Prenylated Flavanone Isolated from Dalea Species as a Potential Multitarget-Neuroprotector in an In Vitro Alzheimer's Disease Mice Model.

Alzheimer's disease (AD) involves a neurodegenerative process that has not yet been prevented, reversed, or stopped. Continuing with the search for natural pharmacological treatments, flavonoids are a family of compounds with proven neuroprotective effects and multi-targeting behavior. The American genus Dalea L. (Fabaceae) is an important source of bioactive flavonoids. In this opportunity, we tested the neuroprotective potential of three prenylated flavanones isolated from Dalea species in a new in vitro pre-clinical AD model previously developed by us. Our approach consisted in exposing neural cells to conditioned media (3xTg-AD ACM) from neurotoxic astrocytes derived from hippocampi and cortices of old 3xTg-AD mice, mimicking a local neurodegenerative microenvironment. Flavanone 1 and 3 showed a neuroprotective effect against 3xTg-AD ACM, being 1 more active than 3. The structural requirements to afford neuroprotective activity in this model are a 5'-dimethylallyl and 4'-hydroxy at the B ring. In order to search the mechanistic performance of the most active flavanone, we focus on the flavonoid-mediated regulation of GSK-3ß-mediated tau phosphorylation previously reported. Flavanone 1 treatment decreased the rise of hyperphosphorylated tau protein neuronal levels induced after 3xTg-AD ACM exposure and inhibited the activity of GSK-3ß. Finally, direct exposure of these neurotoxic 3xTg-AD astrocytes to flavanone 1 resulted in toxicity to these cells and reduced the neurotoxicity of 3xTg-AD ACM as well. Our results allow us to present compound 1 as a natural prenylated flavanone that could be used as a precursor to development and design of future drug therapies for AD.

Synthesis of a [18F]F Estradiol Derivative via Click Chemistry Using an Automated Synthesis Module: In Vitro Evaluation as Potential Radiopharmaceutical for Breast Cancer Imaging.

"Click reactions" are a very useful tool for the selective conjugation of different molecular subunits to produce complex structures in a simple way. In this paper, we present the application of Cu(I)-catalyzed biorthogonal reactions between alkynes and azides to the indirect radiofluorination of an estradiol derivative with potential applications in estrogen receptor imaging. The procedure was fully developed on an automated synthesis platform, and conditions were optimized to achieve the desired product with a reasonable yield without precipitation. Although the biological results were not adequate for a potential radiopharmaceutical, the outcome of this work is valuable since the use of automated platforms is required for the reliable and reproducible preparation of PET radiopharmaceuticals in GMP conditions while limiting the radiation dose rates to the personnel.

Development and Evaluation of 99mTc Tricarbonyl Complexes Derived from Flutamide with Affinity for Androgen Receptor.

With the objective to develop a potential 99mTc radiopharmaceutical for imaging the androgen receptor (AR) in prostate cancer, four ligands bearing the same pharmacophore derived from the AR antagonist flutamide were prepared, labeled with 99mTc, and their structures corroborated via comparison with the corresponding stable rhenium analogs. All complexes were obtained with high radiochemical purity. Three of the complexes were highly stable, and, due to their favorable physicochemical properties, were further evaluated using AR-positive and AR-negative cells in culture. All complexes exhibited considerable uptake in AR-positive cells, which could be blocked by an excess of flutamide. The efflux from the cells was moderate. They also showed significantly lower uptakes in AR-negative cells, indicating interactions with the AR receptor. However, the binding affinities were considerably reduced by the coordination to 99mTc, and the complex that exhibited the best biological behavior did not show sufficient specificity towards AR-positive cells.

Radiosynthesis and validation of [18 F]fluoroestradiol in a Synthra plus research platform for use in routine clinical practice.

In this practitioner protocol, the optimization of the radiochemical synthesis of [18 F]fluoroestradiol (FES) on the Synthra RNplus research automated platform is described in detail and a quality control (QC) summary of three validation productions is presented. In comparison with published synthesis methods developed on other platforms, the yield was considerably improved (40%-45% ndc). The other important improvement is the reduction of the required concentration of H2 SO4 avoiding the production of high concentrations of acidic vapors that can deteriorate the module. Purification was achieved by solid phase extraction, and the required adaptation of an external heating plate to the module to evaporate the ethanol is also described. The product was obtained with high radiochemical purity and fulfilled all the requirements of current Good Manufacturing Practice (cGMP). The final product is formulated as a sterile, pyrogen-free solution suitable for human injection. To the best of our knowledge, this is the first report of FES production using this type of module.

Glycogen Synthase Kinase-3 Maleimide Inhibitors As Potential PET-Tracers for Imaging Alzheimer's Disease: 11C-Synthesis and In Vivo Proof of Concept.

Herein we present the evaluation of 11C-labeled-maleimides as radiotracers for positron emission tomography imaging of GSK-3 associated with Alzheimer's disease (AD). 3-Acetyl-4-(1-[11C]-methyl-1H-indol-3-yl)[1H]pyrrole-2,5-dione ([11C]-2) was obtained by direct methylation using [11C]-CH3I and Cs2CO3 in DMF with a 31 ± 4% radiochemical yield and a radiochemical purity of 97.7 ± 0.8%. [11C]-2 was stable both in its final formulation and in human plasma for 120 min and had a plasma protein binding of 70 ± 1% and a LogD7.4 value of 1.84 ± 0.04. [11C]-2 ex vivo biodistributions in healthy animals demonstrated significant brain uptake and retention, showing its ability to penetrate the intact blood-brain barrier. In vivo PET imaging in mice bearing AD showed, with respect to normal animals, significant differences in uptake in the hypothalamus, the striatum, and the amygdala and a significant increase in amygdala uptake in later stages of the pathology. These results are very promising, and further studies are being performed for a complete validation of this compound as novel tracer for AD.

Development and evaluation of a 99mTc(V)-nitrido complex derived from estradiol for breast cancer imaging.

Estrogen receptors are overexpressed in 70% of breast cancer and identification of their presence is important to select the appropriate treatment. This work proposes the preparation and evaluation of an estradiol derived as potential ER imaging agent. Ethinylestradiol was derivatized to introduce a dithiocarbamate function for Tc coordination. Labeling was achieved through the formation of a symmetric Tc(V)-nitrido complex with a radiochemical purity (RCP) > 95%. Physicochemical evaluation, cell uptake, biodistribution in normal animals and in nude mice bearing induced ER + breast tumors showed promising results.

Synthesis of an Al18F radiofluorinated GLU-UREA-LYS(AHX)-HBED-CC PSMA ligand in an automated synthesis platform.

BACKGROUND: Overexpression of prostatic membrane antigen (PSMA) is associated with the progression and prognosis of prostate cancer. There are numerous studies using this peptide with the 68Ga radionuclide. Previous methods to synthetize 18F-labeled PSMA ligands with complexes [18F]AlF2+ have been achieved. However, these reported syntheses were performed manually, using small volumes. Therefore it is only possible to have the radiopharmaceutical on a small scale, for use in preclinical studies. 18F-labelled tracers allow higher doses increasing the number of examined patients. In addition, late images can be acquired in the case of uptake in lymph nodes, to discard inflammation. It is important to transfer the manual synthesis to an automatic module, producing a batch of the radiopharmaceutical with high activity in a safe and effective way. The aim of this work was to optimize the labeling of [18F]AlF-[GLU-UREA-LYS(AHX)-HBED-CC] in a Tracerlab FXFN® (GE) platform. RESULTS: The labeling up to the reactor corroborates the formation of the complex [18F]AlF-PSMA. After purification by HPLC, the radiopharmaceutical was achieved with a radiochemical purity higher than 90%. The quality control of the final product fulfilled all the requirements in agreement with USP, such as radiochemical purity (greater than 90%) and residual solvents. [18F]AlF-PSMA was obtained with a yield of 18 ± 3% (n = 7), not decay corrected (NCD) starting off from 500 to 2000 mCi the 18F and with a radiochemical purity of 95 ± 3% (n = 7). The product verified stability in the final formulation vial during 4 hs and in human plasma up to 1 h. CONCLUSION: The proposed method allowed the production of [18F]AlF-PSMA with suitable radiochemical purity in a commercial platform. High activities were achieved, with a simple and robust methodology appropriate for clinical purposes.

3-(Benzyloxy)-1-(5-[18F]fluoropentyl)-5-nitro-1H-indazole: a PET radiotracer to measure acetylcholinesterase in brain.

AIM: Noninvasive studies of the acetylcholinesterase (AChE) level in Alzheimer's disease (AD) patients can contribute to a better understanding of the disease and its therapeutic. We propose 3-(benzyloxy)-1-(5-[18F]fluoropentyl)-5-nitro-1H-indazole, [18F]-IND1, structurally related to the AChE-inhibitor CP126,998, as a new positron emission tomography-radiotracer. EXPERIMENTAL: Radiosynthesis, with 18F, stability, lipophilicity and protein binding of [18F]-IND1 were studied. In vivo behavior, in normal mice and on AD mice models, were also analyzed. RESULTS: [18F]-IND1 was obtained in good radiochemical yield, was stable for at least 2 h in different conditions, and had adequate lipophilicity for blood-brain barrier penetration. Biodistribution studies, in normal mice, showed that [18F]-IND1 was retained in the brain after 1 h. In vivo tacrine-blocking experiments indicated this uptake could be specifically due to AChE interaction. Studies in transgenic AD mice showed differential, compared with normal mice, binding in many brain regions. CONCLUSION: [18F]-IND1 can be used to detect AChE changes in AD patients.

Development and characterization of a 99m Tc-tricarbonyl-labelled estradiol derivative obtained by "Click Chemistry" with potential application in estrogen receptors imaging.

Assessment of the presence of estrogen receptors in breast cancer is crucial for treatment planning. With the objective to develop a potential agent for estrogen receptors imaging, we present the development and characterization of a 99m Tc-tricarbonyl-labelled estradiol derivative. Using ethinylestradiol as starting material, an estradiol derivative bearing a 1,4-disubstituted 1,2,3-triazole-containing tridentate ligand system was synthesized by "Click Chemistry" and fully characterized. Labelling with high yield and radiochemical purity was achieved through the formation of a 99m Tc-tricarbonyl complex. The radiolabelled compound was stable, exhibited moderate binding to plasma protein (approximately 33%) and lipophilicity in the adequate range (logP 1.3 ± 0.1 at pH 7.4). Studies in MCF7 showed promising uptake values (approximately 2%). However, more than 50% of the activity is quickly released from the cell. Biodistribution experiments in normal rats confirmed the expected "in vivo" stability of the radiotracer but showed very high gastrointestinal and liver activity, which is inconvenient for in vivo applications. Taking into consideration the well-documented influence of the chelating system in the physicochemical and biological behaviour of technetium-labelled small biomolecules, research will be continued using the same pharmacophore but different complexation modalities of technetium.

Design and development of (99m)tc-'4+1'-labeled dextran-mannose derivatives as potential radiopharmaceuticals for sentinel lymph node detection.

The synthesis, labeling, and biological evaluation of a dextran derivative (DCM-30-iso) as potential radiopharmaceutical for sentinel lymph node imaging is presented. DCM-30-iso bears mannose as active moiety and isocyanide as ligand for technetium through the formation of a '4+1' Tc(III) mixed-ligand complex. A second derivative without mannose (DC-25-iso) was also prepared and evaluated as control. DCM-30-iso and DC-25-iso were synthesized from dextran in four steps (>50% overall yield) and characterized by spectroscopic methods. Labeling with (99m)Tc was achieved by reaction with 2,2',2''-nitrilotris(ethanethiol) and (99m)Tc-EDTA. Radiochemical purity was above 90% and was stable for at least 4 hours postlabeling at 37°C. The identity of the (99m)Tc complex was established through comparative HPLC studies using the well-characterized analogous Re-DC-25-iso complex. Biodistribution and imaging experiments of (99m)Tc-DCM-30-iso showed high uptake in the popliteal lymph node, which could be blocked with preinjection of mannose, and very low uptake in other nodes and organs. The nonmannosylated (99m)Tc-DC-25-iso derivative showed negligible uptake in all lymph nodes. The novel dextran-mannose derivative DCM-30-iso can be successfully labeled with (99m)Tc to give a well-characterized '4+1' complex with favorable biological properties as sentinel lymph node imaging agent.

Synthesis, in vitro and in vivo characterization of two novel 68Ga-labelled 5-nitroimidazole derivatives as potential agents for imaging hypoxia.

INTRODUCTION: Hypoxia imaging is an important field in radiopharmaceutical research since hypoxic cells are very resistant to radiation treatment and diffusional limitations restrict the efficacy of chemotherapy. Gallium-68 is a widely used radionuclide for positron emission tomography (PET) due to the availability of the (68)Ge/(68)Ga-generator. With the aim to develop new potential [(68)Ga]-radiopharmaceuticals for imaging hypoxia, we have synthesized and evaluated two novel (68)Ga-labelled 5-nitroimidazole derivatives. METHODS: Two 5-nitroimidazole derivatives, and were synthesized. Preparation of [(68)Ga]complexes [(68)Ga]-Nit1 and [(68)Ga]-Nit2 was performed at pH 4.5 and 95 °C during 15 minutes and radiochemical purity (RP) was evaluated by reverse phase HPLC. Stability, lipophilicity and plasma protein binding were studied. Biological behaviour in HCT-15 cells both in normoxia and hypoxia has been assessed. Biodistribution in animals bearing induced 3LL Lewis murine lung carcinoma was studied. Comparison with [(18)F]FMISO is also presented. RESULTS: Nit1 and Nit2 have been successfully synthesized. Labelling in high radiochemical purity was achieved for both ligands. Complexes are stable in labelling milieu for at least four hours and in human plasma or in the presence of an excess of DTPA for at least two hours. Both compounds showed high uptake in hypoxic cells in vitro and a very favourable biodistribution profile in mice bearing induced tumours. Results are comparable to those obtained for [(18)F]FMISO. CONCLUSIONS: Selective uptake and retention in tumour together with favourable tumour/muscle ratio make these compounds promising candidates for further evaluation as potential hypoxia imaging agents.

Influence of ligand denticity on the properties of novel 99mTc(I)-carbonyl complexes. Application to the development of radiopharmaceuticals for imaging hypoxic tissue.

An important issue in the development of metal-based radiopharmaceuticals is the selection of the labelling strategy in order to couple the metal to the pharmacophore without losing the biological activity. With the aim to evaluate the correlation between ligand denticity and biological behaviour of the corresponding (99m)Tc complexes, we designed a tridentate and a bidentate 5-nitroimidazole derivatives suitable for (99m)Tc(I) tricarbonyl complexation and with potential use as radiopharmaceuticals towards hypoxic tissue diagnosis. Ligands were synthesized using metronidazol, a pharmaceutical containing the bioreductive pharmacophore as starting material. The chelating units were connected to the pharmacophore using the click reaction of Huisgen. Both (99m)Tc complexes were obtained in high yield and were hydrophilic and stable in labelling milieu. The complex obtained from the tridentate ligand exhibited high stability in human plasma, low protein binding and a favourable biodistribution characterized by low blood and liver uptake, fast elimination and negligible uptake in other organs or tissues. Selective uptake and retention in tumour together with favourable tumour/muscle ratio makes this (99m)Tc-complex a promising candidate for further evaluation as potential hypoxia imaging agent in tumours. The bidentate ligand, on the other hand, yielded a less stable (99m)Tc-complex that experimented hydrolysis in vitro and decomposition in human plasma and showed high protein binding, high blood and liver uptake and moderate excretion. Although selective uptake and retention in tumour was also observed physicochemical and biological behaviour are inadequate for in vivo use, demonstrating that denticity of the ligand is particularly important and that tridentate ligands are preferable in order to prepare (99m)Tc-tricarbonyl complexes for Nuclear Medicine imaging.

Synthesis, in vitro and in vivo characterization of novel 99mTc-'4+1'-labeled 5-nitroimidazole derivatives as potential agents for imaging hypoxia.

UNLABELLED: The evaluation of oxygenation status of solid tumors is an important field of radiopharmaceutical research. With the aim to develop new potential 99mTc-radiopharmaceuticals for imaging hypoxia, we have synthesized two novel isocyanide derivatives of metronidazole, which has demonstrated high affinity for hypoxic tumors in vitro and in vivo. METHODS: Metronidazole derivatives 4-isocyano-N-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]butanamide (M1) and 1-(4-isocyanobutanoyl)-4-[2-(2-methyl-5-nitro-1H-imidazol-1-yl)ethyl]piperazine (M2) were synthesized, and labeling was performed through preparation of their corresponding 99mTc-(4+1) complexes, 99mTc-NS3M1 and 99mTc-NS3M2. The structure of the technetium complexes was corroborated by preparation and characterization of the corresponding rhenium complexes. We have studied the main physicochemical properties (stability, lipophilicity and plasma protein binding). Biological behavior in HCT-15 cells both in oxia and in hypoxia was assessed. Biodistribution in normal mice and in animals bearing induced 3LL Lewis murine lung carcinoma was also studied. RESULTS: Metronidazole derivatives were successfully synthesized. Labeling with high radiochemical purity was achieved for both ligands. 99mTc complexes were stable in labeling milieu and human plasma. However, presence of the piperazine linker in M2 resulted in higher lipophilicity and protein binding. Although cell uptake in hypoxic conditions was observed for both radiotracers, 99mTc-NS3M2 biodistribution was considered unsuitable for a potential radiopharmaceutical due to high liver uptake and poor blood clearance. However, 99mTc-NS3M1 demonstrated a very favorable in vivo profile both in normal mice and in mice bearing induced tumors. CONCLUSION: Selective uptake and retention in tumor together with favorable tumor/muscle ratio make 99mTc-NS3M1 a promising candidate for further evaluation as potential hypoxia imaging agent in tumors.

Evaluación biológica de 99mTc-voriconazol como potencial agente de diagnóstico de infecciones fúngicas por centellografía gamma / Biological evaluation of voriconazole with 99mTc for the diagnosis of fungal infections

El avance del HIV ha favorecido el aumento de infecciones fúngicas como candidiasis y aspergilosis invasivas. Varias clases de antifúngicos son utilizados para el tratamiento de las mismas y éstos pueden ser radiomarcados con un agente emisor gamma que permita la detección mediante centellografia de focos de infección. El Voriconazol es un triazol adecuado para la marcación mediante la formación de un complejo unido al precursor [99mTc(H2O)3(CO)3]+. El objetivo fue marcar y determinar las características fisicoquímicas y biológicas del voriconazol con 99mTc para la detección temprana de infecciones. La pureza radioquímica se determinó por HPLC y permitió establecer que el complejo permanece estable durante al menos 120 min. Los estudios in vivo en modelos de inflamación estéril, infección con C. Albicans y A. Niger mostraron diferenciación de los procesos tanto en biodistribución como en imágenes centellográficas.

The spread of HIV has led to an increase of fungal infections such as candidiasis and invasive aspergillosis. Several types of antifungals are used to treat them and some of them can be radiolabeled with a gamma emitting agent to allow detection by scintigraphy of foci of infection. Voriconazole is a triazole agent, suitable for the synthesis of a complex linked with the precursor [99mTc(H2O)3(CO)3]+. The aim of his work was to label and determine the physicochemical and biological characteristics of voriconazole with 99mTc for the early detection of fungal infections. Radiochemical purity was determined by HPLC and the complex remained stable during at least 120 min. In vivo studies in rats bearing either sterile inflammation, infection with C. Albicans or A. Niger showed differentiation of the processes not only in biosdistribution but also in scintigraphic images.

Marcación de un derivado de glucosa con 99mTc mediante la formación de un complejo Tc(V)-nitruro: estudios preliminares / Labelling of a glucose derivative with 99mTc through the formation of a Tc(V)-nitride symmetrical complex: preliminary studies

La preparación de derivados de glucosa marcados con 99mTc reviste gran interés para la evaluación del consumo de glucosa in vivo en oncología y cardiología nuclear. Este trabajo presenta la marcación de un análogo de glucosa (GLU-DTC) mediante la formación de un complejo Tc(V)-nitruro simétrico. Para ello se incorporó a la biomolécula un grupo ditiocarbamato capaz de coordinar al metal. La marcación fue realizada mediante sustitución de ligandos, obteniéndose una única especie con pureza radioquímica superior al 90 por cientp, la que se mantuvo durante al menos 4 hs. La caracterización fisicoquímica y biológica muestra que el complejo 99mTc(V)-nitruro(GLU-DTC)2 es un compuesto estable y altamente hidrofílico, aunque su unión a proteínas plasmáticas es mayor a la esperada, hecho que justificaría la alta actividad retenida en sangre y en hígado durante la evaluación biológica en ratones CD1 normales. Estos resultados indican que la marcación con 99mTc de este derivado de glucosa produce una alteración significativa de su comportamiento biológico.

The preparation of 99mTc-labeled glucose derivatives is of great interest to evaluate the in vivo glucose uptake in nuclear oncology and cardiology. This paper presents the labelling of a glucose analogue (GLU-DTC) through the formation of a Tc(V)-nitride symmetrical complex. For this purpose, a dithiocarbamate group was incorporated to the biomolecule, in order to coordinate the metal. The labelling reaction was carried out by substitution yielding a single complex with radiochemical purity above 90 percent. This complex was stable for at least 4 hours. The physicochemical and biological characterization shows that the 99mTc(V)-nitride(GLU-DTC)2 complex is a stable and highly hydrophilic compound, although its plasma protein binding is greater than expected, a fact which justifies the high activity retained in blood and liver during the biological evaluation in normal CD1 mice. These results indicate that 99mTc labelling of this glucose derivate alters significantly its biological behaviour.

Synthesis and biological characterisation of novel dithiocarbamate containing 5-nitroimidazole (99m)Tc-complexes as potential agents for targeting hypoxia.

With the aim to develop new potential (99m)Tc-radiopharmaceuticals for imaging hypoxia based on the formation of Tc-nitrido complexes, two novel dithiocarbamate containing metronidazole derivatives (L1 and L2) have been prepared and characterised. The synthesis of L1 and L2 was achieved in excellent yield and high purity. Labelling with (99m)Tc was successfully performed using a low ligand concentration (approximately 2-3mg) and the desired products were obtained with high radiochemical purity (>90%). Lipophilicity, plasma protein binding, and biodistribution in normal- and tumour-bearing-CD1 mice studies were performed to asses the potentiality for nuclear medicine oncology. According to the physicochemical and biological behaviour both in healthy animals and in animals bearing solid tumours complex dtcTc1 could be considered as a starting point for the development of new radiopharmaceuticals for imaging hypoxia.

Preparation and characterization of technetium and rhenium tricarbonyl complexes bearing the 4-nitrobenzyl moiety as potential bioreductive diagnostic radiopharmaceuticals. In vitro and in vivo studies.

The synthesis of a ligand containing a nitrobenzyl group as bioreductive pharmacophore and the preparation of the corresponding technetium and rhenium complexes are presented. (99m)Tc labelling was performed in high yield (>90%) by ligand substitution using fac-[(99m)Tc(CO)(3)(H(2)O)(3)](+) as precursor. The structure of the technetium complex was established by chromatographic comparison with the analogous rhenium compound which was fully characterized by elemental analysis, spectroscopic methods and X-ray crystallography. Reduction potential of the rhenium complex was in the characteristic range for bioreductive compounds. Biodistribution in normal mice was characterized by fast blood and soft tissue depuration and combined excretion via the hepatobiliary and urinary systems. Tumour uptake was low, probably due to low lipophilicity but tumour/muscle ratios were favourable as a consequence of high excretion.

Synthesis and characterization of thiol containing furoxan derivatives as coligands for the preparation of potential bioreductive radiopharmaceuticals.

The synthesis and characterization of thiol-containing 1,2,5-oxadiazole N-oxide (TONO) derivatives and their use as monodentate coligands for the preparation of (99m)Tc complexes is presented. 3-Mercaptomethyl-4-phenyl-1,2,5-oxadiazol N(2)-oxide and 3-(4-mercaptophenylmethylidenhydrazinocarbonyloxymethyl)-4-phenyl-1,2,5-oxadiazol N(2)-oxide were successfully synthesized and combined with the tridentate ligand N,N-bis(2-mercaptoethyl)-N',N'-diethylethylenediamine (BMEDA) to prepare "3+1 mixed ligand" technetium complexes. The( 99m)Tc complexes were obtained in high yield and radiochemical purity using low concentration of ligand and coligand. An alternative procedure using a xantate and a disulphide precursor of 3-mercaptomethyl-4-phenyl-1,2,5-oxadiazol N(2)-oxide yielded the same complex. Biological evaluation of the potentiality of the( 99m)Tc complexes as bioreductive radiopharmaceuticals was performed in normal CD1 mice and in mice bearing induced sarcoma. Tumour uptake was moderate but tumour/soft tissue ratio was favourable. Although these results are encouraging, further development is still necessary in order to achieve higher tumour uptake and lower gastrointestinal activity.

Flow-injection determination of phenylephrine hydrochloride in pharmaceutical dosage forms with on-line solid-phase extraction and spectrophotometric detection.

A flow injection method is proposed for the determination of phenylephrine hydrochloride in pharmaceutical dosage forms. The method involves the use of on-line solid-phase extraction by means of a microcolumn containing Dowex 50W X8 ion-exchange resin for the separation of the analyte prior to colour development and spectrophotometric detection in the visible region. The influence of preconcentration flow, preconcentration pH and elution volume was studied. The method exhibits appropriate linearity (r(2) = 0.9999) which was proved statistically by means of the "F"-test. When applied to commercial samples containing several active ingredients and excipients, a significant reduction of interferences was found. Accuracy, evaluated by means of the spike recovery method was in the range 99.7-100.8%, with precision (R.S.D., %) better than 1%. In order to achieve the automation the system was controlled from a notebook computer by means of a program written in QuickBASIC language. Under these conditions, a sampling frequency of 40 samples per hour could be attained.

Flow-injection spectrophotometric determination of paracetamol in tablets and oral solutions.

A flow injection method is proposed for the determination of paracetamol in pharmaceutical dosage forms. The method is based on the nitration of paracetamol with sodium nitrite, and the absorption of the reaction product is measured at 430 nm in alkaline medium. Unlike other colorimetric methods used for determination of paracetamol, this method does not require the use of heat. The influence of several operating parameters is studied. The method was applied to the determination of paracetamol in oral solutions and in tablets, alone or associated with caffeine. When the results were compared with those obtained by the official HPLC method (USP 24) the relative differences found were from 0.4 to 2.3%, with relative standard deviations below 1%.