[Absorption and distribution of extracts of Elsholtzia blanda in rats].

The study is aimed to establish a RP-HPLC method for determination of luteolin from the extracts of Elsholtzia blanda (EEB) in rats' biological specimen. A RP-HPLC method was established for determination of free and total luteolin in SD rats' plasma and gastrointestinal tract and total luteolin in SD rats' heart, liver, lung and kidney at 0.17, 0.5, 1, 2, 4 and 6 h after administration of EEB to 24 male SD rats (4 rats per one time spot). Luteolin glycoside was hydrolyzed to aglycone luteolin in intestinal tract, and then luteolin was absorbed. The main form of luteolin existed in gastrointestinal tract after administration of EEB is aglycone. The content of luteolin in liver and kidney were higher than that in heart and lung. The content of luteolin in kidney, heart and lung were showed max at 1 h. Its peak time was similar to that in blood. However, in liver, the drug was distributed quickly, and showed max at 0.17 h. And because of the sensitivity of the method, luteolin was not be detected in other tissues. The method is sensitive, specific, accurate, and is appropriate for determination of luteolin in vivo.

[Pharmacokinetics of luteolin from Elsholtzia blanda extracts in rats].

An RP-HPLC method for determination of luteolin from Elsholtzia blanda Benth. extracts in rats' plasma was established and the pharmacokinetics of luteolin in rats was studied. Drug blood samples from caudal vein were gotten after oral administration of luteolin. Plasma samples were determined by RP-HPLC after being deproteinized with trichloroacetic acid and extracted with ethyl acetate. The calibration curve was linear in the range of 0.37-47.27 microg x mL(-1). The limit of quantification was 0.37 microg x mL(-1). The method recovery of luteolin was 93%-99%. The extract recovery was 75%-85%. RSDs of intra-and inter-day precisions were less than 5%. The concentration-time curve of luteolin after oral administration of Elsholtzia blanda Benth. extracts was fitted to two compartment open model. Two factors analysis of variance were adopted in the evaluation of gender and time spots for collection of blood. The result suggested that the gender-based difference in blood-drug concentrations had statistical significance. The metabolite in blood was identified as galcuronide. The method is sensitive, specific, accurate, and is appropriate for determination of luteolin in vivo.

[Research progress on interactions between luteolin (glucosides) and drug-metabolizing enzyme].

The paper summarizes the interactions between luteolin (glucosides) and drug-metabolizing enzyme from the literature of recent years and our research work. The metabolism of luteolin is chiefly mediated by phase II metabolic enzyme. Its glucosides are firstly hydrolyzed into aglycone in intestinal tract, and then absorbed and metabolized. Luteolin has the effect on the induction of CYP3A, and on the inhibition of CYPIA, 1B and 2E. Also, luteolin is an effective inhibitor of CYP2B6, CYP2C9 and CYP2D6. Luteolin can induce and inhibit UGTs and SULTs. It can also inhibit multi ABC transport proteins. Understanding the interactions between luteolin (glucosides) and drug-metabolizing enzyme has an important significance in guiding clinical use of the drug.

[Luteolin excretion after oral administration of Elsholtzia blanda benth extracts in rats].

OBJECTIVE: To observe the excretion of luteolin after oral administration of Elsholtzia blanda benth extracts in rats. METHODS: Samples of urine, feces and bile were collected after oral administration of Elsholtzia blanda benth extracts in rate. After deconjugation with beta-glucuronidase/sulfatase, the levels of luteolin in urine, feces and bile were measured by RP-HPLC. RESULT: The recovery rate of luteolin was 98.0 %-106.0 % and the extract recoveries were 85.0 %-108.0%. Relative standard deviation (RSD) of intra-and inter-day assay was less than 10.0 %. The total accumulative excretion was 37 % (11 % in urine, 26 % in feces and bile). CONCLUSION: The established RP-HPLC method is sensitive, specific, accurate, and is applicable for determination of luteolin in rat urine,feces and bile.

In vitro metabolism of BYZX in human liver microsomes and the structural elucidation of metabolite by liquid chromatography-mass spectrometry method.

In vitro phase I metabolism of BYZX, a novel central-acting cholinesterase inhibitor for the treatment of the symptoms of Alzheimer's disease, was studied in human liver microsomes (HLM) and the metabolite formation pathways were investigated by chemical inhibition experiments and correlation analysis. The residual concentration of substrate and the metabolite formed in incubate were determined by HPLC method. The calibration curves of BYZX were linear over the concentration range from 5.07 microM to 200.74 microM. The relative standard deviations of within day and between day were less than 5% (n=5). The limit of detection (LOD) was 0.18 microg/mL (S/N=3) and the limit of quantification (LOQ) was 0.55 microg/mL (R.S.D.=5.2%, n=5). The determination recoveries of BYZX were in the range of 98.2-104.8%. The apparent K(m) of BYZX in HLM was 53.25+/-17.2 microM, the V(max) was 0.94+/-0.77 microM/min/mg protein, and the intrinsic clearance value (Cl(int)) was 0.018+/-0.02 mL/min/mg protein. Ketoconazole and cyclosporin A were the most potent inhibitors on BYZX metabolism in HLM with IC(50) being 0.89 microM and 18.17 microM, respectively. And the inhibition constant (K(i)) of ketoconazole was 0.42 microM. The metabolite of BYZX was N-des-ethyl-BYZX elucidated by LC-MS-MS. The results demonstrated that the developed HPLC method was reliability, simple technique, and was applicable to be used for the researches of in vitro metabolism of BYZX. CYP3A4 was the major isozyme responsible for BYZX metabolism; N-dealkylation was the major metabolic pathway of BYZX. The predominant metabolite of BYZX was N-des-ethyl-BYZX detected in vitro phase I metabolism in HLM.

[Interaction between (E)-2-(4-(diethylamino methyl) benzylidene)-5,6-dimethoxy-2,3-dihydroinden-one and P-glycoprotein].

Cell lines of Bcap37 and Bcap37/MDR1 (the high P-glycoprotein (P-gp) expressing cell line) were used as model to investigate the different accumulations of (E)-2-(4-(diethylamino methyl) benzylidene)-5,6-dimethoxy-2,3-dihydroinden-one (BYZX) in the two kinds of cells. It was authenticated that whether BYZX was the substrate of P-gp. Meanwhile, the inhibitive effects of BYZX on the P-gp were investigated by determining the fluorescence intensity of rhodamine 123 in the model cells, with and without BYZX. A reversed-phase high-performance liquid chromatography (RP-HPLC) method was used to determine the accumulations of BYZX in the two cells. The results showed that the amount of BYZX accumulation in Bcap37/MDR1 cells were as many as those in Bcap37 cells (P > 0.05), and the concentrations of BYZX accumulated in the Bcap37/MDR1 cells did not increase when co-incubated with P-gp inhibitor verapamil. Furthermore, different concentrations of BYZX also had no effects on the efflux of rhodamine 123 (P > 0.05). These results indicated that there were no interactions between BYZX and P-gp. BYZX will not be pumped out of the cells, and it also not inhibited the P-gp. It was the useful advantage for its absorption.

Determination of rutin deca(H-) sulfate sodium in rat plasma using ion-pairing liquid chromatography after ion-pairing solid-phase extraction.

Rutin deca(H-) sulfate sodium (RDS) is one of the most important drug candidates, which possesses very good activity as inhibitor of the complement system of warm-blooded animals and human immunodeficiency virus (HIV). In order to understand RDS metabolism and disposition, an ion-pairing coupled with solid-phase extraction technique (IP-SPE) was developed to extract RDS from rat plasma sample. Tetrabutyl ammonium bromide (TBAB) buffer (0.2 M, pH 8.0) was used as the ion-pairing extraction reagent and LC-18 was used as SPE sorbent. In addition, an ion-pairing HPLC method was established for the specific determination of RDS. A reversed phase C8 column was used for the separation of RDS and nitrendipine (internal standard). The mobile phase was composed of 10 mM phosphate buffer solution containing 25 mM TBAB-acetonitrile (52:48, v/v, pH 7.5). The calibration curve was linear from 0.3 to 30 nmol/mL. The analytical recovery from rat plasma was found to be 97.9+/-4.1% (n = 15). LOD and LOQ for RDS in plasma were calculated to be 0.12 nmol/mL and 0.30+/-0.024 nmol/mL (R.S.D. = 8.2%, n = 5), respectively. The intra- and inter-day precision was less than 9.2%. The assay was applied to a preliminary pharmacokinetic study in three male rats after those received a single intravenous bolus via caudal vein of 12 micromol/kg RDS.