A chiral HPLC method for the determination of low amounts of D-carnitine in L-carnitine after derivatization with (+)-FLEC

Assessing the In Vitro and In Vivo Performance of L-Carnitine-Loaded Nanoparticles in Combating Obesity

Addressing obesity is a critical health concern of the century, necessitating urgent attention. L-carnitine (LC), an essential water-soluble compound, plays a pivotal role in lipid breakdown via β-oxidation and facilitates the transport of long-chain fatty acids across mitochondrial membranes. However, LC's high hydrophilicity poses challenges to its diffusion through bilayers, resulting in limited bioavailability, a short half-life, and a lack of storage within the body, mandating frequent dosing. In our research, we developed LC-loaded nanoparticle lipid carriers (LC-NLCs) using economically viable and tissue-localized nanostructured lipid carriers (NLCs) to address these limitations. Employing the central composite design model, we optimized the formulation, employing the high-pressure homogenization (HPH) method and incorporating Poloxamer® 407 (surfactant), Compritol® 888 ATO (solid lipid), and oleic acid (liquid oil). A comprehensive assessment of nanoparticle physical attributes was performed, and an open-field test (OFT) was conducted on rats. We employed immunofluorescence assays targeting CRP and PPAR-γ, along with an in vivo rat study utilizing an isolated fat cell line to assess adipogenesis. The optimal formulation, with an average size of 76.4 ± 3.4 nm, was selected due to its significant efficacy in activating the PPAR-γ pathway. Our findings from the OFT revealed noteworthy impacts of LC-NLC formulations (0.1 mg/mL and 0.2 mg/mL) on adipocyte cells, surpassing regular L-carnitine formulations' effects (0.1 mg/mL and 0.2 mg/mL) by 169.26% and 156.63%, respectively (p < 0.05).

Determination of L-Carnitine in Infant Powdered Milk Samples after Derivatization

Herein, a novel analytical method using a high-performance liquid chromatography-fluorescence detector (HPLC/FLD) is developed for rapidly measuring an L-carnitine ester derivative in infant powdered milk. In this study, solid-phase extraction cartridges filled with derivatized methanol and distilled water were used to effectively separate L-carnitine. Protein precipitation pretreatment was carried out to remove the protein and recover the analyte extract with a high recovery (97.16%–106.56%), following which carnitine in the formula was derivatized to its ester form. Precolumn derivation with 1-aminoanthracene (1AA) was carried out in a phosphate buffer using 1-(3-dimethylaminopropyl)-3-ethylcarbodiimide hydrochloride (EDC) as the catalyst. Method validation was performed following the AOAC guidelines. The calibration curves were linear in the L-carnitine concentration range of 0.1–2.5 mg/L. The lower limit of quantitation and limit of detection of L-carnitine were 0.076 and 0.024 mg/L, respectively. The intra- and interday precision and recovery results were within the allowable limits. The results showed that our method helped reduce the sample preparation time. It also afforded higher resolution and better reproducibility than those obtained by traditional methods. Our method is suitable for detecting the quantity of L-carnitine in infant powdered milk containing a large amount of protein or starch.

(+) or (-)-1-(9-fluorenyl)ethyl chloroformate as chiral derivatizing agent: A review

Over the last 30years, (±)-1-(9-fluorenyl)ethyl chloroformate ((±)-FLEC) was used as a chiral derivatizing agent in various analytical applications involving a wide range of endogenous, pharmaceutical and environmentally relevant molecules. This comprehensive review aims to present all the significant aspects related to the state of the art in FLEC labeling and subsequent chiral separation of the resulting diastereomers using LC, SFC and CE techniques.

Bioanalysis and enantioseparation of dl-carnitine in human plasma by the derivatization approach

BACKGROUND

L-carnitine is an over the counter drug, used to treat disorders like cardiomyopathy, skeletal myopathy, hypoglycemia and hyperammonemia. Preparations containing D-carnitine should be avoided by dialysis patients because it has toxic influence on biochemical processes by inhibiting the carnitine acetyltransferase. Therefore, it is of utmost importance to assess and control the content of D-carnitine.

METHODS

A HPLC method was developed and validated for determination and enantiomeric resolution of DL-carnitine in human plasma by derivatization approach. (S)-Naproxen-based three derivatizing reagents were synthesized and applied.

CONCLUSION

The limit of detection values were found to be 1.26 and 1.35 ng ml(-1) for the two isomers. The method is simple, reproducible, and can be used for routine analysis in laboratories for control of enantiomeric purity of carnitine.

In-capillary derivatization with (-)-1-(9-fluorenyl)ethyl chloroformate as chiral labeling agent for the electrophoretic separation of amino acids

An original micellar electrokinetic chromatography (MEKC) method using in-capillary derivatization with a chiral labeling reagent was developed for the separation of amino acid (AA) derivatives. The potential of (-)-1-(9-fluorenyl)-ethyl chloroformate (FLEC) as in-capillary derivatization agent is described for the first time. Several parameters for in-capillary derivatization and subsequent MEKC separation were systematically investigated using experimental designs. Firstly experimental conditions for in-capillary derivatization were optimized using face-centered central composite design (FCCD). Mixing voltage and time as well as concentration of the labeling solution were investigated. Efficient labeling was achieved by sequential injection of AAs and FLEC labeling solution followed by the application of a voltage of 0.2 kV for 570 s. The background electrolyte (BGE) composition was then optimized in order to achieve selectivity. A FCCD was performed with two factors, namely the sodium dodecyl sulfate (SDS) concentration and the percentage of propan-2-ol (IPA). The separation of 12 pairs of derivatized AA (FLEC-AA) diastereomers was achieved with resolution values comprised between 3 and 20. Furthermore, an efficient derivatization and separation of 29 FLEC-AA derivatives were achieved in a single run using a buffer made up of 40 mM sodium tetraborate, 21 mM SDS and 8.5% IPA. The method was successfully applied to the analysis of spiked artificial cerebrospinal fluid (aCSF) sample.

Sensitive determination of D-carnitine as enantiomeric impurity of levo-carnitine in pharmaceutical formulations by capillary electrophoresis-tandem mass spectrometry

In this work, capillary electrophoresis-electrospray ionization-tandem mass spectrometry was applied to the determination of l- and d-carnitine in pharmaceutical formulations. A simple sample treatment procedure consisting of the use of a dilution or an extraction step with water was employed prior to derivatization with 9-fluorenylmethoxycarbonyl (FMOC). The method was validated in terms of selectivity, linearity, accuracy, precision and sensitivity, with a LOD of 10ngmL(-1) for each enantiomer, which was enough to detect enantiomeric impurities up to 0.002% of d-carnitine with respect to the main enantiomer (l-carnitine). Eleven pharmaceutical formulations were analyzed including ampoules, oral solutions, sachets, and tablets. Results showed contents for carnitine comprised between 77 and 101% with respect to the labeled ones in the case of those formulations marketed with the racemate, and from 97 to 102% in those cases where the single enantiomer (l-carnitine) was employed as active ingredient. Percentages for the enantiomeric impurity (d-carnitine) ranging from 0.6 to 1.3% were obtained exceeding the limits established for impurities in drug products. These results corroborate the need of validated analytical methodologies enabling the quality control of pharmaceutical formulations containing carnitine.

(R)-2-{2-[(S)-(2'-Benzo-yloxy-1,1'-binaphthyl-2-yl)oxycarbonyl-amino]-3-phenylpropanamido-meth-yl}pyridinium picrate acetone solvate

In the crystal structure of the title compound, C(43)H(34)N(3)O(5) (+)·C(6)H(2)N(3)O(7) (-)·C(3)H(6)O, the large dimension and shape of the cation are responsible for the elongation of the ortho-rhom-bic unit cell. The ions and acetone mol-ecules are linked together by a system of hydrogen bonds involving an inter-molecular hydrogen bond between one N atom of the cation and the O atom of acetone and two inter-molecular hydrogen bonds between the cation N atoms and the O atoms of the picrate anion. No intra-molecular hydrogen bonds exist in the structure. The dihedral angle between the two naphthalene ring systems is 76.16 (13)°. The chiral C atom has a known R configuration, but this cannot be confirmed from this X-ray analysis.