Manoj Kumar Tikoo

Simultaneous high-performance liquid chromatographic determination of Cedrus deodara active constituents and their pharmacokinetic profile in mice

A specific and sensitive high-performance liquid chromatographic (HPLC) method with photodiode-array (PDA) ultraviolet detection was developed for the simultaneous determination of three bioactive constituents of Cedrus deodara namely wikstromol, matairesinol and dibenzylbutyrolactol in mouse plasma. In solid-phase extraction (SPE) these constituents were successfully separated using a C18 column by isocratic elution using acetonitrile:water containing hexanesulphonic acid, 32:68 (v/v). The flow rate was set at 1ml/min and detector wavelength at 225nm. Good linearity (r2>0.999) was observed over the studied range of 0.015-5.0microg/ml for wikstromol and 0.030-5.0microg/ml for matairesinol and dibenzylbutyrolactol. The CV values of intra-day precision for wikstromol, matairesinol and dibenzylbutyrolactol were in between 1.8-6.9, 1.7-4.9 and 1.6-4.2% and values of inter-day precision were in between 10.4-12.2, 9.7-11 and 10-11.2%, respectively. The extraction recoveries at low to high concentration were greater than 98, 83 and 87% for each analyte, respectively. The LOQ for wikstromol was 0.015microg/ml and for both matairesinol and dibenzylbutyrolactol it was 0.030microg/ml. The developed method was used to determine the pharmacokinetics of the three analytes in mice after intraperitoneal administration of CD-3.

Discovery of novel pyrazolopyrimidinone analogs as potent inhibitors of phosphodiesterase type-5.

Cyclic guanosine monophosphate (cGMP) specific phosphodiesterase type-5 (PDE5), a clinically proven target to treat erectile dysfunction and diseases associated with lower cGMP levels in humans, is present in corpus cavernosum, heart, lung, platelets, prostate, urethra, bladder, liver, brain, and stomach. Sildenafil, vardenafil, tadalafil and avanafil are FDA approved drugs in market as PDE5 inhibitors for treating erectile dysfunction. In the present study a lead molecule 4-ethoxy-N-(6-hydroxyhexyl)-3-(1-methyl-7-oxo-3-propyl-6,7-dihydro-1H-pyrazolo[4,3-d]pyrimidin-5-yl)benzenesulfonamide, that is, compound-4a, an analog of pyrazolopyrimidinone scaffold has been identified as selective PDE5 inhibitor. A series of compounds was synthesized by replacing N-methylpiperazine moiety (ring-C) of sildenafil structure with different N-substitutions towards sulfonamide end. Compound-4a showed lower IC₅₀ value (1.5 nM) against PDE5 than parent sildenafil (5.6 nM) in in vitro enzyme assay. The isoform selectivity of the compound-4a against other PDE isoforms was similar to that of the Sildenafil. In corroboration with the in vitro data, this molecule showed better efficacy in in vivo studies using the conscious rabbit model. Also compound-4a exhibited good physicochemical properties like solubility, caco-2 permeability, cLogP along with optimal PK profile having no significant CYP enzyme inhibitory liabilities. Discovery of these novel bioactive compounds may open a new alternative for developing novel preclinical candidates based on this drugable scaffold.

Nitrofuranyl Methyl Piperazines as New Anti-TB Agents: Identification, Validation, Medicinal Chemistry, and PK Studies.

Whole-cell screening of 20,000 drug-like small molecules led to the identification of nitrofuranyl methylpiperazines as potent anti-TB agents. In the present study, validation followed by medicinal chemistry has been used to explore the structure-activity relationship. Ten compounds demonstrated potent MIC in the range of 0.17-0.0072 μM against H37Rv Mycobacterium tuberculosis (MTB) and were further investigated against nonreplicating and resistant (Rif(R) and MDR) strains of MTB. These compounds were also tested for cytotoxicity. Among the 10 tested compounds, five showed submicromolar to nanomolar potency against nonreplicating and resistant (Rif(R) and MDR) strains of MTB along with a good safety index. Based on their overall in vitro profiles, the solubility and pharmacokinetic properties of five potent compounds were studied, and two analogues, 14f and 16g, were found to have comparatively better solubility than others tested and acceptable pharmacokinetic properties. This study presents the rediscovery of a nitrofuranyl class of compounds with improved aqueous solubility and acceptable oral PK properties, opening a new direction for further development.

Acute, sub-acute and general pharmacological evaluation of 5-(3,4-methylenedioxyphenyl)-4-ethyl-2E,4E-pentadienoic acid piperidide (SK-20): A novel drug bioavailability enhancer

An efflux pump inhibitor, SK-20 (5-(3,4-methylenedioxyphenyle)-4 ethyl-2E,4E-pentadienoic acid piperidide), was assessed for its toxicity at three different pharmacological profiles: acute, sub-acute and general pharmacology with pharmacokinetics. In acute study, the SK-20 was found safe up to a dose of 2000 mg/kg (b.wt.); and at sub-acute, dosages of 50 and 100 mg/kg (b.wt.) were found to be safe. However, dosages of 200 mg or above per kg (b.wt.) showed some morphological alterations in cellular architecture of both liver and kidneys in both sexes, viz., mild vascular congestion along with sporadic hemorrhages and infiltration into renal and hepatic parenchyma by mononucleate cell. General pharmacological studies did not result into any alterations in analgesic, convulsions, rectal temperatures and in the rhythm or the rate of the intestinal motility or the secretion of the bile. While the respiratory and the cardiac rate remained normal, the only parameter to show was the blood pressure, which at all the doses tested, showed a tendency toward reduction. Characteristically, the SK-20 at all doses influenced pentobarbital-induced hypnosis positively and negatively to spontaneous motor activity in a dose dependent manner. Pharmacokinetics of SK-20 revealed it to have retention time at 10.2 min and half life 2.47 h.

Pharmacokinetic interaction of some antitubercular drugs with caraway: implications in the enhancement of drug bioavailability

This study deals with the pharmacokinetic interaction of selected anti-TB drugs with a natural product (CC-1a) derived from caraway (Carum carvi, L.) seed. CC-1a, chemically standardized butanolic fraction, enhanced the plasma levels of rifampicin, pyrazinamide, and isoniazid in Wistar rat, resulting in increased bioavailability indices (Cmax and AUC) of the drugs. Moreover, a 40% reduced dose regimen of these drugs, which additionally contained CC-1a, was equivalent in terms of Cmax and AUC to a normal dose regimen. A permeation-enhancing property of CC-1a across small intestinal absorptive surface was found to be a contributing factor in its bioavailability enhancing profile.

Development and validation of a highly sensitive LC-ESI-MS/MS method for estimation of IIIM-MCD-211, a novel nitrofuranyl methyl piperazine derivative with potential activity against tuberculosis: Application to drug development

In the present study, a simple, sensitive, specific and rapid liquid chromatography (LC) tandem mass spectrometry (MS/MS) method was developed and validated according to the Food and Drug Administration (FDA) guidelines for estimation of IIIM-MCD-211 (a potent oral candidate with promising action against tuberculosis) in mice plasma using carbamazepine as internal standard (IS). Bioanalytical method consisted of one step protein precipitation for sample preparation followed by quantitation in LC-MS/MS using positive electrospray ionization technique (ESI) operating in multiple reaction monitoring (MRM) mode. Elution was achieved in gradient mode on High Resolution Chromolith RP-18e column with mobile phase comprised of acetonitrile and 0.1% (v/v) formic acid in water at the flow rate of 0.4mL/min. Precursor to product ion transitions (m/z 344.5/218.4 and m/z 237.3/194.2) were used to measure analyte and IS, respectively. All validation parameters were well within the limit of acceptance criteria. The method was successfully applied to assess the pharmacokinetics of the candidate in mice following oral (10mg/kg) and intravenous (IV; 2.5mg/kg) administration. It was also effectively used to quantitate metabolic stability of the compound in mouse liver microsomes (MLM) and human liver microsomes (HLM) followed by its in-vitro-in-vivo extrapolation.

Determination of ZSTK474, a novel Pan PI3K inhibitor in mouse plasma by LC–MS/MS and its application to Pharmacokinetics.

Graphical abstract Figure. No caption available. HighlightsSimple, robust, rapid, reproducible method development of ZSTK474 for routine analysis.Full validated LCMS/MS Method.Successfully applied to pharmacokinetics study.Mice pharmacokinetics is first time reported. ABSTRACT ZSTK474, a promising novel anticancer molecule derived from s‐triazine, found to have antitumor activities against different cancer cell lines. However, neither LCMS method nor pharmacokinetics of ZSTK474 has been reported till now. A sensitive, simple, short and specific liquid chromatography tandem mass spectrometry (LCMS/MS) method was developed for the quantification of ZSTK474 in mouse plasma accordance with the US Food and Drug Administration guidelines. Extraction of drug molecule was carried out using protein precipitation. Chromatographic analyte separation was achieved on Atlantis dC18 (4.6 × 50 mm, 3 &mgr;m). Composition of isocratic mobile phase consists of 90% acetonitrile and 0.2% formic acid, at 0.7 mL/min flow rate, having short 2.5 min run time. Method development was validated and found to be linear over a dynamic range between 1.9–1000 ng/mL; having a correlation coefficient (r 2) ≥ 0.9978. The analyte was found to be stable under short and long term storage conditions. LCMS/MS method developed was validated and found to be selective, reproducible, precise and accurate to quantify ZSTK474 in plasma samples, and first time successfully applied to pharmacokinetic studies. Pharmacokinetic data showed fast absorption attaining Cmax at 0.25 h and half life (t1/2) 5.18 h after oral administration of ZSTK474 at 20 mg/kg in mouse.

Re-Validation of New Develop Highly Sensitive, Simple LCMS/MS Method for the Estimation of Rohitukine and its Application in ADME/Pre-Clinical Pharmacokinetics

The purpose of the research was to develop a simple, rapid, accurate, reproducible and sensitive liquid chromatography–tandem mass spectrometry (LC-MS/MS) method for determination of Rohitukine, a chromone alkaloid in plasma. The chromatographic separation was achieved with high resolution RP18e Chromolith column (100 × 4.6 mm, 2 μm) employing a isocratic composition of organic solvent acetonitrile with 0.1% (v/v) formic acid (80:20, %v/v) at a flow rate of 0.5 mL/min. Triple quadrupole mass spectrometry with positive electrospray ionization (ESI) technique operating in multiple reaction monitoring used to estimate MS/MS ion transitions like 306.05>245.10 and 306.05>231.05 for Rohitukine and 330.30>97.0 for IS. Simple single step protein precipitate method was used for sample preparation. The method was validated for specificity, linearity, accuracy, precision, recovery, matrix effect and stability as per FDA guidelines. Linearity of the analyte was acquired throughout the concentration range from 0.1 ng/mL to 1000 ng/mL in mice plasma. Pharmacokinetic study was performed on female BALB/c mice through oral (20 mg/kg) and intravenous (2 mg/kg) route where the oral bioavailability of Rohitukine obtained was 84%. The bioanalytical method was successfully used for determination of plasma protein binding study, permeability and microsomal stability in mouse, rat and human liver microsomes.