable ultra-performance liquid chromatography-tandem mass spectrometer (UPLC-MS/MS) method has been successfully developed for the simultaneous determination of these seven constituents in rat plasma. Chromatographic separation was achieved on a C18 column with a gradient elution program that consists of acetonitrile and water (containing 0.1% formic acid) at a flow rate of 0.35 mL/min. Detection was performed under the multiple reaction monitoring (MRM) in the positive electrospray ionization (ESI) mode. The calibration curves exhibited good linearity (R² > 0.99) over a wide concentration range for all constituents. The accuracies ranged from 92.9% to 107.8%, and the intra-day and inter-day precisions at three different levels were below 15%. Our PK results showed that these seven compounds were quickly absorbed after the administration of the GJK product, and Tmax ranged from 30 min to 189 min. The in vivo concentrations of paeoniflorin and isoliquiritigenin were significantly higher than the reported in vitro effective doses, indicating that they could partly contribute to the therapeutic effect of GJK. Therefore, we conclude that pharmacokinetic studies of representative bioactive chemicals after administration of complex herbal products are not only necessary but also feasible. Moreover, these seven compounds that were absorbed in vivo can be used as indicator standards for quality control and for determining pharmacokinetic behavior of herbal medicines in clinical studies.

Cationic lipid emulsions as potential bioadhesive carriers for ophthalmic delivery of palmatine.

Palmatine (PM) is a potent anti-infective agent used to treat eye diseases. However, PM is less effective for ocular application due to short residence time within the eyes. This study aimed to develop a cationic lipid emulsions (CLEs) for ophthalmic delivery of PM and evaluate its suitability in infection treatment. PM-loaded CLEs (PM-CLEs) were prepared through emulsifying/high-pressure homogenisation and characterised by particle size, ζ potential and morphology. The resulting PM-CLEs possessed a particle size of 192 nm and ζ potential of 45 mV around. In vitro release illustrated that PM was released less from CLEs. Corneal bioadhesion test showed that PM-CLEs exhibited an enhanced ocular residence time. Improved anti-infective activity was achieved in the model of fungus-induced keratitis. Furthermore, PM-CLEs demonstrated predominant cellular uptake and internalisation in the corneal epithelial cells. These results provide proof of concept that CLEs are promising bioadhesive carriers for ophthalmic delivery of PM.

Characterization of human metabolism and disposition of levo-tetrahydropalmatine: Qualitative and quantitative determination of oxidative and conjugated metabolites.

Levo-tetrahydropalmatine (l-THP) is a tetrahydroprotoberberine isoquinoline alkaloid and has been used as an analgesic agent in China for over 50 years. Recent studies revealed that l-THP was effective in the treatment of drug addiction. However, the plasma metabolic profile, mass balance and clearance pathways of l-THP in human remain unknown. In the present study, an analytical strategy was developed for qualitative and quantitative investigation of metabolism and disposition of l-THP in human. Detection and structural characterization of l-THP metabolites were performed using liquid chromatography-quadrupole time-of-flight mass spectrometry. Selected major metabolites in plasma, urine and feces determined by liquid chromatography with UV detection were further quantified using a triple quadruple mass spectrometry and reference standards. A total of 20 metabolites were identified, most of which were formed via demethylation, mono-hydroxylation, and glucuronidation and sulfonation of desmethyl metabolites. Five major metabolites accounted for over 10% of the parent drug concentration in plasma. Major urinary and fecal metabolites and the parent drug that were monitored for 72h accounted for 46.3% of the dose, while only 0.16% of the dose was the unchanged drug. Multiple demethylations followed by glucuronide and sulfate conjugations and renal excretion were the major drug clearance pathways of l-THP in human.