Efficient femtosecond optical parametric generation in group-velocity-matched MgO:PPLN at 10†MHz.

We report on efficient single-pass optical parametric generation (OPG) of broadband femtosecond pulses in the mid-infrared at 10 MHz by exploiting group-velocity-matched interaction in a 42-mm-long MgO:PPLN crystal. Using a microchip-started femtosecond amplified Mamyshev oscillator at 1064 nm as the pump, the OPG source can provide tunable femtosecond pulses across 1516-1566 nm in the signal and 3318-3568 nm in the idler, with slope efficiencies of ∼93% and ∼41%, respectively. For 650 mW of average input pump power, signal powers of up to 283 mW at 1524 nm are generated, with more than 200 mW over the entire tuning range. Idler average powers of up to 104 mW at 3450 nm, with more than 80 mW across the full range, are also obtained. For input pump pulses of ∼182 fs, the generated signal pulses have a duration of ∼460 fs at 1516 nm. The idler pulses have a typical bandwidth of ≥100 nm over the entire tuning range, and as wide as 181 nm at 3457 nm. The OPG source exhibits excellent passive power stability, better than 0.5% rms in the signal and 0.6% rms in the idler, over 1 h, both in Gaussian TEM00 spatial profile with M2 < 1.5.

Volumetry: an alternative to assess therapy response for malignant pleural mesothelioma?

The purpose of our study was to assess robustness of volumetric measurement of malignant pleural mesothelioma (MPM) before and after chemotherapy to modified RECIST (response evaluation criteria in solid tumours) criteria. 30 patients with digitally available chest computed tomography (CT) scans before and after three cycles of chemotherapy were included. Three readers independently assessed tumour response using two different methods: 1) the modified RECIST criteria; and 2) the tumour volumetric approach using dedicated software (Myrian; Intrasense, Paris, France). Inter-rater reliability of unidimensional and volumetric measurements was assessed using intraclass correlation. Tumour response classification for modified RECIST was compared to the volumetric approach applying unidimensional RECIST volumetric equivalent criteria. The determination of unidimensional tumour measurement (RECIST) revealed a low inter-rater reliability (0.55) and a low interobserver agreement for tumour response classification (general κ 0.33). Only 14 patients were classified equally. A high inter-rater reliability (0.99) and interobserver agreement (general κ 0.9) were found for absolute tumour volumes (volumetric measurements). 27 cases were classified equally. The number of cases classified as "stable disease" was higher for the volumetric approach using tumour-equivalent criteria compared to modified RECIST. Volumetric measurement of MPM on CT using Myrian software is a reliable, reproducible and sensitive method to measure tumour volume and, thus, therapy response after induction chemotherapy.

Analysis of Amaryllidaceae alkaloids from Narcissus by GC-MS and capillary electrophoresis.

Amaryllidaceae are known as ornamental plants, furthermore some species of this family contain galanthamine, an acetylcholinesterase inhibitor approved for the treatment of Alzheimer's disease, and other alkaloids with interesting pharmacological activity. In the present work, the quali- and quantitative analysis of Amaryllidaceae-type alkaloids in the bulbs of Narcissus species is presented using different analytical approaches. Extracts of Narcissus pseudonarcissus cv. Carlton and Narcissus jonquilla Quail, were first examined by GC-MS using a Rtx-5 MS (programmed temperature) and the major alkaloids were identified. Together with galanthamine, high contents of haemanthamine, were found. Galanthamine was reliably quantified by GC-MS, whereas haemanthamine partly decomposed under the GC conditions, thus alternative analytical methods were investigated. Firstly, reversed-phase HPLC-ESI-MS was applied to identify and isolate at semipreparative levels haemanthamine. The compound was fully characterized by MS/MS and (1)H NMR and then used as a reference substance. The quantitation of both galanthamine and haemanthamine was then accomplished by capillary electrophoresis with spectrophotometric detection. A non-aqueous (NACE) approach was selected in order to use a running buffer fully compatible with samples in organic solvent. In particular, a mixture methanol-acetonitrile (75:25, v/v) containing ammonium acetate (90 mM) was used as a background electrolyte. The same analytical sample was subjected to GC-MS and NACE analysis; the different selectivity displayed by these techniques allowed different separation profiles that can be useful in phytochemical characterization of the extracts. The GC-MS and NACE methods were validated and applied to the quantitation of galanthamine (GC-MS and NACE) and haemanthamine (NACE) in bulbs of N. jonquilla.

HPLC-DAD and LC-ESI-MS analysis of doxycycline and related impurities in doxipan mix, a medicated premix for incorporation in medicated feedstuff.

HPLC-DAD and LC-ESI-MS methods have been developed for the analysis of doxycycline (DOX), including the identification of the related impurities metacycline (MTC) and 6-epidoxycycline (EDOX) and its determination in a medicated premix. The chromatographic separations have been performed on Luna C18 stationary phase and on Synergi (4 microm) Polar-RP 80A, using both acidic (pH 2.5) and basic (pH 8.0) mobile phases. The Synergi Polar-RP column, in combination with a mobile phase of oxalic acid (0.02 M; pH 2.5)-acetonitrile 82:18 (v/v), allowed the complete separation of MTC, EDOX and DOX. The same separation was also obtained using Luna C18 stationary phase with a pH 8 mobile phase. Application of a LC-ESI-MS system and MS/MS analysis, using both positive and negative polarity, allowed the peak identity to be confirmed. A method based on Luna C18 column and UV detection at 346 nm was validated for the determination of DOX in a medicated premix for incorporation in medicated feedstuff.

Methotrexate determination in pharmaceuticals by enantioselective HPLC.

A simple, sensitive and selective high performance liquid chromatographic method with UV detection for the chiral separation of racemic methotrexate (rac-Mtx) and enantiomeric purity of L-methotrexate in pharmaceutical formulations was developed and validated. The chiral separation was optimized studying both the nature of the stationary phase by using Chirobiotic T, Chiracel OJ and human serum albumin columns and the effect of the mobile phase composition. The best results in terms of enantioresolution and enantioselectivity were achieved with a polar organic mobile phase on Chirobiotic T stationary phase. Essential steps in method validation such as precision, accuracy, suitability and stability were studied according to ICH guidelines. At wavelength 303 nm, the limit of detection (S/N=3) was found to be 0.9 microg/ml for rac-Mtx. The separation of D-Mtx at 0.2% (w/w) level (as limit of quantitation) from the main drug L-Mtx was successfully obtained with 1.72 enantioresolution value. Enantiomeric purity of L-Mtx was determined in pharmaceutical formulations (tablets and injections) with inter- and intra-days relative standard deviation < or = 1.6%. Under the validated stereoselective HPLC conditions for methotrexate, folic acid was also analysed.

In vitro anti-angiogenic effects of Hemidesmus indicus in hypoxic and normoxic conditions.

ETHNOPHARMACOLOGICAL RELEVANCE: The decoction of the roots of Hemidesmus indicus is widely used in the Indian traditional medicine for many purposes and poly-herbal preparations containing Hemidesmus are often used by traditional medical practitioners for the treatment of cancer. In the context of anticancer pharmacology, anti-angiogenic therapy has become an effective strategy for inhibiting new vessel formation and contrast tumor growth. These considerations are supported by the evidence that most tumors originate in hypoxic conditions and limitation of oxygen diffusion stimulates the formation of tumor abnormal microvasculature. Aim of this study was to evaluate the in vitro anti-angiogenic potential of Hemidesmus indicus (0.31-0.93 mg/mL) on human umbilical vein endothelial cells and delineate the main molecular mechanisms involved in its anti-angiogenic activity both in normoxia and hypoxia. MATERIALS AND METHODS: The decoction of Hemidesmus indicus was subjected to an extensive HPLC phytochemical characterization. Its in vitro anti-angiogenic potential was investigated in normoxia and hypoxia. Cell proliferation, apoptosis induction, and inhibition of endothelial cell migration and invasion were analyzed by flow cytometry. The endothelial tube formation assay was evaluated in matrix gel. The capillary tube branch points formed were counted using a Motic AE21 microscope and a VisiCam videocamera. The regulation of key factors of the neovascularization process such as VEGF, HIF-1α and VEGFR-2 was explored at mRNA and protein level by real time PCR and flow cytometry, respectively. RESULTS: Treatment with Hemidesmus resulted in a significant inhibition of cell proliferation and tube formation in both normoxia and hypoxia. Hemidesmus differently regulated multiple molecular targets related to angiogenesis according to oxygen availability. In normoxia, the inhibition of VEGF was the main responsible for its anti-angiogenic effect; the angiogenesis inhibition induced in hypoxia was regulated by a more complex mechanism involving firstly HIF-1α inhibition, and then VEGF and VEGFR-2 down-regulation. Additionally, the inhibition of endothelial cell migration and invasion by Hemidesmus was more pronounced in normoxia than in hypoxia, possibly due to the physiological enhanced induction of invasion characteristic of hypoxia. CONCLUSIONS: Our results indicate that Hemidesmus might represent a promising therapeutic strategy for diseases in which the inhibition of angiogenesis could be beneficial, such as cancer. The antiangiogenic activity of Hemidesmus is based on multiple interactions with critical steps in the angiogenic cascade. VEGF expression stimulated by HIF-1α as well as endothelial cell migration and differentiation represent important targets of Hemidesmus action and might contribute to its cancer therapeutic efficacy that is presently emerging and offer a scientific basis for its use in traditional medicine.

Gut microbiota trajectory in pediatric patients undergoing hematopoietic SCT.

Acute GvHD (aGvHD) is the main complication of hematopoietic SCT (HSCT) during the treatment of hematological disorders. We carried out the first longitudinal study to follow the gut microbiota trajectory, from both the phylogenetic and functional points of view, in pediatric patients undergoing HSCT. Gut microbiota trajectories and short-chain fatty acid production profiles were followed starting from before HSCT and through the 3-4 months after transplant in children developing and not developing aGvHD. According to our findings, HSCT procedures temporarily cause a structural and functional disruption of the gut microbial ecosystem, describing a trajectory of recovery during the following 100 days. The onset of aGvHD is associated with specific gut microbiota signatures both along the course of gut microbiota reconstruction immediately after transplant and, most interestingly, prior to HSCT. Indeed, in pre-HSCT samples, non-aGvHD patients showed higher abundances of propionate-producing Bacteroidetes, highly adaptable microbiome mutualists that showed to persist during the HSCT-induced ecosystem disruption. Our data indicate that structure and temporal dynamics of the gut microbial ecosystem can be a relevant factor for the success of HSCT and opens the perspective to the manipulation of the pre-HSCT gut microbiota configuration to favor mutualistic persisters with immunomodulatory properties in the gut.

WB 4101-related compounds. 2. Role of the ethylene chain separating amine and phenoxy units on the affinity for alpha(1)-adrenoreceptor subtypes and 5-HT(1A) receptors.

WB 4101 (1)-related benzodioxanes were synthesized by replacing the ethylene chain separating the amine and the phenoxy units of 1 with a cyclopentanol moiety, a feature of 6, 7-dihydro-5-[[(cis-2-hydroxy-trans-3-phenoxycyclopentyl)amino]meth yl] -2-methylbenzo[b]thiophen-4(5H)-one that was reported to display an intriguing selectivity profile at alpha(1)-adrenoreceptors. This synthesis strategy led to 4 out of 16 possible stereoisomers, which were isolated in the case of (-)-3, (+)-3, (-)-4, and (+)-4 and whose absolute configuration was assigned using a chiral building block for the synthesis of (-)-3 starting from (+)-(2R)-2, 3-dihydro-1,4-benzodioxine-2-carboxylic acid ((+)-9) and (1S,2S, 5S)-2-amino-5-phenoxycyclopentan-1-ol ((+)-10). The aim of this project was to further investigate whether it is possible to differentiate between these compounds with respect to their affinity for alpha(1)-adrenoreceptor subtypes and the affinity for 5-HT(1A) receptors, as 1 binds with high affinity at both receptor systems. The biological profiles of reported compounds at alpha(1)-adrenoreceptor subtypes were assessed by functional experiments in isolated rat vas deferens (alpha(1A)), spleen (alpha(1B)), and aorta (alpha(1D)) and by binding assays in CHO and HeLa cells membranes expressing the human cloned alpha(1)-adrenoreceptor subtypes and 5-HT(1A) receptors, respectively. Furthermore, the functional activity of (-)-3, (+)-3, (-)-4, and (+)-4 toward 5-HT(1A) receptors was evaluated by determining the induced stimulation of [(35)S]GTPgammaS binding in cell membranes from HeLa cells transfected with human cloned 5-HT(1A) receptors. The configuration of the cyclopentane unit determined the affinity profile: a 1R configuration, as in (+)-3 and (-)-4, conferred higher affinity at alpha(1)-adrenoreceptors, whereas a 1S configuration, as in (-)-3 and (+)-4, produced higher affinity for 5-HT(1A) receptors. For the enantiomers (+)-4 and (-)-4 also a remarkable selectivity was achieved. Functionally, the stereoisomers displayed a similar alpha(1)-selectivity profile, that is alpha(1D) > alpha(1B) > alpha(1A), which is different from that exhibited by the reference compound 1. The epimers (-)-3 and (+)-4 proved to be agonists at the 5-HT(1A) receptors, with a potency comparable to that of 5-hydroxytryptamine.

Dermatan sulfate as useful chiral selector in capillary electrophoresis.

Dermatan sulfate (DS), a complex, polydispersed, sulfate polysaccharide was investigated as a useful chiral selector in capillary electrophoresis for the enantioresolution of a variety of drugs. Analysis was carried out in a fused-silica capillary column of 48.5 cm length (40 cm to detector window) x 50 microns I.D., and the separation buffer consisted of citric acid-Tris containing DS; the applied voltage was 15 kV and the detection wavelength was 220 nm. The effects of buffer pH, the dermatan concentration and run temperature on the enantioseparation and migration were examined. The method was applied to the enantioresolution of a representative set of twenty basic drugs. At all pH values used (3.0, 4.5 and 6.5) the addition of DS resulted in an increased migration time due to analyte-DS interaction. Using DS concentration of 2% (w/W), at pH 4.5, enantiomeric separations could be obtained for more than 50% of the examined drugs; resorcinic drugs; resorcinic moiety was found to be a very favourable structural feature for obtaining high enantioresolution values.

Semisynthetic chondroitins as chiral buffer additives in capillary electrophoresis.

Chemically oversulfated galactosaminoglycans with potential as therapeutic agents (inhibitors of human leukocyte elastase) were tested as chiral selectors in capillary electrophoresis of basic racemates. The high anionic character of these compounds provides them with anodic mobility in acidic buffer; using uncoated capillaries, the enantioresolution of racemic basic drugs was obtained at pH 2.5. Dimethindene, chloroquine and chlorpheniramine were enantioresolved applying negative voltage (-15 kV) while the other analytes (propranolol, pindolol, tetrahydrozoline and cloperastine) exhibited catodic migration. The addition of organic solvents to the running buffer was evaluated in order to increase the resolution; methanol provides the best results and in general, baseline separation of the analytes was reached. The studied oversulfated mucopolysaccharide, shows the same ionic character of heparin but presents different stereochemistry and sites of sulfation. A comparison with heparin, used in the same acidic conditions, may underline the role of ionic, spatial and steric features of glycosaminoglycans in the enantiorecognition.

Determination of 5-aminosalicylic acid related impurities by micellar electrokinetic chromatography with an ion-pair reagent.

A micellar electrokinetic chromatographic (MEKC) method was developed for the quantification of mesalazine or 5-aminosalicylic acid (5-ASA) and its major impurities 3-aminosalicylic acid, salicylic acid, sulfanilic acid and 4-aminophenol. The optimisation of the experimental conditions was carried out considering some important requirements: resolution, reproducibility, detection limits of 0.1% (m/m) or less, short total analysis time. Preliminary investigations employing sodium dodecyl sulfate (SDS) as surfactant did not lead to the necessary resolution of the studied compounds; the addition of tetrabutylammonium bromide (TBAB) to the SDS micellar system resulted in the complete separation of all the compounds. The effects on the separation by several parameters such as TBAB concentration, SDS concentration, background electrolyte pH and concentration, were evaluated. Using a fused-silica capillary (8.5 cm effective length) complete analysis was obtained in a very short time. Under the optimised final conditions [120 mM 3-(cyclohexylamino)-2-hydroxy-1-propanesulfonic acid buffer, pH 10.20, 65 mM SDS in the presence of 55 mM TBAB and 5% methanol] the method was validated for specificity, precision, linearity, limits of detection and quantitation, and robustness: the 5-ASA related impurities can be quantified at least at the 0.1% (m/m) level.

Analytical study of penicillamine in pharmaceuticals by capillary zone electrophoresis.

The ability of capillary zone electrophoresis in the development of analytical methods devoted to the quality control of the thiol drug penicillamine is shown. Using 50 mM phosphate running buffer (pH 2.5), good quantitations of underivatized penicillamine and its disulfide were achieved; detection at 200 nm allowed checking the presence of the disulfide impurity in pharmaceuticals. The use of 1,1-[ethenylidenebis(sulfonyl)]bis-benzene as a thiol specific reagent resulted in an increased sensitivity for the quantitation of D-penicillamine (limit of detection at 200 nm wavelength was 1.5 microM). Introducing beta-cyclodextrin as chiral selector in the running buffer, enantioseparation of D-L-penicillamine was obtained; for this purpose (+)-camphor-10-sulfonic acid, a chiral ion-pairing reagent, was found to be an essential additive in obtaining a baseline separation. The resulting enantioseparative system was validated in order to evaluate the presence of the toxic L-penicillamine enantiomer in pharmaceutical samples.

Design of experiments for capillary electrophoretic enantioresolution of salbutamol using dermatan sulfate.

Statistical experimental design was used for the optimization and for robustness evaluation of a capillary electrophoretic method developed for the enantioresolution of salbutamol. Dermatan sulfate was used as chiral selector. The goal of the study was to obtain an efficient and fast separation. An eight-run Plackett-Burman matrix was used during the optimization process for the screening of the factors and to adjust the experimental domain under study. Response surface methodology was adopted after the screening phase to obtain information about how the factors percentage of chiral selector, pH and voltage affected the considered responses resolution and analysis time. The Derringer desirability function, which makes it possible to combine results obtained for properties measured on different scales, was used to simultaneously optimize the two responses. Robustness testing was carried out using a Plackett-Burman matrix. The method was found robust as regards the response resolution while voltage and chiral selector were found to be critical factors for the robustness of analysis time response. The proposed CE method permitted the complete enantioseparation of racemic salbutamol and was applied to its chiral resolution in spiked urine samples.

Capillary electrophoretic and high-performance liquid chromatographic studies of the enantioselective separation of alpha1-adrenoreceptor antagonists.

Capillary electrophoresis (CE) and chiral stationary phase (CSP) HPLC methods were investigated for the determination of enantiomeric purity of alpha1-adrenoreceptor antagonists related to WB 4101. In the CE study, the enantioseparation of the analytes was performed by studying the effect of different types of cyclodextrin in the buffer, namely heptakis (2,6-di-O-methyl)-beta-cyclodextrin (DMCD), hydroxypropyl-beta-cyclodextrin (HPCD) and beta-cyclodextrin (beta-CD). HPCD was found to be the most effective chiral selector in the enantioseparation of all the compounds, with high resolution values. A HPLC method, using immobilised serum protein columns, human serum albumin (HSA) and alpha1-acid glycoprotein (AGP), was also investigated. Two benzodioxane racemates were well resolved on a mixed tpe (50% HSA and 50% AGP) column, with enantioselective binding on AGP column.

Determination of the dissociation constants (pKa) of basic acetylcholinesterase inhibitors by reversed-phase liquid chromatography.

An RP-HPLC study for the pKa determination of a series of basic compounds related to caproctamine, a dibenzylaminediamide reversible inhibitor of acetylcholinesterase, is reported. The 2-substituted analogues, bearing substituents with different electronegativity, were analysed by RP-HPLC by using C18 C4 stationary phases with a mobile phase consisting of mixture of acetonitrile and triethylamine phosphate buffer (pH range comprised between 4 and 10). Typical sigmoidal curves were obtained, showing the dependence of the capacity factors upon pH. In general, the retention of the investigated basic analytes increased with increasing of the pH. The inflection point of the pH sigmoidal dependence was used for the dissociation constant determination at a fixed acetonitrile percentage. When plotting pKa vs. percent of acetonitrile in the mobile phase for two representative compounds, linear regression were obtained: the y intercept gave the aqueous pKa(w). The pKa estimation by HPLC method was found to be useful to underline the difference of benzylamine basicity produced by the ortho aromatic substituents. The variation of pKa values (6.15-7.80) within the series of compounds was correlated with the electronic properties of the ortho-substituents through the Hammett sigma parameter, whereas the ability of substituents to accept H-bond was found to play a role in determining the conformational behavior of the molecules.

Drug affinity to immobilized target bio-polymers by high-performance liquid chromatography and capillary electrophoresis.

This review addresses the use of high-performance liquid chromatography (HPLC) and capillary electrophoresis (CE) as affinity separation methods to characterise drugs or potential drugs-bio-polymer interactions. Targets for the development of new drugs such as enzymes (IMERs), receptors, and membrane proteins were immobilized on solid supports. After the insertion in the HPLC system, these immobilized bio-polymers were used for the determination of binding constants of specific ligands, substrates and inhibitors of pharmaceutical interest, by frontal analyses and zonal elution methods. The most used bio-polymer immobilization techniques and methods for assessing the amount of active immobilized protein are reported. Examples of increased stability of immobilized enzymes with reduced amount of used protein were shown and the advantages in terms of recovery for reuse, reproducibility and on-line high-throughput screening for potential ligands are evidenced. Dealing with the acquisition of relevant pharmacokinetic data, examples concerning human serum albumin binding studies are reviewed. In particular, papers are reported in which the serum carrier has been studied to monitor the enantioselective binding of chiral drugs and the mutual interaction between co-administered drugs by CE and HPLC. Finally CE, as merging techniques with very promising and interesting application of microscale analysis of drugs' binding parameters to immobilized bio-polymers is examined.

Use of an immobilised human serum albumin HPLC column as a probe of drug-protein interactions: the reversible binding of valproate.

The reversible binding of valproate to human serum albumin determines a decrease of the binding of ligands that selectively bind to site I, site II, and bilirubin binding site. The binding inhibition was followed by displacement chromatography methodology using increasing concentrations of the competitor, i.e. valproate, in the mobile phase. Significant binding inhibition was observed for drugs binding at site I and site II. The greater displacement was observed for the more retained enantiomer of benzodiazepines and profens. A reduction of the affinity was observed also in the case of phenol red, this compound being selected as representative of bilirubin binding site. Difference circular dichroism spectroscopy was also used to characterise the binding of valproate to human serum albumin. This antiepilectic drug was proved to affect the binding at site I, II, and bilirubin binding site. The data have physiological relevance because significant inhibition of the binding resulted at clinic concentrations of valproate.

Stereoselective binding of 2-(4-biphenylyl)-3-substituted-3-hydroxypropionic acids on an immobilised human serum albumin chiral stationary phase.

A series of 2-(4-biphenylyl)-3,3'-hydroxy-substituted phenyl propionic acid, with anti-inflammatory properties, bearing two chiral centres, were studied by HPLC upon HSA-CSP (human serum albumin-based chiral stationary phase). The compounds were analysed in their stereoisomeric erythro and threo forms. The study involved the enantioselective analysis on HSA-CSP, the determination of the racemate lipophilicity (log k'(w)), a QSRR (quantitative structure-retention relationship) analysis and CD study for the assessment of the absolute configuration of the most retained enantiomer. Lipophilicity was found to be an important factor affecting the affinity of the compounds for the HSA stationary phase, but electronic properties seemed to play a role. The position of the substituent of the phenyl group on carbon 3 was found important to modulate stereoselective interaction, the highest value of enantioselectivities being found for the erythro ortho-substituted phenyl derivatives. The previously proposed two steps mechanism of enantiodiscrimination for cyclohexylphenyl substituted derivatives was confirmed for this series of derivatives bearing the biphenylyl moiety.

Studies on the photostability and in vitro phototoxicity of Labetalol.

The purpose of this study was to obtain information on the photochemical and phototoxic properties of Labetalol, a beta-blocker drug. Preliminary information on the drug photoreactivity was achieved using a flow system with a photochemical reactor on-line with a diode array detection system. Photophysical and photochemical investigations on the drug were performed in aqueous solutions at different pH values using spectrophotometric and fluorimetric methods; the photodegradation quantum yield was found to be 2.7 x 10(-3) at pH 5.8 and 1.5 x 10(-2) at pH 11.5. Forced photodegradation of labetalol solutions under exposure to UVA--UVB radiations (xenon arc lamp) was monitored by reversed-phase liquid chromatography. The main photodegradation products were isolated and characterized by NMR and mass spectrometry; labetalol was found to give 3-amino-1-phenylbutane and salicylamide-4-carboxaldehyde as the main photoproducts. Preliminary phototoxic testings on human keratinocyte cultures were performed evaluating the viability of the cells by the neutral-red uptake assay; mutagenic and photomutagenicity tests were also carried out based on Salmonella typhimurium strains. As a result, labetalol was found to be photolabile,mainly in alkaline medium, but evidences of significant phototoxic and photomutagenic effects by the drug were not observed.

Photodegradation studies on Atenolol by liquid chromatography.

The photostability of the beta-blocker drug Atenolol was evaluated at pH 9, 7.4 and 4.0. The drug was exposed to UVA-UVB radiations and the photoproducts were detected by reversed phase LC methods. The photodegradation was found to increase with the pH value decreasing. The major photodegradation product at pH 7.4 was identified as 2-(4-hydroxyphenyl)acetamide. The LC method developed for routine analyses (column: C-18 Alltima; mobile phase: TEA acetate (pH 4; 0.01 M)-acetonitrile 96:4) was found to be suitable for the stability indicating determination of Atenolol in pharmaceutical dosage forms.