Natale Alfredo Santagati

Analysis of aliphatic amines in air samples by HPLC with electrochemical detection.

A method was developed for the analysis of primary aliphatic amines by high performance liquid chromatography coupled with electrochemical detector. The electrochemical oxidation of aliphatic amines derivatized with 2,5-dihydroxybenzaldehyde was investigated at porous graphite electrodes. The derivatization reactions were performed off-line, before the chromatographic separation. The compounds were separated on a reversed phase column with a methanol-acetonitrile-phosphate buffer and detected setting at an oxidation potential of +0.5 V. The influence of the mobile phase buffer concentration and pH on the detector response was also studied. The derivatization was shown to be quantitative and the response linear between 50 and 200 ng/ml. The method is sensitive, selective and could be applicable for the assay of volatile amines in the field of environmental toxicology and also for biological monitoring after occupational exposure.

Enantiomeric separation of amlodipine and its two chiral impurities by nano-liquid chromatography and capillary electrochromatography using a chiral stationary phase based on cellulose tris(4-chloro-3-methylphenylcarbamate).

In this work, a novel polysaccharide‐based chiral stationary phase, cellulose tris(4‐chloro‐3‐methylphenylcarbamate), also called Sepapak 4 has been evaluated for the chiral separation of amlodipine (AML) and its two impurities. AML is a powerful vasodilatator drug used for the treatment of hypertension. Capillary columns of 100 μm id packed with the chiral stationary phase were used for both nano‐LC and CEC experiments. The optimization of the mobile phase composed of ACN/water, (90:10, v/v) containing 15 mM ammonium borate pH 10.0 in nano‐LC allowed the chiral separation of AML and the two impurities, but not in a single run. With the purpose to obtain the separation of the three pairs of enantiomers simultaneously, CEC analyses were performed in the same conditions achieving better enantioresolution and higher separation efficiencies for each compound. To fully resolve the mixture of six enantiomers, parameters such as buffer pH and concentration sample injection have been then investigated. A mixture of ACN/water (90:10, v/v) containing 5 mM ammonium borate buffer pH 9.0 enabled the complete separation of the three couples of enantiomers in less than 30 min. The optimized CEC method was therefore validated and applied to the analysis of pharmaceutical formulation declared to contain only AML racemate.

Inclusion Complexation of 4-Biphenylacetic Acid with β-Cyclodextrin

AbstractThe preparation of an inclusion complex of 4-biphenylacetic acid (BPAA), a non-steroidal antiinflammatory drug, with β-cyclo-dextrin is described. The presumible structure of the inclusion system, the molar ratio, which was found 1:1, and the formation constant were calculated by the analysis of IR, UV, DSC, X-ray diffraction, and 1H-NMR. Dissolution rate and solubility were also studied. BPAA solubility in water resulted significantly (4,2-fold) increased by complexation, such as its dissolution rate which appears, in the first 12 min, 18 times greater for the complex than the drug alone.

Simultaneous determination of amphetamine and one of its metabolites by HPLC with electrochemical detection

A high-performance liquid chromatographic method coupled with electrochemical detector was developed for the separation and quantitation of amphetamine and one of its metabolites, the 4-hydroxynorephedrine. The pre-column derivatisation of these compounds was carried out with 2,5-dihydroxybenzaldehyde as electroactive labelling reagent, in presence of Borohydride Exchange Resin. The new synthetic method developed was fast, clean and high yielding. The analysis was performed in isocratic mode on a reversed phase column 5 microm Hypersil ODS RP-18, 15 cm, using as a mobile phase methanol-NaH(2)PO(4) buffer (50 mM, pH 5.5)(30:70 v/v) containing trietylamine (0.5% v/v) and the products were detected by a porous graphite electrode set at an oxidation potential of +0.6 V. The linearity of response was examined for each derivatised compound and was analysed using solutions in the range 10-40 nmol/ml. The correlation coefficients of the linear regression of the standard curves were greater than 0.99. The method developed in this study was sensitive and very selective. Because of the specificity for primary phenylethylamines, it could be applicable for the assay of other related substances in toxicology and drugs abuse.

4-Quinazolinones: synthesis and reduction of prostaglandin E2 production

We synthesized and evaluated the anti-inflammatory activity of a series of 4-quinazolinone derivatives. Two approaches were used to yield the title compounds. A first group of quinazolinone derivatives was obtained by the appropriate substituted anthranilates. A second group of quinazolinone compounds was prepared through the benzoxazin-4-ones intermediate. The pharmacological results reveal that the synthesized derivatives exhibit a significant anti-inflammatory effect in an experimental ocular inflammation model. In fact, all the tested compounds lowered the prostaglandin E2 (PGE2) production with respect to the control group (P < 0.05). The 3-cyclohexyl-6-chloro-quinazolin-4(3H)-one and 3-cyclohexyl-quinazolin-4(3H)-one derivatives were the most active compounds. These compounds significantly reduced PGE2 levels even more than the reference drug tolmetin and significantly lower protein concentration and polymorphonuclear leukocytes number compared to the control group (P < 0.05). Therefore, these compounds may be useful to prevent ocular inflammatory reactions.

Enhancement of 4-biphenylacetic acid bioavailability in rats by its β-cyclodextrin complex after oral administration

Abstract— 4‐Biphenylacetic acid, a potent non‐steroidal antiinflammatory agent forms a solid inclusion complex with β‐cyclodextrin in a 1:1 molar ratio, which exhibits better solubility and dissolution characteristics than the uncomplexed drug. Following oral administration of the complex to rats, quicker and higher drug plasma concentrations can be achieved than with the drug alone. Parallel studies, using the carrageenan paw oedema test, demonstrate a greater anti‐inflammatory activity of the complex (ED50 of 2·9 mg kg−1 for the complex and of 6·2 mg kg−1 for the free drug). The complex displayed a better gastric tolerability in the rat than drug alone.

Synthesis and spasmolytic action of 2-substituted thienopyrimidin-4-one derivatives.

In the search for novel compounds to treat disorders of smooth muscle function, efforts have focused on some 2‐substituted thieno[2,3‐d]pyrimidin‐4‐onederivatives that show interesting spasmolytic action. Our laboratories have developed a new series of quaternary salts of 2‐substituted thieno[2,3‐d]pyrimidin‐4‐one and thieno[3,2‐d]pyrimidin‐4‐oneisomers with therapeutic potential. These substances were prepared starting from simple derivatives of thiophene. Their spasmolytic activity was evaluated on transmurally stimulated guinea‐pig ileum. The most active compounds (IC50 1.12‐2.71 μM) 7f‐7h, 12d and 12f had the terminal piperidino nucleus in the thioalkyl chain and lacked two methyl groups in the thiophene ring. Their relaxant activity on the isolated ileum was potentiated (approx. 20–25%) by phosphodiesterase inhibitors. Compounds 7f‐h, 12d and 12f were less effective in inhibiting contractions of the guinea‐pig ileum induced by acetylcholine (IC50 26.7–41.4 μM) or histamine (IC5041.5–63.4 μM) and had a moderate binding activity to muscarinic receptors in membrane homogenates from the rat heart (M2 sites; pKi values between 5.55 ± 0.08 and 5.14 ± 0.12; n = 3) and submaxillary gland (M3 sites; pKi values between 6.15 ± 0.07 and 5.76 ± 0.08; n = 3). Action involving soluble guanylyl cyclase or any potential binding to guinea‐pig ventricular L‐type calcium channels was not considered likely. It is concluded that at least two different mechanisms of action contribute to their spasmolytic activity.

Ketoprofen 1-Alkylazacycloalkan-2-one Esters as Dermal Prodrugs: In Vivo and In Vitro Evaluations

Abstract Six new 1-alkylazacycloalkan-2-one esters of ketoprofen (1–6) were synthesized and evaluated as potential dermal prodrugs of ketoprofen. Their lipophilicity by both experimental lipophilicity indices (log k′) and calculated ClogP was also determined. In vitro experiments were carried out to evaluate the chemical and enzymatic stability and permeation through excised human skin of these new ketoprofen derivatives. Furthermore, we investigated the in vivo topical anti-inflammatory activity of ester 5, which showed the best in vitro profile, evaluating the ability of this compound to inhibit methyl nicotinate-induced skin erythema on healthy human volunteers. Esters 1–6 showed increased lipophilicity compared with the parent drug (ketoprofen), good stability in phosphate buffer pH 7.4, and were readily hydrolyzed by porcine esterase. Results from in vitro percutaneous absorption studies showed that, among all esters synthesized, only for esters 1 and 5 did a higher cumulative amount of drug penetrate through the skin, compared with that obtained after topical application of ketoprofen. In vivo results showed an interesting delayed and sustained activity of ester 5, compared with the parent drugs.

Determination of undecylenic and sorbic acids in cosmetic preparations by high performance liquid chromatography with electrochemical detection.

A highly sensitive and selective method for the determination of sorbic (SA) and undecylenic acid (UA) in cosmetic formulations by a high performance liquid chromatography method with electrochemical detection (ECD) is described. The pre-column derivatizations of SA and UA and the internal standard (cyclohexanoic acid (cHA)) were carried out using 1-(2,5-dihydroxyphenyl)-2-bromoethanone (2,5-DBE) as an electroactive labeling reagent previously synthesized in our lab. The resulting electroactive esters were separated by isocratic elution of a 5 micrometer Hypersil CN column with acetonitrile-acetate buffer eluent. The compounds were detected by a porous graphite electrode set at an oxidation potential of +0.45 V. The analytical method developed in this study is suitable for quality control assays of complex cosmetic formulations containing sorbic and/or UA.

Preparation and Biological Evaluation of Ethylcellulose Microspheres Containing Tolmetin

AbstractTolmetin microspheres were prepared by the coacervation process from the ethylcellulose. Microspheres were obtained both in presence and without protecting colloids, such as polyisobutilene (PIB) or ethyl-vinylacetate copolimers (EVA). The effect of these agents on the preparation, drug content, wall thickness, surface morphology, drug dissolution arid release from microspheres, were evaluated. The dissolution rate analysis was carried out also in the presence of a surfactant (Tween 80) at different pH values.In addition, microspheres containing Tolmetin as a core material were submitted to biological tests, in comparison with the free drug, to evaluate upon experimental models the antipyretic activity and the gastric tolerability.