Stephanie E. Martinez

Vorinostat with sustained exposure and high solubility in poly(ethylene glycol)-b-poly(dl-lactic acid) micelle nanocarriers: Characterization and effects on pharmacokinetics in rat serum and urine

The histone deacetylase inhibitor suberoylanilide hydroxamic acid, known as vorinostat, is a promising anticancer drug with a unique mode of action; however, it is plagued by low water solubility, low permeability, and suboptimal pharmacokinetics. In this study, poly(ethylene glycol)-b-poly(DL-lactic acid) (PEG-b-PLA) micelles of vorinostat were developed. Vorinostats pharmacokinetics in rats was investigated after intravenous (i.v.) (10 mg/kg) and oral (p.o.) (50 mg/kg) micellar administrations and compared with a conventional polyethylene glycol 400 solution and methylcellulose suspension. The micelles increased the aqueous solubility of vorinostat from 0.2 to 8.15 ± 0.60 and 10.24 ± 0.92 mg/mL at drug to nanocarrier ratios of 1:10 and 1:15, respectively. Micelles had nanoscopic mean diameters of 75.67 ± 7.57 and 87.33 ± 8.62 nm for 1:10 and 1:15 micelles, respectively, with drug loading capacities of 9.93 ± 0.21% and 6.91 ± 1.19%, and encapsulation efficiencies of 42.74 ± 1.67% and 73.29 ± 4.78%, respectively. The micelles provided sustained exposure and improved pharmacokinetics characterized by a significant increase in serum half-life, area under curve, and mean residence time. The micelles reduced vorinostat clearance particularly after i.v. dosing. Thus, PEG-b-PLA micelles significantly improved the p.o. and i.v. pharmacokinetics and bioavailability of vorinostat, which warrants further investigation.

Enantiospecific pharmacokinetics of isoxanthohumol and its metabolite 8-prenylnaringenin in the rat

SCOPE Isoxanthohumol (IX) is a bioactive dietary prenylflavanone found in hops (Humulus lupulus L.), beer and nutraceuticals. IX is formed in vivo by xanthohumol and is a prodrug of 8-prenylnaringenin (8PN). IX and 8PN chirality has largely been ignored in the literature due to lack of enantiospecific bioanalytical methods. No single dose pharmacokinetic study of IX exists in the literature for any species. This study elucidates the enantiospecific pharmacokinetics of IX in rats and monitors the appearance of 8PN following intravenous and oral administration of ±IX. METHODS AND RESULTS After intravenous (10 mg/kg) or oral (100 mg/kg) administration of ±IX to rats, serum, and urine were collected for 120 h and analyzed for IX and 8PN. Both were found as aglycones and glucuronide conjugates and displayed multiple peaking in serum suggestive of enterohepatic recycling. IX is primarily excreted through nonrenal routes. S-8PN was found excreted in the urine in greater amounts than R-8PN. Bioavailability was determined to be ∼4-5% for IX. CONCLUSION Further enantiospecific pharmacokinetics of IX, subsequent 8PN and other metabolites are warranted along with continued enantiospecific bioactivity studies, especially in relation to gut microbial metabolism of IX and subsequent formation of 8PN.

Chiral analytical method development and application to pre-clinical pharmacokinetics of pinocembrin

An analytical method enabling the detection and quantification of the individual enantiomers of racemic (±) pinocembrin is required to fully characterize its pharmacokinetic disposition. Direct resolution of the enantiomers of pinocembrin was achieved using a novel and simple reversed-phase high-performance liquid chromatography method with electrospray ionization and detection by mass spectrometry in rat serum. A Chiralcel® AD-RH column was employed to perform baseline separation with electrospray positive-mode ionization with selected ion monitoring detection. The standard curves were linear from 0.5 to 100 µg/mL for each enantiomer. The limit of quantification was 0.5 µg/mL. The assay was applied successfully to stereoselective serum disposition of pinocembrin enantiomers in rats. Pinocembrin enantiomers were detected in serum. Both enantiomers had a serum half-life of ~15 min in rats. Similar values of volume of distribution between the enantiomers were also observed: 1.76 L/kg for S-pinocembrin and 1.79 L/kg for R-pinocembrin. Total clearance was 5.527 L//h/kg for S-pinocembrin and 5.535 L/h/kg for R-pinocembrin, and the area under the curve was 1.821 µg h/mL for S-pinocembrin and 1.876 µg h/mL for R-pinocembrin. The large volume of distribution coupled with the short serum half-life suggests extensive distribution of pinocembrin into the tissues.

High-performance liquid chromatographic analysis of lacosamide in canine serum using ultraviolet detection: Application to pre-clinical pharmacokinetics in dogs

A method for analysis of lacosamide [(R)-2-acetamido-N-benzyl-3-methoxypropionamide] is needed for both human and veterinary pharmacokinetic investigations. While lacosamide is currently used to manage partial-onset seizures in humans suffering from epilepsy, it is also presently being investigated for use in the treatment of canine epilepsy in veterinary medicine. Currently, no dosing regimen for the drug exists in dogs. A novel and simple high-performance liquid chromatography method was developed for determination of lacosamide in dog serum. Serum proteins (0.1 mL) were precipitated with -20.0°C acetonitrile after addition of the internal standard, daidzein. Separation was achieved with a Phenomenex® Luna® C₁₈ (2) (5 µm, 250 × 4.60 mm) column with ultraviolet detection at 210 nm. The calibration curves were linear ranging from 0.5 to 25 µg/mL. Precision of the assay was <13% (RSD) and was within 12% for all points in the calibration curve. The limit of quantitation for this method was 0.5 µg/mL. The assay was applied successfully to a pre-clinical study of lacosamide pharmacokinetics in dogs.

Pharmacokinetics of oral rufinamide in dogs

The objective of this study was to determine the pharmacokinetic properties and short-term adverse effect profile of single-dose oral rufinamide in healthy dogs. Six healthy adult dogs were included in the study. The pharmacokinetics of rufinamide were calculated following administration of a single mean oral dose of 20.0 mg/kg (range 18.6-20.8 mg/kg). Plasma rufinamide concentrations were determined using high-performance liquid chromatography, and pharmacokinetic data were analyzed using commercial software. No adverse effects were observed. The mean terminal half-life was 9.86 ± 4.77 h. The mean maximum plasma concentration was 19.6 ± 5.8 μg/mL, and the mean time to maximum plasma concentration was 9.33 ± 4.68 h. Mean clearance was 1.45 ± 0.70 L/h. The area under the curve (to infinity) was 411 ± 176 μg · h/mL. Results of this study suggest that rufinamide given orally at 20 mg/kg every 12 h in healthy dogs should result in a plasma concentration and half-life sufficient to achieve the therapeutic level extrapolated from humans without short-term adverse effects. Further investigation into the efficacy and long-term safety of rufinamide in the treatment of canine epilepsy is warranted.

Preclinical Pharmacokinetics and Pharmacodynamics and Content Analysis of Gnetol in Foodstuffs

Studies were undertaken to evaluate the bioavailability in rats and content analysis of gnetol in Gnetum gnemon products reported to contain gnetol and to examine the pharmacological properties of gnetol in in vitro models including anti‐inflammatory/analgesic, antidiabetic, anti‐adipogenesis, and anticancer activity. Male Sprague–Dawley rats were cannulated and dosed either intravenously with gnetol (10 mg/kg) or orally (100 mg/kg). Various methanolic extractions of G. gnemon products were quantified. Gnetols effect on cell viability in selected cell lines with or without inflammatory stimulus was assessed. α‐Amylase and α‐glucosidase inhibition was evaluated. Cyclooxygenase (COX)‐1, COX‐2, and histone deacetylase inhibition and adipogenesis inhibition were examined. After oral and intravenous administration, gnetol was detected in both serum and urine as the parent compound and as a glucuronidated metabolite. The bioavailability of gnetol was determined to be 6%. Gnetol is rapidly glucuronidated and is excreted in urine and via nonrenal routes. Gnetol was found to exist as an aglycone and as a glycoside in G. gnemon products. Gnetol showed concentration‐dependent reductions in cell viability in cancer cell lines with greatest activity in colorectal cancer and potent COX‐1, histone deacetylase, and weak COX‐2 activities along with limited reduction in inflammation. Gnetol also possessed concentration‐dependent alpha‐amylase, alpha‐glucosidase, and adipogenesis activities. Pretreatment of mice with gnetol was able to increase the latency period to response in analgesia models. Copyright

Pharmacometrics of 3-methoxypterostilbene: a component of traditional chinese medicinal plants.

3-Methoxypterostilbene is a naturally occurring stilbene with potential in the treatment of diabetes. The preclinical pharmacokinetics and pharmacodynamics of 3-methoxypterostilbene were evaluated in the present study. The right jugular veins of male Sprague-Dawley rats were cannulated. The rats were dosed 10 mg/kg or 100 mg/kg of 3-methoxypterostilbene intravenously (IV) or orally (PO), respectively. Serum and urine samples were analyzed using a previously validated reversed-phase HPLC method. Serum AUC, serum t 1/2, urine t 1/2, Cltotal, and Vd for IV dosing were 48.1 ± 23.8 μg/h/mL, 18.9 ± 10.9 h, 9.54 ± 1.51 h, 47.8 ± 23.7 L/h/kg, and 5.11 ± 0.38 L/kg, respectively (mean ± SEM, n = 4) . Serum AUC, serum t 1/2, urine t 1/2, Cltotal, and Vd for PO dosing were 229 ± 44.6 μg/h/mL, 73.3 ± 8.91 h, 20.6 ± 3.01 h, 0.48 ± 0.008 L/h/kg, and 52.0 ± 10.5 L/kg, respectively (mean ± SEM, n = 4). Bioavailability of the stilbene was determined to be 50.6%  ± 10.0%. A 3-methoxypterostilbene glucuronidated metabolite was detected in both serum and urine. 3-Methoxypterostilbene exhibited antidiabetic activity including α-glucosidase and α-amylase inhibition as well as concentration-dependent antioxidant capacity similar to resveratrol. 3-Methoxypterostilbene also exhibited anti-inflammatory activity. 3-Methoxypterostilbene appears to be a bioactive compound and may be useful in reducing postprandial hyperglycemia.

Enantiospecific Analysis of 8-Prenylnaringenin in Biological Fluids by Liquid-Chromatography-Electrospray Ionization Mass Spectrometry: Application to Preclinical Pharmacokinetic Investigations

8-Prenylnaringenin (8PN) is a naturally occurring bioactive chiral prenylflavonoid found most commonly in the female flowers of hops (Humulus lupulus L.). A stereospecific method of analysis for 8PN in biological fluids is necessary to study the pharmacokinetic disposition of each enantiomer. A novel and simple liquid chromatographic-electrospray ionization-mass spectrometry (LC-ESI-MS) method was developed for the simultaneous determination of R- and S-8PN in rat serum and urine. Carbamazepine was used as the internal standard (IS). Enantiomeric resolution of 8PN was achieved on a Chiralpak(®) AD-RH column with an isocratic mobile phase consisting of 2-propanol and 10 mM ammonium formate (pH 8.5) (40:60, v/v) and a flow rate of 0.7 mL/min. Detection was achieved using negative selective ion monitoring (SIM) of 8PN at m/z 339.15 for both enantiomers and positive SIM m/z at 237.15 for the IS. The calibration curves for urine were linear over a range of 0.01-75 µg/mL and 0.05-75 µg/mL for serum with a limit of quantification of 0.05 µg/mL in serum and 0.01 µg/mL in urine. The method was successfully validated showing that it was sensitive, reproducible, and accurate for enantiospecific quantification of 8PN in biological matrices. The assay was successfully applied to a preliminary study of 8PN enantiomers in rat.

Stereospecific analytical method development and preliminary in vivo pharmacokinetic characterization of pinostrobin in the rat.

The complete pharmacokinetic disposition of the chiral flavonoid (±) pinostrobin remains unknown without the development of an analytical method of detection and quantitation of its individual enantiomers. Resolution of the enantiomers of pinostrobin was achieved using as simple high-performance liquid chromatographic method. A Chiralpak(®) AD-RH column was employed to perform baseline separation with UV detection at 287 nm. The standard curves were linear ranging from 0.5 to 100 µg/mL for each enantiomer. The limit of quantification was 0.5 µg/mL. Precision and accuracy of the assay was < 15% (RSD) and was with a bias <15% for all points on the calibration curve. The assay was applied successfully to stereoselective serum disposition of pinostrobin enantiomers in rats. Both enantiomers had a serum half-life of ~7 h. They also shared similar values of volume of distribution (V(d) S-pinostrobin, 8.2 L/kg; V(d) R-pinostrobin, 8.9 L/kg), total clearance (S-pinostrobin CL(total), 0.959 L//h/kg; R-pinostrobin CL(total), 1.055 L//h/kg), and area under the curve (S-pinostrobin AUC(inf), 23.16 µg h/mL; R-pinostrobin AUC(inf), 21.296 µg h/mL). The large volume of distribution suggests extensive distribution of pinostrobin into tissues.

Disposition, Metabolism and Histone Deacetylase and Acetyltransferase Inhibition Activity of Tetrahydrocurcumin and Other Curcuminoids

Tetrahydrocurcumin (THC), curcumin and calebin-A are curcuminoids found in turmeric (Curcuma longa). Curcuminoids have been established to have a variety of pharmacological activities and are used as natural health supplements. The purpose of this study was to identify the metabolism, excretion, antioxidant, anti-inflammatory and anticancer properties of these curcuminoids and to determine disposition of THC in rats after oral administration. We developed a UHPLC–MS/MS assay for THC in rat serum and urine. THC shows multiple redistribution phases with corresponding increases in urinary excretion rate. In-vitro antioxidant activity, histone deacetylase (HDAC) activity, histone acetyltransferase (HAT) activity and anti-inflammatory inhibitory activity were examined using commercial assay kits. Anticancer activity was determined in Sup-T1 lymphoma cells. Our results indicate THC was poorly absorbed after oral administration and primarily excreted via non-renal routes. All curcuminoids exhibited multiple pharmacological effects in vitro, including potent antioxidant activity as well as inhibition of CYP2C9, CYP3A4 and lipoxygenase activity without affecting the release of TNF-α. Unlike curcumin and calebin-A, THC did not inhibit HDAC1 and PCAF and displayed a weaker growth inhibition activity against Sup-T1 cells. We show evidence for the first time that curcumin and calebin-A inhibit HAT and PCAF, possibly through a Michael-addition mechanism.