[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.

[Studies on bioassay-guided anti-inflammatory fraction in bark of Albizia julibrissin combined determination with LC-MS-MS].

OBJECTIVE: To search the anti-inflammatory fraction of Albizia julibrissin. METHOD: Inflammatory model of Kunming mice ear edema induced by croton oil and determination combined with the LC-MS-MS-guided fractionation and isolation were used. RESULT: The n-butanol fraction (AJ-B) obtained from the ethanolic extract of the Cortex albiziae was the major active fraction. The lignan glycosides fraction (AJ-B-1), which was further isolated from AJ-B, showed significant anti-inflammatory activity and exhibited dose-dependent relationship in the dose of 5 to 20 mg x kg(-1). CONCLUSION: The method of bioassay-guided fractionation and isolation combined with the LC-MS-MS determination may be of benefit to the logical studies on the bioactive fractions or constituents of traditional Chinese materia medica.

Determination of rizatriptan in human plasma by liquid chromatographic-eletrospray tandem mass spectrometry: application to a pharmacokinetic study.

A sensitive liquid chromatographic-tandem mass spectrometry(LC-MS/MS) method was developed for the determination of rizatriptan in human plasma. The analytes were extracted from plasma samples by liquid-liquid extraction, separated on a Zorbax XDB C8 column (150 x 4.6 mm i.d.) and detected by tandem mass spectrometry with an electrospray ionization interface. Zomitriptan was used as the internal standard. The method had a lower limit of quantitation of 50 pg/mL for rizatriptan, which showed more sensitivity and speed of analysis compared with reported methods. The within- and between-day precision was measured to be below 11.71% and accuracy between -5.87 and 0.86% for all quality control samples. This quantitation method was successfully applied to the evaluation of the pharmacokinetic profiles of rizatriptan after single oral administration of 5, 10 and 15 mg rizatriptan tablets to 10 healthy volunteers (five males and five females).

[Rapid identification of the isomeric impurity in raw drug of cefepime dihydrochloride by liquid chromatography-tandem mass spectrometry].

AIM: To establish a sensitive and specific liquid chromatography-tandem mass spectrometry (LC-MS/MS) method for the determination of isomeric impurity in raw drug material of cefepime dihydrochloride. METHODS: The HPLC separation experiments were performed on a reversed phase C18 column, with acetonitrile-10 mmol x L(-1) ammonium acetate (5:95) as mobile phase (a flow rate of 0.8 mL x min(-1)). The analytes were determined by electrospray ionization tandem mass spectrometry in positive mode. The chromatogram and mass spectra of cefepime dihydrocloride and its isomeric impurity were obtained by LC-MS/MS. RESULTS: The method can be used for the separation and identification of cefepime dihychrocloride and its isomeric impurity, of which the retention times were 15.28 min and 9.18 min, respectively. Based on the MS/MS spectra of their molecular ions, the different fragmentation pathways of cefepime dihydrocloride and its isomeric impurity were compared and proposed. CONCLUSION: The method was rapid, sensitive and specific. It can be used for the identification of the isomeric purity in raw drug material of cefepime dihydrochloride.

Identification of rat faecal, urinary and biliary metabolites of thionorphine, a novel mixed agonist-antagonist analgesic, using liquid chromatography/electrospray ionization tandem mass spectrometry.

The biotransformation of thionorphine (N-cyclopropylmethyl-7alpha-[(s)-1-hydroxy-1-methyl-3-(2thiophene)-propyl]-6,14-endo-ethano tetrahydrooripavine), a new analgesic, was in-vestigated in rats. The results of metabolite analysis by liquid chromatography/electrospray ionization tandem mass spectrometry with positive ion mode, in which a mobile phase of 10 mM ammonium acetate (pH 3.0)/acetonitrile (25/75) was used, suggested that thionorphine is biotransformed to two potentially active metabolites, the N-dealkylated thionorphine (M-I) and the oxidized thionorphine (M-II), and subsequently form conjugates with glucuronic acid of both thionorphine and the metabolites.

[Determination of glycosides in traditional Chinese medicine liu-wei di-huang by RP-HPLC].

OBJECTIVE: To establish a RP-HPLC method for determination of glycosides in Traditional Chinese Medicine Liu-wei Di-huang. METHOD: The samples were analyzed on an ODS column at 30 degrees C, with mobile phase of methanol/water (33:67) at flow rate 1.0 mL.min and detection at wavelength of 236 nm. RESULT: Three major components reached base-line separation and were identified to be mononiside, loganin, paeoniflorin. Respectively for the three components, linear correlations were found between peak areas and concentrations in the ranges of 7.4-60, 7.7-62 mg.L-1 and 8.5-68 mg.L-1, and the recoveries were 98.8%, 98.3%, 99.6%. CONCLUSION: The established method is proved to be suitable for simultaneous quantification of three major glycosidic components in Liuwei Dihuang decoction and can be used for evaluation of the quality of Liuwei Dihuang preparations.

[Identification of the metabolites of penehyclidine hydrochloride raceme in rats by LC-MS/MS and ion cluster].

AIM: To study the metabolites of penehyclidine hydrochloride (PH) raceme, a new anticholinerigic drug invented by the Institute of Pharmacology and Toxicology, Academy of Military Medical Sciences. METHODS: Three healthy rat urine samples were collected within 24 h after a single i.m. dose of PH raceme and PH-d5 [(5 + 5) mg.kg-1] simultaneously. The eight metabolites of PH raceme were identified by the methods of LC-MS/MS, GC-MS, FAB-MS and the stable isotope ion cluster. Mass spectrometry was operated in the positive mode for the method of LC-MS/MS. RESULTS: M1 and M1* were identified as the oxygenated products of PH in the cyclopentyl group; M2 and M2* were as the hydroxylated products of PH in the cyclopentyl group; M3 and M3* were as the oxygented and hydroxylated products of PH at the meta-position of cyclopentyl group; M4 and M4* were identified as the dihydroxylated metabolites of PH, the hydroxylated position were at the cyclopentyl group and quiniuclidinol ring of PH. Among them, M1 and M1*, M2 and M2*, M3 and M3*, M4 and M4* were the isomers of each other. CONCLUSION: These characteristics can be used for future structure elucidation in studies of the metabolites of PH optical isomers. The structure data of PH metabolites provide important information for the clinical use and for developing better anticholinerigic drug.