[Reverse effect of Yinchenhao decoction in dimethyl nitrosamine-induced hepatic fibrosis in rats].

OBJECTIVE: To discuss the reverse effect of Yinchenhao decoction(YCHD) in dimethyl nitrosamine (DMN)-induced hepatic fibrosis in rats. METHOD: The rat hepatic fibrosis model was established through the intraperitoneal injection with 1% dimethyl nitrosamine (DMN) with a dose of 1.0 mL x kg(-1) x d(-1) for consecutively three weeks, once for the first three days of each. The rats were randomly divided into six groups: the silymarin positive control group (50.0 mg x kg(-1) x d(-1), YCHD high (20.0 g x kg(-1) d(-1)), middle (8.0 g x kg(-1) x d(-1)) and low (3.2 g x kg(-1) x d(-1)) dose groups, the model group and the normal control group. The model group and the normal control group were orally administered with normal saline for consecutively five weeks. The pathologic changes in liver tissues were observed by HE staining. The levels of alanine aminotransferase (ALT), aspartate aminotransferase (AST), g-glutamyltransferase (g-GGT), hyaluronic acid (HA), laminin (LN), collagen type IV (CIV) and type III procollagen amino terminal peptide (PIIINP) in serum were determined. The metabolite profiling of amino acid and the content of hydroxyproline in liver tissues were also measured. RESULT: Compared with the model group, YCHD high and middle dose groups could significantly reverse the pathologic changes in liver tissues of rats. YCHD could reduce the levels of ALT, AST, gamma-GGT, HA, LN, CIV, PIIINP in serum and the content of hydroxyproline in liver tissues in a dose-dependent manner, and altered the metabolite profiling of amino acid in rat liver tissues. CONCLUSION: YCHD has the effect in reversing dimethyl nitrosamine induced hepatic fibrosis in rats.

Determination of metoclopramide in human plasma by LC-ESI-MS and its application to bioequivalance studies.

An LC-MS method for the determination of metoclopramide in human plasma was developed and validated. Sample preparation involved extraction with ethyl acetate. Chromatographic separation was performed on a Thermo Hypersil-Hypurity C18 (150 mm x 2.1 mm, 5 microm) with the mobile phase consisting of 40 mM ammonium acetate-methanol-acetonitrile. A single-quadrupole mass spectrometer with an electrospray interface was operated in the selected-ion monitoring mode to detect the [M+H]+ ions at m/z 300 for metoclopramide and at m/z 384 for the internal standard (prazosin). The method was validated over 0.78-50.00 ng mL(-1) for metoclopramide. The recovery was 67.8-83.1%, and the limit of quantitation (LOQ) detection was 0.78 ng mL(-1) for metoclopramide. The intra- and inter-day precision of the method at three concentrations was 5.0-13.6% with accuracy of 99.2-104.0%. Stability of compounds was established in a battery of stability studies. The method was successfully applied to bioequivalence studies of metoclopramide hydrochloride tablets to obtain the pharmacokinetic parameters.

Effects of Ginkgo biloba extracts on diazepam metabolism: a pharmacokinetic study in healthy Chinese male subjects.

AIM: It has been reported that Ginkgo biloba extract (GBE) is an inducer or inhibitor of microsomal cytochrome P450 (CYP) 2C19, and diazepam is a substrate of CYP2C19. Thus, it could be expected that GBE may alter the metabolism of diazepam. METHODS: The pharmacokinetic parameters of diazepam and one of its metabolites, N-demethyldiazepam, were compared after oral administration of diazepam (10 mg) in the absence or presence of oral GBE (120 mg bid, for 28 days) in 12 healthy volunteers. The pharmacokinetic analysis was performed using a noncompartmental method. RESULTS: The 90% confidence intervals (CIs) of the ratios of mean pharmacokinetic parameters of diazepam presence and absence of GBE were well within the 80-125% bioequivalence range, indicating no pharmacokinetic interaction. The ratio of AUC(0-408) with GBE to AUC(0-408) without GBE was 95.2 (90%CI: 91.6-98.8) and 101.8 (90%CI: 99.4-104.1) for diazepam and N-desmethyldiazepam, respectively. The two drugs were well tolerated, and no drug-related serious adverse events were reported. CONCLUSION: The above data suggest that GBE, when taken in normally recommended doses over a 4-week time period, may not affect the pharmacokinetics of diazepam via CYP2C19 and the excretion of N-desmethyldiazepam in healthy volunteers. No drug-drug interaction was observed between GBE and diazepam.

Quantitative determination of pimozide in human plasma by liquid chromatography-mass spectrometry and its application in a bioequivalence study.

A simple, sensitive and specific LC-ESI/MS method was developed for the determination of pimozide in human plasma. Pimozide and cinnarizine (internal standard) were isolated from plasma samples by liquid-liquid extraction. The chromatographic separation was accomplished on a Thermo Hypersil-HyPURITY C18 reversed-phase column (150mmx2.1mm, i.d., 5microm) with the mobile phase consisting of 5mM ammonium acetate (pH 3.5, adjusted with acetic acid)-methanol-acetonitrile (39:5:56, v/v/v). The lower limit of quantification was 0.02ng/mL, and the assay exhibited a linear range of 0.025-12.800ng/mL. The established method has been successfully applied to a bioequivalence study of 2 pimozide formulations in 32 healthy male Chinese volunteers.

Quantification of prochlorperazine maleate in human plasma by liquid chromatography-mass spectrometry: Application to a bioequivalence study.

A sensitive and specific method using a one-step liquid-liquid extraction with dichloromethane followed by liquid chromatographic-electrospray ionization-mass spectrometric was developed and validated to determine prochlorperazine maleate in human plasma using amitriptyline hydrochloride as an internal standard. The samples were separated using a Thermo Hypersil-Hypurity C18 reversed-phase column (150mmx2.1mm i.d., 5mum). A mobile phase containing 10mM ammonium acetate (pH 3.6)-methanol-acetonitrile (27:68:5, v/v/v) was used isocratically eluting at a flow rate of 0.22ml/min. The average extraction recovery of prochlorperazine and internal standard were 81.8+/-2.2% and 79.5+/-3.7%, respectively. Prochlorperazine maleate and internal standard were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 0.20 to 6.40ng/ml with r(2)=0.9989. The limit of quantification for prochlorperazine maleate in the plasma was 0.20ng/ml. The established method has been successfully applied to a bioequivalence study of two prochlorperazine maleate formulations in 18 healthy male Chinese volunteers.

Role of anandamide transporter in regulating calcitonin gene-related peptide production and blood pressure in hypertension.

OBJECTIVES: To explore the role of anandamide (AEA) transporter in regulating calcitonin gene-related peptide (CGRP) production and blood pressure. METHODS AND RESULTS: Plasma levels of AEA, CGRP, asymmetric dimethylarginine (ADMA) and nitric oxide in patients with essential hypertension, spontaneously hypertensive rats (SHRs) and 2 kidney 1 clip hypertensive rats and the CGRP mRNA expression in dorsal root ganglion of rats were measured. Peripheral blood lymphocytes were isolated to examine the AEA transporter activity, the role of AEA transporter in regulating CGRP mRNA expression or the effect of exogenous ADMA on AEA transporter activity. In both hypertensive patients and SHRs, the plasma level of AEA was elevated, but the AEA transporter activity was attenuated concomitantly with decreased CGRP production. Moreover, plasma ADMA level in SHRs was elevated accompanied by decreased nitric oxide level. By contrast, the plasma AEA level was elevated accompanied by increased CGRP production in 2 kidney 1 clip hypertensive rats, and there were no significant changes in plasma levels of ADMA, nitric oxide and the AEA transporter activity. In vitro, exogenous administration of AEA upregulated CGRP mRNA expression in lymphocytes, which was inhibited by AEA transporter blocker, AM404, and the AEA transporter activity was reduced by ADMA. CONCLUSION: Decreased plasma CGRP level in patients with essential hypertension or SHRs is likely due to the reduced AEA transporter activity, and the increased ADMA level may account for the reduced AEA transporter activity.

Development and validation of LC-MS method for the determination of lisinopril in human plasma and its application in a bioequivalence study.

A rapid, simple, and specific liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method has been developed and validated for the determination of lisinopril in human plasma. Enalaprilat was used as the internal standard (IS). Sample preparation of the serum involved deproteination with methanol twice, repeatedly. Samples were separated using a Thermo Hypersil-HyPURITY C18 reversed-phase column (150 x 2.1 mm i.d., 5 microm). Mobile phase consisted of formic acid solution (pH 2.9)-methanol-acetonitrile (58:25:17, v/v). Lisinopril and its internal standard were measured by electrospray ion source in positive selected ion monitoring mode. The method was validated with a linear range of 2.5-320 ng/mL and the lowest limits of quantitation were 2.5 ng/mL for lisinopril. The extraction efficiencies were approximately 80% and recoveries of method were in range of 94.4-98.2%. The intra-day relative standard deviation (RSD) was less than 8.8% and inter-day RSD was within 10.3%. QC samples were stable when kept at ambient temperature for 24 h, at -20 degrees C for 30 days and after four freeze/thaw cycles. The method has been successfully applied to the evaluation of pharmacokinetics and bioequivalence of 2 lisinopril formulations in 18 healthy Chinese volunteers after an oral dose of 20 mg.

Determination of mianserin in human plasma by high performance liquid chromatography-electrospray ionization mass spectrometry (HPLC-ESI/MS): application to a bioequivalence study in Chinese volunteers.

This study aims to develop a standard protocol for the bioequivalence study of mianserin hydrochloride tablets--a tetracyclic antidepressant drug. For this purpose, a rapid, convenient and selective method using high performance liquid chromatography coupled with electrospray ionization mass spectrometry (HPLC-ESI/MS) has been developed and validated to determine mianserin in human plasma. Mianserin and the internal standard (I.S.), cinnarizine were extracted from plasma by N-hexane:dimethylcarbinol (98:2, v/v) after alkalinized with sodium hydroxide. LC separation was performed on a Thermo Hypersil-Hypurity C18 (5 microm, 150 mm x 2.1 mm) with the mobile phase consisting of 10mM ammonium acetate (pH 3.4)-methanol-acetonitrile (35:50:15, v/v/v) at 0.22 ml/min. The retention time of mianserin and cinnarizine was 3.4 and 2.1 min, respectively. Quadrupole MS detection and quantitation was done by monitoring at m/z 265 [M+H]+ for mianserin and m/z 369 [M+H]+ for cinnarizine. The method was validated over the concentration ranges of 1.0-200.0 ng/ml for mianserin. The recovery was 81.3-84.1%, intra- and inter-day precision of the assay at three concentrations were 9.6-11.4% with accuracy of 97.5-101.2% and the lower limit of quantitation (LLOQ) detection was 1.0 ng/ml for mianserin. The stability of compounds was established in a battery of stability studies, i.e., short-term and long-term storage stability as well as freeze-thaw cycles. This method proved to be suitable for the bioequivalence study of mianserin hydrochloride tablets in healthy human male volunteers.

[High-performance liquid chromatography-mass spectrometry for determining olmesartan in human plasma].

OBJECTIVE: To establish a simple and rapid HPLC-MS method for determining the contents of olmesartan in human plasma. METHODS: Plasma were precipitated with trifluoroacetic acid, then analyzed on an HyPurity C(18) column (150 mm 2.1 mm, 5 microm). Samples at 40 degrees celsius;. The mobile phase consisted of water-methanol- acetonitrile(14:60:26) with a flow rate of 0.22 ml/min. RESULTS: The lower limit of qualification was 25 microg/L. The calibration curve was linear over the range of 25-3200 microg/L (r=0.9998), with the intra-day and inter-day RSD less than 15%. CONCLUSION: The method is sensitive, rapid and suitable for the study of pharmacokinetics and bioavailability of olmesartan.

Fingerprint of Hedyotis diffusa Willd. by HPLC-MS.

A HPLC-MS fingerprint method has been developed based on the consistent chromatographic features of the major chemical constituents among 10 batches of Hedyotis diffusa Willd. Chromatographic separation was conducted on a Hypersil-Keystone Hypurity C(18) column using methanol:water:acetic acid as the mobile phase. Major compounds, including oleanolic acid, ursolic acid and ferulic acid, were analysed by HPLC-MS. Their analysis was ascertained by comparison with data derived from the standard compounds. The HPLC-MS fingerprint was successfully applied to analyse and differentiate samples from different geographical origins, or processing methods. H. diffusa was well distinguished from Hedyotis chrysotricha by HPLC-MS. Therefore the establishment of fingerprint of H. diffusa is critical in assessing and controlling its overall quality.

Quantitative determination of erythromycylamine in human plasma by liquid chromatography-mass spectrometry and its application in a bioequivalence study of dirithromycin.

A sensitive, rapid liquid chromatographic-electrospray ionization mass spectrometric method for determination of erythromycylamine in human plasma was developed and validated. Erythromycylamine in plasma (0.2 mL) was extracted with ethyl acetate, the organic phase was transferred to another clear 1.5 mL Eppendorf tube and evaporated to dryness under gentle nitrogen stream at 45 degrees C, and the residue was dissolved in 100 microL of mobile phase. The samples were separated using a Thermo Hypersil HyPURITY C18 reversed-phase column (150 mm x 2.1 mm I.D., 5 microm). A mobile phase containing 10 mM of ammonium acetate (pH = 6.4)-acetonitrile-methanol (50:10:40, v/v/v) was used isocratically eluting at a flow rate of 0.2 mL/min. Erythromycylamine and its internal standard (IS), midecamycin, were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 4.5 to 720 ng/mL with r = 0.9997. The limit of quantification for erythromycylamine in plasma was 4.5 ng/mL with good accuracy and precision. The mean extraction recovery of the method was higher than 75.1% and 72.7% for erythromycylamine and IS, respectively. The intra-day and inter-day precision ranged from 5.2% to 6.4% and 5.6-9.3% (relative standard deviation, RSD), respectively. The established method has been successfully applied to a bioequivalence study of two dirithromycin formulations for 18 healthy volunteers.

High-performance liquid chromatography with atmospheric pressure chemical ionization and electrospray ionization mass spectrometry for analysis of Angelica sinensis.

An HPLC-PAD-API/MS method for analysing the chemical constituents of Angelica sinensis (A. sinensis) has been developed. ESI and APCI spectra, in both positive ion (PI) and negative ion (NI) modes, provided very useful information concerning the molecular weights of detected compounds. By comparing the retention times, UV spectra, mass spectra and molecular weights of detected compounds with those published in literature, 15 constituents of A. sinensis could be tentatively identified. This technique involving combined MS information may provide an objective, reliable and rapid analytical method for the quality control and database research of traditional Chinese medicines.

Determination of duloxetine in human plasma via LC/MS and subsequent application to a pharmacokinetic study in healthy Chinese volunteers.

BACKGROUND: The pharmacokinetics of duloxetine hydrochloride have been well studied after its approval for clinical use. However, few such data have been reported in the English language literature. We developed a method to determine the pharmacokinetics of duloxetine enteric-coated capsules in healthy Chinese volunteers. METHODS: A rapid and sensitive liquid chromatography-mass spectrometric (LC/MS) method for the determination of duloxetine in human plasma using flupentixol as the internal standard (I.S.) was developed and validated. Sample preparation of the plasma involved deproteination with acetonitrile twice, repeatedly. Samples were then analyzed by HPLC on a Thermo Hypersil-Hypurity C18 column (150 x 2.1 mm, 5 microm). A single-quadrupole mass spectrometer with an electrospray interface was operated in the selected-ion monitoring mode to detect the [M+H](+) ions at 298 m/z for duloxetine and at 435 m/z for the internal standard. RESULTS: Pharmacokinetics were measured in 12 healthy Chinese male volunteers (6 males and 6 females) who received a single regimen with 3 different dosages at 22.4, 44.8 and 67.2 mg of duloxetine enteric-coated capsules. CONCLUSION: A sensitive and specific method for quantifying duloxetine levels in human plasma has been devised and successfully applied to a clinic pharmacokinetic study of an enteric-coated capsule of duloxetine hydrochloride administered as a single oral dose.

Quantitative determination of amantadine in human plasma by liquid chromatography-mass spectrometry and the application in a bioequivalence study.

A sensitive liquid chromatography-electrospray ionization mass spectrometry (LC-ESI-MS) method is developed and validated for rapid determination of amantadine in human plasma. Desloratadine was used as the internal standard (I.S.). Human plasma (0.2 mL) was first alkalified with 100 microL of sodium hydroxide (3M) and then extracted with 1 mL of n-hexane containing 1% isopropanol (v/v) and 10% dichloromethane (v/v) by vortex-mixer for 3 min. The mixture was centrifuged at 14,000 rpm for 5 min. The supernatant was evaporated to dryness and the residue was dissolved in mobile phase. Samples were separated using a Thermo Hypersil-HyPURITYC18 reversed-phase column (150 mm x 2.1 mm i.d., 5 microm). Mobile phase consisted of methanol-acetonitrile-20 mM ammonium acetate (45:10:45, v/v/v) containing 1% acetic acid with pH 4.0. Amantadine and I.S. were measured by electrospray ion source in positive selective ion monitoring mode. The good linearity ranged from 3.9 to 1000 ng/mL and the lowest limit of quantification was 3.9 ng/mL. The extraction efficiencies were approximately 70% and recoveries of method ranged from 98.53 to 103.24%. The intra-day relative standard deviations (R.S.D.) were less than 8.43% and inter-day R.S.D. below 10.59%. The quality control samples were stable when kept at room temperature for 12h, at -20 degrees C for 30 days and after four freeze/thaw cycles. The method has been successfully used to evaluation of the pharmacokinetics and bioequivalence of amantadine in 20 healthy volunteers after an oral dose of 100 mg amantadine.

Level of asymmetric dimethylarginine and carotid atherosclerosis in patients with chronic kidney disease.

OBJECTIVE: To determine the association between asymmetric dimethylarginine (ADMA), an endogenous inhibitor of nitric oxide (NO) synthase, with atherosclerosis in patients with chronic kidney disease (CKD). METHODS: One hundred thirty-eight CKD patients were enrolled in this study. Serum levels of L-arginine, ADMA, and SDMA were measured by high-performance liquid chromatography (HPLC). Common carotid arteries intimae-medial thickness (CCA-IMT), cross-sectional calculated intimae-medial thickness (cIM area) and atherosclerotic plaque were detected by noninvasive high-resolution B-mode ultrasonography. RESULTS: Serum levels of ADMA and SDMA were significantly increased in CKD patients (n=138) compared with age matched healthy subjects (n=42, P<0.01). ADMA and SDMA levels increased with the progression of renal dysfunction and were negatively related to creatinine clearance (Ccr) in pre-dialysis patients (r=-0.315, P<0.05; r=-0.426, P<0.01). Serum levels of ADMA and SDMA in dialysis patients (n=74) were significantly higher than those in pre-dialysis patients (P<0.05). Patients with carotid artery plaques showed significantly higher levels of ADMA compared with those without plaques. Serum levels of ADMA closely correlated with the mean IMT (r=0.471, P<0.01) and cIM area value (r=0.430, P<0.01). These correlations remained significant even after adjusting GFR, age, gender ,and other risk factors for atherosclerosis in the multiple regression analysis. CONCLUSION: Serum levels of ADMA increased with the progression of CKD and may play a role in the pathogenesis of accelerated atherosclerosis in CKD patients.

Quantitative determination of azithromycin in human plasma by liquid chromatography-mass spectrometry and its application in a bioequivalence study.

A sensitive, rapid liquid chromatographic-electrospray ionization mass spectrometric method for determination of azithromycin in human plasma was developed and validated. Azithromycin in plasma (0.2mL) was extracted with methyl tert-butyl ether-hexane (50:50, v/v), organic phase was transferred to another clear 1.5mL Eppendorf tube and evaporated to dryness at 40 degrees C and dissolved in mobile phase, samples were separated using a Thermo Hypersil HyPURITY C18 reversed-phase column (150mmx2.1mm i.d., 5microm), together with a mobile phase containing of 20mM ammonium acetate (pH 5.2)-acetonitrile-methanol (50:40:10, v/v/v) and was isocratically eluted at a flow rate of 0.2mL/min. Azithromycin and its internal standard, clarithromycin, were measured by electrospray ion source in positive selective ion monitoring mode. The method demonstrated that good linearity ranged from 2 to 1000ng/mL with r=0.9977. The limit of quantification for azithromycin in plasma was 2ng/mL with good accuracy and precision. The higher mean extraction recovery, say 81.2% and 75.5% for azithromycin and internal standard (IS), respectively, was obtained in this work. The intra-day and inter-day precision ranged from 4.8% to 8.6% and 6.4% to 10.7% (R.S.D.), respectively. The established method has been successfully applied to bioequivalence study of 2 azithromycin formulations for 24 healthy volunteers.

Identification and determination of nucleosides in Cordyceps sinensis and its substitutes by high performance liquid chromatography with mass spectrometric detection.

Cordyceps sinensis (Cs) is a well-known traditional Chinese medicine (TCM) and Cordyceps mycelia (Cm), a cultured Cordyceps, is a substitute for Cordyceps sinensis. The most important active components in them are nucleosides. A high selective, sensitive and accurate high performance liquid chromatography method with photodiode array detection (DAD) and mass spectrometric detection has been developed for simultaneous separation, identification and quantification of nucleosides in Cs and Cm using a mobile phase including (A) ammonium acetate (40 mM, pH 5.2) and (B) methanol with a gradient system on a 2.0 mm x 150 mm Shimadzu VP-ODS column. The presence of each nucleoside in Cs and Cm was ascertained by comparison of MS data, UV spectra and retention time with standards. LC/ESI-MS in selective ion monitoring (SIM) mode were used for the quantification of nucleosides in Cs and Cm. 2-Chloroadenosine was used as internal standard for this assay. The precisions and accuracies were in the range of 1.5-5.3% and -3.5 to 5.0%, respectively. The limits of detection and quantification for nucleosides were in the order of 0.1-0.6 microg ml(-1) and 0.5-2.0 microg ml(-1), respectively. The recoveries were in the range of 92.0-107.0%. With the developed method, the concentrations of nucleosides in Cs and Cm from different sources were determined. Cs, characterized with far lower concentration of adenosine and cordycepin than Cm, can be very easy to distinguish from Cm. This reliable method would be useful for the study and quality control of Cordyceps sinensis and its substitutes.

LC-DAD-APCI-MS-based screening and analysis of the absorption and metabolite components in plasma from a rabbit administered an oral solution of danggui.

A valid chromatographic fingerprint method using liquid chromatography-diode array detection-atmospheric pressure chemical ionization mass spectrometry in negative mode (LC-DAD-APCI-MS) is proposed for studying the absorption and metabolites of a traditional Chinese medicine (TCM) Angelica sinensis (danggui) in rabbit plasma, after the rabbit is administered with danggui oral solution (DOS). More than thirty-two common components were detected in both DOS and rabbit plasma, which shows that the components in the DOS were absorbed into the body of the rabbit. Of these, senkyunolide I, senkyunolide H, Z-6,7-epoxyligustilide, 3-butylidene-7-hydroxyphthalide, Z-ligustilide, Z-butylidenephthalide, Diels-Alder dimers of ligustilide, linolenic acid, linoleic acid and falcarindiol were tentatively identified from their MS, UV spectra and retention behavior by comparing the results with the published literature. At least ten components were found in rabbit plasma but not in DOS, indicating that these components must be metabolites of some of the components in the original extract. The results prove that the proposed method can be used to rapidly analyze multiple constituents in TCMs, and to screen for bioactive compounds by comparing and contrasting the chromatographic fingerprints of DOS and plasma samples.

[Changes of serum asymmetric dimethylarginine in essential hypertension before and after the treatment].

OBJECTIVE: To investigate the relationship between serum asymmetric dimethylarginine (ADMA) and blood pressure as well as target organ damage in essential hypertension, and to evaluate the effects of enalapril and losartan on them. METHODS: Forty-two newly diagnoszed patients with essential hypertension were randomly divided into enalapril-treated group and losartan-treated group. Serum ADMA, L-arginine, and nitric oxide( NO) were measured before and after the treatment for 8 weeks. Twenty-three healthy volunteers were included as control subjects. RESULTS: The concentrations of ADMA and L-arginine in serum were significantly higher but the level of nitric oxide was relatively lower ( P < 0.01 ) in hypertensive patients than those in control subjects. Serum ADMA was higher in different levels of blood pressure and target organ damage. Treatment with enalapril or losartan for 8 weeks not only reduced blood pressure but also decreased serum ADMA (P <0.01 ). Furthermore, treatment with these drugs also increased the level of serum nitric oxide but didn't change the level of L-arginine. CONCLUSION: The concentrations of serum ADMA and L-arginine were increased, but the level of nitric oxide was decreased in the early stage of essential hypertension. Both enalapril and losartan could ameliorate the endothelial function by reducing the concentration of ADMA.

[Determination of adenosine and cordycepin in Cordyceps sinensis and C. militarris with HPLC-ESI-MS].

OBJECTIVE: HPLC-ESI-MS to establish a method for simultaneous determination of adenosine and cordycepin in Cordyceps sinensis and C. militarris. METHOD: HPLC-ESI-MS method. An electrospray ionization (ESI) interface and selective ion monitoring (SIM) mode were used. The analytical column was a 2.0 mm x 150 mm Shimadzu VP - ODS column and the mobile phase was water (94%), methanol (5%) and formic acid (1%). 2-Chloroadenosine was used as internal standard for this assay. RESULT: The regression equations and coefficient were Y = 0.134 6X + 0.001 29 (r = 0.998 4) for adenosine, Y = 0.216 4X + 0.021 5 (r = 0.999 1) for cordycepin. The liner range was 0.5 approximately 124.5 microg x mL(-1) and 0.5 approximately 136.5 microg x mL(-1) for adenosine and cordycepin, respectively. The average recoveries of adenosine and cordycepin were 95.8% and 98.1%, respectively. CONCLUSION: This method is highly sensitive, fast and selective, which can be used for the determination of nucleosides in C. sinensis and its substitutes. This method can also be applied for the quality control of above herbs.