Simultaneous adsorption of chromate and arsenate onto ferrihydrite/alginate composite beads: Competition and mechanism

Ferrihydrite is an effective adsorbent of chromate and arsenate. In order to gain insight into the application of ferrihydrite in water treatment, macroporous alginate/ferrihydrite beads, synthesized using two different methods (internal and encapsulation processes), were used in this work. The properties of the ferrihydrite were assessed using various techniques, including X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Brunauer-Emmett-Teller (BET) theory, and zetametry. The results showed that the specific surface area of the ferrihydrite was 242 m2/g, and the PZC was pH8. The kinetic and isotherm adsorption properties of the ferrihydrite were evaluated in this study. The results indicate that the pseudo second-order and Freundlich models accurately describe the kinetic and isotherm adsorption properties of chromates and arsenates. For chromate removal, ferrihydrite exhibited a relatively high adsorption capacity (40.7 mgCr/g) compared to other adsorbents. However, the arsenate adsorption capacity of MFHB-SI (140.8 mgAs/g) was shown to be the most optimal. The internal synthesis process was suitable for arsenate retention due to the resulting arsenate precipitation. The competitive adsorption analyses indicated that the presence of chromate does not limit the adsorption of arsenate. However, the presence of arsenate almost completely inhibits the adsorption of chromate when the arsenate concentration is above 50 mg/L, due to the precipitation reaction of arsenate.

Mesoporous silicas: improving the adsorption efficiency of phenolic compounds by the removal of amino group from functionalized silicas

Removal of the amine template enhances the sorption of phenolic pollutants. The sorption capacity could be dependent of the pore size.

Adsorption of basic dyes in single and mixture systems on granular inorganic-organic pillared clays

The adsorption of two basic dyes, CI Basic Yellow 28 and CI Basic Green 4, was studied in single and binary solute systems using two classes of inorganic-organic pillared clay granules as sorbents (300-400 microm and 700-800 microm). These were prepared by high-shear wet granulation from an Al cetyltrimethylammonium bromide intercalated clay powder (particle diameter < 50 microm). Adsorption rate data indicate that BY 28 adsorbs more rapidly than BG 4 and a pseudo-first-order model was found to fit the kinetic curves, with regression coefficients above 0.98. Adsorption isotherms in single solute systems at pH 3 and pH6 were respectively analysed according to the Langmuir and Freundlich models using non-linear regression. Best fits were obtained with the Langmuir model. In binary dye systems the adsorption at three molar ratios (1:9, 1:1 and 9:1) demonstrated that the adsorption of BG 4 was greater than that of BY 28 on all the sorbents studied; this was in agreement with the results obtained for single solute systems. Increasing the granule size decreased dye adsorption, an effect in accordance with the Sheindorf-Rebuhn-Sheintuch model.

Copper and nitrophenol pollutants removal by Na-montmorillonite/alginate microcapsules

The use of renewable bioresources allows the development of low cost adsorbents that are versatile. In the present paper, the affinity and the removal capacity of montmorillonite/alginate microcapsules for a hydrophobic organic pollutant (4-nitrophenol) and an inorganic pollutant (copper) were evaluated. The physicochemical processes through sorption and kinetic experiments under different ratios of montmorillonite vs. alginate and initial contaminant concentrations were investigated. The total weight loss and diameter decrease during the drying process were 90-96% and 64%, respectively. A significant decrease in beads diameter, related to water elimination, has been observed during the first 24h. Structural modifications that occur during the drying process were evaluated using thermal analysis. From correlation coefficients, the second-order equation depicts properly the adsorption of copper by the microbeads adsorption capacity increases to saturation with time; 3 and 6h were needed to reach equilibrium on wet and dry mixed microcapsules. The pseudo-second order model properly depicts the adsorption process of 4-NP onto Na-mont and (Na-mont/SA) mixed microcapsules but failed to reproduce the data observed for the alginate beads. Isotherms data were fitted with good correlation using the Langmuir model; alginate and montmorillonite adsorption capacities (q(m)/wet beads) agree with those obtained by various studies.

Aqueous heavy metals removal on amine-functionalized Si-MCM-41 and Si-MCM-48

Ordered mesoporous silica with hexagonal and cubic structure, type MCM-41 and MCM-48 respectively, were synthesized under basic media using pure silica, cetyltrimethylammonium bromide and tetramethylammonium hydroxide, for MCM-41 and tetraethylorthosilica, cetyltrimethylammonium and NaOH for MCM-48. The expanded materials were prepared by post-synthesis method with N-N dimethyldodecylamine (DMDDA) and dodecylamine (DDA). Small angle X-ray diffraction, nitrogen adsorption-desorption measurements, FT-IR and thermogravimetry were used to characterize the samples. The expanded materials were tested for adsorption of Cd(2+), Co(2+), Cu(2+) and Pb(2+) in aqueous solution. Aminated materials were found to be fast adsorbents for metallic ions cation with affinity for Cu(2+), Pb(2+), than for Cd(2+) and Co(2+) from single solution. In mixed metallic ions cation solutions, competition by the adsorption sites is likely to occur, the adsorption preference is for Cu(2+)and Pb(2+). The kinetic of the reaction is very rapid and follow pseudo-second order and clearly indicated that Langmuir model describe better the for metal ions adsorption on aminated mesoporous material than Freundlich model.

Myriophyllum alterniflorum DC., biomonitor of metal pollution and water quality. Sorption/accumulation capacities and photosynthetic pigments composition changes after copper and cadmium exposure

Watermilfoil genus Myriophyllum could be used in ecological surveys as in-situ biomonitors of metal pollution and water quality due to its ability to accumulate chemicals. The copper and cadmium sorption characteristics of Myriophyllum alterniflorum have been investigated. The Langmuir and Freundlich isotherms were used to model the metal sorption isotherms and the monolayer sorption capacities, as obtained by the Langmuir isotherm, were determined to be 13.9 mg/g and 11.1 mg/g for Cu2+ and Cd2+ respectively. Results have been compared with previous works on watermilfoils and are in accordance with those obtained on Myriophyllum spicatum. The sorption of the two metals was time-dependent and the kinetics fitted the pseudo-second-order equation well. The data were discussed in terms of ionic radii and HSAB concept. The phytotoxic effects assessed by classical (i.e. changes in biomass, node length) and photosynthetic pigments content endpoints have been investigated using chemometric techniques leading to an effect of cadmium onto photosynthetic pigments.

Dietary phytoestrogens: potential selective estrogen enzyme modulators?

Between one-third to one-half of all breast cancers are steroid sensitive. Steroid-pathway enzymes (sulfatase, 17beta-hydroxysteroid dehydrogenases, aromatase and sulfotransferases) are thus prime candidates for therapeutic approaches based on the control of intacrine activity. Some phytoestrogens, ubiquitous in our diet, are inhibitors of these enzymes. Such a therapeutic potential has stimulated research and progress has been achieved during the last years. Complementary to previous reviews on phytoestrogens, this contribution covers the estrogen pathway inhibition effects of these compounds and special attention will be given to isoflavonoids, flavonoids and lignans. Furthermore, the research on structurally-related compounds as therapeutic agents will be discussed briefly.

Pharmacokinetics and metabolism of apigenin in female and male rats after a single oral administration

The metabolism of apigenin, a weak estrogenic flavonoid phytochemical, was investigated in the rat. After a single oral administration of radiolabeled apigenin, 51.0% of radioactivity was recovered in urine, 12.0% in feces, 1.2% in the blood, 0.4% in the kidneys, 9.4% in the intestine, 1.2% in the liver, and 24.8% in the rest of the body within 10 days. Sex differences appear with regard to the nature of compounds eliminated via the urinary route: immature male and female rats, like mature female rats, excreted a higher percentage of the mono-glucuronoconjugate of apigenin than the mono-sulfoconjugate of apigenin (10.0-31.6% versus 2.0-3.6%, respectively). Mature male rats excreted the same compounds in an inverse ratio (4.9% and 13.9%, respectively). Radioactivity appeared in the blood only 24 h after oral administration. Blood kinetics showed a high elimination half-time (91.8 h), a distribution volume of 259 ml, and a plasmatic clearance of 1.95 ml/h. All of the parameters calculated from these experiments suggested a slow metabolism of apigenin, with a slow absorption and a slow elimination phase. Thus, a possible accumulation of this flavonoid in the body can be hypothesized.

Metabolism of apigenin by rat liver phase I and phase ii enzymes and by isolated perfused rat liver

The metabolism of apigenin, a low estrogenic flavonoid phytochemical, was investigated in rat using liver models both in vitro (subcellular fractions) and ex vivo (isolated perfused liver). In vitro, phase I metabolism led to the formation of three monohydroxylated derivatives: luteolin which was the major metabolite (K(m) = 22.5 +/- 1.5 microM; V(max) = 5.605 +/- 0.090 nmol/min/mg protein, means +/- S.E.M.), scutellarein, and iso-scutellarein. These oxidative pathways were mediated by cytochrome P450 monooxygenases (P450s). The use of P450 inhibitors and inducers showed that CYP1A1, CYP2B, and CYP2E1 are involved. In vitro studies of phase II metabolism indicated that apigenin underwent conjugation giving three monoglucuronoconjugates and one monosulfoconjugate. Luteolin led to the formation of four monoglucuronoconjugates, two sulfoconjugates, and one methylconjugate identified as diosmetin. Ex vivo during the apigenin perfusion of an isolated rat liver, none of the phase I metabolites could be recovered. In contrast, two monoglucuronoconjugates and one of the sulfoconjugates of apigenin already identified in vitro were recovered. Moreover, two new derivatives were isolated and identified as a diglucuronoconjugate and a glucuronosulfoconjugate. This work provides new data about the metabolism of apigenin and shows the interest value of using various experimental models in metabolic studies.

Efficient liquid-phase synthesis of 2'-hydroxychalcones

The condensation of 2'-hydroxyacetophenone (1) with aromatic aldehydes (2) in a well closed vessel using microwave irradiation or classical heating at 132 degrees C, provides a fast and simple method for the liquid-phase synthesis of 2'-hydroxychalcones without formation of by-products. Antiproliferative activity of these compounds were evaluated using MCF-7 cells.

Design, synthesis and evaluation of 4-imidazolylflavans as new leads for aromatase inhibition

Two 4-imidazolylflavans were synthesized and their relative stereochemistry was established by 1H and 13C NMR data. These compounds were tested for their activity to inhibit aromatase. It was observed that the introduction of an imidazolyl group at carbon 4 on flavan nucleus led to potent molecules.

New aromatase inhibitors. Synthesis and inhibitory activity of pyridinyl-substituted flavanone derivatives

Two (E)-pyridinyl-substituted flavanone derivatives were synthesized and UV irradiation of these compounds afforded a Z-enriched mixture. These products were tested for their ability to inhibit the cytochrome P450 aromatase. It was observed that the introduction of a pyridinylmethylene group at carbon 3 on flavanone nucleus led to a significant increase of aromatase inhibitory effect. Moreover, configuration had a substantial influence on the aromatase inhibitory activity since (E)-isomers were found to be more active than (Z)-isomers.

Synthesis and aromatase inhibitory activity of flavanones

PURPOSE

Aromatase inhibitors are known to prevent the conversion of androgens to estrogens and play a significant role in the treatment of estrogen dependent diseases such as breast cancer. Some flavonoids have been reported as potent aromatase inhibitors; therefore, in an effort to develop novel anti breast cancer agents, B ring substituted flavanones with a 7-methoxy group on A ring were synthesized and tested to assess their ability to inhibit aromatase activity and to determine the optimal B ring substitution pattern.

METHODS

A series of flavanones was prepared by cyclisation of 2'-hydroxychalcones previously obtained by Claisen-Schmidt condensation and the aromatase inhibitory activity of these compounds was investigated using human placental microsomes and radiolabeled [1,2,6,7-(3)H]-androstenedione as substrate.

RESULTS

Almost all flavanones exhibited inhibitory effect on the aromatase activity but their potency was dependent on their B ring substitution pattern. Hydroxylation at position 3' and/or 4' enhanced the anti-aromatase activity; thus, 3',4'-dihydroxy-7-methoxyflavanone was found to be twice more potent than aminoglutethimide, the first aromatase inhibitor clinically used.

CONCLUSIONS

These results indicated that these flavanones could be considered as potential anti breast cancer agents through the inhibition of aromatase activity and allowed us to select some of these compounds as skeleton for the development of flavonoid structurally-related aromatase inhibitors.

Flavonoids: structural requirements for antiproliferative activity on breast cancer cells

Several classes of flavonoids (flavones, flavanones, 2'-hydroxychalcones and flavan-4-ols) having a variety of substituents on A ring were investigated for their antiproliferative activity against MCF-7 human breast cancer cells. Structure-activity relationships of these compounds were discussed. 2'-hydroxychalcones and methoxylated flavanones were found to be potent inhibitors of MCF-7 cells growth whereas flavones and flavan-4-ols appeared to be weak inhibitory agents except 7,8-dihydroxyflavone.

Chalcones are potent inhibitors of aromatase and 17beta-hydroxysteroid dehydrogenase activities

Chalcones were tested for estimating anti-aromatase, anti-3beta-hydroxysteroid dehydrogenase delta5/delta4 isomerase (3beta-HSD) and anti-17beta-hydroxysteroid dehydrogenase (17beta-HSD) activities in human placental microsomes. In the present study, we have demonstrated for the first time that chalcones are potent inhibitors of aromatase and 17beta-hydroxysteroid dehydrogenase activities: these enzymes being considered as important targets in the metabolic pathways of human mammary hormone-dependent cells. Our results showed that naringenin chalcone and 4-hydroxychalcone were the most effective aromatase and 17beta-hydroxysteroid dehydrogenase inhibitors with IC50 values of 2.6 and 16 microM respectively. In addition, inhibitory effects of some flavones and flavanones were compared to those of the corresponding chalcones. A structure-activity relationship was established and regions or/and substituents essential for these inhibitory activities were determined.

Estrogenic/antiestrogenic and scavenging properties of (E)- and (Z)-resveratrol

Resveratrol, natural compound found in grapes and wine, has been reported to have a variety of health benefit properties. Based on the structural similarity to the synthetic estrogen diethylstilbestrol, we investigated estrogenic/antiestrogenic effects on human breast cancer cell lines, MCF-7 and MVLN, and scavenging properties using DPPH of both (E)- and (Z)-isomers. Both isomers increased the in vitro growth of MCF-7 cell lines at medium concentrations (10 and 25 microM) whereas the low concentrations (0.1 and 1 microM) had no effect and the high concentration (50 microM) decreased the cell growth and was cytotoxic. The 25 microM (E)-isomer alone was able to reduced the proliferation induced by the estradiol. Low concentrations of (E)- and (Z)-resveratrol (0.1 and 1 microM) and medium concentration 10 microM (Z)-resveratrol did not interfere with the estrogen receptor. In contrast, medium concentrations of (E)-resveratrol (10 and 25 microM) and (Z)-resveratrol (25 microM) functioned as superagonists of estradiol. Whatever the model used, MCF-7 or MVLN cell lines, (Z)-resveratrol was less effective than (E)-resveratrol. Extinction of DPPH and Fe(III) reduction experiments showed that both isomers of resveratrol could act as free radicals scavengers or pro-oxidant compounds. The properties of low concentrations of resveratrol raise the possibility that structure-function studies could lead to the development of more selective estrogen receptor agonists and antagonists, which could be useful as a therapeutic agent.

Radiation induced effects on cephalosporins: an ESR study

PURPOSE

This paper reports experimental data on the ESR identification of four irradiated cephalosporins (cefpodoxime, cefsulodin, cefixime and ceftizoxime).

MATERIALS AND METHODS

Equations to describe the ESR curves versus the dose and storage time were developed using mathematical procedures.

RESULTS

Limits of detection (LOD) and limits of quantification (LOQ), estimated on the basis of the S/N ratios are 1.0+/-0.5 kGy and 2.5+/-0.5 kGy respectively. The yield of free radicals are in the range 4.6 10(19) - 2.2 10(20) radicals mol(-1) (G values from 0.1 to 0.4). Besides a very unstable situation (cefsulodin), the time limit of detection of free radicals after storage ranges from about 1 year to over 2 years. These time intervals are comparable with the shelf-life of the antibiotics and to the time limits found for 10 other cephalosporins described previously. Apart from qualitative detection, ESR spectrometry can be used for dose estimation. Exponential loss of ESR signal (first-order reaction) correlates well with the data.

CONCLUSION

Given the sensitivity of ESR spectrometry, this experimental technique is promising for identification of irradiated cephalosporins.

Radiosterilization dosimetry of vitamins: an ESR study

PURPOSE

As an alternative to heat and gas exposure sterilization, ionizing radiation is gaining interest as a sterilization process for medicinal products. Detection and dosimetry of pharmaceutical radiosterilization is a growing concern for numerous government regulatory agencies world-wide.

MATERIALS AND METHODS

Equations to describe the ESR curves versus the dose and storage time were developed using mathematical procedures. For this investigation six vitamins (riboflavin, biotin, thiamine mononitrate, thiamine hydrochloride, folic acid and pyridoxine) were chosen as models.

RESULTS

The yield of free radicals is in the range 1.7 10(18)-7.3 10(19) radicals mol(-1) (G values from 0.0003 to 0.025 mol J(-1)). Apart from qualitative detection, ESR spectrometry can be used for dose estimation; when an exponential function is applied to the variation of peak-to-peak amplitude on dose, the function correlates well with the data. Tests were carried out to investigate whether storage has an effect on the concentration of free radicals. In order to estimate the time limit of detection, decay curves were modelled using a bi-exponential function. From this, the time limit from the irradiation (25 kGy) for identification of irradiated vitamins by ESR was evaluated. In the commercial drug market, radicals should be detected for up to 2 years after irradiation; this probably will be the case for the vitamins studied, with the exception of folic acid and pyridoxine.

CONCLUSION

The detection method based on ESR dosimetry seems promising. ESR dosimetry requires only small samples, and minimal time and effort for sample preparation; the measurement is non-destructive.

Electron spin resonance detection of radiosterilization of pharmaceuticals: application to four nitrofurans

The detection and dosimetry of radiosterilization of pharmaceuticals is a growing concern to numerous government regulatory agencies worldwide. In the absence of suitable detection methods, attention was focused on electron spin resonance (ESR) spectrometry. This paper reports experimental data on ESR dosimetry of irradiated nitrofurans (nitrofurantoin, nifuroxazide, nifurzide and nifurtoinol). Whereas the ESR spectrum of a non-irradiated sample shows no signal, a signal, that is dependent on the irradiation dose is observed with irradiated samples. The number of free radicals was calculated by comparing the second integral from radiosterilized samples and a Bruker strong pitch reference; the values were in the range 1.1 x 10(18)-1.5 x 10(19) radicals mol-1 (G = 0.003-0.03). In addition to qualitative detection, ESR spectrometry can be used for dose determination. When a bi-exponential function is applied to the variation of the peak-to-peak amplitude versus dose, the function correlates well with the data. However, an exponential function, easier to use than a bi-exponential function, will probably be sufficient for dose determination by retrospective dosimetry. Decay of radicals upon storage was modelled using a bi-exponential function. From this, the time limit from the irradiation (25 kGy) for identification of irradiated nitrofurans by ESR can be evaluated. With regard to the commercial aspects of drugs, radicals should be detected up to 2 years after irradiation. The kinetic decrease makes discrimination between irradiated and non-irradiated nitrofurans possible even after storage for up to 2 years, except for nifurtoinol.

ESR spectroscopy applied to the study of pharmaceuticals radiosterilization: cefoperazone

As an alternative to heat and gas exposure sterilization, ionizing radiation is gaining interest as a sterilization process for medicinal products. Nevertheless, essentially for economic profits, an unauthorized and uncontrolled use of radiation process may be expected. In this context, it is necessary to find methods distinguishing between irradiated and unirradiated pharmaceuticals and, in the absence of suitable detection methods, our attention was focused on ESR spectrometry. In this paper, we examine the potential of ESR as an analytical tool in cefoperazone radiosterilization; this cephalosporin is a potential candidate for radiation treatment due to its thermosensitivity. While the ESR spectra of unirradiated sample present no intensity, a signal, dependent of the irradiation dose, is found exclusively in irradiated samples. The number of free radicals (2 x 10(17) radicals per g at 25 kGy) was estimated by comparison of the second integral from radiosterilized samples and DPPH. From this, the G-value could be estimated to 0.3. Limit of detection and limit of quantification are 0.5 kGy and 1 kGy, respectively. Aside from qualitative detection, ESR can be used for dose estimation. The dose-ESR response curves can be simulated by bi-exponential or power functions and the linear function can't be used for simulation even for low doses. Decay of radicals upon storage were simulated using bi-exponential function. The limit of detection of free radicals after irradiation at 25 kGy is 140 days.

Inhibitory effect of curcuminoids on MCF-7 cell proliferation and structure-activity relationships

Curcumin, demethoxycurcumin and bisdemethoxycurcumin are the yellow coloring phenolic compounds isolated from the spice turmeric. This study was part of a program correlating the biological activity and molecular structure of antitumor agents; the effect of these curcuminoids and cyclocurcumin (Cyclocur) was examined on the proliferation of MCF-7 human breast tumor cells. Curcuminoids appeared to be potent inhibitors, whereas Cyclocur was less inhibitory. To contribute to our understanding of the mechanism of antiproliferative activity of curcumin, cell cycle analysis was performed by propidium iodide staining and a flow cytometry technique. Curcumin exerts a cytostatic effect at G2/M which explains its antiproliferative activity. The presence of the diketone moiety in the curcumin molecule seems to be essential for the inhibitory activity.

Radiation-induced effects on cefotaxime: ESR study

As an alternative to heat and gas exposure sterilization, ionizing radiation is gaining interest as sterilization process for medicinal products. Detection and dosimetry of pharmaceuticals radiosterilization is a growing concern to numerous government regulatory agencies worldwide. In this context, it is necessary to find methods distinguishing between irradiated and nonirradiated pharmaceuticals. In the absence of suitable detection methods, our attention was focused on electron spin resonance (ESR) spectrometry. A third generation cephalosporin, cefotaxime, was chosen as model; this antibiotic is a potential candidate for radiation treatment due to its thermosensitivity. While the ESR spectra of a nonirradiated sample presents no signal, a signal, dependent of the irradiation dose, is found in irradiated samples. The number of free radicals was estimated by comparing the second integral from radiosterilized samples and a diphenyl-picrylhydrazyl reference. Estimation of the number of free radicals gives 1.9 x 10(20) radicals mol(-1) at 20 kGy. From this result, the G-value (number of radicals (100eV)(-1)) could be estimated to 0.3. Aside from qualitative detection, ESR spectrometry can be used for dose estimation. When quadratic, exponential or bi-exponential functions are applied to the variation of peak to peak amplitude vs. dose, these functions correlate well with the data. However, it is important to notice that linear function correlates well with the data for doses lower than 20 kGy. Since the radiation dose selected must be always based upon the bioburden of the products and the degree of sterility required (EN 552 and ISO 11137) 25kGy could no longer be accepted as a "routine dose" for sterilizing a pharmaceutical. Doses from 6kGy (ISO 11137) could be investigated and linear regression would appear to be the least expensive route to follow. The free radicals concentration appeared to not decrease during the 57 days of storage; the number generated during the irradiation allows the detection of radiosterilized cefotaxime up to two years after irradiation.

Radiation effects on dopamine and norepinephrine

PURPOSE

Radiation sterilization is becoming increasingly popular for the sterilization of many pharmaceutical products. We have investigated the gamma radiation induced effects on dopamine and norepinephrine by ESR spectroscopy.

RESULTS AND DISCUSSION

Equations to describe the evolution of the ESR curves versus doses and time of storage are presented. Linear regression is, for dopamine hydrochloride, applicable for doses ranging from 10 to 25 kGy. Since the radiation dose selected must always be based upon the bioburden of the products and the degree of sterility required, doses in the range 10-25 kGy could be investigated and linear regression would appear to be the least expensive route to follow and gives good results. The comportment of noradrenaline bitartrate is more complex and the use of linear regression would appear more hazardous especially for low doses. For doses higher than 25 kGy, a more general equation is required. Power function using only 2 parameters could give good results but must be validated. Decay kinetics for radicals versus storage were considered. Non-homogeneous kinetics with time dependent rate constant and bi-exponential function appeared valid to reproduce the decay of radicals for, respectively, dopamine and norepinephrine.

CONCLUSIONS

It is worth noting that, at present, ESR is the only technique which proved to be suitable for identification and quantification purposes in irradiated pharmaceuticals. Moreover, other features such as sensitivity, precision, ease and non-destructive readout make ESR superior to other proposed analytical techniques.

ESR dosimetry of irradiated ascorbic acid

PURPOSE

As an alternative to heat and gas exposure sterilization, ionizing radiation is gaining interest as a sterilization process for medicinal products. The aim of this work was to develop equations to describe the ESR curves versus dose and storage time after gamma irradiation of ascorbic acid. Several ESR data sets previously acquired in this laboratory were adopted to check the performance of the models.

RESULTS

Limit of detection and limit of discrimination are respectively 0.5 kGy and 2 kGy for ascorbic acid. Linear regression is applicable for doses lower than 25 kGy. Since the radiation dose selected must always be based upon the bioburden of the products and the Degree of Sterility required (ANSI/AAMI/ISO 11137), doses in the range 5-25 kGy could be investigated and linear regression would appear to be the least expensive route to follow and gives good results. Quadratic fit, power function, exponential function and bi-exponential functions are of more general applicability to predict irradiation dose. Decay kinetics for radicals versus storage were considered. Nonhomogeneous kinetics with time-dependent rate (diffusion-controlled second-order reaction) and bi-exponential function appeared valid to reproduce the experimental data. Discrimination between irradiated and unirradiated ascorbic acid is possible after a storage of 800 days.

CONCLUSIONS

It is worth noting that, at present, ESR is the only technique which proves to be suitable for identification and quantification purposes in irradiated pharmaceuticals. Moreover, other features such as sensitivity, precision, ease and non-destructive readout make ESR superior to other proposed analytical techniques.

Radiation sterilization of formoterol

PURPOSE

Radiation sterilization is becoming increasingly popular for the sterilization of many pharmaceutical products. We have investigated the gamma radiation induced effects on formoterol fumarate by HPLC and ESR spectroscopy.

RESULTS AND DISCUSSION

Numerical simulation of the evolution of the ESR signal versus dose was performed using linear regression, quadratic fit and power function. The shape of the dosimetric curve is linear in the range 5-30 kGy. Owing to the weak number of free radicals generated during the irradiation, the accuracy of measurements is low. For a dose of 25 kGy, discriminating irradiated from unirradiated samples is possible if the storage period is less than 250 days. The comparison between chromatographic profiles of irradiated and unirradiated samples showed minor differences.

CONCLUSIONS

From our preliminary results, radiosterilization of formoterol fumarate may be technically feasible. Estimation of the irradiation dose by ESR may be possible but, due to the weak number of free radicals generated during the irradiation, the accuracy of measurements appeared low.

The effect of gamma radiation on the degradation of salbutamol

The use of ionizing radiation for sterilization of pharmaceuticals is now a well established technology. Degradation of salbutamol was investigated after gamma irradiation using HPLC and ESR spectroscopy. HPLC evidenced the formation of radiolytic products after gamma irradiation. Salbutamol showed a degradation of nearly 2% at 25 kGy. Sterilization of salbutamol in the liquid state appeared not technically feasible. Simulation of the increase of free radicals versus dose was performed using linear and polynomial regression. These radicals could be detected even after a storage period of more than 12 months.