St. John's wort extract with a high hyperforin content does not induce P-glycoprotein activity at the human blood-brain barrier

St. John's wort (SJW) extract, a herbal medicine with antidepressant effects, is a potent inducer of intestinal and/or hepatic cytochrome P450 (CYP) enzymes and P-glycoprotein (P-gp), which can cause clinically relevant drug interactions. It is currently not known whether SJW can also induce P-gp activity at the human blood-brain barrier (BBB), which may potentially lead to decreased brain exposure and efficacy of certain central nervous system (CNS)-targeted P-gp substrate drugs. In this study, we used a combination of positron emission tomography (PET) imaging and cocktail phenotyping to gain a comprehensive picture on the effect of SJW on central and peripheral P-gp and CYP activities. Before and after treatment of healthy volunteers (n = 10) with SJW extract with a high hyperforin content (3-6%) for 12-19 days (1800 mg/day), the activity of P-gp at the BBB was assessed by means of PET imaging with the P-gp substrate [11C]metoclopramide and the activity of peripheral P-gp and CYPs was assessed by administering a low-dose phenotyping cocktail (caffeine, omeprazole, dextromethorphan, and midazolam or fexofenadine). SJW significantly increased peripheral P-gp, CYP3A, and CYP2C19 activity. Conversely, no significant changes in the peripheral metabolism, brain distribution, and P-gp-mediated efflux of [11C]metoclopramide across the BBB were observed following the treatment with SJW extract. Our data suggest that SJW does not lead to significant P-gp induction at the human BBB despite its ability to induce peripheral P-gp and CYPs. Simultaneous intake of SJW with CNS-targeted P-gp substrate drugs is not expected to lead to P-gp-mediated drug interactions at the BBB.

Pharmacokinetics and Metabolism of Liposome-Encapsulated 2,4,6-Trihydroxygeranylacetophenone in Rats Using High-Resolution Orbitrap Liquid Chromatography Mass Spectrometry

2,4,6-trihydroxy-3-geranylacetophenone (tHGA) is a bioactive compound that shows excellent anti-inflammatory properties. However, its pharmacokinetics and metabolism have yet to be evaluated. In this study, a sensitive LC-HRMS method was developed and validated to quantify tHGA in rat plasma. The method showed good linearity (0.5–80 ng/mL). The accuracy and precision were within 10%. Pharmacokinetic investigations were performed on three groups of six rats. The first two groups were given oral administrations of unformulated and liposome-encapsulated tHGA, respectively, while the third group received intraperitoneal administration of liposome-encapsulated tHGA. The maximum concentration (C_max), the time required to reach C_max (t_max), elimination half-life (t_1/2) and area under curve (AUC_0–24) values for intraperitoneal administration were 54.6 ng/mL, 1.5 h, 6.7 h, and 193.9 ng/mL·h, respectively. For the oral administration of unformulated and formulated tHGA, C_max values were 5.4 and 14.5 ng/mL, t_max values were 0.25 h for both, t_1/2 values were 6.9 and 6.6 h, and AUC_0–24 values were 17.6 and 40.7 ng/mL·h, respectively. The liposomal formulation improved the relative oral bioavailability of tHGA from 9.1% to 21.0% which was a 2.3-fold increment. Further, a total of 12 metabolites were detected and structurally characterized. The metabolites were mainly products of oxidation and glucuronide conjugation.

Pharmacokinetics and tissue distribution of Ebracteolatain A, a potential anti-cancer compound, as determined by an optimized ultra-performance liquid chromatography tandem mass spectrometry method

Ebracteolatain A is a phloroglucinol derivative from the root of Euphorbia ebracteolata Hayata, a Traditional Chinese Medicine also known as Langdu. It has been shown to have good inhibitory effects in breast cancer cells. In this study, a simple, rapid, sensitive, and specific ultra-performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) method was developed and validated to study the pharmacokinetics (PKs) and tissue distribution of Ebracteolatain A in rats. Ebracteolatain A and Magnolol (internal standard) were extracted by the simple protein precipitation extraction technique using methanol as the precipitating solvent. Chromatographic separation was performed using the Agilent Poroshell 120 EC-C₁₈ column with a mobile phase of acetonitrile:0.1% formic acid (70:30, v/v). The protonated analyte was quantitated in negative ionization by MS/MS via multiple reaction monitoring mode. The assay exhibited a linear dynamic range of 2-2000 ng/mL for Ebracteolatain A in biological samples. The lower limit of quantitation was 2 ng/mL. Non-compartmental PK parameters indicated that Ebracteolatain A was well absorbed into the systemic circulation. The absolute bioavailability of Ebracteolatain A was greater when administered by intraperitoneal administration than by oral administration. The tissue distribution study showed that Ebracteolatain A was distributed in the heart, liver, spleen, lung, kidney, brain, stomach, intestine, uterus, ovary, and breast after intravenous injection. The results of this study further our understanding of the in vivo anti-cancer activity of Ebracteolatain A, and shed light on pharmacological strategies that may be useful for the development of novel breast cancer therapeutics.

Determination of phloroglucinol by HPLC-MS/MS and its application to a bioequivalence study in healthy volunteers

OBJECTIVE

The aim of this study was to compare the pharmacokinetic characteristics of phloroglucinol between an orally disintegrating tablet and an orally lyophilized tablet of phloroglucinol in healthy volunteers under fasting condition.

PATIENTS AND METHODS

A rapid and simple method based on high-performance liquid chromatography-tandem mass spectrometry (HPLC-MS/MS) method has been developed and validated for the determination of phloroglucinol in human plasma. The plasma sample was prepared by liquid-liquid extraction, and paracetamol was chosen as the internal standard. Phloroglucinol and IS were separated on a C18 column with a mobile phase consisted of methanol/water (80:20 v/v) with 0.02% formic acid. HPLC-MS/MS analyses were performed on a triple- quadruple tandem mass spectrometer by monitoring protonated parent→daughter ion pairs at m/z 125.0→56.9 for phloroglucinol, and m/z 150.2→107.0 for paracetamol (IS). The method was the high sensitivity with a lower limit of quantification (LLOQ) of 1.976 ng/mL.

RESULTS

Drug and IS were detected by HPLC/MS/MS with negative electrospray ionization (ESI). Accuracy and precision for the assay were determined by calculating the intra- and inter-batch variation of quality control (QC) samples at three concentration levels. The relative standard deviation (RSD) was less than 15.0%. The detection and quantitation of drug and IS within 4.5 min make this method suitable for high-throughput analyses. In this study, the Cmax of phloroglucinol were calculated to 515.6 ± 134.4 ng/mL and 536.0 ± 144.8 ng/mL for the test drug and the reference drug, respectively. The AUC0-t values were 459.5 ± 81.03 ng·mL-1·h and 491.8 ± 95.17 ng·mL-1·h for the test drug and the reference drug; 24 subjects completed the study, respectively. The geometric mean ratio (GMR) and the 90% confidence intervals (CIs) of Cmax and AUC0-t of phloroglucinol were 97.1 (90.2-103.9) and 93.8 (88.7-99.2), respectively.

CONCLUSIONS

The method was employed for the first time during pharmacokinetic studies of phloroglucinol in human plasma following a single dose of phloroglucinol 160 mg tablets. There was no significant difference in pharmacokinetic profiles between the two treatments.

Gastrointestinal modifications and bioavailability of brown seaweed phlorotannins and effects on inflammatory markers

Brown seaweeds such as Ascophyllum nodosum are a rich source of phlorotannins (oligomers and polymers of phloroglucinol units), a class of polyphenols that are unique to Phaeophyceae. At present, there is no information on the bioavailability of seaweed polyphenols and limited evidence on their bioactivity in vivo. Consequently, we investigated the gastrointestinal modifications in vitro of seaweed phlorotannins from A. nodosum and their bioavailability and effect on inflammatory markers in healthy participants. In vitro, some phlorotannin oligomers were identified after digestion and colonic fermentation. In addition, seven metabolites corresponding to in vitro-absorbed metabolites were identified. Urine and plasma samples contained a variety of metabolites attributed to both unconjugated and conjugated metabolites (glucuronides and/or sulphates). In both urine and plasma, the majority of the metabolites were found in samples collected at late time points (6-24 h), suggesting colonic metabolism of high-molecular-weight phlorotannins, with three phlorotannin oligomers (hydroxytrifuhalol A, 7-hydroxyeckol, C-O-C dimer of phloroglucinol) identified in urine samples. A significant increase of the cytokine IL-8 was also observed. Our study shows for the first time that seaweed phlorotannins are metabolised and absorbed, predominantly in the large intestine, and there is a large inter-individual variation in their metabolic profile. Three phlorotannin oligomers present in the capsule are excreted in urine. Our study is the first investigation of the metabolism and bioavailability of seaweed phlorotannins and the role of colonic biotransformation. In addition, IL-8 is a possible target for phlorotannin bioactivity.

Brain Uptake of Tetrahydrohyperforin and Potential Metabolites after Repeated Dosing in Mice

Tetrahydrohyperforin (IDN-5706) is a semisynthetic derivative of hyperforin, one of the main active components of Hypericum perforatum extracts. It showed remarkable positive effects on memory and cognitive performances in wild-type mice and in a transgenic mouse model of Alzheimer's disease, but little was known about the concentrations it can reach in the brain. The investigations reported herein show that repeated treatment of mice with tetrahydrohyperforin (20 mg/kg intraperitoneally, twice daily for 4 days and once on the fifth day) results in measurable concentrations in the brain, up to 367 ng/g brain (∼700 nM) 6 h after the last dose; these concentrations have significant effects on synaptic function in hippocampal slices. The other main finding was the identification and semiquantitative analysis of tetrahydrohyperforin metabolites. In plasma, three hydroxylated/dehydrogenated metabolites were the largest (M1-3) and were also formed in vitro on incubation of tetrahydrohyperforin with mouse liver microsomes; the fourth metabolite in abundance was a hydroxylated/deisopropylated derivative (M13), which was not predicted in vitro. These metabolites were all detected in the brain, with peak areas from 10% (M1) to ∼1.5% (M2, M3, and M13) of the parent compound. In summary, repeated treatment of mice with tetrahydrohyperforin gave brain concentrations that might well underlie its central pharmacological effects. We also provide the first metabolic profile of this compound.

Myrtucommulone from Myrtus communis: metabolism, permeability, and systemic exposure in rats

Nonsteroidal anti-inflammatory drug intake is associated with a high prevalence of gastrointestinal side effects, and severe cardiovascular adverse reactions challenged the initial enthusiasm in cyclooxygenase-2 inhibitors. Recently, it was shown that myrtucommulone, the active ingredient of the Mediterranean shrub Myrtus communis, dually and potently inhibits microsomal prostaglandin E₂ synthase-1 and 5-lipoxygenase, suggesting a substantial anti-inflammatory potential. However, one of the most important prerequisites for the anti-inflammatory effects in vivo is sufficient bioavailability of myrtucommulone. Therefore, the present study was aimed to determine the permeability and metabolic stability in vitro as well as the systemic exposure of myrtucommulone in rats. Permeation studies in the Caco-2 model revealed apparent permeability coefficient values of 35.9 · 10⁻⁶ cm/s at 37 °C in the apical to basolateral direction, indicating a high absorption of myrtucommulone. In a pilot rat study, average plasma levels of 258.67 ng/mL were reached 1 h after oral administration of 4 mg/kg myrtucommulone. We found that myrtucommulone undergoes extensive phase I metabolism in human and rat liver microsomes, yielding hydroxylated and bihydroxylated as well as demethylated metabolites. Physiologically-based pharmacokinetic modeling of myrtucommulone in the rat revealed rapid and extensive distribution of myrtucommulone in target tissues including plasma, skin, muscle, and brain. As the development of selective microsomal prostaglandin E₂ synthase-1 inhibitors represents an interesting alternative strategy to traditional nonsteroidal anti-inflammatory drugs and cyclooxygenase-2 inhibitors for the treatment of chronic inflammation, the present study encourages further detailed pharmacokinetic investigations on myrtucommulone.

Intestinal permeability of antivirus constituents from the fruits of Eucalyptus globulus Labill. in Caco-2 Cell Model

The uptake and transepithelial transport of the three main constituents macrocarpal A (M-A), macrocarpal B (M-B), and cypellocarpa C (Cy-C) from the fruits of Eucalyptus globulus Labill. were investigated. Monolayers of the human intestinal epithelial cancer cell line Caco-2 were incubated with M-A, M-B, and Cy-C to model its intestinal absorption and transport, respectively. The determination of compounds was performed by HPLC. The apparent permeability coefficients (P(app)) for M-A, M-B, and Cy-C in the apical-to-basolateral direction of a Caco-2 monolayer were (1.70+/-0.06)x10(-6), (1.99+/-0.10)x10(-6), and (6.08+/-0.41)x10(-6)cm/s, respectively. In the presence of iodoacetamide, the P(app) of Cy-C were both reducted in apical-to-basolateral and basolateral-to-apical directions. M-A and M-B appear to accumulate in the epithelial cells. The intestinal absorption of M-A, M-B, and Cy-C was passive diffusion as the dominating process and Cy-C was partly ATP-dependent.

Hypericum perforatum: a 'modern' herbal antidepressant: pharmacokinetics of active ingredients

Hypericum perforatum (St John's Wort [SJW]) counts among the most favourite herbal drugs, and is the only herbal alternative to classic synthetic antidepressants in the therapy of mild to moderate depression. Several clinical studies have been conducted to verify the effectiveness of ethanolic or methanolic extracts of SJW. Alcoholic SJW extracts are a mixture of substances with widely varying physical and chemical properties and activities. Hyperforin, a phloroglucinol derivative, is the main source of pharmacological effects caused by the consumption of alcoholic extracts of SJW in the therapy of depression. However, several studies indicate that flavone derivatives, e.g. rutin, and also the naphthodianthrones hypericin and pseudohypericin, take part in the antidepressant efficacy. In contrast to the amount of documentation concerning clinical efficacy, oral bioavailability and pharmacokinetic data about the active components are rather scarce. The hyperforin plasma concentration in humans was investigated in a small number of studies. The results of these studies indicate a relevant plasma concentration, comparable with that used in in vitro tests. Furthermore, hyperforin is the only ingredient of H. perforatum that could be determined in the brain of rodents after oral administration of alcoholic extracts. The plasma concentrations of the hypericins were, compared with hyperforin, only one-tenth and, until now, the hypericins could not be found in the brain after oral administration of alcoholic H. perforatum extracts or pure hypericin. Until now, the pharmacokinetic profile of the flavonoids in humans after oral administration of an alcoholic H. perforatum extract has been investigated in only one study. More data are available for rutin and the aglycone quercetin after administration of pure substances or other flavonoid sources.

St. John's wort (Hypericum perforatum) and breastfeeding: plasma and breast milk concentrations of hyperforin for 5 mothers and 2 infants

BACKGROUND

Herbal preparations for depression, such as St. John's wort, are often preferred over pharmaceutical preparations by mothers and midwives after childbirth because these preparations are available to patients as over-the-counter "natural" treatments and are popularly assumed to be safe. The only existing report on St. John's wort excretion into human milk showed that only 1 active component (hyperforin) was detectable in breast milk, but was not detectable in the infants' plasma. Another report found more cases of minor problems in infants breast-fed by women taking St. John's wort. However, significance was reached only in comparison with disease-matched women (p<.01), not healthy controls (p=.20).

METHOD

Five mothers who were taking 300 mg of St. John's wort 3 times daily (LI 160 [Jarsin], Lichtwer Pharma GmbH; Berlin, Germany) and their breastfed infants were assessed. Thirty-six breast milk samples (foremilk and hindmilk collected during an 18-hour period) and 5 mothers' and 2 infants' plasma samples were analyzed for hyperforin levels by tandem mass spectrometry (LC/MS/MS; limit of quantification=0.1 ng/mL). Data were gathered from January 2001 to February 2002.

RESULTS

Hyperforin is excreted into breast milk at low levels. However, the compound was at the limit of quantification in the 2 infants' plasma samples (0.1 ng/mL). Milk/plasma ratios ranged from 0.04 to 0.13. The relative infant doses of 0.9% to 2.5% indicate that infant exposure to hyperforin through milk is comparable to levels reported in most studies assessing anti-depressants or neuroleptics. No side effects were seen in the mothers or infants.

CONCLUSION

These results add to the evidence of the relative safety of St. John's wort while breast-feeding found in previous observational studies.

Investigation of pharmacokinetic data of hypericin, pseudohypericin, hyperforin and the flavonoids quercetin and isorhamnetin revealed from single and multiple oral dose studies with a hypericum extract containing tablet in healthy male volunteers

Hypericins, hyperforin and flavonoids are discussed as the main components contributing to the antidepressant action of St. John's wort (Hypericum perforatum). Therefore, the objective of the two open phase I clinical trials was to obtain pharmacokinetic data of these constituents from a hypericum extract containing tablet: hypericin, pseudohypericin, hyperforin, the flavonoid aglycone quercetin, and its methylated form isorhamnetin. Each trial included 18 healthy male volunteers who received the test preparation, containing 900 mg dry extract of St John's wort (STW 3-VI, Laif 900), either as a single oral dose or as a multiple once daily dose over a period of 14 days. Concentration/time curves were determined for the five constituents, for 48 h after single dosing and for 24 h on day 14 at the end of 2 weeks of continuous daily dosing. After single dose intake, the key pharmacokinetic parameters were determined as follows: Hypericin: Area under the curve (AUC(0-infinity)) = 78.33 h x ng/ml, maximum plasma concentration (Cmax) = 3.8 ng/ml, time to reach Cmax (tmax) = 7.9 h, and elimination half-life (t1/2) = 18.71 h; pseudohypericin: AUC(0-infinity) = 97.28 h x ng/ml, Cmax = 10.2 ng/ml, tmax = 2.7 h, t1/2 = 17.19 h; hyperforin: AUC(0-infinity) = 1550.4 h x ng/ml, Cmax = 122.0 ng/ml, tmax = 4.5 h, t1/2 = 17.47 h. Quercetin and isorhamnetin showed two peaks of maximum plasma concentration separated by about 3-3.5 h. Quercetin: AUC(0-infinity) = 417.38 h x ng/ml, Cmax (1) = 89.5 ng/ml, tmax (1) = 1.0 h, Cma (2) = 79.1 ng/ml, tmax (2) = 4.4 h, t1/2 = 2.6 h; isorhamnetin: AUC(0-infinity) = 155.72 h x ng/ml, Cmax (1) = 12.5 ng/ml, tmax (1) = 1.4 h, Cmax (2) = 14.6 ng/ml, tmax (2) = 4.5 h, t1/2 = 5.61 h. Under steady state conditions reached during multiple dose administration similar results were obtained. Further pharmacokinetic characteristics calculated from the obtained data were the mean residence time (MRT), the lag-time, the peak-trough fluctuation (PTF), the lowest observed plasma concentration (Cmin), and the average plasma concentration (Cav). The data obtained for the five consitituents generally corresponded well with values previously published. The trial preparation was well tolerated.

High-performance liquid chromatography measurement of hyperforin and its reduced derivatives in rodent plasma

A reverse-phase high-performance liquid chromatography method was developed for the determination of hyperforin and its reduced derivatives octahydrohyperforin and tetrahydrohyperforin in rodent plasma. The procedure includes solid-phase extraction from plasma using the Baker 3cc C8 cartridge, resolution on the Symmetry Shield RP8 column (150 mm x 4.6 mm, i.d. 3.5 microm) and UV absorbance detection at 300 nm. The assay was linear over a wide range, with an overall coefficient of variation less than 10% for all compounds. The precision and accuracy were within acceptable limits and the limit of quantitation was sufficient for studies preliminarily assessing the disposition of tetrahydrohyperforin and octahydrohyperforin in the mouse and rat.

Investigation of the bioavailability of hypericin, pseudohypericin, hyperforin and the flavonoids quercetin and isorhamnetin following single and multiple oral dosing of a hypericum extract containing tablet

The objective of these two open phase I clinical trials was the investigation of the bioavailability of five constituents from a hypericum extract containing tablet, which are discussed as the components contributing to the antidepressant action. Each trial included 18 healthy male volunteers who received the test preparation, containing 612 mg dry extract of St John's wort (STW-3, Laif 600), either as a single oral dose or as a multiple once daily dose over a period of 14 days. Concentration/time curves were determined for hypericin, pseudohypericin, hyperforin, the flavonoid aglycone quercetin, and its methylated form isorhamnetin for 48 h after single dosing and for 24 h on day 14 at the end of 2 weeks of continuous daily dosing. After single dose intake, the key pharmacokinetic parameters were determined as follows: hypericin: area under the curve (AUC(0-infinity)) = 75.96 h x ng/ml, maximum plasma concentration (Cmax) = 3.14 ng/ml, time to reach Cmax (t(max)) = 8.1 h, and elimination half-life (t1/2) = 23.76 h; pseudohypericin: AUC(0-infinity) = 93.03 h x ng/ml, Cmax = 8.50 ng/ml, t(max) = 3.0 h, t1/2 = 25.39 h; hyperforin: AUC(0-max) = 1009.0 h x ng/ml, Cmax = 83.5 nglml, t(max) = 4.4 h, t1/2 = 19.64 h. Quercetin and isohamnetin showed two peaks of maximum plasma concentration separated by about 4 h. Quercetin: AUC(0-infinity) = 318,7 h x ng/ml, Cmax (1) = 47.7 ng/ml, t(max) (1) = 1.17 h, Cmax (2) = 43.8 ng/ml, t(max) (2) = 5.47 h, t1/2 = 4.16 h; isorhamnetin: AUC(0-infinity) = 98.0 h x ng/ml, Cmax (1) = 7.6 ng/ml, t(max) (1) = 1.53 h, Cmax (2) = 9.0 ng/ml, t(max), (2) = 6.42 h, t1/2 = 4.45 h. Under steady state conditions reached during multiple dose administration similar results were obtained. Further pharmacokinetic characteristics calculated from the obtained data were the mean residence time (MRT), the lag-time, the peak-trough fluctuation (PTF), the lowest observed plasma concentration (Cmin), and the average plasma concentration (Cav). The data obtained for hypericin, pseudohypericin and hyperforin generally corresponded well with values previously published, with some deviations observed for the extent of absorption of hypericin and the time course of absorption and elimination of hyperforin. The kinetic characteristics of the hypericum flavonoids are reported here for the first time. The trial preparation was well tolerated.

Determination of phloroglucinol in human plasma by high-performance liquid chromatography-mass spectrometry

A sensitive and selective liquid chromatographic method coupled with mass spectrometry (LC-MS) was developed for the quantification of phloroglucinol in human plasma. Resorcinol was used as internal standard, with plasma samples extracted using ethyl acetate. A centrifuged upper layer was then evaporated and reconstituted with mobile phase. The reconstituted samples were injected into a C(18) XTerra MS column (2.1 x 100 mm) with 3.5-microm particle size. The analytical column lasted for at least 500 injections. The mobile phase was 15% acetonitrile (pH 3.0), with flow-rate at 200 microl/min. The mass spectrometer was operated in negative ion mode with selective ion monitoring (SIM). Phloroglucinol was detected without severe interferences from plasma matrix when used negative ion mode. Phloroglucinol produced a parent molecule ([M-H](-)) at m/z 125 in negative ion mode. Detection of phloroglucinol in human plasma was accurate and precise, with quantification limit at 5 ng/ml. This method has been successfully applied to a study of phloroglucinol in human specimens.

Pharmacokinetic and tumour-photosensitizing properties of methoxyphenyl porphyrin derivative

The photokilling activity of 5-[4-N-(2',6'-dinitro-4'-trifluoromethylphenyl) aminophenyl]-10,15,20-tris(2,4,6-trimethoxy phenyl) porphyrin (CF3) was evaluated on a Hep-2 human larynx-carcinoma cell line. An apoptotic mechanism of cell death was found at low irradiation doses. Pharmacokinetic and tumour-photosensitizing properties were studied in mice. The results show that a different mechanism of cell death can be induced depending on the irradiation doses in the photodynamic treatments with CF3, which makes this agent an interesting sensitizer for potential tumour photosensitizer.

[Bioavailability of phloroglucinol in man]

This work reports a bioavailability study between two oral dosage forms containing 125.2 mg active phloroglucinol. Twelve healthy volunteers subjects received a sublingual administration of both dosage forms, a flash liberation tablet and a freeze-dried reference tablet (lyoc), according to a randomized and cross-over design. An accurate, sensitive and specific high performance liquid chromatographic method was developed for the determination of free phloroglucinol as well as its conjugated metabolites, that allowed as to clarify phloroglucinol pharmacokinetic behaviour in man, specially its important metabolisation, its poor systemic bioavailability after oral administration and its total urinary elimination mainly under metabolized form. Total plasmatic phloroglucinol pharmacokinetic profiles led to pertinent parameters needed for statistical bioequivalence study, i.e. T1/2 alpha, T1/2 beta, AUC, Tmax, Cmax and MRT. The mean comparative values of these parameters showed the equivalent performances of both oral dosage forms studied and the statistical tests performed (ANOVA, Westlake and two one-sided t test) concluded to their bioequivalence.

Determination of phloroglucinol in human plasma by gas chromatography-mass spectrometry

A specific and sensitive method has been developed for the determination of phloroglucinol in plasma; it involves an optimized procedure for blood sampling designed to minimize the in vitro oxidation of the molecule, and gas chromatography-mass spectrometry after silylation of the compound. The method allowed a reliable determination of phloroglucinol in plasma. The precision and accuracy of the assay, reported as coefficients of variation, were below 15%. Using a plasma sample of 0.25 ml, the limit of quantitation was 5 ng/ml with a precision of 17.4%, which is sensitive enough for pharmacokinetic studies. Stability studies under different conditions revealed that ascorbic acid limits the degradation of phloroglucinol in plasma during storage at freezer temperatures.