Ultrasound-assisted ionic liquid dispersive liquid–liquid microextraction coupled with high performance liquid chromatography for sensitive determination of trace celastrol in urine

Miniaturized ionic liquid dispersive liquid-liquid microextraction in a coupled-syringe system combined with UV for extraction and determination of danazol in danazol capsule and mice serum

In this study, for the first time, a coupled 1-mL microsyringe system was utilized to perform a miniaturized ionic liquid dispersive liquid-liquid microextraction (IL-DLLME) method. Danazol was extracted and determined via the developed method followed by micro-volume ultraviolet spectroscopy (UV). The extraction process was carried out by the injection of extraction solvent ionic liquid 1-octyl-3-methylimidazolium hexafluorophosphate [C8mimPF6] into sample solution (syringe A), and then rapid shoot the solution into syringe B. After that the shooting was repeated several times at a rate of 1 cycle/s. The extraction procedure was induced by the formation of cloudy solution, which was composed of fine drops of [C8mimPF6] dispersed entirely into sample solution with the help of shooting without any dispersive solvent, ultrasonication or high temperature. Several important parameters affecting the extraction efficiency were studied and optimized. Under the optimized conditions, the limit of detection (LOD) was 0.055 μg/mL (capsule) or 0.054 μg/mL (serum) at a signal-to-noise ratio of 3. The calibration curve was linear over the range of 0.62-25 μg/mL. The proposed method was successfully applied to danazol capsule and the real mice serum samples and good spiked recoveries in the range of 90.5-103.4% were obtained. The obtained results of this work were in good agreement with the results of HPLC.

Dispersive micro-solid phase extraction based on self-assembling, ionic liquid-coated magnetic particles for the determination of clofentezine and chlorfenapyr in environmental water samples

Two ionic liquid-coated-Fe3O4 magnetic particles (IL-Fe3O4 MPs) were developed for use in two types of dispersive micro-solid phase extraction (D-μ-SPE) for the high-performance liquid chromatographic analysis of clofentezine and chlorfenapyr in environmental water samples. Self-assembling IL-Fe3O4 MPs were used in D-μ-SPE as adsorbents. Two D-μ-SPE extraction methods, namely, direct dispersive micro-solid phase extraction (d-D-μ-SPE) and in situ solvent formation-based dispersive micro-solid phase extraction (ISF-D-μ-SPE), were proposed, using [C8MIM][PF6] to extract analytes through two pathways. Lower IL doses were required in the extraction process compared with those in other IL-based methods. Fe3O4 MPs can also be recycled and reused after extraction and are thus environmentally friendly. These newly developed methods were demonstrated to be feasible for use in the quantitation of clofentezine and chlorfenapyr at trace levels, with lower limit of detection values ranging from 0.4 to 0.5 ng mL(-1) for d-D-μ-SPE and 0.4 ng mL(-1) for ISF-D-μ-SPE. Finally, relative standard deviations of less than 6.0% were obtained.

Determination of pesticide residues in ginseng by dispersive liquid-liquid microextraction and ultra high performance liquid chromatography-tandem mass spectrometry

A procedure involving acetonitrile-based extraction combined with dispersive liquid-liquid microextraction (DLLME) and detection by ultra high performance liquid chromatography-tandem mass spectrometry (UHPLC-MS/MS) was used for determination of 39 pesticides in ginseng. The extraction of pesticide residues in ginseng was performed with acetonitrile, applying QuEChERS methodology, and the extract was further disposed by DLLME method before analyzed by UHPLC-MS/MS. The average recoveries ranged from 70 to 120% for 82% of the analytes with RSD lower than 15%. The calibration curves obtained with blank matrices were linear with a correlation coefficient of over 0.99. The limits of detection were between 0.01 and 1.0μg/kg. Matrix effects were studied by comparing solvent calibration curves and matrix-matched calibration curves. The results indicate the feasibility of this method for the determination of 39 pesticides in ginseng.

Enantioselective analysis of ranolazine and desmethyl ranolazine in microsomal medium using dispersive liquid–liquid microextraction and LC–MS/MS

Background: An enantioselective bioanalytical method using dispersive liquid–liquid microextraction (DLLME) and LC–MS/MS was developed for the chiral analysis of ranolazine (RNZ) and one of its metabolites (desmethyl ranolazine [DRNZ]). Results: The analytes were extracted from microsomal medium by DLLME, using chloroform as extractor solvent and acetone as dispersive solvent. The enantiomers of RNZ and DRNZ were analyzed simultaneously for the first time using a Chiralcel OD-H®. Method validation showed recoveries in the order of 55 and 45%, and LLOQ of 25 and 10 ng ml-1 for the enantiomers of RNZ and DRNZ, respectively. Linearity was established in the concentration range of 10 to 1000 and 25 to 2500 ng ml-1 for each DRNZ and RNZ enantiomer, respectively. Conclusion: The unprecedented use of DLLME was demonstrated to be very useful for sample preparation of microsomal matrix. Furthermore, the in vitro metabolism of RNZ was enantioselective.

Analysis of losartan and carvedilol in urine and plasma samples using a dispersive liquid–liquid microextraction isocratic HPLC–UV method

Background: A simple, precise and sensitive HPLC method has been developed for simultaneous determination of carvedilol and losartan in human plasma and urine samples. The analytes were extracted by a dispersive liquid–liquid microextraction method. A mobile phase of 15 mM sodium dihydrogen phosphate buffer (pH 4.0)/acetonitrile/2-propanol (70/27.5/2.5, v/v/v) was used to separate the drugs using a Waters® ODS column (250 × 4.6 mm) and detected by a UV detector at 222 nm. Results: The developed method is selective for studied drugs possessing a linearity range of 0.1–1.0 and 0.05–0.75 µg/ml, respectively, for losartan and carvedilol with precision <15%. The accuracy is better than 15% and the mean recovery of carvedilol and losartan was 98.9 and 100.2% for plasma and 100.7 and 100.5% for urine samples, respectively. Conclusion: The developed method is applicable for therapeutic drug monitoring and PK analyses.

Oral bioavailability and gender-related pharmacokinetics of celastrol following administration of pure celastrol and its related tablets in rats

ETHNOPHARMACOLOGICAL RELEVANCE

Celastrol is a natural compound extracted from the traditional Chinese medicinal herb, Thunder God Vine (TGV). Owing to its potential anti-inflammatory and antitumor effects, celastrol has been considered as a promising candidate for drug development.

AIM OF THE STUDY

To establish a sensitive LC-MS/MS method to investigate the pharmacokinetic properties of celastrol in rats. Key pharmacokinetic issues of celastrol including oral bioavailability, comparative pharmacokinetics between pure compound and tablet preparation, as well as gender-related pharmacokinetic difference are to be addressed for the first time.

MATERIALS AND METHODS

Sprague-Dawley rats were administrated an intravenous dose (100 μg kg(-1)) of pure celastrol and an oral dose (1000 μg kg(-1)) of pure celastrol and TGV tablets (corresponding to 534 μg kg(-1) of celastrol), respectively. At different time points, the concentration of celastrol in rat plasma was determined by a sensitive and well-validated LC-MS/MS method. Main pharmacokinetic parameters including area under the plasma concentration-time curve (AUC), maximal plasma concentration (Cmax), the time for maximal concentration (Tmax) and mean residence time (MRT) were estimated by Drug and Statistic1.0 pharmacokinetic software (Chinese Pharmacological Association, Anhui, PR China). Statistical analysis was performed using two one-side t test with p-values less than 0.05 as the level of significance.

RESULTS

The standard curve of celastrol showed good linearity in the concentration range of 0.11~54.3 ng mL(-1) in our current method, with acceptable selectivity, precision, recovery, and stability. The oral absolute bioavailability of celastrol significantly increased from 17.06% for pure celastrol to 94.19% for TGV tablets containing equivalent celastrol. After oral administration of TGV tablets, the Cmax and AUC values of celastrol in female rats were (32.03±8.41) μg L(-1) and (379.49±118.19) μg h L(-1), which were significantly higher (p<0.01) than that in males with the values of (14.31±7.33) μg L(-1) and (188.17±92.33) μg h L(-1).

CONCLUSION

Celastrol administered orally in the rat was poorly absorbed into the systemic circulation. However, the poor absorption of celastrol could be greatly improved when celastrol-containing TGV tablets orally administered, and thereby the oral bioavailability of celastrol was significantly increased. As for gender difference, female rats showed significantly better absorption of celastrol than males.