Simultaneous determination of berberine in rat blood, liver and bile using microdialysis coupled to high-performance liquid chromatography

Development of an accurate synchronous transport signal hand-held sensing platform for fluorescence-based berberine on-site detection

BACKGROUND

Berberine is widely used in clinical treatment because of its wide antibacterial spectrum and low toxic side effects. However, its abuse could lead to bacterial resistance and several other adverse effects. In addition, measuring the content of berberine in environmental water samples helps to monitor its accumulation and metabolism in ecosystems. Traditional detection methods usually need to be carried out in the laboratory, involving complex processing procedures, which are not only time-consuming, but also unfavorable for rapid response and decision-making. Therefore, it is necessary to develop portable instruments to provide reasonable guidance on the addition and intake of berberine to reduce the harm caused by its abuse.

RESULTS

In this work, an accurate synchronous transport signal hand-held sensing platform (STSHSP) with a low-cost, easy-to-manufacture, independent use was developed by using photoelectric conversion technology, Bluetooth technology, remote synchronous signal technology, electrical technology, and 3D printing technology. To verify the performance of STSHSP, a 5-oxo-2,3-dihydro-5H-thiazolo [3,2-a] pyridine-3,7-dicarboxylic acid (TPDCA) with ultra-high quantum yield was designed and synthesized as a probe. TPDCA exhibited bright blue fluorescence under the ultraviolet light of 365 nm which could be quenched by berberine through the inner filter effect. In the range of 0.1-80 μg/mL, the voltage displayed by the prepared STSHSP has a good linearity with the berberine concentration (R2 = 0.9997) with a detection limit of 28.32 ng/mL. The portable sensor demonstrated good stability, accuracy, and reliability in detecting actual river water, urine, traditional Chinese medicine, and its preparation samples.

SIGNIFICANCE

The sensor with its compact structure, portability, and simple operation was suitable for in-situ detection with accurate, reliable, and feasible results, which is beneficial for improving drug quality and ensuring human health. Fortunately, the device could transmit the information to the control center and/or a third-party supervision institution in real-time, which could effectively eliminate the trust crisis. The sensor has broad application prospects in the field of environmental water quality detection and drug safety.

Tetraphenylethylene sulfonate derivative as turn-on fluorescent sensor for berberine chloride detection in aqueous solution

A negatively-charged tetraphenylethylene derivative (TPE-SE) was designed and synthesized as turn-on fluorescent sensor for berberine chloride (BBC) detection in aqueous solution. The fluorescent property and detection mechanism were elucidated by UV-vis absorption spectra, photoluminescence spectra, dynamic light scattering experiments. The results reveal that the BBC can lead to aggregation-induced emission of TPE-SE due to the electrostatic interactions, endowing TPE-SE with excellent turn-on detecting ability, high selectivity and sensitivity to BBC. The detection limit is as low as 6.58 × 10^-6M. These results should be applicable to fabricate special turn-on fluorescent sensors towards various antibiotics, and it is crucially important for achieving reasonable control and intake of small biomolecules.

Anti-inflammatory efficacy of Berberine Nanomicelle for improvement of cerebral ischemia: formulation, characterization and evaluation in bilateral common carotid artery occlusion rat model

BACKGROUND

Berberine (BBR) is a plant alkaloid that possesses anti-inflammatory and anti-oxidant effects with low oral bioavailability. In this study, micelle formulation of BBR was investigated to improve therapeutic efficacy and examined its effect on the secretion of inflammatory cytokines in cerebral ischemia in the animal model.

MATERIAL AND METHODS

Nano formulation was prepared by thin-film hydration method, and characterized by particle size, zeta potential, morphology, encapsulation efficacy, and drug release in Simulated Gastric Fluid (SGF) and Simulated Intestine Fluid (SIF). Then, Wistar rats were pretreated with the drug (100 mg/kg) and nano-drug (25, 50, 75, 100 mg/kg) for 14 days. Then, on the fourteenth day, stroke induction was accomplished by Bilateral Common Carotid Artery Occlusion (BCCAO); after that, Tumor Necrosis Factor - Alpha (TNF-α), Interleukin - 1 Beta (IL-1ß), and Malondialdehyde (MDA) levels were measured in the supernatant of the whole brain, then the anti-inflammatory effect of BBR formulations was examined.

RESULT AND DISCUSSION

Micelles were successfully formed with appropriate characteristics and smaller sizes than 20 nm. The Poly Dispersity Index (PDI), zeta potential, encapsulation efficacy of micelles was 0.227, - 22 mV, 81%, respectively. Also, the stability of nano micelles was higher in SGF as compared to SIF. Our outcomes of TNF-a, IL-1B, and MDA evaluation show a significant ameliorating effect of the Berberine (BBR) and BBR-loaded micelles in pretreated groups.

CONCLUSION

Our experimental data show that pretreated groups in different doses (nano BBR 100, 75, 50 mg/kg, and BBR 100 mg/kg) successfully showed decreased levels of the inflammatory factors in cerebral ischemia compared with the stroke group and pretreated group with nano BBR in the dose of 25 mg/kg. Nano BBR formulation with a lower dose can be a better candidate than conventional BBR formulation to reduce oxidative and inflammatory factors in cerebral ischemia. Therefore, BBR-loaded micelle formulation could be a promising protective agent on cerebral ischemia.

A Validated Liquid Chromatographic Method for Berberine Analysis in Tissue and Application

Simple and rapid high-performance liquid chromatography methods were developed for the determination of berberine (BB) in various rat tissues so as to evaluate a P-gp inhibitor, glycyrrhetinic acid (GA), on BB's oral bioavailability. Acetonitrile was used to extract BB from tissues and showed different extraction recoveries in diverse tissues. The intra- and interday precision and accuracy were less than 10%. Long-term stability, pre (post) -preparative stability, and freeze-thaw stability were evaluated, and the results showed it could meet the need of this study. The proposed methods were subsequently applied to investigate the possible drug-drug interaction of GA and BB in vivo from the aspect of tissue distribution. The results showed that no significant difference was found between the group of low dose and high dose at the same time point. The tissue distributions show a saturated model, i.e., the content of BB in tissue tends to be constant while its dose is more than 200 mg/kg. Besides, the contents of BB ranged from high to low according to the order of the liver, kidney, and spleen. The BB content in the liver is especially high as compared to other tissues.

Berberine-Loaded Liposomes for the Treatment of Leishmania infantum-Infected BALB/c Mice

Berberine (BER)—an anti-inflammatory quaternary isoquinoline alkaloid extracted from plants—has been reported to have a variety of biologic properties, including antileishmanial activity. This work addresses the preparation of BER-loaded liposomes with the aim to prevent its rapid liver metabolism and improve the drug selective delivery to the infected organs in visceral leishmaniasis (VL). BER liposomes (LP-BER) displayed a mean size of 120 nm, negative Z-potential of −38 mV and loaded 6 nmol/μmol lipid. In vitro, the loading of BER in liposomes enhanced its selectivity index more than 7-fold by decreasing its cytotoxicity to macrophages. In mice, LP-BER enhanced drug accumulation in the liver and the spleen. Consequently, the liposomal delivery of the drug reduced parasite burden in the liver and spleen by three and one logarithms (99.2 and 93.5%), whereas the free drug only decreased the infection in the liver by 1-log. The organ drug concentrations—far from IC₅₀ values— indicate that BER immunomodulatory activity or drug metabolites also contribute to the efficacy. Although LP-BER decreased 10-fold—an extremely rapid clearance of the free drug in mice—the value remains very high. Moreover, LP-BER reduced plasma triglycerides levels.

Preparation and Evaluation of Antidiabetic Agents of Berberine Organic Acid Salts for Enhancing the Bioavailability

Berberine has many pharmacological effects, such as antidiabetic, antimicrobial, anti-inflammatory, and antioxidant, but the question remains on how its low oral bioavailability has greatly limited its clinical application. As a safer hypoglycemic agent, we must evaluate the bioavailability of berberine organic acid salts (BOAs) to ensure that the bioavailability of berberine is not negatively affected. It has been proven that the bioavailability of BOAs is higher than that of BH (berberine hydrochloride); especially BF (berberine fumarate) and BS (berberine succinate), which are improved by 1.278-fold and 1.313-fold, respectively. After 1 h of oral administration, berberine mainly acted on the stomach of mice, it also influenced the liver, kidney, lungs, and intestines after 4 h. The accumulation of BF in the lung is more evident than BH. Our analysis shows that these results are closely related to the regulation of organic acids and berberine in the intestinal tract, they also indicate the influence of intestinal flora on berberine metabolism.

Determination of berberine hydrochloride using a fluorimetric method with silica nanoparticles as a probe

The interaction of silica nanoparticles (SiO₂NPs) with berberine hydrochloride (BRH) was studied in aqueous solution at pH 9.0 and room temperature by using fluorophotometry. Based on a significant enhancement of the fluorescence intensity of the SiO₂NPs–BRH aggregates, a spectrofluorimetric method which was simple, sensitive and green was developed for the determination of BRH in aqueous solution. The linear range of the method was from 2.0–50.0 μg L⁻¹ with a detection limit of 0.73 μg L⁻¹. There was no interference from the compounds normally used to formulate pharmaceutical tablets. The proposed method was applied to the determination of BRH in tablets with satisfactory results and good consistency with the results obtained by standard methods.

A simple, green and sensitive spectrofluorimetric method was proposed for the determination of berberine hydrochloride (BRH) in aqueous solution.

Preparation, pharmacokinetics and tumour-suppressive activity of berberine liposomes

Objectives

Berberine (BBR) has shown promising antitumour effects in vitro. However, intravenous administration of BBR solution is complicated by lethal adverse cardiovascular effects. The aim of this study was to prepare common and polyethylene glycol (PEG)-modified long-circulating BBR liposomes and evaluate their efficacy and safety as potential antitumour agents.

Methods

Physiochemical properties of common and long-circulating BBR liposomes were characterized including particle size, Zeta potential and thermal stability. Pharmacokinetic and tissue distribution study of liposomal BBR was performed in rats and tumour-bearing nude mice, respectively. Antitumour efficacy and safety were observed in SGC-7901 tumour-xenografted mice.

Key findings

Berberine liposomes showed homogenous morphology, storage stability and sustained-releasing behaviour in vitro. BBR liposomes led to significantly increased circulation retention of BBR in comparison with BBR solution. In tumour-bearing mice, BBR liposomes selectively increased BBR concentrations in the liver, spleen, lung and tumour, while conferred lower distribution to the heart and kidney. Importantly, chronic administration of BBR liposomes proved effective and safe in suppressing the tumour growth in nude mice, especially the PEG-modified long-circulating liposomes.

Conclusion

Our study suggested that BBR liposomes may provide a safe form of intravenous drug therapy for strengthening the antitumour effects of BBR.

Improve bile duct-targeted drug delivery and therapeutic efficacy for cholangiocarcinoma by cucurbitacin B loaded phospholipid complex modified with berberine hydrochloride

In present study, a novel phospholipid complex loaded cucurbitacin B modified with berberine hydrochloride (CUB-PLC-BER) was prepared by a simple solvent evaporation method with the aim of improving bile duct-targeted drug delivery and therapeutic efficacy for cholangiocarcinoma (CC). The complex's physicochemical properties were systemically investigated in terms of scanning electron microscopy (SEM), x-ray diffraction (XRD) and infrared absorption spectroscopy (IR). In vivo and in vitro antitumor studies, CUB-PLC-BER and the unmodified cucurbitacin B-phospholipid complex (CUB-PLC) presented stronger antitumor efficacy against human cholangiocarcinoma cells (QBC939 cells) than free cucurbitacin B (CUB), while phospholipids (PL) itself had no significant toxicity. Besides that, CUB-PLC showed the advantage over the free CUB and CUB-PLC-BER with regard to the inhibition of tumor growth in vivo antitumor study. Failure to establish the orthotopic CC model, the study attempted to measure the level of CUB in plasma and in bile to explore bile duct-targeted effect indirectly. In the pharmacokinetics study in rats, the average values of Cmax and AUC0-8h of CUB-PLC-BER group in rat bile were higher than those of CUB-PLC, while an opposite result was found in plasma. Meanwhile, the Cmax, AUC0-8h and AUC0-24h of CUB were the least both in plasma and in bile. The results indicated that the CUB-PLC-BER tended to provide a high and prolonged drug concentration to bile duct, and PL played a central role in internalizing CUB into cells to improve the water insoluble drug's permeability, which was of great benefit to enhance the bioavailability of CUB and improve therapeutic efficacy of CC. These results elucidated the potential of CUB-PLC-BER as drug delivery system for improving bile duct-targeted and therapeutic efficacy for CC.

Daily administration times of canhuang tablet based on a pharmacodynamic/pharmacokinetic model in jaundiced rats

OBJECTIVE

To study the daily administration times of Canhuang tablet (CHT) for treating jaundice in rats based on a pharmacodynamic/pharmacokinetic model.

METHODS

Rats were modeled by 4% 1-Naphthylisothiocyanate (75 mg/kg, p.o.). After 48 h, CHT was given (p.o.) at 0.75 g/kg once a day, 0.375 g/kg twice a day, and 0.25 g/kg three times a day. Blood was collected from the orbital sinus at different intervals. Levels of liver enzymes and bilirubin were detected using these blood samples. Bile was collected and determined after the first administration of CHT. High-performance liquid chromatography was used to determine the concentration of berberine in bile simultaneously. Time-effect and time-dose curves were then obtained.

RESULTS

Compared with rats taking CHT twice and three times a day, the total amount of bile within 10 h of rats taking CHT once a day were 1.32- and 1.47-fold higher, respectively. There was good consistency between the pharmacokinetics of berberine and the pharmacodynamics of the effect on liver enzymes and bilirubin in vivo. The pharmacokinetic analyses showed that rats administered CHT once daily maintained a higher concentration of berberine in bile for a longer period than rats administered CHT two- and three-times daily.

CONCLUSION

In jaundiced rats, taking CHT once a day is better than taking CHT twice or three times a day. These data may provide a reference for the clinical application of CHT.

Update on berberine in nonalcoholic Fatty liver disease

Berberine (BBR), an active ingredient from nature plants, has demonstrated multiple biological activities and pharmacological effects in a series of metabolic diseases including nonalcoholic fatty liver disease (NAFLD). The recent literature points out that BBR may be a potential drug for NAFLD in both experimental models and clinical trials. This review highlights important discoveries of BBR in this increasing disease and addresses the relevant targets of BBR on NAFLD which links to insulin pathway, adenosine monophosphate-activated protein kinase (AMPK) signaling, gut environment, hepatic lipid transportation, among others. Developing nuanced understanding of the mechanisms will help to optimize more targeted and effective clinical application of BBR for NAFLD.

A novel UPLC-MS/MS method for simultaneous quantification of rhein, emodin, berberine and baicalin in rat plasma and its application in a pharmacokinetic study

BACKGROUND

Dahuang Huanglian Xiexin Decoction (DHXD) is a classical formula in traditional Chinese medicines. In this study, a novel UPLC-MS/MS method was developed for the simultaneous quantification of rhein, emodin, berberine and baicalin, the major bioactive compounds of DHXD in rat plasma.

RESULTS

The method possessed high sensitivity and ultrashort analysis time (7 min). Linearity, accuracy, precision and extraction recovery of four analytes were all satisfactory. The method was then successfully applied in a pharmacokinetic study of four bioactive components after a single oral administration of DHXD extract to rats.

CONCLUSION

The method was applicable for simultaneous bioanalysis of rhein, emodin, berberine and baicalin.

Analysis of four alkaloids of Coptis chinensis in rat plasma by high performance liquid chromatography with electrochemical detection

A sensitive and precise high performance liquid chromatography (HPLC)-electrochemical detection (ECD) method has been developed for the simultaneous determination of four isoquinoline alkaloids including berberine, jatrorrhizine, coptisine and palmatine in Chinese medicine Coptis chinensis. The typical HPLC analysis was performed on WondaSil(®) C18-WR column (250×4.6 mm, 5 μm) with the mobile phase comprising 40 mM phosphate buffer (pH 7.0)-acetonitrile (40:60, v/v) at the flow rate of 0.8 mL min(-1). The electrochemical detection employed a three electrode system with a bare glassy carbon electrode at +1.3 V versus the Ag/AgCl reference electrode. The limits of detection (LODs) of four alkaloids ranged from 0.01 to 0.03 μmol L(-1) and the LOD of berberine was 80 times lower than LOD obtained by UV detection. The rat plasma samples were assayed after oral administration of the traditional Chinese medicine Coptis chinensis by the proposed HPLC-ECD method. The recoveries of this method were ranging from 88.0 to 116%, with the relative standard deviation lower than 3.1% for intra-day precision and 5.7% for inter-day precision. These results show that HPLC-ECD is a useful tool for the quality control of herbal medicine Coptis chinensis and also for pharmacokinetic studies.

Pharmacokinetics of Berberine in Rat Thalamus After Intravenous Administration of Coptidis Rhizoma Extract

A rapid and simple high-performance liquid chromatographic method for determination of berberine in rat thalamus was described in this study. Thalamus samples were pretreated by protein precipitation with methanol and acetonitrile. Berberine was determined using a Hypersil C 18 column with an isocratic mobile phase of acetonitrile — 0.05 M potassium dihydrogen phosphate (containing 0.5% triethylamine, pH 3.0) (30:70 v/v) and with UV detection at 265 nm. The lower limit of quantification for berberine in thalamus was 24 ng/ml, and the lowest concentration of berberine determined in rat thalamus samples was 47.5 ng/ml at 48 hours. The calibration curve for berberine was linear ( r 2 = 0.9994) over the concentration range 24–6000 ng/ml. At this concentration range, the overall recoveries (91.20%–93.24%) for berberine were determined and the accuracy of the intra- and inter-day assays from rat thalamus were less than 6% RSD. Following intravenous administration of 10.2 mg/kg of Coptidis Rhizoma (CR) extract containing 3 mg/kg berberine into rats, the thalamus level of berberine increased rapidly ( t 1/2α = 1.93 hours ), peaked at 2.48 hours with a concentration of 271 ng/g, and had a slow elimination rate ( t 1/2β = 14.6 hours ), which suggested that berberine might directly act on certain regions of the thalamus, have pharmacological effects on some cerebral dysfunctions, and be an active ingredient of Huang Lian Jie Du Tang for the treatment of cerebral disease.

Neuropharmacological and pharmacokinetic properties of berberine: a review of recent research

Objectives

This review summarizes recent research on the neuropharmacological and pharmacokinetic properties of berberine, an isoquinoline alkaloid extracted from Coptidis rhizoma.

Key findings

Berberine has multiple neuropharmacological properties, such as neuroprection, anti-neuronal apoptosis, improvement of cerebral microcirculation and anti-Alzheimer's disease, and so on. The pharmacokinetic characteristics of berberine are that it is not easily absorbed and it is not stable in the gastrointestinal tract of animals or humans.

Summary

Further studies need to be carried out to develop berberine as a drug for nervous system diseases, such as brain ischaemia and Alzheimer's disease, that has favorable pharmacokinetic properties.

Protective effects of berberine against low-density lipoprotein (LDL) oxidation and oxidized LDL-induced cytotoxicity on endothelial cells

The oxidative modification of low-density lipoprotein (LDL) is thought to have a central role in the pathogenesis of atherogenesis. Berberine, a natural constituent of plants of the genera Coptis and Berberis, has several anti-inflammation and anticancer biological effects. However, its protective effects on LDL oxidation and endothelial injury induced by oxLDL remain unclear. In this study, we evaluated the antioxidative activity of berberine and how berberine rescues human umbilical vein endothelial cells (HUVECs) from oxidized LDL (oxLDL)-mediated dysfunction. The antioxidative activity of berberine was defined by the relative electrophoretic mobility of oxLDL, fragmentation of ApoB, and malondialdehyde production via the Cu(2+)-mediated oxidation of LDL. Berberine also inhibited the generation of ROS and the subsequent mitochondrial membrane potential collapse, chromosome condensation, cytochrome C release, and caspase-3 activation induced by oxLDL in HUVECs. Our results suggest that berberine may protect LDL oxidation and prevent oxLDL-induced cellular dysfunction.

Determination of berberine in human plasma by liquid chromatography-electrospray ionization-mass spectrometry

A liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method for the determination of berberine in human plasma using chlorobenzylidine as the internal standard (IS) has been developed and validated. The plasma samples were prepared by LLE and the analytes were chromatographically separated on a Hanbon Lichrospher 5-C18 HPLC column under gradient elution with a mobile phase consisted of acetonitrile and 10mm ammonium acetate buffer containing 0.1% formic acid. Berberine was determined with electrospray ionisation-mass spectrometry (ESI-MS). LC-ESI-MS was performed in the selected-ion monitoring (SIM) mode using target ions at M(+)m/z 336.1 for berberine and M(+)m/z 464.1 for the IS. Calibration curve was linear over the range of 0.020-3.0 ng/ml. The lower limit of quantification (LLOQ) was 0.020 ng/ml. The intra- and inter-run variability values were less than 6.7 and 7.7%, respectively. The method has been successfully applied to determine the plasma concentration of berberine in healthy Chinese volunteers.

Simultaneous determination of baicalin, rhein and berberine in rat plasma by column-switching high-performance liquid chromatography

A simple HPLC method using column-switching and ultraviolet detection was developed for the simultaneous determination of baicalin (BA), rhein (RH) and berberine (BE) in rat plasma. Plasma samples were injected directly onto a Capcell Pak MF C(8) column (150 mm x 4.6 mm i.d.) to remove protein and to be pre-separated by an isocratic elution using 50 mmol/L phosphate sodium (pH 6.85)-acetonitrile (10:1, v/v). After the drug-containing fractions were transferred to a Kromasil C(18) column (150 mm x 4.6 mm i.d.) by a valve switching step, the valve position was switched back and the main separation was performed by an isocratic elution using triethylamine adjusted 20 mmol/L phosphoric acid (pH 6.78)-acetonitrile (4:1, v/v). The flow rate was always 1.0 mL/min. The calibration curve showed excellent linear relationship (r>or=0.9997) over the concentration range of 0.4-7.9 microg/mL for baicalin, 0.2-7.8 microg/mL for rhein and 0.4-7.7 microg/mL for berberine in rat plasma. The intra- and inter-day assay precisions (R.S.D.) of three analytes were in the range of 0.34-4.3% and the accuracies were between 98.0% and 102.4%. Their recoveries were all greater than 95%. The method was successfully applied to the multi-constituents plasma concentration-time curve study after oral administration of a traditional Chinese medicine prescription Xiexin-Tang in rats.

Simultaneous determination of berberine and palmatine in rat plasma by HPLC–ESI-MS after oral administration of traditional Chinese medicinal preparation Huang-Lian-Jie-Du decoction and the pharmacokinetic application of the method

A sensitive and specific liquid chromatography-electrospray ionization-mass spectrometry (LC-ESI-MS) method has been developed and validated for the identification and quantification of berberine and palmatine in rat plasma. After the addition of the internal standard (IS) and alkalization with 0.5M sodium hydroxide solution, plasma samples were extracted by ethyl ether and separated by HPLC on a Shim-pack ODS (4.6 microm, 150 mm x 2.0mm i.d.) column using a mobile phase composed of A (0.08% formic acid and 2 mmol/l ammonium acetate) and B (acetonitrile) with linear gradient elution. Analysis was performed on a Shimadzu LC/MS-2,010A in selected ion monitoring (SIM) mode with a positive electrospray ionization (ESI) interface. [M](+)=336 for berberine; 352 for palmatine and [M+H](+)=340 for IS were selected as detecting ions, respectively. The method was validated over the concentration range of 0.31-20 ng/ml for berberine and palmatine. Inter- and intra-CV precision (R.S.D.%) were all within 15% and accuracy (%bias) ranged from -5 to 5%. The lower limits of quantification were 0.31 ng/ml for both analytes. The extraction recovery was on average 68.6% for berberine, 64.2% for palmatine. The validated method was used to study the pharmacokinetic profile of berberine and palmatine in rat plasma after oral administration of Huang-Lian-Jie-Du decoction.

Application of microdialysis to study thein vivo release of pingyangmycin fromin situ gels in rabbits

Microdialysis was used together with HPLC to monitor the local concentration of pingyangmycin hydrochloride (PYM) after embolizing rabbit ear-veins with an injectable sustained release formulation, PYM-Zein/PYM-Zein-sucrose acetate isobutyrate (SAIB), in situ gel. The dialysis probe was perfused at 2 microL/min. The in vivo recovery was 46.6 3.1% (n = 4). The samples were injected directly into HPLC. PYM was detected using UV detector at 291 nm. Separation from other components in the dialysate was performed using a Discovery((R)) RP-Amide C(16) column within 12 min. The response for PYM in the dialysate was linear (r(2) > 0.996) over the range of 2.5-212 microg/mL. The limit of detection and limit of quantitation of PYM in the dialysate were 0.4 and 1.5 microg/mL, respectively. The results demonstrated that the in situ gel of PYM-Zein-SAIB could extend the release of PYM to 4 days. SAIB could significantly cut down the initial burst of PYM from the in situ gels (p < 0.05).

Kinetic difference of berberine between hippocampus and plasma in rat after intravenous administration of Coptidis rhizoma extract

In order to investigate the pharmacokinetics of berberine in Coptidis rhizoma extract in rat hippocampus and plasma, a simple and accurate high-performance liquid chromatography method was employed in this study. Berberine was determined using a Hypersil C(18) column with an isocratic mobile phase of acetonitrile-0.05 M potassium dihydrogen phosphate (containing 0.5% triethylamine, pH 3.0) and with UV detection at 236 nm. The lower limit of quantification for berberine in both hippocampus and plasma was 24 ng/ml, and the lowest concentrations of berberine determined in rat hippocampus and plasma samples were 30.7 ng/ml at 48 h and 38.5 ng/ml at 4 h, respectively. The calibration curve for berberine was linear over the concentration range 24--6000 ng/ml. At this concentration range, the overall recoveries (90.6--94.2%) for berberine were determined and the accuracy of intra- and inter-day assays from rat samples were less than 7% RSD. Following intravenous administration of C. rhizoma extract at a dose of 10.2 mg/kg containing 3 mg/kg berberine, berberine in the plasma eliminated rapidly (t(1/2 beta)=1.13 h). However, berberine in the hippocampus increased rapidly (t(1/2 alpha)=0.215 h), peaked at 3.67 h with a concentration of 272 ng/g, and had a slow elimination rate (t(1/2 beta)=12.0 h), which suggests that berberine could have a direct action on neuron and accumulate in the hippocampus. This study first showed the pharmacokinetic characteristics of berberine in rat hippocampus and the kinetic characteristics of berberine are dissimilar in the hippocampus and plasma.

Microdialysis—theoretical background and recent implementation in applied life-sciences

In the past decade microdialysis has become a method of choice in the study of unbound tissue concentrations of both endogenous and exogenous substances. Microdialysis has been shown to offer information about substances directly at the site of action while being well tolerable and safe. The large variety of its field of application has been demonstrated. However, a few challenges have to be met to make this method generally applicable in routine applications. This review will provide an overview over theoretical aspects that have to be considered during the implementation of microdialysis. Moreover, a comparison between microdialysis and other tissue sampling techniques will demonstrate advantages and limitations of the methods mentioned. Subsequently, it will present a critical synopsis of a variety of scientific/biomedical applications of this method with emphasis on the most recent literature, focussing on target tissues while giving examples of substances examined. It is concluded that microdialysis will be of great value in future investigations of pharmacokinetics, pharmacodynamics and in monitoring of disease status and progression.

Hepatobiliary excretion of berberine

Berberine is a bioactive herbal ingredient isolated from the roots and bark of Berberis aristata or Coptis chinensis. To investigate the detailed pharmacokinetics of berberine and its mechanisms of hepatobiliary excretion, an in vivo microdialysis coupled with high-performance liquid chromatography was performed. In the control group, rats received berberine alone; in the drug-treated group, 10 min before berberine administration, the rats were injected with cyclosporin A (CsA), a P-glycoprotein (P-gp) inhibitor; quinidine, both organic cation transport (OCT) and P-gp inhibitors; SKF-525A (proadifen), a cytochrome P450 inhibitor; and probenecid to inhibit the glucuronidation. The results indicate that berberine displays a linear pharmacokinetic phenomenon in the dosage range from 10 to 20 mg kg(-1), since a proportional increase in the area under the concentration-time curve (AUC) of berberine was observed in this dosage range. Moreover, berberine was processed through hepatobiliary excretion against a concentration gradient based on the bile-to-blood distribution ratio (AUC(bile)/AUC(blood)); the active berberine efflux might be affected by P-gp and OCT since coadministration of berberine and CsA or quinidine at the same dosage of 10 mg kg(-1) significantly decreased the berberine amount in bile. In addition, berberine was metabolized in the liver with phase I demethylation and phase II glucuronidation, as identified by liquid chromatography/tandem mass spectrometry. Also, the phase I metabolism of berberine was partially reduced by SKF-525A treatment, but the phase II glucuronidation of berberine was not obviously affected by probenecid under the present study design.

β-Phenylethylamines and the isoquinoline alkaloids

This review covers beta-phenylethylamines and isoquinoline alkaloids derived from them, including further products of oxidation. condensation with formaldehyde and rearrangement, some of which do not contain an isoquinoline system, together with naphthylisoquinoline alkaloids, which have a different biogenetic origin. The occurrence of the alkaloids, with the structures of new bases, together with their reactions, syntheses and biological activities are reported. The literature from July 2002 to June 2003 is reviewed, with 568 references cited.

Assaying protein unbound drugs using microdialysis techniques

Compared with traditional sampling methods, microdialysis is a technique for protein unbound drug sampling without withdrawal of biological fluids and involving minimal disturbance of physiological function. Conventional total drug sample consists of unbound drugs and protein bound drugs, which are loosely bound to plasma proteins such as albumin and alpha-1 acid glycoprotein, forming an equilibrium ratio between bound and unbound drugs. However, only the unbound fraction of drug is available for absorption, distribution, metabolism and elimination, and delivery to the target sites for pharmacodynamic actions. Although several techniques have been used to determine protein unbound drugs from biological fluids, including ultrafiltration, equilibrium dialysis and microdialysis, only microdialysis allows simultaneous sampling of protein unbound chemicals from plasma, tissues and body fluids such as the bile juice and cerebral spinal fluid for pharmacokinetic and pharmacodynamic studies. This review article describes the technique of microdialysis and its application in pharmacokinetic studies. Furthermore, the advantages and limitations of microdialysis are discussed, including the detailed surgical techniques in animal experiments from rat blood, brain, liver, bile duct and in vitro cell culture for unbound drug analysis.