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Parasitic diseases are still responsible for many health problems. Among them, African trypanosomiasis or sleeping sickness caused by Trypanosoma brucei, malaria transmitted by Plasmodium species of which the most dangerous is Plasmodium falciparum and leishmaniasis. Plant biodiversity and knowledge of traditional healing allow, as it was the case for artemisinin, to open new ways in the field of therapeutic. In this work, we analyzed the activity of several plants from Benin selected by ethnobotanical and bibliographical studies. These plants are used in traditional medicine as antimalarials. Crude extracts from powders of leaves, twigs, roots or aerial parts were prepared by maceration. These extracts were studied for their antiparasitic activities by in vitro tests on Plasmodium falciparum, Trypanosoma brucei brucei and Leishmania mexicana mexicana. In addition, cytotoxicities were analysed to determine the selectivity of crude extracts. The dichloromethane extracts of Keetia leucantha were selected and known antiparasitc compounds were identified and quantified by LC-MS. As they could not account for the total activity observed, we isolated by bioguided fractionation several triterpenic esters, vanillin derivatives, a sterol and a coumarin. The structure determination of isolated compounds was performed by NMR studies and high resolution mass spectrometry. We also identified and quantified by GC-MS the major volatile constituents from the essential oil of leaves. The isolated compounds were studied in vitro for their antiplasmodial, antitrypanosomal and antileishmanial activities. Several of them showed a sub-micromolar antiplasmodial activity, including some triterpenic esters which are 10 to 100 times more active than ursolic acid. In addition, we tested the in vivo antimalarial activity of some extracts: the dichloromethane extract of twigs of Keetia leucantha showed 40.7 % inhibition in mice infected by Plasmodium berghei at 100 mg/kg/day and the total aqueo, Les maladies parasitaires posent encore de nombreux problèmes de santé. Parmi celles-ci, citons la trypanosomiase africaine ou maladie du sommeil dont l’agent responsable est le Trypanosoma brucei, la malaria transmise par le Plasmodium dont l’espèce la plus dangeureuse est le Plasmodium falciparum et la leishmaniose. La richesse de la biodiversité végétale et la connaissance des thérapeutiques traditionnelles sont susceptibles, comme ce fut le cas pour l'artémisinine, d’ouvrir de nouvelles voies dans le domaine de la thérapeutique antipaludéenne, c’est pourquoi nous avons analysé l’activité de plusieurs plantes. Celles-ci ont été sélectionnées par des études ethnobotaniques et bibliographiques au Bénin parmi celles utilisées en médecine traditionnelle comme antipaludiques. Des extraits bruts à partir des poudres de feuilles, de tiges, de racines ou de la partie aérienne ont été réalisés par macérations. Ces extraits ont été étudiés pour leur activité antiparasitaire par des tests in vitro sur Plasmodium falciparum, sur Trypanosoma brucei et Leishmania mexicana mexicana. De plus, des tests de cytotoxicité ont été réalisés afin de déterminer la sélectivité des extraits. Les extraits dichlorométhanes de Keetia leucantha ont été sélectionnés. Certains composés connus ont été identifiés directement sur l’extrait brut par LC-MS et certains d’entre eux ont également été quantifiés. A partir de l’extrait dichlorométhane des poudres de feuilles et de tiges du Keetia leucantha, nous avons isolé par fractionnement bioguidé ou chimioguidé plusieurs acides et esters triterpéniques, un stérol et une coumarine. La détermination structurale des molécules isolées a été réalisée par des études RMN et les masses exactes ont été déterminées en spectrométrie de masse haute résolution. Nous avons également identifié et quantifié les principaux composés volatils issus de l’huile essentielle par GC-MS. Les molécules ainsi isolées ont été étudiées pour leur activité antiplasmodiale, antile, (FARM 3) -- UCL, 2012

The aim of this study is to evaluate the specificities of the irradiation of drugs in frozen aqueous solution. The structures of the degradation products were determined to gain insight into the radiolysis mechanisms occurring in frozen aqueous solutions. Metoclopramide hydrochloride and metoprolol tartrate were chosen as models. The frozen solutions were irradiated at dry ice temperature by high energy electrons at various doses. The drug purity (chemical potency) and the radiolysis products were quantified by HPLC-DAD. Characterization of the degradation products was performed by LC-APCI-MS-MS. The structures of the radiolysis products detected in irradiated frozen aqueous solutions were compared to those detected in solid-state and aqueous solutions (previous studies). For both metoclopramide and metoprolol, solute loss upon irradiation of frozen aqueous solutions was negligible. Five radiolysis products present in traces were identified in irradiated metoclopramide frozen solutions. Three of them were previously identified in solid-state irradiated metoclopramide crystals. The two others were formed following reactions with the hydroxyl radical (indirect effect). Only one fragmentation product was observed in irradiated metoprolol frozen solutions. For both drugs, radiosterilization of frozen solutions, even at high doses (25kGy), was found to be possible.

The aim of this study was to assess the feasibility of radiosterilization of drugs aqueous solutions and to evaluate the effects of some additives, such as mannitol, nicotinamide and pyridoxine, which might protect the drug from degradation. Metoclopramide was selected as a model drug. The structures of the degradation products were determined to gain insight on the radiolysis mechanisms in aqueous solution in order to design strategies to lower the drug degradation. Metoclopramide hydrochloride aqueous solutions with and without excipients were irradiated either with gamma rays or high-energy electrons. HPLC-DAD was used to measure the loss of chemical potency and to quantify the degradation products which were also characterized by LC–APCI–MS-MS. Metoclopramide recovery for gamma and electron beam-irradiated solutions containing either mannitol, pyridoxine or nicotinamide meets the pharmacopoeial specifications for metoclopramide content up to a 15 kGy irradiation so that metoclopramide solutions containing these excipients might be radiosterilized at 15 kGy either with gamma rays or high-energy electrons. Structures are proposed for the majority of radiolysis products. Similar radiolysis products were detected for gamma and electron beam irradiations but the chromatographic profiles were different (differences in the distribution of radiolysis products).

In this work, the radiolysis mechanisms in solids as well as in liquid and frozen aqueous solutions have been studied. Liquid chromatography tandem mass spectrometry has evolved so that mass spectral information can now be used to determine the most probable structures of radiolysis products, even those present in traces amounts. Theoretical routes explaining the formation of radiolysis products can be deduced from their structures. The development of strategies to limit the degradation of the active pharmaceutical ingredient during irradiation of the drug requires a better knowledge of the radiolysis mechanisms responsible for the drug degradation. Metoclopramide, an antiemetic drug, has been selected as a model, due to the variety of its chemical bonds. In the solid state, radiation-induced degradation of the drug was very low (<0.1%) and only four radiolysis products were detected in traces. The "major" radiolysis product was formed after the loss of the chlorine by dissociative electron capture. For metoclopramide liquid aqueous solutions, the loss of the drug was important (~30% loss at 25 kGy) and several radiolysis products were detected. The majority of the degradation products were generated following the attacks of hydroxyl radicals and aqueous electrons. The loss of metoclopramide could be lowered up to acceptable levels (<10% loss) provided that radioprotective additives were added and the irradiation dose was limited to 15 kGy, which could be sufficient to reach the required SAL. The selected excipients were mannitol (which reacts mainly with the hydroxyl radical), nicotinamide and pyridoxine that react with both the aqueous electron and the hydroxyl radical. The irradiation of frozen aqueous solutions allowed to minimize the loss of active substance even for a 25 kGy dose. This approach seems to be the most promising method for terminal sterilization of aqueous solutions by ionizing radiations. The major radiolysis product was formed after the attack o, (FARM 3)--UCL, 2007

The classical methods of chromatographic identification of compounds were based on calculation of retention indices by using different stationary phases. The aim of the work was to differentiate essential oils extracted from different plant species by identification of some of their major compounds. The method of identification was based on the calculation of new retention indices of essential oils compounds fractionated on a polar chromatographic column with temperature programming system. Similar chromatograms have been obtained on the same column for one plant family with two different temperature gradients allowing the rapid identification of essential oils of different species, sub-species or chemotypes of Citrus, Mentha and Thymus.

The degradation of irradiated human insulin in aqueous solutions was investigated in order to protect the protein against ionizing radiation. The influence of the drug concentration, excipients and irradiation temperature were studied. Aqueous solutions at pH 2 were irradiated by gamma rays or by accelerated electrons. Two different high-performance liquid chromatography (HPLC) methods were used: reverse-phase high-performance liquid chromatography (RP-HPLC)/UV and size exclusion liquid chromatography (SEC/UV) to investigate both the fragmentation and the formation of higher molecular weight proteins. In solution without excipients irradiated at ambient temperature at 10 kGy, the loss of human insulin is almost complete. Addition of radio-protecting excipients (free radicals scavengers) and cryo-irradiation allowed to decrease insulin degradation. The best radio-protector used was ascorbic acid in aqueous solution and oxidized glutathione in the frozen solutions. Only the combination of these two approaches (addition of scavenger and freezing) enables the irradiated human insulin in aqueous solution to meet the European Pharmacopoeia requirements for chemical potency (>or=90%).

The microbiological contamination of raw plant materials is common and may be adequately reduced by radiation processing. This study evaluated the effects of gamma- and e-beam ionizing radiations (25 kGy) on three plants used as food or as medicinal products (Thymus vulgaris L., Eucalyptus radiata D.C., and Lavandula angustifolia Mill.) as well as their effects on extracted or commercial essential oils and pure standard samples. Comparison between irradiated and nonirradiated samples was performed by GC/FID and GC/MS. At the studied doses, gamma and e-beam ionizing radiation did not induce any detectable qualitative or quantitative significant changes in the contents and yields of essential oils immediately after ionizing radiation of plants or commercial essential oils and standards. As the maximum dose tested (25 kGy) is a sterilizing dose (much higher than doses used for decontamination of vegetable drugs), it is likely that even decontamination with lower doses will not modify yields or composition of essential oils of these three plants.

PURPOSE: To study the chemical modifications induced upon irradiation of solid human insulin at radiosterilization doses and investigate the influence of the absorbed dose on radiolysis. MATERIALS AND METHODS: Volatile radiolytic products were monitored by gas chromatography coupled with mass spectrometry (GC-MS) and non-volatile products by two different high performance liquid chromatography (HPLC) methods: the formation of higher molecular weight proteins was assessed by size exclusion liquid chromatography whereas assays for related compounds and chemical potency tests were carried out using reverse-phase HPLC-UV. Conformational changes were investigated by measurements of circular dichroism. RESULTS: After gamma irradiation at 10 kGy, the recovery of insulin was 96.8%; higher molecular weight proteins accounted for 0.35% (relative peak area) and other related compounds (including A21 desamido insulin) represented 1.29%. No major structural changes and no volatile radiolytic compounds were detected. CONCLUSION: Human insulin samples irradiated in the solid-state at 10 kGy (gamma rays) and 14 kGy (electron-beam) meet the European Pharmacopoeia requirements and can be considered as quite stable towards radiation from a chemical analysis viewpoint.

The aim of this work is to investigate the feasibility of radiation sterilization of ketoprofen from a chemical point of view. Although irradiated ketoprofen has already been studied in the literature [Katusin-Razem et al., Radiat. Phys. Chem. 73 111-116 (2005)], new results, on the basis of electron spin resonance (ESR) measurements and the use of hyphenated techniques (GC-MS and LC-MS), are obtained. The ESR spectra of irradiated ketoprofen consists of four unresolved resonance peaks and the mean G-value of ketoprofen is found to be 4 +/- 0.9 nmoles/J, which is very small. HPLC-UV analyses indicate that no significant loss of ketoprofen is detected after irradiation. LC-MS-MS analyses show that the structures of the non-volatile final products are similar to ketoprofen. Benzaldehyde is detected in the irradiated samples after dynamic-extraction GC-MS. The analyses show that ketoprofen is radioresistant and therefore might be radiosterilized.

E-beam and gamma products from the radiolysis of aqueous solutions of (+/-)-metoprolol tartrate, saturated in nitrogen, are analyzed by HPLC with on-line mass and UV detectors. The structures of 10 radiolytic products common to e-beam and gamma irradiations are elucidated by comparing their fragmentation pattern to that of (+/-)-metoprolot. Two of the radiolytic products are also metabolites. Different routes for the formation of the radiolytic products are proposed. (c) 2006 Published by Elsevier Ltd.

Purpose Study the radiolysis of solid-state metoclopramide hydrochloride at various absorbed doses. Elucidate the structure of the degradation products to gain information on the radiolysis mechanisms. Methods Solid-state metoclopramide samples were irradiated at several doses with gamma rays and high-energy electrons to evaluate the influence of the dose rate. High-performance liquid chromatography with a diode array detector was used to measure the chemical potency as a function of the absorbed dose and to quantify the degradation products. The characterization of degradation products was performed by liquid chromatography/atmospheric pressure chemical ionization/tandem mass spectrometry. Results The degradation of solid-state metoclopramide after irradiation was negligible. No qualitative or quantitative differences were observed between gamma and electron beam irradiations (no dose rate effect). Four degradation products that were similar to metoclopramide were detected in trace levels (below 0.1% of the drug concentration) and were not unique to irradiation because they were found in lower amounts in unirradiated metoclopramide. The major degradation product formed after radiation was due to the loss of the chlorine atom from the metoclopramide molecule. Conclusion Solid-state metoclopramide is radioresistant from a chemical point of view and therefore could be a suitable candidate for radiosterilization studies by either gamma rays or high-energy electrons.

Purpose: To study the degradation of human insulin induced upon irradiation at radiosterilization doses (10 kGy). Results: The chemical analysis of irradiated solid-state insulin by EPR, chromatography and circular dichroism has shown the radioresistance of human insulin at 10 kGy: radical yield ca. 10-9 mole.J-1, human insulin content > 95 %, low percentage of various degradation products. However, in aqueous solution, the degradation of human insulin was high at 10 kGy. The addition of radioprotecting excipients and cryoirradiation reduced insulin degradation. A satisfactory content of human insulin (>90 %) may only be achieved by a combination of these two methods. Conclusion: At solid-state, from a chemical analysis viewpoint, radiosterilization of human insulin is feasible at 10 kGy. In aqueous solution, radiosterilization of human insulin could be considered but should require an appropriate formulation and cold irradiation process., L'objectif est l'étude de la dégradation de l'insuline humaine induite lors de l'irradiation à l'état solide et en solution aqueuse à des doses de radiostérilisation (10 kGy). Résultats: A l'état solide, l'analyse chimique de l'insuline par divers techniques telles que la RPE, la chromatographie et le dichroïsme circulaire montre que l'insuline est radiorésistante à la dose de 10 kGy: rendement radicalaire ca. 10-9 mole.J-1, pureté en insuline supérieure à 95 %, pourcentage de produits de dégradation négligeable. Par contre, en solution aqueuse, l'insuline humaine est détruite à cette dose. L'addition de radioprotecteurs ou la cryoirradiation réduit la dégradation de l'insuline lors de l'irradiation. C'est seulement la combinaison de ces deux approches qui a permis d'obtenir un pourcentage en insuline supérieur à 90 %. Conclusions: A l'état solide, du point de vue chimique, la radiostérilisation de l'insuline humaine est un choix recommandable à 10 kGy. En solution aqueuse, la radiostérilisation pourra être considérée mais exigerait une formulation appropriée et un procédé d'irradiation à froid., Thèse de doctorat en sciences pharmaceutiques (FARM 3) -- UCL, 2006

Radio-induced modifications in proteins have been studied using several techniques. Electron paramagnetic resonance (EPR) was used to characterize free radicals, and analysis methods (high-performance liquid chromatography, capillary electrophoresis) were employed to visualize final degraded forms. Whereas EPR indicates that perthiyl radicals are formed, analysis does not detect any compound in which such bonds would be broken. Since EPR signals decay with time, it is concluded that rearrangements occur at subsequent steps, in which the solvent used during the analysis might play a role.

Essential oils of Helichrysum faradifani were isolated from fresh or dry plant parts by steam distillation with yields from 0.1-0.8%. Analysis of the oils by GC and GUMS enabled the identification of 49 components, of which alpha-fenchene (trace-27.3%), beta-caryophyllene (14.8-29.2%) and P-himachalene (15.7-36.6%) were most predominant.

In this paper, the products studied are cefazolin, glucagon and dobutamine HCl. The radioresistance of pharmaceuticals may depend on the conditions of irradiation. The best is to irradiate the drugs in solid state and the chemical transformations can be reduced also by lowering the temperature of the liquid. In solid state. the dose rate has no influence on the decomposition for the selected molecules and it should be noted that drug excipients selected for bioavailability reasons are not always radioprotectors. These results are important from a technical point of view in pharmaceutical industry. (C) 2004 Elsevier Ltd. All rights reserved.

The irradiation of reduced (GSH) or oxidized (GSSG) glutathione in the solid state was performed using gamma-rays from Co-60 or high-energy electrons from an accelerator. In GSSG, perthiyl radicals (GSS') were created in addition to carbon-centred radicals as seen by electron paramagnetic resonance spectroscopy. The quantity was independent of the dose rate (electrons or gamma-rays) and of the presence of oxygen. In GSH, perthiyl radicals were also created, although in a smaller quantity. Among end-products in irradiated GSSG, we find GSH. Thus, sulphur functions are reduced by irradiation in the solid state.

La radiostérilisation a fait l'objet de nombreuses études fondamentales sur des solides irradiés lors des thèses précédentes du laboratoire. Les solutions aqueuses n'ont pas encore été étudiées à des doses de stérilisation (15-25 kGy) et ne sont pas proposées pour la radiostérilisation. Les substances actives dissoutes sont très sensibles à l'ionisation de l'eau qui fournit des espèces réactives oxydantes et réductrices. Une première partie de l'étude a recours à la radiolyse impulsionnelle pour évaluer les valeurs des constantes de vitesse de ces espèces réactives sur le tartrate de métoprolol. La réaction du radical hydroxyle produit par l'eau sur le métoprolol est très rapide, une valeur de 5.2 x 109 M-1 s-1 est mesurée pour la moyenne des constantes de vitesse. L'utilisation d'un programme de simulation cinétique qui inclut les constantes de vitesse pour toutes les espèces réactives conduit à une perte du principe actif de 50% pour des doses de l'ordre de 5 kGy et une concentration initiale de 1 mg ml-1. Les mesures chromatographiques ne confirment pas l'importance de cette perte mais elle reste supérieure à 50% pour des doses de 15 kGy. Cette "protection" est attribuée aux produits de radiolyse qui s'accumulent dans le milieu. Par ailleurs, l'addition de substances radioprotectrices avant l'irradiation permet de rendre la perte acceptable à des doses utiles. Une recherche des paramètres importants avait pointé "l'intensité de dose" efficace à des intensités trop élevées en pratique. Notons que l'étude des produits de radiolyse conduit à l'hypothèse de mécanismes différents pour des intensités usuelles en gamma et en électrons accélérés., Past studies of the laboratory, on the fundamental mechanisms of irradiated solid state drugs, have contributed to the radiosterilization of drugs in the solid state. Drugs in aqueous solution have not yet been studied at sterilization doses (15-25 kGy) and radiosterilization is not proposed for drugs in aqueous media. The drug solute is degraded by the reactive species formed by the water ionization, which may be oxidizing or reducing agents. The first part of the study, measures the reaction rate constants of the reactive species from the water radiolysis with metoprolol tartrate by the technique of pulse radiolysis. The hydroxyl radical is found to react rapidly with metoprolol, with an average rate constant of 5.2 x 109 M-1 s-1. A computer simulation program that includes all the reactions of the water radiolysis and models the drug solute degradation showed a 50% loss for absorbed doses of about 5 kGy and a drug solute concentration of 1 mg ml-1. The quantitative measurements by chromatography do not confirm such a high loss in the drug solute; they show a loss higher than 50% for absorbed doses of about 15 kGy. This "protection" is attributed to the radiolytic products that accumulate in the solution. The use of radioprotectors limited the drug solute degradation to acceptable limits for such absorbed doses. The study of the parameters governing the radiostability of drugs in aqueous solution suggested the use of very high dose rates which are not technically feasible. The study on the radiolytic products, lead to a hypothesis of different mechanisms for gamma and e-beam irradiations with typical dose rates., Thèse de doctorat en sciences pharmaceutiques (FARM 3) -- UCL, 2005

PURPOSE: The radiolytic products of eight beta-blockers were studied in order to understand the mechanisms of irradiation of drugs in the solid state. METHODS: The drugs were analyzed by high-performance liquid chromatography coupled to a diode array detector in order to observe the degradation of the main compound after irradiation and in order to study the nonvolatile final products on more concentrated solutions of irradiated drugs. RESULTS: The first test assessed that the main compound was not significantly degraded after gamma irradiation for any of the eight beta-blockers. A more complete study, which consisted on separating the nonvolatile products and on quantifying them, indicated first that the radiolytic products could reach the number of 14 and moreover that some could exceed the 0.1% threshold at 30 kGy. Eventually, radiolytic yields were compared with radical yields previously determined. CONCLUSIONS: The sensitivity of the first test can be discussed. It seems that, to study the feasibility of the radiosterilization, a complete study of the products of degradation is needed. Moreover, no correlation between radical and final products could be established, which denies that the former would be the precursors of the latter.

The purpose of this study was to provide insight into the processes that occur after the irradiation of solid-state drugs. Electron paramagnetic resonance (EPR) experiments were performed at two different frequencies, X-band (about 9.5 GHz) and Q-band (about 34 GHz), to identify the radicals present in irradiated captopril. The results confirmed that an irradiated drug can trap several main radicals. Moreover, the radical composition varied as a function of the treatment. In addition, non-volatile final products were studied by liquid chromatography coupled to UV and to mass spectrometry (LC-MS). The variation of the radical composition did not influence the profile of the final products; this appears to indicate that, in the case of captopril, the trapped radicals observed by EPR are not the main precursors of the final products. Finally, high-performance liquid chromatography data appear to indicate that radiosterilization of captopril is feasible.

The identification of radicals trapped in irradiated drugs can be very intricate. A multi-frequency electron paramagnetic resonance (EPR) study is proposed to resolve this problem. The Q-band (ca. 34 GHz) comparison with X-band (ca. 9 GHz) did not show significant differences for the four beta-blockers studied (atenolol, esmolol, nadolol and propranolol). The use of a higher frequency (285 GHz) was required. It enabled us to determine the g -tensor values of the radicals present in atenolol and esmolol, respectively, g(1) = 2.0086, g(2) = 2.0059 and g(3) = 2.0021 and g(1) = 2.0066, g(2) = 2.0044 and g(3) = 2.0021. The latter was assigned as a phenoxyl radical, which can not be the case for the former. Therefore, radicals produced in esmolol may result from a more complex mechanism than the abstraction followed by the diffusion of an H atom inside the solid. In addition, two molecules as similar as atenolol and esmolol hydrochloride do not contain the same radicals after irradiation. These two conclusions drawn from the EPR results on beta-blockers show clearly the importance of continuing the investigations on radiolytic mechanisms in solid-state drugs.

Up-to-now, the studies on the radiosterilization of solid-state drugs were essentially focused on its radical part. The main conclusions from these works are that irradiated drugs contain stable trapped radicals and, therefore, that Electron Paramagnetic Resonance (EPR), which enables to detect paramagnetic species with a high sensitivity (10-9 M) is the technique that could be used to detect irradiated drugs versus non-irradiated ones. On this basis, we have wondered if we could consider that radicals are the precursors of the final products and hence be an indicator of the degradation of the active compound. This would propose EPR as a test to determine if a drug could withstand radiosterilization. Thus, in the first place, we have further investigated radicals qualitatively and quantitatively and then, we have determined their influence on the final products. From the failure of establishing correlation between the radiolytic species studied, it seems that, on the opposite of the generally accepted ideas, the radicals do not play a major part in the formation of the final products of solid-state drugs. The consequences on the radiolytic mechanisms and on the choice of the analytical techniques, suitable as a test, will be discussed. ..., Thèse de doctorat en sciences pharmaceutiques (FARM 3)--UCL, 2004

PURPOSE: Study of the radical mechanisms in the radiosterilization of metoprolol tartrate aqueous solutions in order to determine the parameters governing its radiostability. METHODS: Pulse radiolysis with pseudo-first-order kinetics to measure Ihe reaction rate constants of hydrated electrons and hydroxyl radicals with metoprolol tartrate. Chemsimul was used to solve the decay kinetics of transients and to simulate the radiolysis of metoprolol tartrate solutions. RESULTS: Hydrated electrons react with metoprolol and the tartrate ion with rate constants of 6.8 x 10(7) M(-1) s(-1) and 1.7 x 10(7) M(-1) s(-1), respectively. Hydroxyl radicals react with metoprolol and the tartrate ion with rate constants of 5.2 x 10(9) M(-1) s(-1) and 5.5 x 10(8) M(-1) s(-1), respectively. The hydroxyl-metoprolol transients are found to scavenge the superoxide anion (5.5 x 10(10) M(-1) s(-1)), react with oxygen (1.0 x 10(8) M(-1) s(-1)), and follow a biradical decay (2.0 x 10(8) M(-1) s(-1). A simplified radical mechanism is used to simulate the loss of potency of metoprolol tartrate aqueous solutions during radiosterilization. CONCLUSIONS: To decrease the loss of potency of metoprolol tartrate. the sterilization dose must be lowered and very high dose rates used.

The nonvolatile radiolytic compounds produced by irradiation of cefotaxime were studied by a liquid chromatography-electrospray mass spectrometry method. Full scan LC-MS was first performed in order to obtain the m/z value of the protonated molecules of all detected peaks. LC-MS-MS was then carried out on the compounds of interest. A comparison between the MS-MS spectrum of cefotaxime and those of the radiolytic compounds showed that their fragmentation patterns were very similar suggesting that they were structural analogues of the main drug. The examination of the two main fragmentation pathways also permitted the location of the modified substructures. Moreover, it was shown that some stereoisomers appeared with the irradiation process. The complete fragmentation pattern of cefotaxime was studied by MSn and used to obtain information about the structure of the radiolytic compounds. A complete structure was proposed for four of these.

The effects of radiosterilization on the purity profile of cefotaxime were evaluated by a liquid chromatography-diode array method. Numerous new radiolytic compounds were detected in very small amount. They were quantified and it appeared that none was present above the level of 0.1% of the main compound and the total amount was only of 0.72%. Despite the low quantities present, some radiolytic compounds had UV spectra which could justify the apparition of a yellow coloration detected after irradiation. Others had UV spectra similar to that of cefotaxime, suggesting similarity in the molecular structures. Finally, some mechanisms of formation were proposed for four radiolytic compounds which were identified by mass spectrometry in a former study. (C) 2001 Elsevier Science Ltd. All rights reserved.