Voltammetric and Square-Wave Anodic Stripping Determination of Amlodipine Besylate on Gold Electrode

The oxidative behaviour of amlodipine besylate was studied. The gold electrode and Au/o-MWCNT (oxidized multi-wall carbon nanotubes) were used for determination of amlodipine besylate standard and as a content of Alopres tablet, in 0.05 M NaHCO3 and in phosphate buffer (pH=11) by cyclic voltammetry and square-wave anodic stripping voltammetry. Electrode surfaces were characterized by AFM in the presence of amlodipine and the concentrations of drugs in electrolytes were simultaneously followed by HPLC. The linear dependency of the anodic currents of amlodipine besylate as standard and in Alopres tablet vs. concentration was observed in both electrolytes, but in phosphate buffer for the higher concentrations. The peak currents obtained in all experiments are more than fifty-fold higher comparing to all previously published results concerning the glassy carbon electrode and the carbon paste electrode. The gold electrode is better catalyst for anodic oxidation of amlodipine besylate than glassy carbone. The results obtained with Au/o-MWCNT show lower anodic activity comparing to previously published GC/o-MWCNT. GC/o-MWCNT is better catalyst than Au/o-MWCNT under similar experimental conditions

The electrochemical investigation of inclusion complexes of nifedipine and amlodipine with ß-cyclodextrin and (2-hydroxypropyl)-ß-cyclodextrin

The electrochemical behavior of inclusion complexes of nifedipine (Nif) and amlodipine (Aml), a long-acting calcium channel blockers dihydropyridine (DHP) class, with ß-cyclodextrin (ßCD) and (2-hydroxypropyl)-ß-cyclodextrin (HPßCD), is examined using cyclic and square wave voltammetry in 0.05 M NaHCO3 and phosphate buffer (pH=11) on a gold electrode. The voltammograms show a single irreversible anodic wave with the current controlled by adsorption. It was found that phosphate buffer favorites the electrochemical activity of both complexes of Nif with the linear dependency of the oxidative currents on their concentrations. In phosphate buffer, only HPßCD-Aml complex showed linear dependency of the oxidative currents on the concentration. In 0.05 M NaHCO3 as electrolyte only HPßCD-Nif exhibited apparent activity. The initial potential of the anodic reaction as well as the value of the potential for anodic currents maximum of all the examined complexes in both electrolytes were shifted to the positive direction compared to their standards. In addition, the value of anodic currents decreased

Voltammetric and Square-Wave Anodic Stripping Determination of Amlodipine Besylate on Gold Electrode

The oxidative behaviour of amlodipine besylate was studied. The gold electrode and Au/o-MWCNT (oxidized multi-wall carbon nanotubes) were used for determination of amlodipine besylate standard and as a content of Alopres tablet, in 0.05 M NaHCO3 and in phosphate buffer (pH=11) by cyclic voltammetry and square-wave anodic stripping voltammetry. Electrode surfaces were characterized by AFM in the presence of amlodipine and the concentrations of drugs in electrolytes were simultaneously followed by HPLC. The linear dependency of the anodic currents of amlodipine besylate as standard and in Alopres tablet vs. concentration was observed in both electrolytes, but in phosphate buffer for the higher concentrations. The peak currents obtained in all experiments are more than fifty-fold higher comparing to all previously published results concerning the glassy carbon electrode and the carbon paste electrode. The gold electrode is better catalyst for anodic oxidation of amlodipine besylate than glassy carbone. The results obtained with Au/o-MWCNT show lower anodic activity comparing to previously published GC/o-MWCNT. GC/o-MWCNT is better catalyst than Au/o-MWCNT under similar experimental conditions

The Electrochemical Investigation of Inclusion Complexes of Nifedipine and Amlodipine with beta-Cyclodextrin and (2-Hydroxypropyl)-beta-Cyclodextrin

The electrochemical behavior of inclusion complexes of nifedipine (Nif) and amlodipine (Aml), a long-acting calcium channel blockers dihydropyridine (DHP) class, with beta-cyclodextrin (beta CD) and (2-hydroxypropyl)-beta-cyclodextrin (HP beta CD), is examined using cyclic and square wave voltammetry in 0.05 M NaHCO3 and phosphate buffer (pH=11) on a gold electrode. The voltammograms show a single irreversible anodic wave with the current controlled by adsorption. It was found that phosphate buffer favorites the electrochemical activity of both complexes of Nif with the linear dependency of the oxidative currents on their concentrations. In phosphate buffer, only HP beta CD-Aml complex showed linear dependency of the oxidative currents on the concentration. In 0.05 M NaHCO3 as electrolyte only HP beta CD-Nif exhibited apparent activity. The initial potential of the anodic reaction as well as the value of the potential for anodic currents maximum of all the examined complexes in both electrolytes were shifted to the positive direction compared to their standards. In addition, the value of anodic currents decreased

The electrochemical investigation of inclusion complexes of nifedipine and amlodipine with ß-cyclodextrin and (2-hydroxypropyl)-ß-cyclodextrin

The electrochemical behavior of inclusion complexes of nifedipine (Nif) and amlodipine (Aml), a long-acting calcium channel blockers dihydropyridine (DHP) class, with ß-cyclodextrin (ßCD) and (2-hydroxypropyl)-ß-cyclodextrin (HPßCD), is examined using cyclic and square wave voltammetry in 0.05 M NaHCO3 and phosphate buffer (pH=11) on a gold electrode. The voltammograms show a single irreversible anodic wave with the current controlled by adsorption. It was found that phosphate buffer favorites the electrochemical activity of both complexes of Nif with the linear dependency of the oxidative currents on their concentrations. In phosphate buffer, only HPßCD-Aml complex showed linear dependency of the oxidative currents on the concentration. In 0.05 M NaHCO3 as electrolyte only HPßCD-Nif exhibited apparent activity. The initial potential of the anodic reaction as well as the value of the potential for anodic currents maximum of all the examined complexes in both electrolytes were shifted to the positive direction compared to their standards. In addition, the value of anodic currents decreased

Determination of amlodipine and nifedipine by electrochemical and others analytical methods.

Predmet ove doktorske disertacije je ispitivanje elektrohemijske aktivnosti amlodipina i nifedipina odnosno proučavanje odabranih 1,4-dihidropiridinskih lekova koji se kao blokatori Ca2+-kanala koriste u terapiji kardiovaskularnih oboljenja. Ispitivano je elektrohemijsko ponašanje amlodipina i nifedipina u čistim (kao aktivni farmaceutski ingredienti) i različitim komercijalnim oblicima, kao i u kompleksima sa različitim ciklodekstrinima. Elektrohemijske reakcije su praćene pomoću različitih elektrohemijskih metoda (prvenstveno ciklične voltametrije i voltametrije sa pravougaonim impulsima) na elektrodi od zlata i na elektrodi od zlata modifikovanoj o-MWCNT. Za analizu elektrolita korišćene su druge analitičke metode (HPLC, LC-MS) radi potvrde podataka dobijenih elektrohemijskim ispitivanjima. Takođe je ispitivana stabilnost ovih preparata, koji su radi toga bili podvrgnuti kiseloj i alkalnoj hidrolizi, oksidaciji, fotolizi i degradaciji pri zagrevanju kao i elektrohemijskoj degradaciji. U tom cilju, radi proučavanja povećanja stabilnosti sintetizovani su i analizirani ciklodekstrinski kompleksi amlodipina i nifedipina. Naučni cilj ovog rada je da se ispitivanjem elektrohemijske aktivnosti i odgovarajućim transformacijama amlodipina i nifedipina razviju metode za njihovo kvalitativno i kvantitativno određivanje i da se analizom dobijenih smeša nakon određenih reakcija utvrdi priroda transformacija ispitivanih molekula. Rezultati koji su proistekli iz istraživanja ove doktorske disertacije treba da doprinesu razvoju novih elektrohemijskih metoda za kvalitativno i kvantitativno određivanje amlodipina i nifedipina. Proučavana je elektrohemijska aktivnost inkluzionih kompleksa amlodipina i nifedipina sa ciklodekstrinima i uticaj strukture dobijenih ciklodekstrinskih kompleksa na elektrohemijsko ponašanje, što je od izuzetnog značaja pri ispitivanju aktivnih farmaceutskih supstanci i farmaceutskih preparata.The subject of this PhD thesis is examination of electrochemical activity of amlodipine and nifedipine, a 1,4-dihydropyridine type of Ca2+ channel blockers used in treatment of cardiovascular diseases. It was investigated the electrochemical behavior of amlodipine and nifedipine as active pharmaceutical ingredients, in different commercial pharmaceutical dosage forms as well as in complexes with different cyclodextrins. Electrochemical reactions were followed by using of different electrochemical methods (primary cyclic voltammetry and square wave voltammetry) on gold electrode and Au/o-MWCNT. For analysis of the electrolytes other analytical methods (HPLC, LC-MS) were used in order to confirm the data obtained by electrochemical investigation. It was also investigated stability of these preparations which were therefore exposed to hydrolysis in acid and alkaline conditions, oxidation, photolysis, temperature degradation and electrochemical degradation. In order to study stability enhancement the appropriate cyclodextrin complexes of amlodipine and nifedipine were synthesized and analyzed. The scientific aim of this study was to test the electrochemical activity and by appropriate transformations to develop methods for qualitative and quantitative determination of amlodipine and nifedipine as well as by analysis of the obtained mixture after certain reactions to determine the nature of transformations of examined molecules. The results arising from the research of this PhD thesis should contribute to development of new electrochemical methods for qualitative and quantitative determination of amlodipine and nifedipine. The electrochemical activity of inclusion complexes of amlodipine and nifedipine with cyclodextrins and influence of the structure of the obtained complexes on electrochemical behavior were studied which is of great importance in the study of active pharmaceutical ingredients and pharmaceutical preparations

Determination of amlodipine and nifedipine by electrochemical and others analytical methods.

Predmet ove doktorske disertacije je ispitivanje elektrohemijske aktivnosti amlodipina i nifedipina odnosno proučavanje odabranih 1,4-dihidropiridinskih lekova koji se kao blokatori Ca2+-kanala koriste u terapiji kardiovaskularnih oboljenja. Ispitivano je elektrohemijsko ponašanje amlodipina i nifedipina u čistim (kao aktivni farmaceutski ingredienti) i različitim komercijalnim oblicima, kao i u kompleksima sa različitim ciklodekstrinima. Elektrohemijske reakcije su praćene pomoću različitih elektrohemijskih metoda (prvenstveno ciklične voltametrije i voltametrije sa pravougaonim impulsima) na elektrodi od zlata i na elektrodi od zlata modifikovanoj o-MWCNT. Za analizu elektrolita korišćene su druge analitičke metode (HPLC, LC-MS) radi potvrde podataka dobijenih elektrohemijskim ispitivanjima. Takođe je ispitivana stabilnost ovih preparata, koji su radi toga bili podvrgnuti kiseloj i alkalnoj hidrolizi, oksidaciji, fotolizi i degradaciji pri zagrevanju kao i elektrohemijskoj degradaciji. U tom cilju, radi proučavanja povećanja stabilnosti sintetizovani su i analizirani ciklodekstrinski kompleksi amlodipina i nifedipina. Naučni cilj ovog rada je da se ispitivanjem elektrohemijske aktivnosti i odgovarajućim transformacijama amlodipina i nifedipina razviju metode za njihovo kvalitativno i kvantitativno određivanje i da se analizom dobijenih smeša nakon određenih reakcija utvrdi priroda transformacija ispitivanih molekula. Rezultati koji su proistekli iz istraživanja ove doktorske disertacije treba da doprinesu razvoju novih elektrohemijskih metoda za kvalitativno i kvantitativno određivanje amlodipina i nifedipina. Proučavana je elektrohemijska aktivnost inkluzionih kompleksa amlodipina i nifedipina sa ciklodekstrinima i uticaj strukture dobijenih ciklodekstrinskih kompleksa na elektrohemijsko ponašanje, što je od izuzetnog značaja pri ispitivanju aktivnih farmaceutskih supstanci i farmaceutskih preparata.The subject of this PhD thesis is examination of electrochemical activity of amlodipine and nifedipine, a 1,4-dihydropyridine type of Ca2+ channel blockers used in treatment of cardiovascular diseases. It was investigated the electrochemical behavior of amlodipine and nifedipine as active pharmaceutical ingredients, in different commercial pharmaceutical dosage forms as well as in complexes with different cyclodextrins. Electrochemical reactions were followed by using of different electrochemical methods (primary cyclic voltammetry and square wave voltammetry) on gold electrode and Au/o-MWCNT. For analysis of the electrolytes other analytical methods (HPLC, LC-MS) were used in order to confirm the data obtained by electrochemical investigation. It was also investigated stability of these preparations which were therefore exposed to hydrolysis in acid and alkaline conditions, oxidation, photolysis, temperature degradation and electrochemical degradation. In order to study stability enhancement the appropriate cyclodextrin complexes of amlodipine and nifedipine were synthesized and analyzed. The scientific aim of this study was to test the electrochemical activity and by appropriate transformations to develop methods for qualitative and quantitative determination of amlodipine and nifedipine as well as by analysis of the obtained mixture after certain reactions to determine the nature of transformations of examined molecules. The results arising from the research of this PhD thesis should contribute to development of new electrochemical methods for qualitative and quantitative determination of amlodipine and nifedipine. The electrochemical activity of inclusion complexes of amlodipine and nifedipine with cyclodextrins and influence of the structure of the obtained complexes on electrochemical behavior were studied which is of great importance in the study of active pharmaceutical ingredients and pharmaceutical preparations

Examination of localization of silymarin and fatty oil in Silybum marianum (L.) Gaertn. fruit

Physical characteristics and localization of flavonoids and fatty oil in Silybum marianum (L.) Gaertn. fruit of different origin were examined. Physical characteristics of the fruit were determined by its origin, and samples cultivated on plantations were, concerning their colour, shine, shape and size, very similar to those they originated from. By examination of the fruit size, we wanted to give our contribution to the choice of adequate equipment for picking, cleaning and packing of the fruit. Using a suitable mechanical procedure, the separation of the fruit into its inner part (endosperm) and outer cover (testa) was carried out. The Soxhlet extraction was carried out using petroleum ether (40-70°C) and methanol, The silymarin content (calculated as silibinin) was spectrophotometrically determined in the whole fruit (1.94-2.45%) and its respective parts: endosperm (0.19-0.33%) and testa (4.75-6.01%). By evaporation of petroleum ether extracts under the lowered pressure we determined the oil content in the whole fruit (19.38-24.08%), endosperm (27.85-34.19%) and testa (2.45-4.34%). We also established that more than 94% of silymarin was located in the testa more than 88% of fatty oil was localized in the fruit endosperm. The obtained results indicated that it was better to use testa, than whole fruit, when extracting silymarin

Determination of total lipids and characterization of marigold flower extracts (Calendula officinalis)

Bioactive extracts from marigold flower are important ingredients for parapharmaceutical and cosmetic preparations. Their antiflogistic holeretic.antimicrobic, antidermatic and anticancer effects are due to the presence of flavonoids, carotenoids, etheric oils, and terpenoids. This study presents the results of spectrophotometric investigation for the overall carotene content calculated as (3-caroten (442 nm), visual and physico-chemical characteristics according to Ph.Jug. V in oil extracts of marigold flower obtained by maceration (room temperature and 70°C) and percolation (room temperature) with olive oil and sunflower oil by original procedures.The largest content of (3-carotene (57.5 mg/kg of oil extracts) is in the oil extract obtained by maceration for 72 hours with olive oil (solvomodulus 1:5 m/m) at room temperature

Examination of Localization of Silymarin and Fatty Oil in Silybum marianum (L.) Gaertn. Fruit

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