Ioannis Niopas

Pharmacokinetics of the citrus flavanone aglycones hesperetin and naringenin after single oral administration in human subjects

Background and objective:Hesperetin and naringenin, the aglycones of the flavanone glycosides hesperidin and naringin, occur naturally in citrus fruits. They exert interesting pharmacological properties such as antioxidant, anti-inflammatory, blood lipid and cholesterol lowering and are considered to contribute to health benefits in humans. However, no information is available on the pharmacokinetics of the citrus flavanones hesperetin and naringenin after their oral administration to humans as pure aglycones. Therefore, the objective of the present investigation was the evaluation of the pharmacokinetic parameters of hesperetin and naringenin in plasma and urine, after their single oral administration in humans in the form of solid dispersion capsules, and also to improve the absorption rate of flavanones by using aglycones rather than the naturally occurring glycosides.Design:Six healthy volunteers received orally 135 mg of each compound, hesperetin and naringenin, under fasting conditions. Blood samples were collected at 14 different time points over a 12 h period. Urine was collected over 24 h, in five sequential timed intervals. Plasma and urine hesperetin and naringenin concentrations, after enzymatic hydrolysis of their conjugated forms, were measured using validated high-pressure liquid chromatography methods. Pharmacokinetic parameters for hesperetin and naringenin, such as Cmax, Tmax, AUC0−t, AUC0−∞, CL/F, V/F, t1/2, MRT, Ae, Ae(0–24), and Rmax were calculated from their plasma or urine concentrations.Results:Pharmacokinetic analysis showed that both hesperetin and naringenin were rapidly absorbed and their concentrations in plasma observed 20 min after dosing and reached a peak in 4.0 and 3.5 h, respectively. The mean peak plasma concentration (Cmax) for hesperetin and naringenin were 825.78±410.63 ng/ml (2731.8±1358.4 nmol/l) and 2009.51±770.82 ng/ml (7386.6±2833.4 nmol/l), respectively and the mean AUC0−∞ values were 4846.20±1675.99 ng h/ml and 9424.52±2960.52 ng h/ml for hesperetin and naringenin, respectively. The elimination half-life for hesperetin was found to be 3.05±0.91 h and for naringenin 2.31±0.40 h, respectively. The mean values of the relative cumulative urinary excretion, as percentage of the administered dose, for hesperetin and naringenin, were found to be 3.26±0.44 and 5.81±0.81%, respectively.Conclusions:Oral administration of the flavanone aglycones, hesperetin and naringenin, lead to their rapid absorption as their conjugated forms. The cumulative urinary recovery data indicated low bioavailability for both flavanone aglycones, owing to extensive first-pass metabolism partly by cleavage of the C-ring by the enzymes of intestinal bacteria leading to degradation products such as phenolic acids.

Simultaneous reversed-phase high-performance liquid chromatographic method for the determination of diosmin, hesperidin and naringin in different citrus fruit juices and pharmaceutical formulations

Diosmin, hesperidin and naringin are flavonoid glycosides that occur naturally in citrus fruits. They exert a variety of pharmacological properties such as anti-inflammatory, antioxidant and free radical scavenging and antiulcer effects and also inhibit selected cytochrome P-450 enzymes resulting in drug interactions. A reversed-phase high-performance liquid chromatographic method has been developed for the simultaneous determination of diosmin, hesperidin and naringin in different citrus fruit juices and pharmaceutical preparations. Diosmin, hesperidin, naringin and the internal standard rhoifolin were separated using tetrahydrofuran/water/acetic acid (21:77:2, v/v/v) as the mobile phase at 34 degrees C, using a C8 reversed-phase column. The method was linear in the 0.25-20.0 microg/ml concentration range for all three flavonoid glycosides (r>0.999). The method has been successfully applied to the determination of all three flavonoid glycosides in several samples of different citrus fruit juices sold in Greece and for the determination of diosmin and hesperidin in pharmaceutical preparations.

Determination of indomethacin and mefenamic acid in plasma by high-performance liquid chromatography

Indomethacin and mefenamic acid are widely used clinically as non-steroidal anti-inflammatory agents. Both drugs have also been found effective to produce closure of patent ductus arteriosus in premature neonates. A simple, rapid, sensitive and reliable HPLC method is described for the determination of indomethacin and mefenamic acid in human plasma. As these drugs are not applied together, the compounds are alternately used as analyte and internal standard. Plasma was deproteinized with acetonitrile, the supernatant fraction was evaporated to dryness and the resulting residue was reconstituted in the mobile phase and injected into the HPLC system. The chromatographic separation was performed on a C18 column (250 x 4.6 mm I.D.) using 10 mM phosphoric acid-acetonitrile (40:60, v/v) as the mobile phase and both drugs were detected at 280 nm. The calibration graphs were linear with a correlation coefficient (r) of 0.999 or better from 0.1 to 10 micrograms/ml and the detection limits were 0.06 micrograms/ml for indomethacin and 0.08 micrograms/ml for mefenamic acid, for 50-microliters plasma samples. The method was not interfered with by other plasma components and has been found particularly useful for paediatric use. The within-day precision and accuracy of the method were evaluated for three concentrations in spiked plasma samples. The coefficients of variation were less than 5% and the accuracy was nearly 100% for both drugs.

The phytochemical analysis and antioxidant activity assessment of orange peel (Citrus sinensis) cultivated in Greece-Crete indicates a new commercial source of hesperidin

The flavonoid content of several methanolic extract fractions of Navel orange peel (flavedo and albedo of Citrus sinensis) cultivated in Crete (Greece) was first analysed phytochemically and then assessed for its antioxidant activity in vitro. The chemical structures of the constituents fractionated were originally determined by comparing their retention times and the obtained UV spectral data with the available bibliographic data and further verified by detailed LC-DAD-MS (ESI+) analysis. The main flavonoid groups found within the fractions examined were polymethoxylated flavones, O-glycosylated flavones, C-glycosylated flavones, O-glycosylated flavonols, O-glycosylated flavanones and phenolic acids along with their ester derivatives. In addition, the quantitative HPLC analysis confirmed that hesperidin is the major flavonoid glycoside found in the orange peel. Interestingly enough, its quantity at 48 mg/g of dry peel permits the commercial use of orange peel as a source for the production of hesperidin. The antioxidant activity of the orange peel methanolic extract fractions was evaluated by applying two complementary methodologies, DPPH(*) assay and the Co(II)/EDTA-induced luminol chemiluminescence approach. Overall, the results have shown that orange peel methanolic extracts possess moderate antioxidant activity as compared with the activity seen in tests where the corresponding aglycones, diosmetin and hesperetin were assessed in different ratios.

Smoking impact on CYP1A2 activity in a group of patients with schizophrenia

The purpose of the present study was to assess the impact of smoking on the metabolism of psychotropic drugs in a group of patients with schizophrenia, by measuring CYP1A2 activity. This activity was assessed by the molar ratio (MR) of caffeine metabolites in urine [(AFMU+1U+1X)/17U] and saliva (17X/137X). Participants were 40 patients with schizophrenia: 30 current cigarette smokers and 10 nonsmokers. The two groups (smokers and nonsmokers) differed significantly in their ratio of men to women (83% men and 17% women were among smokers compared with 50% men and 50% women nonsmokers). No other group differences were found regarding age, level of education, PANSS, extrapyramidal symptoms, age of symptoms onset, antipsychotic doses (chloropromazine equivalents), and anticholinergic drug used. Smokers had significant higher MR in urine (P<0.001) as well as in saliva (P=0.001) than nonsmokers, suggesting a higher activity of CYP1A2 dependent on smoking. When gender was used as a covariate, the differences between the two groups remained significant for MR. Cigarette smoking may be a factor influencing the plasma levels of antipsychotics that metabolized through CYP1A2. Clinicians should weight the possibility that smoking and the subsequent modulation of antipsychotic metabolism may be the main reason of treatment resistance. Furthermore, any attempt to reduce or cease smoking in patients with schizophrenia necessitates close monitoring of drug doses, because untoward adverse effects may emerge.

Bioaccumulation of trimethoprim, sulfamethoxazole and N-acetyl-sulfamethoxazole in Artemia nauplii and residual kinetics in seabass larvae after repeated oral dosing of medicated nauplii

Abstract The pharmacokinetics of trimethoprim (TMP), sulfamethoxazole (SMX) and its metabolite N-acetyl-sulfamethoxazole (N-acetyl-SMX), were studied in Artemia nauplii as a function of the duration and temperature of their storage, following their enrichment with the therapeutics using the bioencapsulation technique. A marked decrease in the therapeutic content of the nauplii was observed upon storage at 18°C and 25°C and it was concluded that medicated nauplii should either be administered fresh to fish larvae or after storage for 8 h at 5°C, at the most. Under the latter conditions, satisfactory levels of TMP and SMX were achieved, high survival rates and dry weight contents of the nauplii were preserved and minimal leakage of the therapeutics to the environment was secured. Treatment of seabass larvae with one, three, six or ten doses of medicated Artemia nauplii, showed that maximum levels of the therapeutics are achieved in fish larvae when 10 doses are used. Following the treatment scheme of oral administration of 10 doses of medicated Artemia nauplii to fish larvae, the residual kinetics of TMP, SMX and N-acetyl-sulfamethoxazole were studied in seabass larvae. TMP and SMX showed different kinetic characteristics. A steady state of SMX concentration is considered to be achieved in fish body tissue during the 5-day medication period. TMP, SMX as well as the metabolite N-acetyl-sulfamethoxazole, were detectable in small amounts in fish body tissue even 100 h-post treatment. These data suggest that oral medication of fish larvae through the use of Artemia nauplii as a carrier of therapeutics, appears to be a quite promising approach to be used as an alternative method of treatment, which could minimize some of the problems arising from the methods currently in use.

Determination of nifedipine in human plasma by solid-phase extraction and high-performance liquid chromatography: validation and application to pharmacokinetic studies.

Nifedipine, a dihydropyridine calcium channel antagonist, is widely used in the treatment of hypertension and other cardiovascular disorders. A simple, rapid, sensitive, precise and accurate HPLC method, using solid-phase extraction, for the quantitation of nifedipine in human plasma was developed and validated. The calibration graphs were linear in the 5-400 ng/ml concentration range (r>0.999). Recovery for nifedipine was greater than 93.9% and for internal standard nitrendipine was 96.1%. Intra-day and inter-day precision ranged from 1.4 to 4.2 and 3.9 to 5.6%, respectively. Intra-day and inter-day accuracy was ranged from 94.5 to 98.0 and 93.1 to 98.0%, respectively. The method was not interfered with by other plasma components and was applied for the determination of nifedipine in pharmacokinetic study after single oral administration of 10 mg nifedipine to 18 healthy male subjects.

A validated high-performance liquid chromatographic method for the determination of glibenclamide in human plasma and its application to pharmacokinetic studies.

Glibenclamide is a potent second generation oral sulfonylurea antidiabetic agent widely used for the treatment of type II diabetes melitus. A rapid, sensitive, precise, accurate and specific HPLC assay for the determination of glibenclamide in human plasma was developed and validated. After addition of flufenamic acid as internal standard, the analytes were isolated from human plasma by liquid-liquid extraction. The method was linear in the 10-400 ng/ml concentration range (r > 0.999). Recovery for glibenclamide was greater than 91.5% and for internal standard was 93.5%. Within-day and between-day precision, expressed as the relative standard deviation (RSD%), ranged from 1.4 to 5.9% and 5.8 to 6.6%, respectively. Assay accuracy was better than 93.4%. The assay was used to estimate the pharmacokinetics of glibenclamide after oral administration of a 5 mg tablet of glibenclamide to 18 healthy volunteers.

Controlled release of 5-fluorouracil from microporous zeolites.

UNLABELLED Zeolite particles with different pore diameter and particle size were loaded with the model anticancer drug 5-fluorouracil. The loaded zeolites were characterized by means of SEM, XRD, DSC, XPS, N2 physisorption and FT-IR. Higher loading of 5-FU was observed for NaX-FAU than BEA. Release studies were carried out in HCl 0.1N. Release of 5-FU from NaX-FAU showed exponential-type behaviour with the drug fully released within 10 min. In the case of BEA, the kinetics of 5-FU shows a multi-step profile with prolonged release over time. Molecular dynamics simulations showed that diffusion of the drug molecule through the BEA framework is lower than for NaX-FAU due to increased van der Waals interaction between the drug and the framework. The effect of zeolitic particles on the viability of Caco-2 monolayers showed that the NaX-FAU particles cause a reduction of cell viability in a more pronounced way compared with the BEA particles. FROM THE CLINICAL EDITOR This article describes zeolite-based nanoparticles in generating time-controlled release of 5-FU from zeolite preparations for anti-cancer therapy.

Simultaneous determination of the flavonoid aglycones diosmetin and hesperetin in human plasma and urine by a validated GC/MS method: in vivo metabolic reduction of diosmetin to hesperetin

Diosmetin and hesperetin are the aglycones of the flavonoid glycosides diosmin and hesperidin which occur naturally in citrus fruit. A GC/MS method for the simultaneous determination of diosmetin and hesperetin in human plasma and urine has been developed and validated. The method was linear in the 2-300 ng/mL concentration range for both diosmetin and hesperetin in plasma and urine (r > 0.999). The precision of the method was better than 6.01 and 7.16% for diosmetin and hesperetin, respectively, and the accuracy was 96.76-100.40% and 95.00-105.50% for diosmetin and hesperetin, respectively. The lower limit of quantitation was found to be 2 ng/mL for both analytes in plasma and urine. Recovery of diosmetin, hesperetin and internal standard naringenin was greater than 82.5%. The method has been applied for the determination of diosmetin and hesperetin in plasma and urine samples obtained from a healthy male subject following a single oral 1000 mg dose of the flavonoid glycoside diosmin. The presence of hesperetin in plasma and urine samples indicates the metabolic reduction of diosmetin to its flavanone analogue hesperetin through reduction of the 2,3 double bond of the C-ring by the enzymes of bacteria of the intestinal microflora.