Comparative pharmacokinetics and the bioavailability of escin Ib and isoescin Ib following the administration of escin, pure escin Ib and isoescin Ib in rats.

ETHNOPHARMACOLOGICAL RELEVANCE: Adequate pharmacokinetic data of escin, a natural mixture of triterpene saponins used for the treatment of chronic venous insufficiency, hemorrhoids, inflammation and edema, is of special interest in view of the growing use of escin agent in clinical medicine. However, pharmacokinetic data are inadequate to support their clinical indication. Escin Ib and isoescin Ib are the chief active ingredients in escin, pharmacokinetics study of them would be helpful for improving the practice of escin application. The goals of this study are to determine the plasma concentration of escin Ib and isoescin Ib using an established liquid chromatography tandem mass spectrometry (LC-MS/MS) method and to compare the pharmacokinetics and bioavailability of these compounds in rats when administered as pure isomers or as sodium escinate. MATERIALS AND METHODS: Five groups of Wistar rats (n=6 per group) were treated with either an intravenous (IV) dose (2.78mg/kg) of sodium escinate (corresponding to 0.5mg/kg of escin Ib and 0.5mg/kg of isoescin Ib), an IV dose (0.5mg/kg) and an oral dose (4mg/kg) of pure escin Ib or isoescin Ib. The concentrations of escin Ib and isoescin Ib in rat plasma were determined by LC-MS/MS at various times following the administration of the drugs. The pharmacokinetic parameters were estimated by a non-compartmental analysis and then subjected to statistical analysis. RESULTS: The administration of sodium escinate, which contains the two isomers, gave rise to higher terminal phase half-life (t1/2) and mean residence time (MRT) values for both escin Ib and isoescin Ib compared to the corresponding compounds administered alone. The absorption of escin Ib and isoescin Ib was very poor, with the oral bioavailability (F) values of <2% observed for both compounds. The two compounds were found to isomerize in vivo, wherein the conversion of escin Ib to isoescin Ib was much easier than that of isoescin Ib to escin Ib. CONCLUSIONS: A comparison of the pharmacokinetics of escin Ib and isoescin Ib administered alone and together in rats suggests that the administration of herbal preparations of escin in a clinical setting may result in a longer duration of action than the administration of each isomer alone. The interconversion of escin Ib and isoescin Ib when administered alone indicates that the administration of one isomer results in exposure to the other isomer.

Comparative pharmacokinetics and bioavailability of escin Ia and isoescin Ia after administration of escin and of pure escin Ia and isoescin Ia in rat.

ETHNOPHARMACOLOGICAL RELEVANCE: Escin Ia and isoescin Ia have been traditionally used clinically as the chief active ingredients of escin, a major triterpene saponin isolated from horse chestnut (Aesculus hippocastanum) seeds for the treatment of chronic venous insufficiency, hemorrhoids, inflammation and edema. AIM OF THE STUDY: To establish a sensitive LC-MS/MS method and investigate the pharmacokinetic properties of escin Ia and isoescin Ia in rats and the pharmacokinetics difference of sodium escinate with pure escin Ia and isoescin Ia. The absolute bioavailability of escin Ia and isoescin Ia and the bidirectional interconversion of them in vivo were also scarcely reported. MATERIALS AND METHODS: Wister rats were administrated an intravenous (i.v.) dose (1.7 mg/kg) of sodium escinate (corresponding to 0.5mg/kg of escin Ia and 0.5mg/kg of isoescin Ia, respectively) and an i.v. dose (0.5mg/kg) or oral dose (4mg/kg) of pure escin Ia or isoescin Ia, respectively. At different time points, the concentrations of escin Ia and isoescin Ia in rat plasma were determined by LC-MS/MS method. Main pharmacokinetic parameters including t(1/2), MRT, CL, V(d), AUC and F were estimated by non-compartmental analysis using the TopFit 2.0 software package (Thomae GmbH, Germany) and statistical analysis was performed using the Student's t-test with P<0.05 as the level of significance. RESULTS: After administration of sodium escinate, the t(1/2) and MRT values for both escin Ia and isoescin Ia were larger than corresponding values for the compounds given alone. Absorption of escin Ia and isoescin Ia was very low with F values both <0.25%. Escin Ia and isoescin Ia were found to form the other isomer in vivo with the conversion of escin Ia to isoescin Ia being much extensive than from isoescin Ia to escin Ia. CONCLUSION: Comparison of the pharmacokinetics of escin Ia and isoescin Ia given alone and together in rat suggest that administration of herbal preparations of escin for clinical use may provide longer duration of action than administration of single isomers. The interconversion of escin Ia and isoescin Ia when given alone indicates that administration of one isomer leads to exposure to the other.

A liquid chromatography-tandem mass spectrometry method for the simultaneous quantification of escin Ia and escin Ib in human plasma: application to a pharmacokinetic study after intravenous administration.

A rapid and sensitive liquid chromatography-tandem mass spectrometry (LC-MS/MS) method was developed and validated for simultaneous quantification of escin Ia and escin Ib in human plasma. After a solid-phase extraction (SPE), the analytes were separated on a Zorbax Extend C(18) column by isocratic elution with a mobile phase of methanol-acetonitrile-10 mm ammonium acetate (27:27:46, v/v/v) at a flow rate of 1.0 mL/min and analyzed by mass spectrometry in the positive ion multiple reaction monitoring mode. The precursor to product ion transitions of m/z 1131.8 → 807.6 was used to quantify escin Ia and escin Ib. Good linearity was achieved over a wide range of 2.00-900 ng/mL for escin Ia and 1.50-662 ng/mL for escin Ib. The intra- and inter-day precisions (as relative standard deviation) were less than 11% for each QC level of escin Ia and escin Ib. The accuracies (as relative error) were within ±5.27% for escin Ia and within ±4.07% for escin Ib. The method was successfully employed in a pharmacokinetic study after a single intravenous infusion administration of sodium aescinate injection containing 10 mg escin to each of the 10 healthy volunteers.

Simultaneous analysis of isomers of escin saponins in human plasma by liquid chromatography-tandem mass spectrometry: application to a pharmacokinetic study after oral administration.

A rapid and sensitive bioassay based on liquid chromatography-tandem mass spectrometry (LC-MS/MS) for the simultaneous determination of four isomeric escin saponins (escin Ia, escin Ib, isoescin Ia and isoescin Ib) in human plasma has been developed and validated. Sample preparation of plasma after addition of telmisartan as internal standard (I.S.) involved solid-phase extraction (SPE) on C18 cartridges. Separation was based on reversed phase chromatography using gradient elution with methanol-acetonitrile (50:50, v/v) and 10 mM ammonium acetate solution (pH 6.8). MS/MS detection in the positive ion mode used multiple reaction monitoring of the transition at m/z 1113.8-->807.6. Stability issues with the four saponins required the addition of formic acid to plasma samples prior to storage at -80 degrees C and analysis within 30 days. The method was linear at concentrations up to 10 ng/mL with correlation coefficients>0.996 for all analytes. The lower limit of quantitation (LLOQ) for all four saponins was 33 pg/mL. Intra- and inter-day precisions (as relative standard deviation) were all <15% and accuracies (as relative error) in the range -5.3% to 6.1%. The method was successfully applied to a pharmacokinetic study of escins in healthy volunteers after oral administration of sodium aescinate tablets containing 60 mg escin saponins.

Measurement of the bioavailability of aescin-containing extracts.

OBJECTIVE: In horse chestnut seed extracts (HCSE), the triterpene saponin mixture aescin is considered the active principle. The bioavailability and pharmacokinetics of different HCSE preparations have been studied under single and repeated applications using a radioimmunological method (RIA) developed to identify beta-aescin, one of the pharmacologically active fractions of the saponin mixture. In this paper, the available pharmacokinetic data are reviewed and the observed heterogenicity between comparable studies is discussed. DATA SOURCES: Pharmacokinetic data from 5 single- and 4 multiple-dose bioequivalence studies with HCSE-containing products, were measured by the same analytical laboratory using the same RIA. EVALUATION: In studies where procedures were identical the pharmacokinetic data of beta-aescin show high variations. Even under steady-state conditions a considerable variability for the same HCSE product is obtained. CONCLUSION: Formal reasons like study design and medications can be ruled out as a source of pharmacokinetic variation. In extracts of herbal drugs like HCS, the relative concentration of the individual saponin fractions can considerably differ from batch to batch. For immunological methods, identification of such antigens with intermolecular variability, e.g., the structural aescin analogs, is of unknown validity. Therefore the shape of the concentration-time curve would only show an approximation of the time course but not for the absolute concentrations. A specific validation procedure for the RIA must be developed, otherwise a LC-MS/MS-method of sufficient sensitivity should be elaborated.

[Pharmaokinetics of beta-escin after administration of various Aesculus extract containing formulations]. / Pharmakokinetik von beta-Aescin nach Gabe verschiedener Aesculus-Extrakt enthaltender Formulierungen.

With a specific radioimmunoassay the pharmacokinetics and relative bioavailability of escin was measured after administration of different formulations containing Aesculus-extract. Of special interest was the relative bioavailability of escin after administration of a newly developed film-coated tablet with sustained release in comparison to a reference formulation. In a cross-over steady-state study in 24 volunteers bioequivalence of test and reference preparation could be demonstrated. The 90% confidence interval of the AUC (O-tau) was 98.3 to 120.9%.

[Dialysability of aescin]. / Untersuchungen zur Dialysierbarkeit von Aescin.

In experiments with an artificial kidney (Hollow Fiber Kidney) it could be shown that aescin (Reparil) is fully dialysable. The rate of elimination is mainly dependent on the protein binding (ca. 90%) and not on the permeation rate through the membrane. The concentration of aescin in a serum sample decreased exponentially over a 6-h dialysis period to one-third of the initial concentration.

Animal experiments on the question of the renal toleration of the horse chestnut saponin aescin.

The possibility that aescin might have a nephrotoxic side effect has been investigated by clearance studies in kidneys of healthy rats and by toleration studies in rats with damaged kidneys. The effect of aescin, both free and albumin-bound, on renal tubular transport processes was studied in the model of the isolated, artificially perfused frog kidney. The rates at which different concentrations of aescin were bound to rat plasma proteins were determined in vitro. The clearance of i.v. aescin was 13% of creatinine clearance and 7% of p-aminohippurate (PAH) clearance; this rules out the tubular secretion of aescin. No deaths occurred among aminonucleoside-damaged rats given i.v. sodium aescinate 2.2 mg/kg, but rats damaged with mercuric chloride or uranyl nitrate had exactly the same mortality rate as those given 2.2 mg/kg i.v. of sodium aescinate alone. The rats received four injections in all of aescin 0.35 mg/kg i.v., given at intervals of two days. Aescin had no effect on renal damage caused by aminonucleoside, mercuric chloride or uranyl nitrate. Aescin concentrations of 0.2 mg/l and 2.0 mg/l in the perfusion fluid increased the excretion of Na+ and glucose by the frog kidney and reduced the reabsorption of both these substances. With a sodium aescinate concentration of 5 mg/l the production of urine ceased. When 1% (w/v) of albumin was added to the perfusion fluid, even sodium aescinate 5 mg/l had no effect on the tubular transport of Na+, glucose and water. The fact that about 50% of aescin was not bound to plasma protein in vitro suggests that some of the small amount of aescin in the glomerular filtrate is reabsorbed in the tubules.