Biomedical subjects

V Cavrini

Publications and source records attributed to V Cavrini.

At least 55 records · Page 3Linked to original sources

PubMed1998

Acetylcholinesterase inhibitors: synthesis and structure-activity relationships of omega-[N-methyl-N-(3-alkylcarbamoyloxyphenyl)- methyl]aminoalkoxyheteroaryl derivatives.

Acetylcholinesterase (AChE) inhibitors are one of the most actively investigated classes of compounds in the search for an effective treatment of Alzheimer's disease. This work describes the synthesis, AChE inhibitory activity, and structure-activity relationships of some compounds related to a recently discovered series of AChE inhibitors: the omega-[N-methyl-N-(3-alkylcarbamoyloxyphenyl)methyl]aminoalkoxy xanthen-9-ones. The influence of structural variations on the inhibitory potency was carefully investigated by modifying different parts of the parent molecule, and a theoretical model of the binding of one representative compound to the enzyme was developed. The biological properties of the series were investigated in some detail by considering not only the activity on isolated enzyme but the selectivity with respect to butyrylcholinesterase (BuChE) and the in vitro inhibitory activity on rat cerebral cortex as well. Some of the newly synthesized derivatives, when tested on isolated and/or AChE-enriched rat brain cortex fraction, displayed a selective inhibitory activity and were more active than physostigmine. In particular, compound 13, an azaxanthone derivative, displayed the best rat cortex AChE inhibition (190-fold higher than physostigmine), as well as a high degree of enzyme selectivity (over 60-fold more selective for AChE than for BuChE). When tested in the isolated enzyme, compound 13 was less active, suggesting some differences either in drug availability/biotransformation or in the inhibitor-sensitive residues of the enzyme when biologically positioned in rat brain membranes.

Acetylcholinesterase↗

PubMed1998

Dermatan sulfate as useful chiral selector in capillary electrophoresis.

Dermatan sulfate (DS), a complex, polydispersed, sulfate polysaccharide was investigated as a useful chiral selector in capillary electrophoresis for the enantioresolution of a variety of drugs. Analysis was carried out in a fused-silica capillary column of 48.5 cm length (40 cm to detector window) x 50 microns I.D., and the separation buffer consisted of citric acid-Tris containing DS; the applied voltage was 15 kV and the detection wavelength was 220 nm. The effects of buffer pH, the dermatan concentration and run temperature on the enantioseparation and migration were examined. The method was applied to the enantioresolution of a representative set of twenty basic drugs. At all pH values used (3.0, 4.5 and 6.5) the addition of DS resulted in an increased migration time due to analyte-DS interaction. Using DS concentration of 2% (w/W), at pH 4.5, enantiomeric separations could be obtained for more than 50% of the examined drugs; resorcinic drugs; resorcinic moiety was found to be a very favourable structural feature for obtaining high enantioresolution values.

Animals↗

PubMed1998

Capillary electrophoretic and high-performance liquid chromatographic studies of the enantioselective separation of alpha1-adrenoreceptor antagonists.

Capillary electrophoresis (CE) and chiral stationary phase (CSP) HPLC methods were investigated for the determination of enantiomeric purity of alpha1-adrenoreceptor antagonists related to WB 4101. In the CE study, the enantioseparation of the analytes was performed by studying the effect of different types of cyclodextrin in the buffer, namely heptakis (2,6-di-O-methyl)-beta-cyclodextrin (DMCD), hydroxypropyl-beta-cyclodextrin (HPCD) and beta-cyclodextrin (beta-CD). HPCD was found to be the most effective chiral selector in the enantioseparation of all the compounds, with high resolution values. A HPLC method, using immobilised serum protein columns, human serum albumin (HSA) and alpha1-acid glycoprotein (AGP), was also investigated. Two benzodioxane racemates were well resolved on a mixed tpe (50% HSA and 50% AGP) column, with enantioselective binding on AGP column.

Adrenergic alpha-1 Receptor Antagonists↗

PubMed1998

Vasoactive cocktails for erectile dysfunction: chemical stability of PGE1, papaverine and phentolamine.

PURPOSE: Vasoactive cocktails are widely used in diagnosing and treating erectile dysfunction, especially in poor responders to prostaglandin E1 (PGE1). However, very little information as to their chemical interactions and stability is available, despite the huge amount of published work regarding their clinical efficacy. Obviously, medical and legal problems are involved. MATERIALS AND METHODS: We analyzed four kinds of vasoactive cocktails, composed of papaverine, phentolamine and PGE1 in different combinations, using High Performance Liquid Chromatography analysis after 5 to 60 days of storage at temperatures between 2 and 8C. SPSS MANOVA analysis and a t-test for paired samples were used for statistical purposes. RESULTS: Papaverine and phentolamine concentrations showed no significant variations during the 2 month study, ranging from a minimum of 96.75+/-1.20 to a maximum of 103.00+/-0.20% of the starting values. In the same period, PGE1 showed an accelerated degradation profile, reaching concentration values, after 60 days, of 76.00+/-2.28% and 70.20+/-2.02% when added to phentolamine or papaverine respectively and 70.00+/-2.40% with both. CONCLUSIONS: Papaverine and phentolamine are characterized by chemical stability when blended together or with PGE1. Papaverine and/or phentolamine increase the naturally occurring degradation of PGE1 in physiological solution. This effect is most evident in the first 10 days. Papaverine has the greatest deteriorating effect on PGE1. A safe and proper use of these cocktails should take into account the variations of PGE1 concentration.

Adrenergic alpha-Antagonists↗

PubMed1998

HPLC analysis of pharmaceutical estrogens in raw materials and dosage forms.

The use of HPLC with fluorescence detection (lambda ex = 280 nm; lambda em = 410 or 312 nm) in combination with a postcolumn on line photochemical derivatization was investigated for the analysis of conjugated and unconjugated estrogens and their correlated impurities. The column effluents were subjected on-line to UV irradiation (254 nm) and the photo induced modifications were useful for the identification of the various estrogens. The proposed HPLC methods were successfully applied to the analysis of commercially available conjugated estrogens (raw materials and pharmaceuticals) and estrogen samples. The assays results relative to the pharmaceutical formulations were in agreement with those obtained by a reference HPLC method with UV detection (lambda = 280 nm).

Chromatography, High Pressure Liquid↗

PubMed1998

GC-MS analysis of incenses for possible presence of allergenic nitromusks.

A Gas chromatographic method with mass detector was developed to identify and determine nitromusks in incense sticks of different origin (India, China, Tibet). The proposed method was found useful to correlate dermatological allergic reactions with the use and composition of commercial incense sticks. The incense sticks were powdered, extracted with methanol and after the addition of 1-eicosanol as internal standard, injected into the GC-MS, using 25 m bonded phase fused capillary column methyl, 5% phenyl silicone (0.32 mm I.D., 0.25 microns film thickness). Musk ambrette was identified and determined in one kind of chinese incense together with musk ketone and musk xylene. The latter compound was also found alone in another kind of chinese incense.

Allergens↗

PubMed1998

HPLC-fluorescence determination of unconjugated estrogens in pharmaceuticals.

A fluorimetric liquid chromatographic method (lambda(ex) = 280 nm; lambda(em) = 312 nm) was developed for measurements of unconjugated estrogens (estradiol and estriol) in pharmaceutical dosage forms using a reversed-phase column with water acetonitrile at different composition as mobile phase. The in vitro release profiles of three different estradiol transdermal therapeutic systems were determined through a medical-grade silicone rubber subdermal implant material membrane, using a modified Franz diffusion apparatus at 37 degrees C in presence of PEG 400. The HPLC method possesses advantages of rapidity, simplicity and accuracy.

Administration, Cutaneous↗

PubMed1998

Determination of imidazole antimycotics in creams by supercritical fluid extraction and derivative UV spectroscopy.

A supercritical fluid extraction (SFE) method was developed for the isolation of imidazole antimycotic drugs (miconazole, econazole, clotrimazole and bifonazole) from cream preparations. The SFE process involved static (1 min) and dynamic (4 min) extraction steps using pure and 10% methanol modified carbon dioxide. The SFE step was then followed by derivative UV spectrophotometric analysis. The method proved to be suitable for quality control assays of the examined antimycotics in commercial cream formulations.

Antifungal Agents↗

PubMed1997

Enantioselective separation of chiral arylcarboxylic acids on an immobilized human serum albumin chiral stationary phase.

A series of 12 chiral arylcarboxylic acids were chromatographed on an immobilized human serum albumin chiral stationary phase (HSA-CSP). The effects of solute structure on chromatographic retentions and enantioselective separations were examined by linear regression analysis and the construction of quantitative structure-enantioselective retention relationships. Competitive displacement studies were also conducted using R-ibuprofen as the displacing agent. The results indicate that the enantioselective retention of the solutes takes place at the indole-benzodiazepine site (site II) on the HSA molecule and that chiral recognition is affected by the hydrophobicity and steric volume of the solutes. The displacement studies also identified a cooperative allosteric interaction induced by the binding of R-ibuprofen to site II.

Binding Sites↗

PubMed1997

Analysis of ACE inhibitors in pharmaceutical dosage forms by derivative UV spectroscopy and liquid chromatography (HPLC).

Derivative UV spectroscopy and high performance liquid chromatography (HPLC) were applied to the determination of angiotensin-converting enzyme (ACE) inhibitors in their pharmaceutical dosage forms. For spectrophotometric determinations, the more appropriate derivative order was selected for each drug: ramipril (third-order), benazepril (second-order), enalapril maleate (second-order), lisinopril (first- and second-order) and quinapril (first-order). Reverse phase HPLC procedures (ODS column) were developed able to provide a single, symmetric peak for each drug; mixtures A-B, where A is 20 mM sodium heptansulphonate (pH 2.5) and B is acetonitrile-THF (95:5 v/v), proved to be suitable mobile phases to obtain selective separations of the cited ACE inhibitors. At ambient temperature, a low pH value (2.5) was found to be critical to avoid peak splitting and band broadening.

Angiotensin-Converting Enzyme Inhibitors↗

PubMed1997

HPLC-fluorescence determination of chlorocresol and chloroxylenol in pharmaceuticals.

The use of 2-chloro-6,7-dimethoxy-3-quinolinecarboxaldehyde as a fluorogenic labelling reagent in pre-column derivatization for the HPLC separation of chlorophenols has been investigated. The compound reacts (50 min at 110 degrees C) with 2- and 4-chlorophenols to give fluorescent ethers that can be separated by reversed-phase HPLC and detected at lambda exc = 360 nm, lambda em = 500 nm. The experimental conditions for derivatization and chromatographic separation are discussed. Applications for the determination of chlorocresol (4-chloro-3-cresol) and chloroxylenol (4-chloro-3,5-xylenol) in pharmaceutical formulations (creams, ointments) are described.

Calibration↗

PubMed1996

Application of high-performance liquid chromatography with diode-array detection and on-line post-column photochemical derivatization to the determination of analgesics.

HPLC analyses of pharmaceutical dosage forms containing analgesics and related compounds (acetylsalicyclic acid, paracetamol, propyphenazone, caffeine and chlorpheniramine) were performed on C18 and cyano columns under reversed-phase conditions. The performance of the methods was enhanced by introducing postcolumn on-line photochemical derivatization in combination with a diode-array detection. The column effluents were subjected on-line to UV irradiation (254 nm) and the characteristic photo-induced spectral modifications were useful for the unambiguous identification of the various analgesic compounds. The proposed HPLC methods were successfully applied to the analysis of commercially available analgesic dosage forms.

Analgesics, Non-Narcotic↗

PubMed1996

On-line post-column photochemical derivatization in liquid chromatographic--diode-array detection analysis of binary drug mixtures.

HPLC methods were developed for the analysis of pharmaceutical creams containing binary drug mixtures (betamethasone valerate-chlorocresol; hydrocortisone-miconazole nitrate; desonide pivalate-chlorhexidine; dexamethasone-clotrimazole; triamcinolone acetonide-econazole nitrate). The chromatographic separations were performed on C-18 and cyano columns under reversed-phase conditions. A post-column on-line photochemical reactor (irradiation at 254 nm) was arranged between the analytical column and the diode-array detector to enhance the performance of the method. Two UV spectra (photoreactor on and off) were obtained for each analyte and these additional sources of information proved to be useful for the unambiguous identification of the various analytes. The method was applied to the quality control of commercial creams using a solid-phase extraction procedure for the sample clean-up.

Administration, Topical↗

PubMed1996

A comparative evaluation of three detectors in the HPLC analysis of sodium fusidate.

A reversed phase liquid chromatographic (HPLC) method is proposed for the determination of sodium fusidate, a steroid antibiotic, in a commercial ointment using three different detectors: a) fluorescence detector, after a preliminary derivatization with 2-bromoacetyl-6-methoxynaphthalene (Br-AMN), b) UV detection and c) evaporative light scattering detector (ELSD). Fluorescent derivatization was applied directly to the diluted sample, without any purification, whilst UV and ELSD detectors involved a preliminary liquid-liquid extraction procedure to obtain accurate analysis data.

Anti-Bacterial Agents↗

PubMed1995

HPLC analysis of liquorice triterpenoids--applications to the quality control of pharmaceuticals.

A reversed-phase HPLC method is proposed for the separation of five liquorice triterpenoids, 18 beta glycyrrhetic acid (beta GA), 18 alpha glycyrrhetic acid (alpha GA), 24-hydroxy-18 beta-glycyrrhetic acid (24-OH-beta GA), alpha and beta liquiritic acid (alpha and beta LA), with potentially different biological activities. The method has been developed by studying the influence of the type of stationary phase, pH, amine modifier and organic modifier on the resolution of the five compounds. The optimized chromatographic conditions were then successfully applied to the analysis of alpha- and beta-GA in pharmaceutical preparations (toothpaste and creams) on a reversed-phase Phenomenex Ultracarb 5 ODS (30) column (150 x 4.6 mm i.d.), using as the mobile phase acetonitrile-THF-0.010 M dioctylammonium phosphate buffer (pH 6.5) (25:20:55, v/v/v) at a flow-rate of 0.8 ml min-1. SPE methods with diolic and C18 sorbents were developed to isolate and concentrate the analytes and to enhance the sensitivity for the determination of alpha-GA as an impurity in the beta-GA preparations. The method was found to be reliable and suitable for the quality control of beta-GA preparations.

Anti-Infective Agents↗

PubMed1995

Analysis of aliphatic dicarboxylic acids in pharmaceuticals and cosmetics by liquid chromatography (HPLC) with fluorescence detection.

2-Bromoacetyl-6-methoxynaphthalene has been found to be a useful prechromatographic fluorescent labelling reagent for the analysis of dicarboxylic acids. The derivatization reaction of azelaic acid and meglutol with this reagent yieded stable and highly fluorescent diesters which could be analysed by reversed-phase HPLC with fluorescence detection. According to the nature of the sample, the derivatization reaction could be carried out in acetonitrile or in an aqueous micellar system. The proposed methods proved to be suitable for the quality control of various complex pharmaceutical and cosmetic formulations of the azelaic acid and meglutol.

Chromatography, High Pressure Liquid↗

PubMed1995

Analysis of pharmaceutical creams: a useful approach based on solid-phase extraction (SPE) and UV spectrophotometry.

Solid-phase extraction (SPE) using C-18, diol and ion-exchange sorbents followed by UV spectrophotometric (conventional and derivative mode) assay was applied to the analysis of basic, acidic and neutral drugs commercially available in creams. A representative set of drugs (promethazine, chlorhexidine, benzydamine, ketoprofen, ibuprofen, fentiazac, piroxicam, fluorouracil, crotamiton and hydrocortisone acetate) was selected, and for each drug the appropriate SPE conditions (adsorption, washing and elution) were investigated to obtain a practical and reliable sample clean-up. It was shown that the developed SPE procedures were capable of removing interfering cream components (excipients including preservatives) allowing accurate spectrophotometric analyses to be performed. In some applications, derivative spectrophotometry was advantageous over the conventional absorption mode with respect to higher selectivity and versatility.

Pharmaceutical Preparations↗

PubMed1994

HPLC determination of glutathione and L-cysteine in pharmaceuticals after derivatization with ethacrynic acid.

Ethacrynic acid and its methyl ester are proposed as useful pre-chromatographic derivatization reagents for the HPLC analysis (UV detection) of reduced glutathione (GSH) and L-cysteine. The optimum experimental conditions for the thiol derivatization, the removal of the excess reagent by liquid-liquid or solid-phase extraction and the reversed-phase chromatographic separations of the thiol adducts were investigated. The method was applied to the HPLC determination of GSH and L-cysteine in commercial formulations and proved to be suitable for the HPLC determination of oxidized glutathione (GSSG) after reduction to GSH using dithiothreitol (DTT).

Calibration↗