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Su Zeng

Publications and source records attributed to Su Zeng.

At least 37 records · Page 2Linked to original sources
PubMed2004

Simultaneous determination of luteolin and apigenin in dog plasma by RP-HPLC.

A specific and accurate high-performance liquid chromatographic method has been developed and validated for the simultaneous determination of luteolin and apigenin in the plasma of dog. The sample was treated with 6.0% perchloric acid to precipitate the protein. Luteolin and apigenin were extracted with ethyl acetate. The organic layer separated was dried and reconstituted in the mobile phase. The HPLC separation was performed on C18 column and the UV detector was set at 350 nm. The standard curve for luteolin and apigenin in plasma were linear over the range of 38.5-4350 and 16.5-1860 ng/ml, with the correlation coefficients 0.9996 and 0.9999, respectively. The assay recoveries for luteolin and apigenin ranged from 102.7 to 104.5% and 93.8-101.8%, respectively. The intra- and inter-day precisions (R.S.D.) for luteolin and apigenin were all less than 7.9%. The sample was stable within 24 h at 4 degrees C storage, 30 days at -20 degrees C storage, and undergoing four freeze-thaw-assay cycles. The limits of detection (LOD) of luteolin and apigenin were 1.82 and 1.94 ng/ml, while the limits of quantification (LOQ) were 7.84 and 6.29 ng/ml, respectively. The method developed was applied successfully to study pharmacokinetics of the effective composition (luteolin) of Chrysanthemum morifolium extract in dogs after single dose of oral administration.

Administration, Oral↗
PubMed2004

Cloning and expression of human UDP-glucuronosyltransferase 1A4 in Bac-to-Bac system.

UDP-glucuronosyltransferases (UGTs) catalyze the transfer of glucuronic acid from uridine diphosphate-glucuronic acid (UDP-GA) to compounds with amine, hydroxyl, and carboxylic acid moieties. N-glucuronidation is an important pathway for elimination of many tertiary amine therapeutic agents used in humans. UGT1A4 has been reported to be specific for glucuronidating primary, secondary, and tertiary amines, forming N-glucuronides. To further investigate the drugs metabolized by UGT1A4, the Bac-to-Bac expression system was used to express the recombinant UGT1A4 with His-tag on the C-terminal. The His-tagged recombinant UGT1A4 expressed in Spodoptera frugiperda (Sf9) cells were detected using anti-His antibody and the molecular weight of the recombinant protein was approximately 55kDa. The enzyme activity towards imipramine in cell homogenate protein was found to be 83.14+/-15pmol/min/mg protein (n=3) with 0.5mM imipramine by HPLC, but was not detectable in blank Sf9 cells. It paved the way for the further studies for drug glucuronidation by UGT1A4. The purification of the UGT1A4 can be done by Ni-resin. This is helpful to do research on the structure of the UFT1A4.

Animals↗
PubMed2004

Simultaneous determination of the enantiomers of esmolol and its acid metabolite in human plasma by reversed phase liquid chromatography with solid-phase extraction.

A stereoselective RP-high performance liquid chromatography (HPLC) assay to determine simultaneously the enantiomers of esmolol and its acid metabolite in human plasma was developed. The method involved a solid-phase extraction and a reversed-phase chromatographic separation with UV detection (lambda = 224 nm) after chiral derivatization. 2,3,4,6-tetra-O-acetyl-beta-d-glucopyranosyl isothiocyanate (GITC) was employed as a pre-column chiral derivatization reagent. The assay was linear from 0.09 to 8.0 microg/ml for each enantiomer of esmolol and 0.07-8.0 microg/ml for each enantiomer of the acid metabolite. The absolute recoveries for all enantiomers were >73%. The intra- and inter-day variations were <15%. The validated method was applied to quantify the enantiomers of esmolol and its metabolite in human plasma for hydrolysis studies.

Adrenergic beta-Antagonists↗
PubMed2004

Stereoselective RP-HPLC determination of esmolol enantiomers in human plasma after pre-column derivatization.

A stereoselective reversed-phase HPLC assay to determine S-(-) and R-(+) enantiomers of esmolol in human plasma was developed. The method involved liquid-liquid extraction of esmolol from human plasma, using S-(-)-propranolol as the internal standard, and employed 2,3,4,6-tetra-O-acetyl-beta-d-glucopyranosyl isothiocyanate as a pre-column chiral derivatization reagent. The derivatized products were separated on a 5-microm reversed-phase C18 column with a mixture of acetonitrile/0.02 mol/L phosphate buffer (pH 4.5) (55:45, v/v) as mobile phase. The detection of esmolol derivatives was made at lambda=224 nm with UV detector. The assay was linear from 0.035 to 12 microg/ml for each enantiomer. The analytical method afforded average recoveries of 94.8% and 95.5% for S-(-)- and R-(+)-esmolol, respectively. For each enantiomer, the limit of detection was 0.003 microg/ml and the limit of quantification for the method was 0.035 microg/ml (RSD<14%). The reproducibility of the assay was satisfactory.

Calibration↗
PubMed2004

Separation of rutin nona(H-) and deca(H-) sulfonate sodium by ion-pairing reversed-phase liquid chromatography.

Ion-pairing reversed-phase liquid chromatography (RPLC) was used to separate two polysulfonates, rutin nona(H-) sulfonate sodium and rutin deca(H-) sulfonate sodium, which have very similar chemical structures. The final product always contained both of them when one of the compounds was synthesized. Baseline separation was achieved on a C8-bonded silica column at ambient temperature. The eluent was acetonitrile-15 mM phosphate buffer solution containing 20 mM TBA (pH 6.0) (46:54, v/v). The calibration plot was linear in the concentration range 0.5-200 microg ml(-1) for both analytes. The limits of detection (LODs; 254 nm) were 0.03 microg ml(1-) for rutin nona(H-) sulfonate sodium and 0.04 microg ml(-1) for rutin deca(H-) sulfonate sodium. Three batches of rutin deca(H-) sulfonate sodium were analyzed using the assay; the results showed that the analytical performance is really satisfactory.

Chromatography, Liquid↗
PubMed2004

Establishment of a P-glycoprotein substrate screening model and its preliminary application.

AIM: To establish a high P-glycoprotein (P-gp) expressing cell line as a model for studying drug absorption and distribution, and to explore the preliminary application of this screening model. METHODS: A full-length MDR1 cDNA fragment in plasmid pMDRA1 was first subcloned into plasmid pET28a(+), then MDR1 cDNA was cut from the recombinant plasmid with double-digestion and ligated into the mammalian expression vector pcDNA3.1(+). The recombinant plasmid pcDNA3.1(+)/MDR1 was transfected into breast cancer cell line Bcap37 using the Superfect transfection reagent. Several stably transfected clones were obtained after selection with G418. Real-time fluorescent quantitative RT- PCR and Western blot methods were used to detect the expression of P-gp, and the cellular location of the expressed protein was determined by immunohistochemical staining. Drug sensitivity assay was used to evaluate the biological function of expressed P-gp. Concentration of quercetin in cells was determined by high-performance liquid chromatography (HPLC). RESULTS: The recombinant plasmid was confirmed to be inserted in the correct orientation by restrictive enzyme digestion and DNA sequencing. Real-time fluorescent quantitative RT-PCR showed a higher level of P-gp mRNA in transfected cells compared to that in the control cells, and the Western blot result also indicated that P-gp expression in transfected cells was higher than that in control cells. The immunohistochemical staining showed that the expressed P-gp was localized on cell membranes. Drug sensitivity assay showed that the IC50 for adriamycin and colchicine of the transfected cells was higher than that of the control cells. The concentration of quercetin in model cells was lower than that in control cells by HPLC. After P-gp inhibitor verapamil was administered, the concentration of quercetin in model cells was increased. CONCLUSION: A high P-gp expressing cell line can be established, which could provide a suitable in vitro model system for studying drug intestinal absorption mechanism, predicting the drug permeability characteristics and screening new multi-drug resistance reversing agents. With this model, quercetin can be found to be transported by P-gp, and it is a P-gp substrate.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed2004

Direct determination of S-(-)- and R-(+)-propranolol glucuronide in rat hepatic microsomes by RP-HPLC.

Propranolol, available commercially as a racemic mixture, is a non-selective beta-adrenergic blocking agent used in the treatment of hypertension, angina pectoris and cardiac arrhythmias. We have developed and validated an RP-HPLC assay method for direct determination of R-(+)- and S-(-)-propranolol glucuronide in rat hepatic microsomes to investigate the enantioselectivity of propranolol glucuronidation metabolism. A baseline separation of propranolol glucuronide enantiomers was achieved on a 5 microm reversed-phase ODS column, with a mixture of phosphate buffer (pH 3.5, 0.067 mol/L) and methanol (55:45, v/v) as mobile phase. Ultraviolet detection was set at 220 nm, and p-nitrobenzoic acid was used as internal standard. The standard curve of assay for R-(+)- and S-(-)-propranolol glucuronide in spiked microsomal incubate showed good linearity throughout the concentration range from 0.50 to 20.0 micromol/L. The analytical method affords average recovery of 99.8 and 100.1% for R-(+)- and S-(-)-propranolol glucuronide, respectively. The method provides a high sensitivity and good precision for R-(+)- and S-(-)-propranolol glucuronide (RSD < 10%). The LOD was 0.15 micromol/L and the LOQ was 0.5 micromol/L (RSD < 8%, n = 5) for both R-(+)- and S-(-)-propranolol glucuronide. The method is simple, precise and accurate, and is suitable for quantifying the propranolol glucuronides enantiomers in rat hepatic microsomes.

Adrenergic beta-Antagonists↗
PubMed2004

[Effects of microsome enzyme induced by phenobarbarbital on the stereoselectivity of recemic propranolol glucuronidation metabolism].

OBJECTIVE: To study the stereoselectivity of R-(+) and S-(-)-propranolol glucuronidation and metabolic interaction between R(+)- and S-(-)-propranolol. METHODS: A RP-HPLC analytical method was developed for determination of R-(+)-and S-(-)-propranolol glucuronide (PG) incubated with rat hepatic microsome induced with phenobarbital (PB). The method was applied to investigate the stereoselectivity metabolism of racemic propranolol glucuronidation in vitro. RESULT: In control and PB group, the concentration of R-(+)-PG produced at different substrates was higher than that of S-(-)-PG. Compared with the control, the V(max) and Cl(int) for R(+)-and S-(-)-propranolol increased significantly the K(m) for R(+)-propranolol was elevated, while that for S-(-) propranolol was decreased. CONCLUSION: There is a stereoselectivity in glucuronidation of propranolol in rat hepatic microsome induced with PB and R-(+)-propranolol is preferred. Metabolic interaction between R-(+)-and S-(-)-propranolol exists with a concentration-dependent mode.

Animals↗
PubMed2004

[Direct resolution of calcium folinate stereoisomers using a bovine serum albumin chiral HPLC column].

OBJECTIVE: To establish a direct and fast method separating calcium levofolinate and calcium dextrofolinate in a bovine serum albumin stationary phase chiral column. METHODS: Using EC150/4 RESOLVOSIL BSA-7(150 mm x 4 mm) chiral separation column, with 0.20 mol/L, pH=5.0 phosphate buffer as mobile phase HPLC method was performed to separate calcium folinate enantiomers. RESULT: The capacity factor and resolution of the two calcium folinate enantiomers were greatly affected by mobile phase buffer concentration,pH and the column temperature. And the retention time of calcium levofolinate and calcium dextrofolinate were 18.5 min and 22.6 min, respectively. The resolution, R(s)=1.49. CONCLUSION: Calcium folinate enantiomers are separated successfully using this method.

Chromatography, High Pressure Liquid↗
PubMed2004

[Glucuronidation and in vitro interaction of Ginkgo flavonoids with other drugs].

OBJECTIVE: To obtain the information on the glucuronidation of Ginkgo flavonoid and the interaction profile of Ginkgo flavones with other drugs in vitro. METHODS: Ginkgo flavonoids (quercetin, isorhamnetin and keampferol) and other drugs were co-incubated with rat hepatic microsome at 25 degree; the residual concentrations of flavonoids were determined by HPLC. The enzymatic parameters of quercetin, isorhamnetin and keampferol metabolism were assessed. The interactions between flavonoids and these drugs on glucuronidation were observed. RESULT: The K(m) values were ( 24+/-0.05), (148+/-0.09) and (110+/-0.03) micromol/L and the V(max) values were (60+/-0.21), (48+/-0.02) and (34+/-0.02) micromol x g(-1) x min(-1) for quercetin, isorhamnetin and kaempferol, respectively. The IC(50) of nifedipine propafenone ipriflavone and diphenytriazol on flavonoids metabolism were 54 - 70, 69 - 122, 85 - 98 and 210 - 362 micromol, respectively. The inhibition constants (Ki) of diphenytriazol propafenone and ipriflavone on quercetin, isorhamnetin and keampferol metabolism were (57.6, 50.5, 33.1) (33.6, 59.5, 45.2) and(13.7,24.0,15.7) microg/ml respectively. The ratio [I]/[Ki] of the plasma concentration and inhibition constant for propafenone was 0.002 - 0.003. CONCLUSION: The metabolic level of quercetin is the strongest among three Ginkgo flavonoids. Nifedipine propafenone and ipriflavone inhibit the metabolism of quercetin, isorhamnetin and keampferol at different levels. Because of the interaction between Ginkgo flavonoids with nifedipine, caution must be taken when two drugs are used together clinically.

Animals↗
PubMed2004

[Determination of luteolin and luteolin-7-beta-D-glucoside in Chrysanthemum morfolium Ramat. from different collection time by RP-HPLC].

OBJECTIVE: To observe the content variation of luteolin and luteolin-7-beta-D-glucoside in Chrysanthemum morifolium Ramat. (CMR) from different collection time. METHODS: RP-HPLC was used to analyze these two components in CMR collected in 2001 and 2002. RESULT: The content of luteolin was significantly lower than that of luteolin-7-beta-D-glucoside. Furthermore, the former showed no marked changes during collection, while the latter did not varied markedly in early collection but decreased significantly in later collection. CONCLUSION: The content of luteolin-7-beta-D-glucoside reflects the quality of Chrysanthemum morifolium Ramat. more viably than that of luteolin.

Chromatography, High Pressure Liquid↗
PubMed2004

[Determination of three formulations of pilocarpine in rabbit ocular aqueous by RP-HPLC].

OBJECTIVE: To develop an RP-HPLC method for assay of pilocarpine in rabbit ocular aqueous humor. METHODS: The RP-HPLC method was performed on a column of ODS-C(18) with the mobile phase consisting of 0.5% of triethylamine (TEA) of phosphate solutions (10 mmol/L, pH 2.5) and acetonitrile (98/2,v/v). The detection wavelength was 215 nm and flow rate was 1.0 ml/min. Ninety albino rabbits were divided into 3 groups (30 in each):group 1 received 50 microl of eye drops containing 1% generic pilocarpine, group 21% mixture pilocarpine solution consisting of aqueous sample and liposome and group 31% liposome pilocarpine, respectively. The aqueous humor was withdrawn at 5, 10, 30, 40, 60, 90, 120, 180, 240 and 360 min. Pilocarpine was extracted from aqueous humor with dichloromethane. RESULT: The linear calibration curve was obtained in the concentration range of 0.1 - 20 microg/ml. The average recovery was (68.1+/-2.7)% (n=9). Inter-day and intra-day RSD were 4.33% and 2.87%, respectively. In three formations 1% liposome pilocarpine was the best for the areas under curve and measurable amounts. CONCLUSION: The RP-HPLC method is simple and reliable for pilocarpine measurement in ocular aqueous. Liposome formulation can significantly increase the bioavailability of pilocarpine in ocular aqueous.

Animals↗
PubMed2004

Determination of gemcitabine and its metabolite in human plasma using high-pressure liquid chromatography coupled with a diode array detector.

AIM: To establish a high-pressure liquid chromatography (HPLC) method for determination of the concentration of gemcitabine (dFdC) and its metabolite (dFdU) in human plasma. METHODS: Plasma 1.0 mL spiked with floxuridine as an internal standard was extracted with 3.0 mL of methanol-acetonitrile (v/v, 1:9). The supernatant was evaporated at 60 centigrade and the residue was reconstituted with 0.5 mL of the solution used as the mobile phase. After centrifugation, 50 microL of the supernatant was injected into the HPLC system. Separation was achieved on a C18 (4.6 mm multiply 50 mm, 5 microm) column at 25 centigrade with the flow rate of the mobile phase set to 0.8 mL/min. The compounds were detected at 268 nm. The mobile phase consisted of 40.0 mmol/L acetate ammonium buffer solution (pH 5.5) and acetonitrile (v/v, 97.5:2.5). RESULTS: The linear range was 0.20-10.0 mg/L (r=0.9999) for dFdC and 0.50-50.0 mg/L (r=0.9999) for dFdU. The limit of detection (LOD) was 0.10 mg/L for dFdC and 0.25 mg/L for dFdU, while the limit of quantification (LOQ) was 0.20 mg/L (RSD<10 %) for dFdC and 0.50 mg/L (RSD<3 %) for dFdU. The average recovery of dFdC and dFdU by this method were 103.3 % and 98.7 %, respectively. For intra-day and inter-day, the corresponding standard deviations of the measurements of dFdC and dFdU were both less than 5.5 %. CONCLUSION: An analytical method was established to measure the concentrations of dFdC and dFdU in human plasma and was effectively applied to the dFdC and dFdU pharmacokinetic studies of 8 Chinese patients with malignant tumors.

Antimetabolites, Antineoplastic↗
PubMed2003

In vitro metabolism of zolmitriptan in rat cytochromes induced with beta-naphthoflavone and the interaction between six drugs and zolmitriptan.

Zolmitriptan is a novel and highly selective 5-HT(1B/1D) receptor agonist used as an acute oral treatment for migraine. There are few reports regarding the in vitro metabolism of zolmitriptan. Previous studies indicated zolmitriptan was metabolized via CYP1A2 in human hepatic microsomes. In order to study the enzyme kinetics and drug interaction, the metabolism of zolmitriptan and possible drug-drug interactions were investigated in rat hepatic microsomes induced with different inducers. An active metabolite, N-demethylzolmitriptan, was detected and another minor, inactive metabolite that was reported in human hepatic microsomes was not detected in this study. The enzyme kinetics for the formation of N-demethylzolmitriptan from zolmitriptan in rat liver microsomes pretreated with BNF were 96+/-22 microM (K(m)), 11+/-3 pmol min(-1)mg protein(-1) (V(max)), and 0.12+/-0.02 microl min(-1)mg protein(-1) (CL(int)). Fluvoxamine and diphenytriazol inhibited zolmitriptan N-demethylase activity catalyzed by CYP1A2 (K(i)=3.8+/-0.3 and 3.2+/-0.1 microM, respectively). Diazepam and propranolol elicited a slight inhibitory effect on the metabolism of zolmitriptan (K(i)=70+/-11 and 90+/-18 microM, respectively). Cimetidine and moclobemide produced no significant effect on the metabolism of zolmitriptan. Fluvoxamine yielded a k(inactivation) value of 0.16 min(-1), and K(i) of 57 microM. The results suggest that rat hepatic microsomes are a reasonable model to study the metabolism of zolmitriptan, although there is a difference in the amount of minor, inactive metabolites between human hepatic microsomes and rat liver microsomes. The results of the inhibition experiments provided information for the interactions between zolmitriptan and drugs co-administrated in clinic, and it is helpful to explain the drug-drug interactions of clinical relevance on enzyme level. This study aso demonstrated that fluvoxamine may be a mechanism-based inactivator of CYP1A2.

Animals↗
PubMed2003

Determination of diphenytriazol (DL111-IT) and its related impurities by RP-HPLC with DAD.

An analytical method was developed for determining diphenytriazol and its related impurities in oil injection by using RP-HPLC with DAD and diazepam as internal standard. The C(18) column was used as analytical column. Mobile phase consisted of methanol-potassium dihydrogen phosphate solutions (10 mmol l(-1), pH 7.5) (7:3, v/v). The standard curve was linear in the concentration range from 2 to 100 microg ml(-1) for diphenytriazol. The analytical method afforded average recoveries of 100.3+/-1.9% (n=9) and the relative standard deviation (RSD) was less than 2% for within-day and between-day precision. The limit of detection and of quantitation for the assay were 15 and 40 ng, respectively. The method was simple, accurate and allowed to be used as analytical method for the routine quality control of diphenytriazol injection. Diphenytriazol injection showed a high stability to the heat (60 degrees C) and the light (4000 lx).

Chromatography, High Pressure Liquid↗
PubMed2003

[Stereoselective determination of propranolol enantiomer in transgenic cell lines expressing human cytochrome P450].

OBJECTIVE: To establish a chiro chromatography for studying the stereoselective metabolism of propranolol (PL) in S(9) incubates prepared from transgenic cell lines expressing human cytochrome P450. METHODS: The concentration of each enantiomer in S(9) incubates was determined through precolumn derivatization with GITC, followed by RP-HPLC assay using S-(+)-propafenone as internal standard. RESULTS: Baseline separations among the diastereomers of S(-)-P, internal standard and R(+)-PL were achieved on Shimpack CLC C(18)ODS column, with UV detection and methanol:water:glacial acetic acid (67/33/0.05,v/v/v) as mobile phase. The assay was simple, accurate, precise and specific. The linear range was from 5 to 500 micromol/L for each enantiomer. The limit of quantitation (LOQ) for the method was 5 micromol/L for the S(-)-and R(+)-PL, respectively (n=5, RSD<10%). The analytical method afforded average recoveries of 98.7 and 98.1% for S(-)- and R(+)-PL, respectively. The reproducibility of the assay was good (RSD<10%). The time-dependent studies showed that PL had the stereoselectivity of S-(-)-isomer in metabolism via CYP2C18 and the stereoselectivity of R-(+)-isomer in metabolism via CYP2C9. CONCLUSION: The method allows to study of stereoselective metabolism of PL in vitro.

Chromatography, High Pressure Liquid↗
PubMed2003

[Determination of amlodipine in CYP3A4 cDNA-expressed cells by HPLC].

OBJECTIVE: To establish a RP-HPLC method for the determination of amlodipine after metabolism by cytochrome P450 cDNA-expressed cells. METHODS: The determination was performed on a C(18) reversed phase column with a mobile phase composed of acetonitrile phosphates buffer (45:55, v/v, pH 4.5) with UV detection (lambda250nm). Propranolol was used as the internal standard. RESULT: The standard curve was linear over the concentration range of 0.2 - 30.0 microg/ml (r=0.9993), and the limits of determination was 20 ng/ml (S/N >or=3), the limits of quantity was 0.2 microg/ml (recovery 104.0%, RSD 11.4%, n=5). The recovery for this assay was (98.2+/-2.4)%, precision for inter-assay and intra-assay was <10 % and 6 %, respectively. CONCLUSION: The HPLC method established is simple, accurate and suitable for the determination of amlodipine in cytochrome p450 cDNA-expressed cells.

Amlodipine↗