M.V.N. Kumar Talluri

Separation of stereoisomers of sertraline and its related enantiomeric impurities on a dimethylated β-cyclodextrin stationary phase by HPLC

A reversed-phase high-performance liquid chromatographic (HPLC) method was developed and validated for evaluating the chiral discrimination ability of CYCLOBOND I 2000 DM chiral stationary phase (CSP) towards sertraline and its related enantiomers. The effect of pH, buffer concentration as well as nature of organic modifier, flow rate and temperature on enantioselectivity was investigated. The developed reversed-phase chromatographic conditions were able to separate not only the enantiomers of sertraline but also its process related chiral impurities. The method was validated for determination of enantiomeric purity of sertraline HCl in drug substances and formulations.

Identification of hydrolytic and isomeric N-oxide degradants of vilazodone by on line LC–ESI–MS/MS and APCI–MS

The present study reports the degradation behavior of a new antidepressant drug, vilazodone, under various stress conditions as per International Conference on Harmonization guidelines (ICH, Q1A(R2). The investigation involved monitoring decomposition of the drug under hydrolytic (acidic, basic and neutral), oxidative, photolytic and thermal stress conditions and identifying degradation products. A rapid, precise, accurate and robust ultra high performance liquid chromatography (UPLC) method has been developed on a Waters CSH Phenyl-Hexyl column (100 mm × 2.1 mm, 1.7 μm) using gradient elution of 10mM ammonium acetate buffer (pH 5.0) and acetonitrile as mobile phase. The drug was found to be degraded in hydrolytic (acidic and basic) and oxidative conditions, whereas it was stable under neutral hydrolytic, photolytic and thermal stress conditions. The method was extended to quadrupole time-of-flight mass spectrometry (QTOF-MS) for the structural characterization of degradation products. It has been observed that isomeric N-oxide degradation products were formed under oxidative stress condition. The exact location of N-oxidation in the drug was investigated using atmospheric pressure chemical ionization (APCI) due to the formation of characteristic fragment ions. These fragment ions resulted from Meisenheimer rearrangement owing to thermal energy activation at the vaporizer of APCI source. All degradation products were comprehensively characterized by UPLC-ESI-MS/MS and UPLC-APCI-MS experiments. The most probable mechanisms for the formation of degradation products have also been proposed. The method was validated in terms of specificity, linearity, accuracy, precision, and robustness as per ICH guidelines.

Characterization of stress degradation products of mirabegron using UPLC-QTOF-MS/MS and in silico toxicity predictions of its degradation products

Mirabegron is a novel beta-3 adrenergic receptor agonist in the treatment of overactive bladder disorder. The drug was subjected to hydrolytic, photolytic, thermal and oxidative stress conditions as per the International Conference on Harmonization guidelines (ICH) Q1A (R2) to understand the degradation profile of the drug. The safety of the drug may be affected by degradation products present in the drug. As a result, identification and characterization of degradation products has become very important in drug development processes. In this study, a simple, rapid, precise and accurate ultra performance liquid chromatography (UPLC-PDA) method has been developed on a Waters CSH C18 column (100 mm × 2.1 mm, 1.7 μm) using gradient elution of ammonium acetate (10 mM, pH 5) and acetonitrile as mobile phase. Mirabegron was found to degrade under hydrolytic and oxidative stress conditions while it was stable under thermal and photolytic conditions. A total of seven degradation products were characterized by UPLC-MS/MS in positive ion mode, combined with accurate mass measurements. The proposed structures of the degradation products have been rationalized by appropriate mechanisms. Additionally, in silico toxicity was predicted for all degradant products by using TOPKAT and DEREK softwares to enhance the safety of the drug.

Development and validation of a reversed phase liquid chromatographic method for separation and determination of related-substances of modafinil in bulk drugs.

A reversed-phase high-performance liquid chromatographic (RP-HPLC) method for determination and evaluation of purity of modafinil in bulk drugs using Kromasil C(18) column with acetonitrile: 0.02M ammonium acetate as a mobile phase in gradient elution mode at 30 degrees C and detection at 225nm using photodiode array detector has been developed. The effects of pH, temperature and the percent of organic modifier on resolution were studied. Related substances, viz, sulphide, sulphoxide, sulphones of the modafinil, acid and ester derivatives, were separated and quantified. The method was found to be simple, rapid, selective and capable of detecting all process related impurities at trace levels in the finished products of modafinil with detection limits of 0.6-2.4x10(-8)g. The method was validated with respect to accuracy, precision, linearity, ruggedness, and limits of detection and quantification. It was found to be suitable not only for monitoring the reactions during the process development but also quality assurance of modafinil.

Structural characterization of alkaline and oxidative stressed degradation products of lurasidone using LC/ESI/QTOF/MS/MS.

A selective, accurate, precise and robust stability indicating liquid chromatography assay method was developed for the monitoring of a novel antipsychotic drug, lurasidone, in the presence of its degradation products (DPs). Also, we investigated degradation behavior of the drug under various stressed conditions such as hydrolytic (acidic, basic and neutral), oxidation, photolytic and thermal. The drug was found to be degraded under base hydrolytic and oxidative conditions, while it was stable in acid and neutral hydrolytic, photolytic and thermal conditions. The method showed adequate separation of lurasidone and its DPs on Xterra C18 (150 mm × 4.6 mm i.d., 3.5 μm) column using 20 mM ammonium formate (pH 3.0): acetonitrile as a mobile phase in gradient elution mode at a flow rate of 0.6 mL/min. This method was extended to liquid chromatography electrospray ionization quadrupole time-of-flight mass spectrometry (LC/ESI/QTOF/MS/MS) for structural characterization of DPs. A total of five DPs were characterized by LC/ESI/QTOF/MS/MS studies. Most probable mechanisms for the formation of DPs were proposed. The developed method was validated in terms of specificity, linearity, accuracy, precision, and robustness as per International Conference on Harmonization Guideline Q2 (R1).

LC–ESI-MS determination and pharmacokinetics of adrafinil in rats

A highly sensitive and specific liquid chromatography/tandem mass spectrometric (LC-MS/MS) method for investigating the pharmacokinetics of adrafinil in rats was developed. Rat serum pretreated by solid-phase extraction (SPE) was analyzed by LC-MS/MS with an electrospray ionization (ESI) interface. The mobile phase consisted of acetonitrile:water:acetic acid (35:65:0.1, v/v/v) in an isocratic elution mode pumped at 1.0 ml/min. The analytical column (250 mm x 4.6 mm i.d.) was packed with Kromasil C(18) material (5.0 microm). The standard curve was linear from 16.5 to 5000 ng/ml. The assay was specific, accurate (R.S.D.<2.6%), precise and reproducible (within- and between-day precisions R.S.D. <7.0% and <9.0%, respectively). Adrafinil in rat serum was stable over three freeze-thaw cycles at ambient temperature for 6 h. The method had a lower limit of quantitation of 16.5 ng/ml, which offered high sensitivity for the determination of adrafinil in serum. The method was successfully applied to pharmacokinetic studies of adrafinil after an oral administration to rats.

Rapid structural characterization of in vivo and in vitro metabolites of tinoridine using UHPLC–QTOF–MS/MS and in silico toxicological screening of its metabolites

Tinoridine is a nonsteroidal anti-inflammatory drug and also has potent radical scavenger and antiperoxidative activity. However, metabolism of tinoridine has not been thoroughly investigated. To identify in vivo metabolites, the drug was administered to Sprague-Dawley rats (n = 5) at a dose of 20 mg kg(-1), and blood, urine and feces were collected at different time points up to 24 h. In vitro metabolism was delved by incubating the drug with rat liver microsomes and human liver microsomes. The metabolites were enriched by optimized sample preparation involving protein precipitation using acetonitrile, followed by solid-phase extraction. Data processes were carried out using multiple mass defects filters to eliminate false-positive ions. A total of 11 metabolites have been identified in urine samples including hydroxyl, dealkylated, acetylated and glucuronide metabolites; among them, some were also observed in plasma and feces samples. Only two major metabolites were formed using liver microsomal incubations. These metabolites were also observed in vivo. All the 11 metabolites, which are hitherto unknown and novel, were characterized by using ultrahigh-performance liquid chromatography-quadrupole time-of-flight tandem mass spectrometry in combination with accurate mass measurements. Finally, in silico toxicological screening of all metabolites was evaluated, and two metabolites were proposed to show a certain degree of lung or liver toxicity.

Quality by design based development of a selective stability-indicating UPLC method of dolutegravir and characterization of its degradation products by UPLC-QTOF-MS/MS

Dolutegravir (DTG), a selective human immunodeficiency virus (HIV) integrase enzyme inhibitor, was subjected to hydrolytic (acidic, alkaline and neutral), oxidative, photolytic and thermal stress conditions as per the ICH guidelines. The drug degraded under hydrolytic and photolytic stress conditions, while it was stable under oxidative and thermal conditions. A total of 14 hitherto unknown degradation products were formed. The quality by Design (QbD) principle was applied to develop a fast and selective separation of dolutegravir and its degradation products. The developed methodology was based on a design of experiment (DOE) approach to investigate the critical process parameters of chromatographic systems. Effective chromatographic separation was achieved on a Waters Acquity UPLC using a phenyl hexyl (100 × 2.1 mm, 1.7 μm) column with the gradient elution of 10 mM acetate buffer (pH 4.0) and methanol as the mobile phase. The gradient program was set from 15% to 65% of methanol over 5 min (then held for 6 min) at a flow rate of 0.3 mL min−1. The method was extended to UPLC-quadrupole time-of-flight tandem mass spectrometry (QTOF-MS/MS) for the structural characterization of fourteen degradation products, which includes two new diastereomers, H3 (4S, 12aS) and H4 (4R, 12aR), and two carboxylated degradation products (H1 and H2), formed under hydrolytic stress conditions. The drug also degraded to ten different products (P1–P10) under photolytic stress conditions.

First report on the pharmacokinetic profile of nimbolide, a novel anticancer agent in oral and intravenous administrated rats by LC/MS method

Nimbolide is a novel, natural compound with promising potential as a drug candidate for anticancer activity. It is isolated from the Indian traditional medicinal plant Azadirachta indica popularly known as neem. The present study was undertaken to explore the oral bioavailability and pharmacokinetic characteristics of nimbolide in rats using the LC/QTOF/MS method. A simple protein precipitation method using acetonitrile was employed for extracting nimbolide from rat plasma. The chromatographic separation of nimbolide and the internal standard (regorafenib) was attained on an Aquity BEH C18 column (100 × 2.1 mm, 2.7 μm), using ACN and 0.1% of formic acid in water as mobile phase components in a gradient elution mode at a flow rate of 0.45 mL/min over a short run time of 4 min. A mass detection was carried out using target ions of [M + H]+ at m/z 467.2074 for nimbolide and m/z 483.0847 for the internal standard. The LC/MS method was validated and all the parameters were found well within the specified limits. The calibration curve was constructed in the range of 1-1000 ng/mL. The method shows good accuracy (91.66-97.12%) and precision (intra 2.21-6.92% CV and inter-day 2.56-4.62% CV). This developed LC/MS method was effectively applied to the pharmacokinetic study of nimbolide upon oral and intravenous administration in rats. In concordance with its physicochemical properties and high lipophilicity, we found that it shows poor oral absorption at different doses (10, 30 and 50 mg/kg). As expected, higher plasma levels were observed upon intravenous (10 mg/kg) administration. This method can be extended for evaluation of drug interaction and drug metabolism in rats as well as in humans. Moreover, our rapid and sensitive method may cater the need to accelerate the preclinical formulation development and lead optimization for future drug development of this potent anticancer agent. Further, our oral bioavailability studies demonstrated that nimbolide possesses poor oral absorption, which could be the probable reason for the delay in therapeutic translation of this promising agent for clinical use.

Selective separation and characterisation of stress degradation products and process impurities of prucalopride succinate by LC-QTOF-MS/MS

The present study reports the degradation behaviour of a new prokinetic agent, Prucalopride succinate, under various stress conditions as per International Conference on Harmonization guidelines (ICH, Q1A (R2)). The investigation involved monitoring decomposition of the drug under hydrolytic (acidic, basic and neutral), oxidative, photolytic and thermal stress conditions followed by characterization of the degradation products (DPs) and process related impurities (IMPs). A rapid, precise, accurate and robust reverse phase high performance liquid chromatography (RP-HPLC) method has been developed involving mobile phase of 20mM ammonium bicarbonate buffer and acetonitrile: methanol (80:20v/v) on a Waters Xbridge-C8 (150mm×4.6mm i.d., 3.5μm) column using gradient elution. The drug was found to be degraded in hydrolytic (acidic) and oxidative conditions, whereas it was stable under basic and neutral hydrolytic, photolytic and thermal stress conditions. The method was extended to LC-ESI-QTOF-MS/MS for the structural characterization of DPs and process related IMPs. Structural characterization was carried out based on the generated molecular formula of DPs and its fragment ions. It has been observed that two major DPs were formed under each acid hydrolysis and oxidative stress conditions. The most probable mechanisms involved in the formation of DPs were also proposed. Finally, the method was validated in the term of specificity, linearity, accuracy, precision, and robustness as per ICH guidelines, Q2 (R1).