[Simultaneous determination of salidroside and tyrosol in Beagle dog plasma using UHPLC-MS/MS after pre-column dansyl chloride derivatization].

A pre-column derivatization method combined with UHPLC-MS/MS was developed for the simultaneous determination of salidroside and tyrosol in Beagle dog plasma. After protein precipitation by acetonitrile, the liquid supernatant was treated with dansyl chloride under dark conditions at 60 ℃ for 30 min, and then, the sample solution was extracted using methyl tertiary butyl ether. The multiple reaction monitoring in positive ion mode was used for MS detection of the tested analytes with the specific ion transitions of m/z 534.2→372.0 for salidroside derivative, m/z 372.0→171.0 for tyrosol derivative and m/z 506.0→171.0 for arbutin derivative. The chromatograph separation was achieved on an ACQUITY UPLC® BEH C18 column (100 mm × 2.1 mm, 1.7 µm) with a gradient mobile phase consisting of acetonitrile (0.1% formic acid)-water (10% acetonitrile, 0.1% formic acid) for 9 min. The assay showed a good linearity over the range of 0.02/0.1 − 20/10 µmol·L−1 with a lower limit of quantitation of 0.02 and 0.1 µmol·L−1 for salidroside and tyrosol in dog plasma, respectively. The intra- and inter-day precisions were all less than 8.68%, and the accuracy was within ±11.4%. The established method with a high sensitivity, good specificity and reliability was appropriate for simultaneous determination of salidroside and tyrosol in dog plasma and successfully applied to a pharmacokinetic study after intragastric administration of salidroside to Beagle dogs.

[The in vitro transport mechanism of bentysrepinine: a novel anti-hepatitis B virus drug candidate].

Bentysrepinine (Y101), a derivative of phenylalanine dipeptide, is a novel drug candidate for the treatment of hepatitis B virus (HBV) infection. Our previous preclinical pharmacokinetic study showed that its in vivo absorption and distribution characteristics were probably related to transmembrane transport after Y101 was administered intragastically in rats. In this study, Caco-2 and MDCK-MDR1 cell models were used to investigate interactions between Y101 and P-gp through the apparent permeation coefficient (P(app)) and efflux ratio (RE); the results showed that Y101 was a substrate of P-gp. In addition, gene-transfected cell models, HEK293-h OATP1B1, HEK293-h OATP2B1 and CHO-PEPT1 were used to evaluate the affinity to OATP1B1, OATP2B1 and PEPT1. The results suggest that Y101 has a weak inhibitory effect on OATP1B1 and OATP2B1, and Y101 may not be substrates of OATP1B1, OATP2B1 or PEPT1. The above results can be used to explain the in vivo absorption and distribution characteristics, and to provide a scientific basis for the further development of Y101.

[The in vitro inhibition and induction of cytochrome P450 activities by bentysrepinine: a novel candidate of anti-hepatitis B virus drug].

Bentysrepinine (Y101), a derivative of phenyalanine dipeptide, has a novel mechanism in the treatment of hepatitis B virus (HBV) infection with a good anti-HBV effect. In the present study, a fluorometric-based high throughput method using cytochrome P450 (CYP) screening kit was adopted to evaluate in vitro inhibition potential of Y101 on CYP isoenzymes by calculating remaining enzyme activities and inhibitory potential (IC(50) values) using the determined values of fluorescence intensity. The result showed that Y101 exhibited little activity in the inhibition of CYP1A2, CYP3A4, CYP2C9, CYP2C19 and CYP2D6 (IC(50) > 100 µmol·L(-1)). Y101 was used to treat human primary hepotocytes for 72 h, and the enzyme activities of CYP1A2, CYP2B6 and CYP3A4 were determined with a cocktail of probe substrates for the three CYP isoforms. The metabolites were simultaneously determined using a LC-MS/MS method. Y101 had no activity in the induction of CYP1A2, CYP2B6 and CYP3A4 on the basis of the following results: 1 The ratio of enzyme activities between test and control groups were all below than 1 (varied from 0.662 to 0.928); 2 The induction potential of Y101 were lower than forty percent compared with that of positive groups. The above results suggest that Y101 has little activity in the regulation of metabolic drug-drug interactions based on the CYP isoform changes following co-administration of drugs.

The Targeted-liposome Delivery System of Antitumor Drugs.

The liposome delivery system has been intensively explored as novel drug delivery system (DDS) for antitumor drugs, due to its safety, selective cytotoxicity, long circulation and slow elimination in blood, which is favorable for cancer therapy. The liposome-based chemotherapeutics are used to treat a variety of cancers to enhance the therapeutic index of antitumor drugs. Here, the author reviewed the important targets for cancer therapy and the pharmacokinetic behavior of liposomal drugs in vivo, as well as the application of the targeting liposomal system in cancer therapy. Considering further application for clinical use, the great challenges of the liposome-based delivery system were also proposed as follows: 1) prepare stealth liposome with steric stabilization and further enhance the therapeutic effects and safety; 2) explore more safe clinical targets and complementary or different types of targeting liposome; 3) thirdly, more investment is needed on the research of pharmacokinetics of the elements such as the ligands (antibody), PEG and lipids of liposome delivery system as well as safety evaluation. Considering the complex process of the liposomal encapsulation drugs in vivo, the author inferred that there are maybe different forms of the encapsulation drug to be internalized by the tumor tissues at the same time and space, although there are little reports on it.

[Simultaneous determination of clevidipine butyrate and its metabolite clevidipine acid in dog blood by liquid chromatography-tandem mass spectrometry].

A rapid, sensitive and simple liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for the simultaneous determination of clevidipine butyrate and its primary metabolite clevidipine acid in dog blood. After one-step protein precipitation with methanol, the chromatographic separation was carried out on an Ecosil C18 column (150 mm x 4.6 mm, 5 µm) with a gradient mobile phase consisting of methanol and 5 mmol · L(-1) ammonium formate. A chromatographic total run time of 13.0 min was achieved. The quantitation analysis was performed using multiple reaction monitoring (MRM) at the specific ion transitions of m/z 454.1 [M-H]- --> m/z 234.1 for clevidipine butyrate, m/z 354.0 [M-H]- --> m/z 208.0 for clevidipine acid and m/z 256.1 [M-H]- --> m/z 227.1 for elofesalamide (internal standard, IS) in the negative ion mode with electrospray ionization (ESI) source. The linear calibration curves for clevidipine butyrate and clevidipine acid were obtained in the concentration ranges of 0.5-100 ng · mL and 1-200 ng · mL(-1), separately. The lower limit of quantification of clevidipine butyrate and clevidipine acid were 0.5 ng · mL(-1) and 1 ng · mL(-1). The intra and inter-assay precisions were all below 12.9%, the accuracies were all in standard ranges. Stability testing indicated that clevidipine butyrate and clevidipine acid in dog blood with the addition of denaturant methanol was stable under various processing and/or handling conditions. The validated method has been successfully applied to a pharmacokinetic study of clevidipine butyrate injection to 8 healthy Beagle dogs following intravenous infusion at a flow rate of 5 mg · h(-1) for 0.5 h.

Inhibitory effect of medicinal plant-derived carboxylic acids on the human transporters hOAT1, hOAT3, hOATP1B1, and hOATP2B1.

A significant number of organic carboxylic acids have been shown to influence the absorption and distribution of drugs mediated by organic anion transporters (OATs). In this study, uptake experiments were performed to assess the inhibitory effects of cinnamic acid, ferulic acid, oleanolic acid, deoxycholic acid, and cynarin on hOAT1, hOAT3, hOATP1B1, and hOATP2B1. After a drug-drug interaction (DDI) investigation, cinnamic acid, ferulic acid, deoxycholic acid, and cynarin were found and validated to inhibit hOAT1 in a competitive manner, and deoxycholic acid was found to be an inhibitor of all four transporters. The apparent 50% inhibitory concentrations of cinnamic acid, ferulic acid, deoxycholic acid, and cynarin were estimated to be 133.87, 3.69, 90.03 and 6.03 µmol·L(-1) for hOAT1, respectively. The apparent 50% inhibitory concentrations of deoxycholic acid were estimated to be 9.57 µmol·L(-1) for hOAT3, 70.54 µmol·L(-1) for hOATP1B1, and 168.27 µmol·L(-1) for hOATP2B1. Because cinnamic acid, ferulic acid, and cynarin are ingredients of food or food additives, the present study suggests there are new food-drug interactions to be disclosed. In addition, deoxycholic acid may be used as a probe for studying the correlation of OATs and OATPs.

Simultaneous determination of evodiamine and evodine in Beagle dog plasma using liquid chromatography tandem mass spectrometry.

A sensitive, rapid, and specific liquid chromatography/tandem mass spectrometry assay has been established and validated for the quantitation of evodiamine and evodine in Beagle dog plasma. Plasma samples of 0.2 ml were processed by liquid-liquid extraction with n-hexane/ethyl acetate (2:1, v/v). Chromatographic separations were done on a Symmetry C18 column (100 mm × 4.6 mm, ID, 5 µm) at 35°C with a linear gradient of methanol and 20 mM ammonium formate containing 0.2% formic acid. Evodiamine, evodine, and glibenclamide [internal standard (IS)] were ionized with an electrospray ionization source operated in positive ion mode. The MS/MS transitions were m/z 304.1 â†’ 161.1 for evodiamine, m/z 471.2 â†’ 425.1 for evodine, and m/z 494.1 â†’ 369.1 for IS. Calibration curves were linear over the concentration range of 0.1-100 ng/ml for evodiamine and 0.5-500 ng/ml for evodine. The mean extraction recoveries were 88.10 ± 3.21% for evodiamine and 81.24 ± 4.07% for evodine. The intra- and inter-day precisions were less than 11.10% and 12.81%, and the accuracy was within ± 11.76% for both analytes. Evodiamine and evodine were stable during storage and analytical periods. The validated method has been successfully applied to a pharmacokinetic study of evodiamine and evodine in beagle dogs after oral administration.

Drug metabolism and pharmacokinetics of nanodrugs from Chinese medicines and natural products.

Over the past few years, nanoscale Chinese medicine has become one of focuses in modern Chinese medicine research. There is an increasing need for a more systematic study on the basic issues involved in traditional Chinese medicine and a more active participation of researchers in the application area of nanoscale traditional Chinese drugs. In this review, author analyzed the current applications of nanotechnology in research and development of drugs from natural products and herbal medicines involving traditional Chinese medicines, and also discussed the bio-medicinal evaluation issues on ADME including bio-distribution and metabolism of nanodrugs. Author noted that great challenges faced in nanodrugs from herb drugs and natural products are the follows: (1) the first challenge is to prepare nanodrug delivery system and quantitatively evaluate the therapeutic effects and safety; (2) the second challenge is to clarify the concrete metabolism course; and (3) the third challenge is to study the pharmacokinetics of nanodrugs.

Herb-drug interactions involving drug metabolizing enzymes and transporters.

Herbal medicines and their active ingredients are widely used worldwide, and they have become an important part of clinical medicine. The combined use of herbs and drugs has increased the possibility of pharmacokinetic and pharmacodynamic interactions. Clinical studies have demonstrated that the combined use of herbs and drugs can enhance or attenuate the drug efficacy and toxicity. The herb-drug combinations may reduce a drug efficacy and lead to treatment failure when long-term administration. Case reports detailing serious clinical adverse reactions have promoted studies on the interactions between herbs and drugs. This review highlights recent knowledge to discuss herb-drug interactions involving metabolizing enzymes and drug transporters. Drug transporters are widely present in body and play an important role in the absorption, distribution, excretion and metabolism, efficacy, and toxicity of drugs. Investigation of transporters has developed rapidly since 1990s, the effects of many transporters on the pharmacokinetics of drugs and herb-drug interactions have been reported. Some concepts on drug transporters issued experimentally and clinically drug-drug and herb-drug interactions have applied in many studies. Methodology studies are very important for understanding the mechanism, considerations and evaluation of experiments and clinical studies on drug metabolizing enzymes and transporters in drug-drug interactions.

[Determination of icaritin in rat plasma by HPLC-MS/MS].

The paper is to report the development of a high-performance liquid chromatographic/tandem mass spectrometry (HPLC-MS/MS) method for the determination of icaritin (ICT) in rat plasma. After precipitated with acetonitrile from the plasma, ICT was isolated chromatographically on a Dikma C18 column. The mobile phase consisted of acetonitrile-water-acetic acid (72 : 28 : 1.5, v/v/v). Electrospray ionization (ESI) source was applied and operated in the positive ion mode. Multiple reaction monitoring (MRM) mode with the transitions of m/z 387 --> m/z 313 and m/z 331 --> m/z 315 were used to quantify ICT and the internal standard, respectively. The linear calibration curve was obtained in the concentration range of 2.5-1,000 ng x mL(-1). The lower limit of quantification was 2.5 ng x mL(-1). The inter- and intra-day precision (RSD) were less than 9.63%, and the accuracy (relative error) was within +/-7.42%. The method was proved to be suitable for the pharmacokinetics of ICT, which offers advantages of high sensitivity and selectivity.

[Determination of tamsulosin in dog plasma by a high sensitive liquid chromatography-tandem mass spectrometric method].

To develop and validate a liquid chromatography-tandem mass spectrometric (LC-MS/MS) method for the determination of tamsulosin in dog plasma after oral administration of controlled-release tablet of tamsulosin hydrochloride, the samples and the internal standard, diphenhydramine, were extracted from dog plasma by n-hexane-dichloromethane (2 : 1), and separated on a Bonchrom XBP-C18 column using a mobile phase consisted of methanol-acetonitrile-ammonium formate (10 mmol x L(-1)) (30 : 40 : 30, v/v/v), at a flow rate of 0.4 mL x min(-1). Mass spectrometric detection was operated on a triple quadrupole tandem mass spectrometer equipped with atmospheric pressure chemical ionization (APCI) source in positive mode. Quantification was performed using selected reaction monitoring (SRM) of the transitions m/z 409 --> 228 for tamsulosin and m/z 256 --> 167 for the internal standard, respectively. The linear concentration ranges of the calibration curves for tamsulosin were 0.02 - 50 ng x mL(-1). The lower limit of quantification was 0.02 ng x mL(-1). The accuracy ranged from -2.61% to 8.82% in terms of relative error (RE). The intra- and inter-day relative standard deviation (RSD) across three-run validations were lower than 9.72%. The method was proved to be highly sensitive, selective, and had been successfully applied to the pharmacokinetic study after an oral administration of 0.4 mg tamsulosin hydrochloride controlled release preparations to dogs.