Liquid chromatographic separation and thermodynamic investigation of stereoisomers of darunavir on Chiralpak AD-Hcolumn

Enantiomeric Separation and Thermodynamic Investigation of (R)-N-Tert-Butoxy Carbonyl-Piperidine-3-Carboxylic Acid Hydrazide, a Key Starting Material of Zidebactam

A new selective, accurate and precise chiral high-performance liquid chromatography method for the separation of (R)-N-tert-butoxy carbonyl-piperidine-3-carboxylic acid hydrazide (RE) and its enantiomer was developed. RE is a key starting material of novel β-lactam enhancer drug Zidebactam. Chiral resolution of more than 10 was achieved on Chiralpak IA column using mobile phase consisting of n-hexane, ethanol in the ratio of 70:30, v/v. The flow rate of the mobile phase was 1.0 mL min-1 and the column oven temperature was 30°C. Detection was carried out at 225 nm. The developed method was validated as per the International Conference on Harmonization guideline. Limit of detection and limit of quantification of the enantiomeric impurity (S)-N-tert-butoxy carbonyl-piperidine-3-carboxylic acid hydrazide (SE) was 2.5 and 7.5 μg mL-1, respectively. Mean recovery of the SE was 96.83 ± 1.4%. The effect of thermodynamic parameters on the chiral separation was evaluated.

Darunavir: A comprehensive profile

Darunavir: (3R,3aS,6aR)-hexahydrofuro[2,3-b]furan-3-yl [(2S,3R)-4-{[(4-aminophenyl)sulfonyl] (isobutyl)amino}-3-hydroxy-1-phenyl-2-butanyl]carbamate is a synthetic non-peptide protease inhibitor. On June 2006, it was first approved by the Food and Drug administration (FDA) for treatment of resistant type-1 of the human immunodeficiency virus (HIV). In July 2016, the FDA expanded the approval for use of darunavir in pregnant women with HIV infection. Darunavir prevents the replication of HIV virus by inhibiting the catalytic activity of the HIV-1 protease enzyme, and selectively inhibits the cleavage of HIV encoded Gag-Pol polyproteins in virus-infected cells, which prevents the formation of mature infectious virus particles. Darunavir is unique among currently available protease inhibitors because it maintains antiretroviral activity against a variety of multidrug-resistant HIV strains. This article discusses, by a critical extensive review of the literature, the description of darunavir in terms of its names, formulae, elemental composition, appearance, and use in the treatment of HIV-infected patients. The article also discusses the methods for preparation of darunavir, its physical-chemical properties, analytical methods for its determination, pharmacological properties, and dosing information.

Liquid Chromatographic Separation and Thermodynamic Investigation of Ethyl Nipecotate Enantiomers on Immobilized Amylose-Based Chiral Stationary Phase

Ethyl nipecotate enantiomers are widely used as chiral building blocks in the synthesis of drug substances. An efficient and economic chiral high-performance liquid chromatographic method for determination of enantiomeric purity of ethyl nipecotate is developed and validated. Chiral separation was achieved on immobilized amylose-based stationary phase using a mixture of n-hexane: ethanol: diethylamine (80:20:0.1, v/v/v) as mobile phase. Resolution between R-(-)-ethyl nipecotate (REN) and S-(+)-ethyl nipecotate (SEN) peaks was found to be 3.59. The detector response of SEN exhibited an excellent linearity over the concentration range of 4.5–120 μg mL−1. The limit of detection and limit of quantification for SEN were 0.016 and 0.045 μg and REN were 0.015 and 0.043 μg, respectively. The influence of column oven temperatures on chiral retention and separation was studied in the range of 25°C to 50°C; the thermodynamic parameters ΔH°, ΔS° and ΔG° were evaluated from van’t Hoff plots and used to explain the strength of interaction between analyte and stationary phase.

Characterization of the Oxidative Degradation Product of Darunavir by LC-MS/MS

A rapid, selective, and reliable LC-MSⁿ method has been developed and validated for the isolation and structural characterization of the degradation product of darunavir (DRV). DRV, an HIV-1 protease inhibitor, was subjected to intrinsic oxidative stress conditions using 30% hydrogen peroxide and the degradation profile was studied. The oxidative degradation of DRV resulted in one degradation product. The unknown degradation product was separated on a Hibar Purospher C₁₈ (250 mm × 4.6 mm; 5 µm) column by using 0.01 M ammonium formate (pH 3.0) and acetonitrile as mobile phase in the ratio of 50:50, v/v. The eluents were monitored at 263 nm using a UV detector. The isolated degradation product was characterized by UPLC-Q-TOF and its fragmentation pathway was proposed. The proposed structure of the degradation product was confirmed by HRMS analysis. The developed stability-indicating LC method was validated with respect to accuracy, precision, specificity/selectivity, and linearity. No prior reports were found in the literature about the oxidative degradation behavior of DRV.

Dried blood spot analysis of (+) and (-) darunavir enantiomers on immobilized amylose tris-(3, 5-dimethylphenylcarbamate) LC and its application to pharmacokinetics

Dried blood spot analysis is an innovative novel blood sampling technique gaining interest in drug discovery and development processes owing to its inherent advantages over the conventional whole blood, plasma or serum sample collection. The present manuscript describes the development and validation of a highly sensitive and precise method of evaluation of pharmacokinetics of (+) and (-) darunavir enantiomers on rat dried blood spots. The enantiomers on rat dried blood spots were extracted into methanol and separated by LC on a Chiralpak IA column using hexane and ethanol containing 0.1% DEA (75:25, v/v) as a mobile phase at 20°C; both the enantiomers were detected at 266 nm using a photodiode array detector. The method was validated in terms of selectivity, linearity, accuracy, precision and stability as per the US Food and Drug and Administration guidelines. The hematocrit effect on extraction recovery was evaluated and the mean recoveries of (-) and (+) enantiomers of darunavir from dried blood spots were found to be 85.76 and 88.91% respectively. The intra- and inter-day precision and accuracy were 3.1-8.4 and 0.8-4.8% respectively. The developed method was successfully applied to a pharmacokinetic study of (+) and (-) enantiomers of darunavir on rat dried blood spots.

Development of a Validated LC Method for Separation of Process-Related Impurities Including the R-Enantiomer of S-Pramipexole on Polysaccharide Chiral Stationary Phases

Despite the availability of a few methods for individual separation of S-pramipexole from its process-related impurities, no common liquid chromatography (LC) method is reported so far in the literature. The present article describes the development of a single-run LC method for simultaneous determination of S-pramipexole and its enantiomeric and process-related impurities on a Chiralpak AD-H (150 x 4.6 mm, 5μm) column using n-hexane/ethanol/n-butylamine (75:25:0.1 v/v/v) as a mobile phase in an isocratic mode of elution at a flow rate of 1.2 ml/min at 30°C. The chromatographic eluents were monitored at a wavelength of 260 nm using a photodiode array detector. Excellent enantioseparation with good resolutions (Rs ≥ 2.88) and peak shapes (As ≤ 1.21) for all analytes was achieved. The proposed method was validated according to International Conference Harmonization (ICH) guidelines in terms of accuracy, precision, sensitivity, and linearity. Limits of quantification of impurities (0.25-0.55 μg/ml) indicate the highest sensitivity achievable by the proposed method. The method has an advantage of selectivity and suitability for routine determination of not only chiral impurity but also all possible related substances in active pharmaceutical ingredients of S-pramipexole.