Ashok K. Shakya

Orotransmucosal drug delivery systems: A review

Oral mucosal drug delivery is an alternative method of systemic drug delivery that offers several advantages over both injectable and enteral methods and also enhances drug bioavailability because the mucosal surfaces are usually rich in blood supply, providing the means for rapid drug transport to the systemic circulation and avoiding, in most cases, degradation by first-pass hepatic metabolism. The systems contact with the absorption surface resulting in a better absorption, and also prolong residence time at the site of application to permit once or twice daily dosing. For some drugs, this results in rapid onset of action via a more comfortable and convenient delivery route than the intravenous route. Not all drugs, however, can be administered through the oral mucosa because of the characteristics of the oral mucosa and the physicochemical properties of the drug. Although many drugs have been evaluated for oral transmucosal delivery, few are commercially available. The clinical need for oral transmucosal delivery of a drug must be high enough to offset the high costs associated with developing this type of product. Transmucosal products are a relatively new drug delivery strategy. Transmucosal drug delivery promises four times the absorption rate of skin. Drugs considered for oral transmucosal delivery are limited to existing products, and until there is a change in the selection and development process for new drugs, candidates for oral transmucosal delivery will be limited. The present papers intend to overview a wide range of orotransmucosal routes being potentially useful for transmucosal drug delivery and remind us of the success achieved with these systems and the latest advancement in the field.

Palatal mucosa as a route for systemic drug delivery: A review.

Rapid developments in the field of molecular biology and gene technology resulted in generation of many macromolecular drugs including peptides, proteins, polysaccharides and nucleic acids in great number possessing superior pharmacological efficacy with site specificity and devoid of untoward and toxic effects. However, the main impediment for the oral delivery of these drugs as potential therapeutic agents is their extensive pre-systemic metabolism, instability in acidic environment resulting into inadequate and erratic oral absorption. Parenteral route of administration is the only established route that overcomes all these drawbacks associated with these orally less/inefficient drugs. But, these formulations are costly, have least patient compliance, require repeated administration, in addition to the other hazardous effects associated with this route. Over the last few decades pharmaceutical scientists throughout the world are trying to explore transdermal and transmucosal routes as an alternative to injections. Historically, oral transmucosal drug delivery has received intensive interest since ancient times for the most widely utilized route of administration for the systemic delivery of drugs. In more recent years, better systemic bioavailability of many drugs has been achieved by oromucosal route. Among the various transmucosal sites available, soft-palatal mucosa was also found to be the most convenient and easily accessible novel site for the delivery of therapeutic agents for systemic delivery as retentive dosage forms, because it has abundant vascularization and rapid cellular recovery time after exposure to stress. Smooth surface of the soft palate and its good flexibility are prerequisites to prevent mechanical irritation and local discomfort. The objective of this review is to provide an update on the most promising advances in novel non-invasive soft-palatal route and the conceptual and technical approaches to the design and formulation of soft-palatal drug delivery systems. In this area, the development of mucoadhesive delivery systems appears to be the most promising strategy.

Synthesis and Antibacterial Properties of New 8-Nitrofluoroquinolone Derivatives

The objective of this research was the preparation of new 8-nitrofluoroquinolone models and investigation of their antibacterial properties. The work initially involved large scale preparation of the synthon 7-chloro-1-cyclopropyl-6-fluoro-8-nitro-4-oxo-1,4-dihydroquinoline-3-carboxylic acid (3), followed by introduction of substituted primary amine appendages at the C-7 position to give derivatives 9a-g, in which the amino group is appended to substituted benzenes or aromatic heterocycles, is part of a primary alpha-amino acid or just a simple primary aliphatic amine. This nucleophilic aromatic substitution step was a very simple procedure since the 8-nitro group of the above synthon facilitated the addition of weak nucleophiles at C-7. All compounds prepared were fully identified and characterized using NMR, IR, EA and MS, and were consistent with expected structures. The prepared targets and the intermediates have shown interesting antibacterial activity against gram positive and/or gram negative strains. In particular, the p-toluidine, p-chloroaniline and aniline derivatives showed good activity against S. aureus with MIC range approximately 2-5 microg/mL. In conclusion, more lipophilic groups seem to enhance activity against gram positive strains.

Synthesis, characterization, and antimicrobial activity of some new coumarin derivatives

A number of new [(4-methyl-2-oxo-2H-chromen-7-yl)amino]methylcoumarins (5a–c), benzofuran (6), and benzoxazol (7) were synthesized through the reaction of 7-amino-4-methylcoumarin (1) with a number of organic halides. In addition, series of N-substituted 2-[(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetohydrazide (11a–h) and (12a–d) were prepared from the reaction of 2-[(4-methyl-2-oxo-2H-chromen-7-yl)oxy]acetohydrazide (8) with corresponding heteroaryl/alkyl halides (2–4, 9, and 10). The synthesized compounds were characterized by elemental analysis and by spectroscopic techniques such as 1H-NMR, 13C-NMR, and mass spectrometry and were tested for their in vitro antimicrobial activity. The newly synthesized compounds exerted significant inhibitory activity against the growth of tested bacterial strains and a few of them are found to be potent antimicrobial agents.

Simultaneous determination of triprolidine and pseudoephedrine in human plasma by liquid chromatography-ion trap mass spectrometry

A highly efficient, selective and specific method for simultaneous quantitation of triprolidine and pseudoephedrine in human plasma by liquid chromatography-ion trap-tandem mass spectrometry coupled with electro spray ionization (LC-ESI-ion trap-tandem MS) has been validated and successfully applied to a clinical pharmacokinetic study. Both targeted compounds together with the internal standard (gabapentin) were extracted from the plasma by direct protein precipitation. Chromatographic separation was achieved on a C(18) ACE((R)) column (50.0mmx2.1mm, 5mum, Advance Chromatography Technologies, Aberdeen, UK), using an isocratic mobile phase, consisting of water, methanol and formic acid (55:45:0.5, v/v/v), at a flow-rate of 0.3mL/min. The transition monitored (positive mode) was m/z 279.1-->m/z 208.1 for triprolidine, m/z 165.9-->m/z 148.0 for pseudoephedrine and m/z 172.0-->m/z 154.0 for gabapentin (IS). This method had a chromatographic run time of 5.0min and a linear calibration curves ranged from 0.2 to 20.0ng/mL for triprolidine and 5.0-500.0ng/mL for pseudoephedrine. The within- and between-batch accuracy and precision (expressed as coefficient of variation, %C.V.) evaluated at four quality control levels were within 94.3-106.3% and 1.0-9.6% respectively. The mean recoveries of triprolidine, pseudoephedrine and gabapentin were 93.6, 76.3 and 82.0% respectively. Stability of triprolidine and pseudoephedrine was assessed under different storage conditions. The validated method was successfully employed for the bioequivalence study of triprolidine and pseudoephedrine formulation in twenty six volunteers under fasting conditions.

Synthesis and biological evaluation of 2-[substituted acetyl]amino-5-alkyl-1,3,4-thiadiazoles

Abstract Some new N-substituted acetyl derivatives of 2-amino-5-alkyl-1,3,4-thiadiazoles have been prepared and investigated for antihistaminic and spasmolytic activity on guine pig ileum. A few of the compounds showed encouraging effects. In addition, some of the compounds also showed anti-inflammatory activity.

Molecular Modeling, Synthesis and Pharmacological Evaluation of 1,3,4- Thiadiazoles as Anti-inflammatory and Analgesic Agents

A series of novel substituted 2-amino-5-(1-(4-isobutylphenyl)ethyl)-1,3,4-thiadiazoles were designed, synthesized and evaluated as anti-inflammatory and analgesic agents. Compounds were characterized by elemental and spectroscopic analysis. Compounds possessing significant activities were screened for ulcerogenic activity. Compound-5 (2-(4-isobutylphenyl)-N-(5-(1-(4- isobutylphenyl)ethyl)-1,3,4-thiadiazol-2-yl)-propanamide) produces significant in vitro antiinflammatory activity (72.5%) as compared to ibuprofen (47.7%), while compound-3f (2-(Ncyclohexyl- N-methylamino)-N-(5-(1-(4-isobutylphenyl)-ethyl)-1,3,4-thiadiazol-2-yl)-acetamide) showed 64.1% activity. Results indicate that compound-4 (N-(5-(1-(4-isobutyl-phenyl)-ethyl)-1,3,4-thiadiazol-2-yl)-acetamide) exhibited highest analgesic activity (69.8%), where as compound-5 possessed 65.5% activity. Structure based drug design was also investigated to reveal the mechanism of action and specificity of our compounds against COX-2 enzyme. Anti-inflammatory activity and ulcerogenic potential were in agreement with the molecular modeling studies carried out on cycloxygenase enzyme.

Fatty Acids Analysis, Antioxidant and Biological Activity of Fixed Oil of Annona muricata L. Seeds

The total oil yield and the fatty acid composition were determined in the Annona muricata L. fixed oil using organic solvent extraction and GC-FID. The seeds were found to contain about ~21.5% of crude fixed oil on a dry weight basis. The crude oil containing fatty acid was converted into methyl esters and analysed by GC-FID. Fourteen fatty acids were identified using GC-FID. The major monounsaturated and saturated fatty acids were oleic acid (39.2%) and palmitic acid (19.1–19.2%), respectively, whereas the α-linolenic acid (1.2%) and linoleic acid (34.9%) were polyunsaturated fatty acid. The other saturated acids were stearic acid (3.3%), arachidic acid (0.4%), myristic acid (0.1%), heptadecanoic acid (0.1%), behenic acid (0.1%), and lignoceric acid (0.1%). Some of the fatty acids have not been reported earlier from the oil of Annona muricata L. Fixed oil exhibited significant free radical scavenging activity which was measured using DPPH and is also known to inhibit the gastrointestinal motility significantly.

Design, synthesis and evaluation of benzofuran-acetamide scaffold as potential anticonvulsant agent

Abstract A series of N-(2-(benzoyl/4-chlorobenzoyl)-benzofuran- 3-yl)-2-(substituted)-acetamide derivatives (4a-l, 5a-l) was synthesized in good yield. All synthesized compounds were in agreement with elemental and spectral data. The anticonvulsant activity of all synthesized compounds was assessed against the maximal electroshock induced seizures (MES) model in mice. Neurotoxicity was evaluated using the rotarod method. The majority of compounds exhibited anticonvulsant activity at a dose of 30 mg kg-1 body mass during 0.5-4 h, indicating their ability to prevent seizure spread at low doses. Relative to phenytoin, [N-(2-(4-chlorobenzoyl)benzofuran-3-yl)-2-(cyclohexyl( methyl) amino)-acetamide] (5i) and [N-(2-(4-chlorobenzoyl)benzofuran-3-yl)-2-(4-methylpiperidin-1- yl)-acetamide] (5c) demonstrated comparable relative anticonvulsant potency of 0.74 and 0.72, respectively, whereas [(N-(2-(4-chlorobenzoyl)benzofuran-3-yl)-2-(4-(furan-2-carbonyl)-piperazin-1-yl)-acetamide] (5f) exhibited the lowest relative potency of 0.16. The ALD50 of tested compounds ranged from 1.604 to 1.675 mmol kg-1 body mass. The ED50 of synthesized compounds ranged from 0.055 to 0.259 mmol kg-1 (~23.4 to 127.6 mg kg-1) body mass. The pharmacophore mapping of the examined compounds on standard drugs (phenobarbital, phenytoin, ralitolin and carbamazepine) strongly suggests that these compounds may exert their anticonvulsant activity via the same established mechanism as that of known drugs.

Stability-Indicating HPLC Determination of Gemcitabine in Pharmaceutical Formulations

A simple, sensitive, inexpensive, and rapid stability indicating high performance liquid chromatographic method has been developed for determination of gemcitabine in injectable dosage forms using theophylline as internal standard. Chromatographic separation was achieved on a Phenomenex Luna C-18 column (250 mm × 4.6 mm; 5μ) with a mobile phase consisting of 90% water and 10% acetonitrile (pH 7.00 ± 0.05). The signals of gemcitabine and theophylline were recorded at 275 nm. Calibration curves were linear in the concentration range of 0.5–50 μg/mL. The correlation coefficient was 0.999 or higher. The limit of detection and limit of quantitation were 0.1498 and 0.4541 μg/mL, respectively. The inter- and intraday precision were less than 2%. Accuracy of the method ranged from 100.2% to 100.4%. Stability studies indicate that the drug was stable to sunlight and UV light. The drug gives 6 different hydrolytic products under alkaline stress and 3 in acidic condition. Aqueous and oxidative stress conditions also degrade the drug. Degradation was higher in the alkaline condition compared to other stress conditions. The robustness of the methods was evaluated using design of experiments. Validation reveals that the proposed method is specific, accurate, precise, reliable, robust, reproducible, and suitable for the quantitative analysis.