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.

Combining SEM, TEM, and micro-Raman techniques to differentiate between the amorphous molecular level dispersions and nanodispersions of a poorly water-soluble drug within a polymer matrix.

The aim of the present study was to experimentally examine whether poorly water-soluble drugs dispersed in a polymeric matrix exist as amorphous nanodispersions or molecularly dispersed compounds. Felodipine (Felo) dispersed in PVP matrix (solid dispersion) was used as a model drug in this study. Drug/polymer ratios have an impact on the drug average particle size, morphology and dissolution profile while solid dispersions containing up to 50wt% Felo are completely amorphous. SEM, TEM micrographs, and micro-Raman mapping reveal that Felo is dispersed in the form of nanoparticles into the PVP matrix. Due to the high spatial resolution of TEM, it was established that these nanoparticles are not uniform particles, but rather agglomerates of individual particles with sizes smaller than 5-10nm. Moreover, micro-Raman mapping allowed us to observe the size and spatial distribution of domains where the drug existed as molecularly or nanodispersed. Experimental evidence presented in this work contradicts the common belief that amorphous poorly water-soluble drugs exist only in the state of molecular dispersion inside a polymer matrix by showing that both types of dispersions (molecular-level and nanodispersions) can coexist.

Compressed collagen sponges as gastroretentive dosage forms: in vitro and in vivo studies.

The objective of the present investigations was to develop oblong tablets which expand after contact with gastrointestinal fluids within a few minutes to a length of 4-6 cm and which should remain in the stomach for a prolonged period of time due to their size. The tablets were prepared from riboflavin-containing collagen sponges using a computer controlled single punch tablet machine. The collagen material was compressed to oblong tablets with dimensions of 3.5 mm x 9 mm x 18 mm. In vitro investigations were carried out to characterise drug release. The model drug riboflavin was released from the collagen tablets over 12h. The gastrointestinal retention time of the new dosage form was indirectly estimated by determining the duration of riboflavin excretion after oral intake of the tablet. A crossover in vivo study with 12 healthy male and female subjects was performed. The renal excretion of riboflavin was measured after oral administration of collagen tablets and small sustained release hydrocolloid tablets as reference preparation. The amount of riboflavin excreted into the urine was enhanced after administration of the expanding collagen tablets in comparison with the hydrocolloid tablets. The differences were statistically significant after 5, 6, 8, 9, 10 and 12 h.

A validated solid-phase extraction HPLC method for the simultaneous determination of the citrus flavanone aglycones hesperetin and naringenin in urine.

A simple, specific, precise, accurate, and robust HPLC assay for the simultaneous analysis of hesperetin and naringenin in human urine was developed and validated. Urine samples were incubated with beta-glucuronidase/sulphatase and the analytes were isolated by solid-phase extraction using C18 cartridges and separated on a C8 reversed phase column using a mixture of methanol/water/acetic acid (40:58:2, v/v/v) at 45 degrees C. The method was found to be linear in the 50-1200 ng/ml concentration range for both hesperetin and naringenin (r > 0.999). The accuracy of the method was greater than 94.8%, while the intra- and inter-day precision for hesperetin was better than 4.9 and 8.2%, respectively and for naringenin was better than 5.3 and 7.8%, respectively. Recovery for hesperetin, naringenin and internal standard 7-ethoxycoumarin was greater than 70.9%. The method has been applied for the determination of hesperetin and naringenin in urine samples obtained from a male volunteer following a single 300 mg oral dose of each of the corresponding flavanone glycosides hesperidin and naringin. The intra- and inter-day reproducibility through enzyme hydrolysis was less than 3.9% for both total (free + conjugated) hesperetin and naringenin. Stability studies showed urine quality control samples to be stable for both hesperetin and naringenin through three freeze-thaw cycles and at room temperature for 24 h (error < or = 3.6%).

Evaluation of the bioequivalence and pharmacokinetics of two lisinopril tablet formulations after single oral administration in healthy volunteers.

An open, two-period, randomized, crossover trial of two lisinopril (1-[N2-[(S)-1-carboxyl-3-phenylpropyl]-L-lysil]-L-proline, CAS 76547-98-3) formulations (Adicanil as test and another commercially available preparation as reference) was performed in 24 healthy volunteers. A single 20 mg oral dose of lisinopril was administrated and pharmacokinetic parameters were compared. Lisinopril plasma concentrations were measured by a fully validated LC-MS method. The parametric 90% confidence intervals of the geometric mean values of the test/reference ratios were 95.38% to 105.94% (point estimate: 100.52%) for AUC(0-last), 94.01% to 103.47% (point estimate: 98.63%) for AUC(0-infinity) and 92.34% to 103.97% (point estimate: 97.98%) for Cmax, being within the acceptance criteria for bioequivalence (80%-125%). T(1/2), k(el) and Tmax values were also tested and the difference was not statistically significant. Therefore, it is concluded that the test and the reference lisinopril formulations are bioequivalent both in the extent and the rate of absorption.

Validated high-performance liquid chromatographic method utilizing solid-phase extraction for the simultaneous determination of naringenin and hesperetin in human plasma.

Naringenin and hesperetin, the aglycones of the flavanone glucosides naringin and hesperidin occur naturally in citrus fruits. They exert a variety of pharmacological effects such as antioxidant, blood lipid-lowering, anticarcinogenic and inhibit selected cytochrome P-450 enzymes resulting in drug interactions. A specific, sensitive, precise, and accurate solid-phase extraction high-performance liquid chromatographic (HPLC) assay for the simultaneous determination of naringenin and hesperetin in human plasma was developed and validated. After addition of 7-ethoxycoumarin as internal standard, plasma samples were incubated with beta-glucuronidase/sulphatase, and the analytes were isolated from plasma by solid-phase extraction using C(18) cartridges and separated on a C(8) reversed phase column with methanol/water/acetic acid (40:58:2, v/v/v) as the eluent at 45 degrees C. The method was linear in the 10-300 ng/ml concentration range for both naringenin and hesperetin (r>0.999). Recovery for naringenin, hesperetin and internal standard was greater than 76.7%. Intra- and inter-day precision for naringenin ranged from 1.4 to 4.2% and from 1.9 to 5.2%, respectively, and for hesperetin ranged from 1.3 to 4.1% and from 1.7 to 5.1%, respectively. Accuracy was better than 91.5 and 91.3% for naringenin and hesperetin, respectively.

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.

Development of a liquid chromatography-mass spectrometry method for monitoring the angiotensin-converting enzyme inhibitor lisinopril in serum.

In this study, a sensitive, specific, precise and accurate method for lisonopril quantitative determination in human serum was developed and validated. The method comprises lisinopril isolation from serum by means of solid-phase extraction followed by its quantification by liquid chromatography-mass spectrometry. Chromatographic separation was performed at 55 degrees C on Kromasil C(18) 5 micrometer 250x3.2 mm HPLC column with mobile phase composed of 50 mM ammonium formate buffer (pH 3)-acetonirile-methanol (72:7:21, v/v/v). A Finnigan AQA benchtop mass spectrometer with a pneumatically assisted electrospray (ES) interface and a single quadrupole mass filter was used to detect and quantify lisinopril in column effluent. Ion signals were acquired by selected ion monitoring of the protonated lisinopril ion m/z=406.5 (M+1). The detector response was linear with r>0.9993 in the investigated concentration range 6-150 ng/ml. The mean recovery of lisinopril from serum samples was 88%. The limit of quantitation for lisinopril was 6 ng/ml with a signal-to-noise ratio at this concentration level S/N=34.75+/-3.9 (n=4).