Development of NIRS method for quality control of drug combination artesunate-azithromycin for the treatment of severe malaria

Near infrared spectroscopy (NIRS) methods were developed for the determination of analytical content of an antimalarial-antibiotic (artesunate and azithromycin) co-formulation in hard gelatin capsule (HGC). The NIRS consists of pre-processing treatment of spectra (raw spectra and first-derivation of two spectral zones), a unique principal component analysis model to ensure the specificity and then two partial least-squares regression models for the determination content of each active pharmaceutical ingredient. The NIRS methods were developed and validated with no reference method, since the manufacturing process of HGC is basically mixed excipients with active pharmaceutical ingredients. The accuracy profiles showed β-expectation tolerance limits within the acceptance limits (±5%). The analytical control approach performed by reversed phase (HPLC) required two different methods involving two different preparation and chromatographic methods. NIRS offers advantages in terms of lower costs of equipment and procedures, time saving, environmentally friendly.

In vitro release and stability of an artesunate rectal gel suitable for pediatric use

The rectal route is indicated to treat patients with rapidly evolving malaria who cannot take oral medication to prevent progression to severe forms of the disease. Improvement can be made in terms of rectal bioavailability and stability of current formulations. We studied a new two-compartment, muco-adhesive gel formulation of artesunate which is adapted for use in children and storage in tropical climates. The formulation contains 50mg of artesunate per gram of gel. Because of its instability in aqueous solutions, artesunate is in the dry component of the gel with Carbopol and separate from the liquid phase until reconstitution. Artesunate is stable in the dry blend for 6 months at 45 degrees C and 60% RH. The gel should be used between 1 and 72 h after being reconstituted. Artesunate release was measured by with a rapid, simple and reliable HPLC-UV which allowed the analysis of artesunate and dihydroartemisinin with an analysis time at 3 min. The amount of artesunate released over 6h was 56 +/- 0.97%. Compared to the reference suspension, total release and dissolution efficiency were lower and rate of release was slower (time to 50% dissolution 271 +/- 21 min), probably because of the higher viscosity of the gel, but the drug release profiles were similar. The calculated in vitro release exponent (n) value suggested that artesunate is released from the gel by non-Fickian transport.

Determination of N,N'-ethylenebisstearamide additive in polymer by normal phase liquid chromatography with evaporative light scattering detection

A new method for N,N'-ethylenebisstearamide (EBS) analysis was developed and validated in normal phase-HP liquid chromatography (NP-HPLC) with diol column at 50 degrees C with 100% CHCl(3) at 1 mL min(-1) and evaporative light scattering detection with elution time at 3.0 min. EBS solubility was the best at 0.80 gL(-1) in CHCl(3)/methanol 90:10. The molecular structure of commercial samples of EBS was determined by GC-MS which ascertained that the main structure is C18/C18 at approximately 45%. The remaining part was constituted by molecules with different alkyl chain length. The HPLC quantification method was proved linear (r=0.9983), accurate (99.6%) and precise (1.95%). Limit of quantification (LOQ) and limit of detection (LOD) were equal to 2.0 and 0.8 microg mL(-1), respectively. The suitability of this method was assessed with a dissolution/precipitation extraction procedure of EBS from ethylene vinyl acetate (EVA) polymer which showed that other additives and polymer do not interfere with EBS analysis. The intra-day and day-to-day precisions of extraction method were equal to 9.1% and 9.9%, respectively.

Stability of artesunate in pharmaceutical solvents

Stability of artesunate (ART) was established in three pharmaceutical solvents. The chromatographic conditions developed for this study were acetonitrile:potassium phosphate buffer 10 mM (40:60, v:v; pH 2.9) at 0.7 mL min(-1) with UV detection at 220 nm using a short X-Terra RP C18 column (50 mm x 3 mm, 3.5 microm). This isocratic condition led to the separation between ART and its main degradation products (i.e. alpha-DHA and beta-DHA) with analysis time of less than 4 min. The retention factors are 1.49, 2.26 and 2.79 min for alpha-DHA, beta-DHA and ART, respectively. This method was proved linear (r(2)=0.9995), accurate (R.S.D.=0.20), precise (R.S.D.=0.74) and robust. The system performance remained unaffected by pH variation from 2.6 to 3.2 and variation of acetonitrile percentage from 38 to 42. Stability of ART was assessed in ethanol, propylene glycol (PG) and polyethylene glycol 400 (PEG 400). Unfortunately none of these solvents prevented ART from degradation longer than 3 months. In ethanol, significant degradation of ART occurred after 3 months at room temperature and this degradation was characterised by numerous degradation products. In PEG 400, significant degradation was observed after only 1 month, however DHA was the unique degradation product, which is also an efficient anti-malarial drug.

Development and validation of a capillary electrophoresis method for the determination of sulfate in effervescent tablets

A suitable capillary electrophoresis (CE) method was developed and validated for sulfate anion determination in effervescent tablets of Digedryl. The large excess of other ions in the matrix (i.e. excipients) constituted the main difficulty of this method's development. So an original analytical procedure for both the conditioning and rinsing of the capillary was purposed including a running electrolyte constituted by boric acid 20 mM and hexamethonium dibromide 0.75 mM at pH 8.00. Separation was carried out on a 60.2 cm (50 cm to the detector) x 0.75 microm i.d. fused-silica capillary at a potential of -29 kV and 35 degrees C. Indirect UV detection was performed at a wavelength of 254 nm using a background electrolyte containing potassium chromate. Nitrate anion was used as an internal standard for quantification. This CE method was validated in terms of selectivity, linearity, accuracy and precision.

Molecular lipophilicity determination of a huperzine series by HPLC: comparison of C18 and IAM stationary phases

Two hydrophobic parameters (logkw-C18 and logkw-IAM, respectively) of a huperzine A series were extrapolated by high performance liquid chromatography (HPLC) using both C18 and immobilised artificial membrane (IAM) columns. A mathematical correlation between C18 and IAM hydrophobic parameters was completed, suggesting a similar behaviour on both columns. This behaviour was principally led by hydrophobic forces. The theoretical lipophilicity (logP) of each compound was computed using Pallas software and compared to experimental values, showing a similar lipophilic behaviour. Finally, the huperzine logkw-IAM and logkw-C18 values were correlated with the relative bound percentage of huperzine in human serum albumin, confirming that hydrophobic forces are predominant in the huperzine-HSA binding mechanism.

Direct determination of niflumic acid in a pharmaceutical gel by ATR/FTIR spectroscopy and PLS calibration

A simple, rapid and convenient analytical method without sample handling procedure is proposed for the determination of niflumic acid in a pharmaceutical gel with attenuated total reflectance/Fourier transform infrared spectroscopy (ATR/FTIR). A partial least square (PLS) calibration model for the prediction of niflumic acid contents was developed using 81 and 27 spectra of standard gels as training and validation sets, respectively. The used spectral range of niflumic acid for the establishment of this model was 2300-1100 cm(-1). All spectra were obtained in the transmittance mode, then normalized and first derivative transformed. The model yielded a regression coefficient R2 equal to 1 for the training set and a root mean square error of prediction (RMSEP) equal to 0.2 for the validation set. The percentage recoveries of the method for the analysis of Niflugel ranged from 96.60 to 101.02%.

Protonation equilibrium and lipophilicity of moxifloxacin

This study was performed to characterise the protonation equilibrium at the molecular level and pH-dependent lipophilicity of moxifloxacin. After determining macro- and micro-constants, distribution features of four microspecies in aqueous phase were assessed. The apparent partition coefficient versus pH profile of moxifloxacin showed a parabolic curve in n-octanol/buffer system which reached near pI. The true partition coefficient was calculated from the log P(app) and microconstants values.

Determination of pKa values of 2-amino-2-oxazolines by capillary electrophoresis

The dissociation constants of new 2-amino-2-oxazolines were determined by capillary electrophoresis (CE) as a new technique. A method based on a linear model has been used in the CE determination. A series of eight 2-amino-2-oxazolines are investigated to determine their ionization constant. Among them, three new oxazolines synthesized are presented. The Ka values were obtained from the plots of reciprocal effective mobility against inverse concentrations of protons. The potentiometric method (PM) was performed as a comparative method. No significant differences were observed between the determined dissociation constants using both methods. Thus, the pKa values have been found to vary between 8.55 and 8.68.

Separation of new antidepressants and their metabolites by micellar electrokinetic capillary chromatography

Selective serotonin reuptake inhibitors (SSRIs), serotonin noradrenergic reuptake inhibitors (SNaRIs) and noradrenergic and specific serotoninergic antidepressant (NaSSA) are widely used in the treatment of depression. An increase in antidepressant intoxications led to the development of reliable analytical methods for their analysis. A new determination procedure for these compounds (milnacipran, venlafaxine, desmethylvenlafaxine, mirtazapine, desmethylmirtazapine, citalopram, desmethylcitalopram, fluvoxamine, paroxetine, sertraline and fluoxetine) was developed by micellar electrokinetic capillary chromatography (MEKC) with diode array detection (DAD). Separation and determination were optimised on an uncoated fused-silica capillary (600 mm, 75 microm I.D.). The migration buffer consisted of 20 mM sodium borate, pH 8.55, with 20 mM SDS and 15% isopropanol, at an operating voltage of 25 kV. The column temperature was maintained at 40 degrees C. Injection in the capillary was performed in the hydrodynamic mode (0.5 p.s.i., 15 s). In these conditions, the migration time of the antidepressants was less than 11 min. In most cases, calibration curves were established for 30 - 2000 ng/ml (r > 0.995). The limit of detection and the limit of quantification were ranged between 10 and 20 and between 20 and 30 ng/ml, respectively, for all the molecules. This method allowed the determination of some of these compounds in biological fluids (blood, urine) in post-mortem cases. Samples (1 ml) were extracted with diethyl ether (5 ml) at pH 9.6 and reconstituted in diluted migration buffer. Similar results were obtained by a HPLC-DAD determination, performed as a reference method. These results suggest that this MEKC method can be useful for the determination of new antidepressants in post-mortem cases.

Spectrophotometric, spectrofluorimetric, HPLC and CZE determination of mirtazapine in pharmaceutical tablets

Four analytical methods have been developed for the quality control of tablets containing mirtazapine: spectrophotometry, spectrofluorimetry, high performance liquid chromatography (HPLC) and capillary zone electrophoresis (CZE). All the methods only require a simple extraction procedure of mirtazapine from the tablets before analysis. The concentration of mirtazapine in solutions was determined in the linearity range of 5-25 microg/ml at lambda=315 nm for spectrophotometry and at lambda=220 nm for HPLC and CZE. Spectrofluorimetric determinations were achieved at lambda(excitation)=328 nm and lambda(emission)=415 nm in the linearity range of 2-25 ng/ml. All the methods gave similar results and were validated for selectivity, linearity, precision and sensitivity. Spectrometric methods gave slightly higher RSD values (up to 2.54%). The four methods were directly and easily applied to the pharmaceutical preparation with accuracy, resulting from recovery experiments between 99.72% in HPLC and 101.47% in spectrofluorimetry.

Comparison of high-performance liquid chromatography and capillary zone electrophoresis for the determination of parabens in a cosmetic product

A high-performance liquid chromatographic method (HPLC) and a capillary zone electrophoresis method (CZE) have been developed for the analysis of methylparaben, ethylparaben, propylparaben and butylparaben in a commercial cosmetic product. A very simple extraction procedure with acidified diethylether was developed. The HPLC method involved a C18 reversed-phase column and a gradient of methanol and water-acetic acid (1%). Electrophoretic separation was performed on a fused-silica capillary with a mixed 15 mM tetraborate buffer (pH 9.2) and methanol (85:15, v/v). The calibration curves were linear from 1 to 40 microg/ml in HPLC and from 5 to 200 microg/ml in CZE. The limit of detection in CZE (0.21 microg/ml) was higher than in HPLC (0.05 microg/ml). Repeatability and intermediate precision were satisfactory for both methods (RSD values < 3.23% in HPLC and < 3.26%, in CZE). Only HPLC allowed the separation of butylparaben isomeric forms when CZE analysis was less time and reagents consuming. These results suggest that HPLC and CZE coupled with a simple extraction process are both suitable for parabens determination in cosmetic products.

Determination of urea, allantoin and lysine pyroglutamate in cosmetic samples by hydrophilic interaction chromatography

A new HPLC method using a Polyhydroxyethyl A column involving hydrophilic interaction chromatography (HILIC) is described for the simultaneous determination of urea, allantoin and lysine pyroglutamate in a cosmetic cream. Validation of the method was accomplished with respect to linearity, repeatability and limits of detection/quantification. Compound recoveries approach 100% with acceptable RSD values. The method is very simple since no derivatisation is necessary. Furthermore, it allows the rapid and direct chromatographic analysis of urea and hence could provide an alternative to other methods used to determine this compound in biological or cosmetic samples.

A pharmacophore for high affinity PAF antagonists. II. Hydrophobicity study using the molecular lipophilicity potential

Platelet-activating factor (PAF) is a powerful phospholipid-derived autacoid involved in many physiopathological mechanisms. Many PAF antagonists have been synthesized and evaluated as therapeutic candidates. In a previous report, we have described an electronic pharmacophore of PAF antagonists using the molecular electrostatic potential. In the present study, a molecular lipophilicity potential is used to compare the hydrophobic properties of 49 "heterocyclic sp2 nitrogen' highly potent PAF antagonists, belonging to six structurally different series (nine hetrazepines, five pyrrolo[1,2-c]thiazoles, 14 carboxamides, nine dihydropyridines, nine pyridinyl-thiazolidines and three imidazo[4,5-c]pyridines). Their common features consist of three hydrophilic (HYD2, HY14(3)B and HYD3) and two lipophilic zones (LIP3 and LIP4), defining the lipophilic pharmacophore of the antagonists. This pharmacophore is also characterized by several zone-to-zone distances: HYD3-HYD2 = 1.3 +/- 1.0 A, HY3B-HYD2 = 7.8 +/- 1.1, HYD3-HY3B = 5.1 +/- 1.1 A, LIP4-LIP3 = 5.4 +/- 1.1 A, LIP3-HYD2 = 11.3 +/- 1.6 A, LIP3-HY3B = 5.9 +/- 1.0 A, LIP3-HYD3 = 4.3 +/- 0.9 A, LIP4-HYD2 = 14.7 +/- 1.6 A, LIP4-HY3B = 8.1 +/- 1.2 A and LIP4-HYD3 = 3.9 +/- 1.1 A. These results represent a new step in the determination of a global pharmacophore for PAF antagonists.

A pharmacophore for high affinity PAF antagonists. I. Electronic model using molecular electrostatic potential

PAF is a powerful phospholipid-derived autacoid involved in many physio-pathological mechanisms. Many PAF antagonists have been synthesized and assayed for therapeutic purposes. In this study, molecular electrostatic potential is used to compare the electronic properties of 48 'heterocyclic sp2 nitrogen' highly potent PAF antagonists, belonging to six series (nine hetrazepines, five pyrrolo[1,2-c]thiazoles, 14 carboxamides, nine dihydropyridines, nine pyridinylthiazolidines and two imidazo[4,5-c]pyridines). Their common features consist of three main electronegative zones (A, B1 and B2) describing the electronic pharmacophore of these ligands. The high affinity of these PAF antagonists seems to be related to this electronegative system A-B(x), which is characterized by three distances A-B1 (9.3 +/- 1.0 A), A-B2 (13.4 +/- 0.7 A) and B1-B2 (4.9 +/- 0.9 A). Moreover, B1 and B2 may surround a common anchorage point in the binding site of the receptor.

Determination of a PAF antagonist pharmacophore using combined Molecular Electrostatic Potential and Molecular Lipophilicity Potential

PAF is a potent lipid mediator involved in many pathological disorders, such as platelet aggregation, immuno-inflammatory reactions, vascular disorders, septic shock and bronchoconstriction. We chose to study the electronic and lipophilic properties of eleven PAF antagonists, comprising five tetrahydrofuran derivatives, four hetrazepines, the ginkgolide BN-52021 and the pyrrolo-thiazole derivative RP-59227. A Molecular Electrostatic Potential (MEP) contour drawn at -25 kCal/Mol shows three electronegative areas in most compounds. Two areas can be considered as analogous to those described in the so-called "Cache-Oreille" (Earmuff) Model. Molecular Lipophilicity Potential (MLP) analysis allows us to characterise one hydrophilic area, localised at the same place as one of the electronegative areas, and two lipophilic areas, of which the biggest draws a typical "sock" contour. These three areas represent the minimal requirements for a high affinity to the PAF receptor. MEP and MLP results are here combined to propose a pharmacophore for PAF antagonists, including two lipophilic areas, two hydrophilic and electronegative areas and an electronegative zone with no particular hydrophilic behaviour.

Molecular modeling of 5-HT3 receptor antagonists: geometrical, electronic and lipophilic features of the pharmacophore and 3D-QSAR study

If the geometrical pharmacophore of 5-HT3 receptor antagonists has been proposed by different authors, the electronic and lipophilic features of the ligands had to be precised. A 3-D QSAR study has enlightened the importance of three parameters derived from molecular electrostatic and molecular lipophilicity potentials. A multiple linear regression equation has been established. Its predictive character (non specific binding of 3[H]-ICS 205-930) has been tested with success for three different new ligands.

Lipophilicity force field profile: an expressive visualization of the lipophilicity molecular potential gradient

This paper proposes a new tool that allows us to see the following in the same frame: (1) 3D geometrical features of a molecule, and (2) pseudo-3D representation of the lipophilicity molecular potential. It thus becomes very easy to compare the lipophilicity molecular potential gradient of different molecules having the same pharmacological properties. An example of two structurally dissimilar anti-PAF molecules is given.