Comparative permeability of three saikosaponins and corresponding saikogenins in Caco-2 model by a validated UHPLC-MS/MS method

Saikosaponins(SSs)are the main active components extracted from Bupleuri Radix(BR)which has been used as an important herbal drug in Asian countries for thousands of years.It has been reported that the intestinal bacteria plays an important role in the in vivo disposal of oral SSs.Although the deglycosylated derivatives(saikogenins,SGs)of SSs metabolized by the intestinal bacteria are speculated to be the main components absorbed into the blood after oral administration of SSs,no studies have been reported on the characteristics of SGs for their intestinal absorption,and those for SSs are also limited.Therefore,a rapid UHPLC-MS/MS method was developed to investigate and compare the apparent permeability of three common SSs(SSa,SSd,SSb2)and their corresponding SGs(SGF,SGG,SGD)through a bidirectional transport experiment on Caco-2 cell monolayer model.The method was validated according to the latest FDA guidelines and applied to quantify the six analytes in transport medium samples extracted via liquid-liquid extraction(LLE).The apparent permeability coefficient(Papp)determined in this study indicated that the permeability of SGs improved to the moderate class compared to the corresponding parent compounds,predicting a higher in vivo absorption.Moreover,the efflux ratio(ER)value demonstrated an active uptake of SSd and the three SGs,while a passive diffusion of SSa and SSb2.

Predicting the grades of Astragali radix using mass spectrometrybased metabolomics and machine learning

Astragali radix(AR,the dried root of Astragalus)is a popular herbal remedy in both China and the United States.The commercially available AR is commonly classified into premium graded(PG)and ungraded(UG)ones only according to the appearance.To uncover novel sensitive and specific markers for AR grading,we took the integrated mass spectrometry-based untargeted and targeted metabolomics approaches to characterize chemical features of PG and UG samples in a discovery set(n=16 batches).A series of five differential compounds were screened out by univariate statistical analysis,including arginine,calycosin,ononin,formononetin,and astragalosideⅣ,most of which were observed to be accumulated in PG samples except for astragalosideⅣ.Then,we performed machine learning on the quantification data of five compounds and constructed a logistic regression prediction model.Finally,the external validation in an independent validation set of AR(n=20 batches)verified that the five compounds,as well as the model,had strong capability to distinguish the two grades of AR,with the prediction accuracy>90%.Our findings present a panel of meaningful candidate markers that would significantly catalyze the innovation in AR grading.

Determination of torasemide in human plasma and its bioequivalence study by high-performance liquid chromatography with electrospray ionization tandem mass spectrometry

A sensitive and selective method using high-performance liquid chromatography coupled with elec- trospray ionization tandem mass spectrometry （HPLC-ESI-MS） to determine the concentration of tor- asemide in human plasma samples was developed and validated. Tolbutamide was chosen as the internal standard （IS）. The chromatography was performed on a GI Sciences Inertsil ODS-3 column （100 mm× 2.1 mm i.d., 5.0 μm） within 5 min, using methanol with 10 mM ammonium formate （60：40, v/ v） as mobile phase at a flow rate of 0.2 mL/min. The targeted compound was detected in negative io- nization at m/z 347.00 for torasemide and 269.00 for IS. The linearity range of this method was found to be within the concentration range of 1-2500 ng/mL （r=0.9984） for torasemide in human plasma. The accuracy of this measurement was between 94.05% and 103.86%. The extracted recovery efficiency was from 84.20% to 86.47% at three concentration levels. This method was also successfully applied in pharmacokinetics and bioequivalence studies in Chinese volunteers.

Comparison of ESI–and APCI–LC–MS/MS methods:A case study of levonorgestrel in human plasma

Electrospray ionization(ESI) and atmospheric pressure chemical ionization(APCI) techniques for liquid chromatography–tandem mass spectrometry(LC–MS/MS) determination of levonorgestrel were evaluated.In consideration of difference in ionization mechanism,the two ionization sources were compared in terms of LC conditions,MS parameters and performance of method.The sensitivity for detection of levonorgestrel with ESI was 0.25 ng/m L which was lower than 1 ng/m L with APCI.Matrix effects were evaluated for levonorgestrel and canrenone(internal standard,IS) in human plasma,and the results showed that APCI source appeared to be slightly less liable to matrix effect than ESI source.With an overall consideration,ESI was chosen as a better ionization technique for rapid and sensitive quantification of levonorgestrel.The optimized LC–ESI–MS/MS method was validated for a linear range of 0.25–50 ng/m L with a correlation coefficient ≥0.99.The intra-and inter-batch precision and accuracy were within 11.72% and 6.58%,respectively.The application of this method was demonstrated by a bioequivalence study following a single oral administration of 1.5 mg levonorgestrel tablets in 21 Chinese healthy female volunteers.

Separation and determination of acetyl-glutamine enantiomers by HPLC–MS and its application in pharmacokinetic study

A high-performance liquid chromatography coupled with mass spectrometry(HPLC–MS) method was established for the separation and determination of acetyl-glutamine enantiomers(acetylL-glutamine and acetylD-glutamine) simultaneously. Baseline separation was achieved on Chiralpak AD-H column(250 mm ×4.6 mm, 5 μm). n-Hexane(containing 0.1% acetic acid) and ethanol(75:25, v/v) were used as mobile phase at a flow rate of 0.6 m L/min. The detection was operated in the negative ion mode with an ESI source. [M-H]-m/z187.0540 for enantiomers and [M-H]-m/z 179.0240 for aspirin(IS) were selected as detecting ions. The linear range of the calibration curve for each enantiomer was 0.05–40 μg/m L. The precision of this method at concentrations of 0.5–20 μg/m L was within 7.23%, and the accuracy was 99.81%–107.81%. The precision at LOQ(0.05 μg/m L) was between 16.28% and 17.56%, which was poor than that at QC levels. The average extraction recovery was higher than 85% for both enantiomers at QC levels. The pharmacokinetics of enantiomers was found to be stereoselective. There was not chiral inversion in vivo or in vitro between enantiomers.

Identification of impurities in nafamostat mesylate using HPLC-ITTOF/MS:A series of double-charged ions

Nafamostat mesylate is a serine protease inhibitor used in the treatment of acute pancreatitis.The impurities in nafamostat mesylate,the active pharmaceutical ingredient(API),were profiled via high performance liquid chromatography tandem ion trap coupled with time-of-flight mass spectrometer(HPLC-IT-TOF/MS).The chromatography was performed on an ACE-3 C18 column(200 mm4.6 mm,3 mm)using methanol and 0.1%formic acid in purified water as mobile phase at a flow rate of 1.0 mL/min.The ions were detected by IT-TOF/MS with a full-scan mass analysis from m/z 100 to 800.In total,eleven impurities were detected in nafamostat mesylate API.The impurity profile was estimated based on the HPLC-IT-TOF/MS data,including accurate masses,MSn fingerprints of fragmentation pathways and a series of double-charged ions.Finally,seven impurities were identified and reported for the first time.The results will provide technical support for the quality control and clinical safety of nafamostat mesylate.

Functional metabolomics reveal the role of AHR/GPR35 mediated kynurenic acid gradient sensing in chemotherapy-induced intestinal damage

Intestinal toxicity induced by chemotherapeutics has become an important reason for the interruption of therapy and withdrawal of approved agents. In this study, we demonstrated that chemotherapeutics-induced intestinal damage were commonly characterized by the sharp upregulation of tryptophan(Trp)àkynurenine(KYN)àkynurenic acid(KA) axis metabolism. Mechanistically,chemotherapy-induced intestinal damage triggered the formation of an interleukin-6(IL-6)àindoleamine2,3-dioxygenase 1(IDO1)àaryl hydrocarbon receptor(AHR) positive feedback loop, which accelerated kynurenine pathway metabolism in gut. Besides, AHR and G protein-coupled receptor 35(GPR35) negative feedback regulates intestinal damage and inflammation to maintain intestinal integrity and homeostasis through gradually sensing kynurenic acid level in gut and macrophage, respectively. Moreover, based on virtual screening and biological verification, vardenafil and linagliptin as GPR35 and AHR agonists respectively were discovered from 2388 approved drugs. Importantly, the results that vardenafil and linagliptin significantly alleviated chemotherapy-induced intestinal toxicity in vivo suggests that chemotherapeutics combined with the two could be a promising therapeutic strategy for cancer patients in clinic.This work highlights GPR35 and AHR as the guardian of kynurenine pathway metabolism and core component of defense responses against intestinal damage.

Pharmacometabolomic prediction of individual differences of gastrointestinal toxicity complicating myelosuppression in rats induced by irinotecan

Pharmacometabolomics has been already successfully used in toxicity prediction for one specific adverse effect. However in clinical practice, two or more different toxicities are always accompanied with each other, which puts forward new challenges for pharmacometabolomics. Gastrointestinal toxicity and myelosuppression are two major adverse effects induced by Irinotecan(CPT-11),and often show large individual differences. In the current study, a pharmacometabolomic study was performed to screen the exclusive biomarkers in predose serums which could predict late-onset diarrhea and myelosuppression of CPT-11 simultaneously. The severity and sensitivity differences in gastrointestinal toxicity and myelosuppression were judged by delayed-onset diarrhea symptoms, histopathology examination, relative cytokines and blood cell counts. Mass spectrometry-based non-targeted and targeted metabolomics were conducted in sequence to dissect metabolite signatures in predose serums. Eventually,two groups of metabolites were screened out as predictors for individual differences in late-onset diarrhea and myelosuppression using binary logistic regression, respectively. This result was compared with existing predictors and validated by another independent external validation set. Our study indicates the prediction of toxicity could be possible upon predose metabolic profile. Pharmacometabolomics can be a potentially useful tool for complicating toxicity prediction. Our findings also provide a new insight into CPT-11 precision medicine.