Monika Dąbrowska

Analytical approaches to determination of carnitine in biological materials, foods and dietary supplements.

l-Carnitine is a vitamin-like amino acid derivative, which is an essential factor in fatty acid metabolism as acyltransferase cofactor and in energy production processes, such as interconversion in the mechanisms of regulation of cetogenesis and termogenesis, and it is also used in the therapy of primary and secondary deficiency, and in other diseases. The determination of carnitine and acyl-carnitines can provide important information about inherited or acquired metabolic disorders, and for monitoring the biochemical effect of carnitine therapy. The endogenous carnitine pool in humans is maintained by biosynthesis and absorption of carnitine from the diet. Carnitine has one asymmetric carbon giving two stereoisomers d and l, but only the l form has a biological positive effect, thus chiral recognition of l-carnitine enantiomers is extremely important in biological, chemical and pharmaceutical sciences. In order to get more insight into carnitine metabolism and synthesis, a sensitive analysis for the determination of the concentration of free carnitine, carnitine esters and the carnitine precursors is required. Carnitine has been investigated in many biochemical, pharmacokinetic, metabolic and toxicokinetic studies and thus many analytical methods have been developed and published for the determination of carnitine in foods, dietary supplements, pharmaceutical formulations, biological tissues and body fluid. The analytical procedures presented in this review have been validated in terms of basic parameters (linearity, limit of detection, limit of quantitation, sensitivity, accuracy, and precision). This article presented the impact of different analytical techniques, and provides an overview of applications that address a diverse array of pharmaceutical and biological questions and samples.

Lipophilicity study of eight cephalosporins by reversed-phase thin-layer chromatographic method.

The lipophilicity (R(M0)) and specific hydrophobic surface area for the representatives of four generation cephalosporins have been determined by reversed-phase thin-layer chromatography, and the effect of different mobile-phase modifiers (such as methanol, acetonitrile, acetone, 1,4-dioxane and 2-propanol) on the retention has been studied. The compounds studied showed typical retention behavior; their R(M) values decreased linearly with increasing concentration of the organic modifier in the eluent. The linear correlations between the volume fraction of the organic solvent and the R(M) values over a limited range were established for each solute, resulting in high values of correlation coefficients (>0.95 in most cases). R(M) values were determined by various concentrations of organic modifier, and the correlation obtained was extrapolated to 0% of organic modifier. Chromatographically established logP (R(M0)) parameters were compared with computationally calculated partition coefficients values (AClogP, ALOGP, KOWWIN, ALOGPs, XLOGP2, MLOGP and XLOGP3) and experimental octanol-water logP values (measured by the shake flask method). The received results demonstrate that RP-TLC may be a good alternative technique for analytics in describing the lipophilic nature of investigated cephalosporins as well as the activity.

Lipophilicity study of some non-steroidal anti-inflammatory agents and cephalosporin antibiotics: A review

Lipophilicity properties have long been considered a vital component of drug discovery and development, providing insight into the role of molecular properties in the biological activity of known and new compounds. An extensive survey of the literature published in analytical and pharmaceutical chemistry journals has been conducted. Separation, optical, electrochemical and calculation methods which were developed and used for determination of lipophilicity non-steroidal anti-inflammatory agents and cephalosporin antibiotics in drugs and biological materials, have been reviewed. This review covers over 100 miscellaneous methods. Presented review highlighted some recent developments and new techniques that have been used in the lipophilicity detection of two different kinds of drugs.

Stability Analysis of Cefaclor and Its Inclusion Complexes of β-Cyclodextrin by Thin-Layer Chromatography and Densitometry

The stability of cefaclor and its inclusion complex of β-cyclodextrin was investigated, including an effect of pH solution, temperature, and incubation time. Favorable retention parameters (RF, Rs, α) were obtained under developed conditions, which guarantee good separation of studied components. The degradation processes were described with kinetic and thermodynamic parameters (k, t0.1, t0.5, and Ea). The identification of degradation products was performed with the application of proton nuclear magnetic resonance spectrometry and thin-layer chromatography with densitometry.

Simultaneous identification and quantitative analysis of eight cephalosporins in pharmaceutical formulations by TLC-densitometry

A rapid, accurate, and sensitive densitometric TLC method has been established and validated for simultaneous analysis of eight β-lactam antibiotics (cephalexin, cefadroxil, and cefazolin (first-generation), cefaclor, cefuroxime, and cefuroxime axetil (second-generation), and ceftriaxone and cefotaxime (third-generation)). Chromatographic separation was achieved on silica gel F254 plates with chloroform-ethyl acetate-glacial acetic acid-water 4:4:4:1 (v/v) as mobile phase. Densitometric detection was performed at 275 nm. Statistical evaluation showed the performance of the method was satisfactory. Accuracy was in the range 98.30–100.85% and precision, as RSD, was from 0.4 to 2.45%.

Separation, identification, and quantitative analysis of the epimers of cefaclor by TLC-densitometry

The epimers of cefaclor have been separated, identified, and analyzed quantitatively by TLC. The stationary phase was silica gel 60 F254, modified with β-cyclodextrin, and the mobile phase was chloroform-ethyl acetate-glacial acetic acid-water 4:4:4:1 (v/v). Chromatograms were developed at 5°C, dried at room temperature, and analyzed densitometrically at 274 nm, the wavelength of maximum absorption. Under these conditions good separation of the epimers was achieved (RF 0.26 and 0.33). UV and1H NMR spectra were used to identify the epimers. The method is characterized by high sensitivity (LOD 0.24 and 0.27 µg per band for the epimers at RF 0.26 and 0.33, respectively, LOQ of 0.74 and 0.83 µg per band, respectively, and high accuracy (recovery between 100.03 and 100.81%) and precision (RSD from 0.67 to 1.73%).

Chromatographic techniques in analysis of cyclooxygenase-2 inhibitors in drugs and biological samples

Non-steroidal anti-inflammatory drugs, as a therapeutic class, are among the most often used active pharmaceutical ingredients in heath care in the world. They are mostly available without prescription and often used for treatment of fever and pain. An extensive research of the literature published in analytical and pharmaceutical chemistry journals has been conducted and the chromatographic methods which were used for the purity, stability and pharmacokinetic studies of the cyclooxygenase-2 inhibitors, in formulations and biological materials have been reviewed. The methodology for the analysis of selected drugs is very well documented and many examples are available in the literature. The common use of chromatographic techniques with various detection attachments provide possibility for monitoring of drugs in therapy.

A degradation study of cefepime hydrochloride in solutions under various stress conditions by TLC–densitometry

A rapid, accurate and sensitive thin-layer chromatography (TLC) method with densitometric detection has been developed and validated for the determination of cefepime in pharmaceuticals. Chromatographic separation was achieved on a silica gel TLC F254 plates with a mobile phase consisting of ethanol-2-propanol-glacial acetic acid 99.5%-water (4:4:1:3, v/v). Densitometric detection was carried out at wavelength of 266 nm in reflectance/absorbance mode. The validation of the method was found to be satisfactory with high accuracy (from 99.24 to 101.37%) and precision (RSD from 0.06 to 0.36%). Additionally, the stability of cefepime in solution was investigated, including the effect of pH, temperature and incubation time. Favorable retention parameters (Rf , Rs, α) were obtained under the developed conditions, which guaranteed good separation of the studied components. The degradation process of cefepime hydrochloride was described by kinetic and thermodynamic parameters (k, t0.1 , t0.5 and Ea ). Moreover, the chemical properties of degradation products were characterized by the Rf values, absorption spectra, HPLC-MS/MS and TLC-densitometry analysis. As the method could effectively separate the active substance from its main degradation product (1-methylpyrrolidine), it can be employed as a method to indicate the stability of this drug.

TLC assay of l-carnitine in dietary supplements

The application of a simple, selective, precise, and accurate thinlayer chromatographic method for quantification of l-carnitine in dietary food supplements, including drinks, capsules, and tablets, was reported. The high-performance thin-layer chromatography (HPTLC)-cellulose plates as stationary phase, and mixture: methanol-water-glacial acetic acid (10:2:0.1 v/v) as mobile phase were chosen. The chromatograms were analyzed densitometrically in the maximum absorption at 420 nm, after ninhydrin-based derivatization reaction. The analytical procedure has been validated in terms of basic parameters, such as linearity, precision, and accuracy. The developed method is characterized by LOD sensitivity of 2.51 µg per spot, as well as LOQ for 7.61 µg per spot and high accuracy established by recovery studies between 99.50% and 103.60 % with good precision (RSD below 1.55%). Presented TLC method illustrated suitability for routine qualitative and quantitative analyses of l-carnitine in dietary supplements.

Identification and quantitative determination of nabumetone in pharmaceutical preparations by TLC-densitometry

A simple, selective, and sensitive thin-layer chromatography (TLC) method is described for the identification and determination of nabumetone in pharmaceutical products. The mobile phase was constituted by the following mixture: n-hexane-chloroform-glacial acetic acid 4:1:1 (v/v/v); and the stationary phase was TLC plate of silica gel 60 F254. The chromatograms were developed and analyzed densitometrically at λ1 = 270 nm and λ2 = 330 nm. RF values and UV spectra were used to identify the compounds. The developed method was characterized by high sensitivity (LOD and LOQ (limits of detection and quantitation) from 0.23 µg per band to 1.00 mg per band), high accuracy (recovery about 100%), and good precision ((relative standard deviation, RSD <2%).