K.L. Dhar’s research while affiliated with Guru Nanak Dev University and other places

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Publications (159)


Synthesis and Characterization of Piperine analogs as Potent Staphylococcus aureus NorA Efflux Pump Inhibitors
  • Article

January 2019

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11 Reads

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5 Citations

Chemical Methodologies

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K.L. Dhar

Curcumin–Zn(II) complex for enhanced solubility and stability: an approach for improved delivery and pharmacodynamic effects

April 2015

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591 Reads

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48 Citations

The aim of present investigation was to prepare Curcumin-Zn(II) complex in a view to enhance solubility, stability and pharmacodynamic effect in experimentally induced ulcerative colitis. Curcumin-Zn(II) complex was prepared by stirring curcumin with anhydrous zinc chloride at a molar ratio of 1:1. The prepared curcumin metallocomplex was characterized by TLC, FTIR, UV spectroscopy and (1)H NMR. In vitro kinetic degradation and solubility of Curcumin and Curcumin-Zn(II) complex was analyzed spectrophotometrically. Pharmacodynamic evaluation of curcumin and its metal complex was assessed in ulcerative colitis in mice. Curcumin showed chelation with zinc ion as confirmed by the TLC, FTIR, UV spectroscopy and (1)H NMR. The results of TLC [Rf value], IR Spectroscopy [shifting of stretching vibrations of υ(C=C) and υ(C=O)], UV spectra [deconvoluted with absorption band at 432-466.4 nm] of Curcumin-Zn(II) complex compared to curcumin confirmed the formation of metallocomplex. (1)HNMR spectra of Curcumin-Zn(II) showed the upfield shift of Ha and Hb. Kinetic stability studies showed metallocomplex with zinc exhibited good stability. In vivo study revealed significant reduction in severity and extent of colonic damage with Curcumin-Zn(II) which were further confirmed by histopathological study. This study recognizes higher solubility and stability of Curcumin-Zn(II) complex and suggested better pharmacodynamic effects.


(a) Comparative dissolution profile of curcumin loaded microsponges (F1–F9). (b) In vitro release profile of F7 with and without RCC.
3D bar surface chart depicting the influence of independent variables over dependent variables.
Histology of colonic section of (a) normal group, (b) acetic acid induced colitis group, (c) curcumin treated group, and (d) curcumin loaded microsponges treated group.
(a) Comparative dissolution profile of curcumin loaded microsponges (F1–F9). (b) In vitro release profile of F7 with and without RCC.
3D bar surface chart depicting the influence of independent variables over dependent variables.

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Curcumin Loaded Microsponges for Colon Targeting in Inflammatory Bowel Disease: Fabrication, Optimization, and In Vitro and Pharmacodynamic Evaluation
  • Article
  • Full-text available

July 2014

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514 Reads

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68 Citations

The present study was aimed to develop and optimize the microsponges of curcumin for colon specific drug delivery in a view to bypass the upper gastrointestinal tract (GIT) for enhanced therapeutic effect. Microsponges were developed by quasi emulsion solvent diffusion method using 3(2) full factorial design. Prepared microsponges were optimized in order to analyze the effects of independent variables (volume of ethanol and Eudragit L100) on the encapsulation efficiency, particle size, and drug release. The optimized formulation was subjected to in vivo study using acetic acid induced colitis model in rats. The F7 was selected as optimized formulation based on particle size of 41.63 μm, % entrapment efficiency of 78.13%, and % cumulative drug release of 84.12%, and desirability factor of 0.83. Release studies revealed that microsponges prevented the premature release of curcumin in upper GIT and specifically released the drug at colonic pH. The drug release profile of F7 formulation was subjected to different kinetic models and based upon the best correlation coefficient (r (2) = 0.9927) the release was found to follow Higuchi model, which suggested diffusion as the main mechanism of drug release. Pharmacodynamic study showed that curcumin loaded microsponges causes a significant decrease in edema, necrosis, and hemorrhage of colon as compared to free curcumin. This study proves that curcumin loaded microsponges may act as a promising drug delivery system for treatment of ulcerative colitis.

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PH triggered delivery of curcumin from Eudragit-coated chitosan microspheres for inflammatory bowel disease: Characterization and pharmacodynamic evaluation

April 2014

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127 Reads

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51 Citations

Objective: This investigation deals with the development and evaluation (in vitro and in vivo) of pH triggered Eudragit-coated chitosan microspheres of curcumin (CUR) for treating ulcerative colitis. Methods: CUR-loaded chitosan microspheres were initially prepared by emulsion cross linking method followed by coating with Eudragit S-100. The pharmacodynamics of the developed formulation was analyzed in mice by acetic acid induced colitis model. Results: The developed microspheres were of uniform spherical shape with high entrapment efficiency. CUR-chitosan microspheres showed less intense peaks compared to free CUR confirming inclusion of drug within microspheres as revealed by X-ray diffractogram. Uncoated CUR-chitosan microspheres exhibited burst release within initial 4 h while microspheres coated with Eudragit S-100 prevented premature release of CUR and showed controlled release up to 12 h following Higuchi model. In vivo organ biodistribution study showed negligible amount of CUR in stomach and small intestine confirming integrity of microsphere in upper gastrointestinal tract (GIT). In vivo study revealed significant reduction in severity and extent of colonic damage with CUR-loaded microspheres as compared to pure CUR which was further confirmed by histopathological study. Conclusion: In vitro and in vivo studies proved the developed formulations as a promising system for pH-dependent delivery of drug to colon in ulcerative colitis.


ChemInform Abstract: Rational Approaches, Design Strategies, Structure Activity Relationship and Mechanistic Insights for Anticancer Hybrids

March 2014

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421 Reads

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406 Citations

European Journal of Medicinal Chemistry

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K.L. Dhar

A Hybrid drug which comprises the incorporation of two drug pharmacophores in one single molecule are basically designed to interact with multiple targets or to amplify its effect through action on another bio target as one single molecule or to counterbalance the known side effects associated with the other hybrid part(.) The present review article offers a detailed account of the design strategies employed for the synthesis of anticancer agents via molecular hybridization techniques. Over the years, the researchers have employed this technique to discover some promising chemical architectures displaying significant anticancer profiles. Molecular hybridization as a tool has been particularly utilized for targeting tubulin protein as exemplified through the number of research papers. The microtubule inhibitors such as taxol, colchicine, chalcones, combretasatin, phenstatins and vinca alkaloids have been utilized as one of the functionality of the hybrids and promising results have been obtained in most of the cases with some of the tubulin based hybrids exhibiting anticancer activity at nanomolar level. Linkage with steroids as biological carrier vector for anticancer drugs and the inclusion of pyrrolo [2,1-c] [1,4]benzodiazepines (PBDs), a family of DNA interactive antitumor antibiotics derived from Streptomyces species in hybrid structure based drug design has also emerged as a potential strategy. Various heteroaryl based hybrids in particular isatin and coumarins have also been designed and reported to posses' remarkable inhibitory potential. Apart from presenting the design strategies, the article also highlights the structure activity relationship along with mechanistic insights revealed during the biological evaluation of the hybrids.


Development and Optimization of Osmotically Controlled Asymmetric Membrane Capsules for Delivery of Solid Dispersion of Lycopene

January 2014

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148 Reads

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11 Citations

The aim of the present investigation is to develop and statistically optimize the osmotically controlled asymmetric membrane capsules of solid dispersion of lycopene. Solid dispersions of lycopene with β-cyclodextrin in different ratios were prepared using solvent evaporation method. Solubility studies showed that the solid dispersion with 1 : 5 (lycopene : β-cyclodextrin) exhibited optimum solubility (56.25 mg/mL) for osmotic controlled delivery. Asymmetric membrane capsules (AMCs) were prepared on glass mold pins via dip coating method. Membrane characterization by scanning electron microscopy showed inner porous region and outer dense region. Central composite design response surface methodology was applied for the optimization of AMCs. The independent variables were ethyl cellulose (X 1), glycerol (X 2), and NaCl (X 3) which were varied at different levels to analyze the effect on dependent variables (percentage of cumulative drug release (Y 1) and correlation coefficient of drug release (Y 2)). The effect of independent variables on the response was significantly influential. The F18 was selected as optimized formulation based on percentage of CDR (cumulative drug release) of 85.63% and correlation coefficient of 0.9994. The optimized formulation was subjected to analyze the effect of osmotic pressure and agitational intensity on percentage of CDR. The drug release was independent of agitational intensity but was dependent on osmotic pressure of dissolution medium.




Quantitative Determination of a Novel Pseudoalkaloid Colchatetralene Isolated from the Mycoflora of Gloriosa superba Linn by HPTLC

October 2013

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26 Reads

The Natural Products Journal

A High performance thin layer chromatography (HPTLC) method was developed and optimized for determination of colchatetralene, a new bioactive alkaloid isolated from the chloroform extract of an endophytic fungus, isolated from surface sterilized seeds of Gloriosa superba Linn. The development of method involved evaluation and optimization of the various stages of sample preparation, chromatographic separation, detection and quantification. The method employed aluminum backed pre coated TLC plates (silica gel 60F254) as the stationary phase. The mobile phase system consisted of ethyl acetate-methanol-water (10:1.5:1, v/v/v) at room temperature (25 ± 2°C). Densitometric analysis was carried out in the absorbance/reflectance mode at the wavelength of 236nm. The system was found to give compact spots for colchatetralene (Rf value of 0.36 ± 0.03). The linear regression analysis data for the calibration plots showed good linearity (r² = 0.99601 ± 0.002) in the concentration range 200–1200 ng spot⁻¹. The method was validated according to the International Conference on Harmonization (ICH) guidelines for precision, accuracy, recovery and robustness. The limits of detection and quantification were 20 and 60 ng per spot, respectively.


Citations (74)


... The synergism of piperine and aminoglycoside antibiotic, namely gentamicin when administered as nano-liposomes, demonstrated high effectiveness against MRSA infection [92,113,114]. Apart from naturally occurring piperine, its synthetic analogues such as 5-(2,2-dimethylchroman-6-yl)-4-methyl-penta-2,4-dienoic acid ethyl ester and 5-(2,2-Dimethyl-chroman-6yl)-4-methyl-2E,4E-pentadienoic acid pyrrolidine were also found to inhibit NorA efflux pumps expressed in Staphylococcus aureus [27,115]. ...

Reference:

Phytochemicals as Antimicrobials: Prospecting Himalayan Medicinal Plants as Source of Alternate Medicine to Combat Antimicrobial Resistance
Synthesis and Characterization of Piperine analogs as Potent Staphylococcus aureus NorA Efflux Pump Inhibitors
  • Citing Article
  • January 2019

Chemical Methodologies

... The number of germinated seeds was analysed using analysis of deviance, root length using analysis of variance from the Apiaceae family as derivatives of sesquiterpenes daucanes. Compound C17H26O4 was reported either as siol acetate in Sium latifolium (Casinovi et al. 1983) and S. latijugum (Pandita et al. 1984) or as 11-(acetyl)torilolone in Daucus carota (Yi et al. 2009), whereas compound C27H36O5 may represent a trisubstituted daucane with angeloyloxy and benzoyloxy moiety that has been reported from Ferula communis (Miski and Mabry 1985). More research is needed to assign bioactivity to these compounds and to clarify their structure. ...

1-alpha-acetoxy-6-alpha-hydroxy-9-oxo-carot-2-ene, a new derivative from Sium latijugum seeds
  • Citing Article
  • January 1984

Indian Journal of Chemistry

... The most valuable are ketones 15 [51,52] that are obtained via two-step synthesis involving reaction of bromohydrin 14 with silver(I) oxide; aldehyde 17 and unsaturated ketone 18 prepared from ketoaldehyde 16. Novel oxygen and nitrile derivatives with interesting olfactory characteristics can be prepared via carbon chain elongation procedures [53,54,[55][56][57][58]. ...

ChemInform Abstract: SOME NOVEL REARRANGEMENTS OF MONOTERPENES WITH NBS/DMF REAGENT
  • Citing Article
  • February 1985

Chemischer Informationsdienst

... Four compounds were rapidly screened from A. sparsifolia, as illustrated in Figure 5, and their structures were then identified using MS and NMR. As shown in Figure S6, compounds 1-4 Figure S6 and Table S2), these compounds were identified as 4-methoxy-5-methyl coumarin (1), cupressuflavone (2), amentoflavone (3), and 3,4-dimethoxy-5-methyl coumarin (4), respectively [29][30][31][32]. The active compounds in S5-C from the C. arabica extract exhibited very low polarity ( Figure 6); thus, it was difficult to purify them. ...

Chemical constituents of Juniperus semiglobosa
  • Citing Article
  • January 1996

... (Wang et al., 2002) (PAI, Kagawa et al., 1993) R=CH 2 OAc 15-Acetoxy-3α-Hydroxy- J. pseudosabina Hook. (Dhar et al., 1990) 8(17),13-labdadiene R=COOH 3α-Hydroxy-labda-8 J. communis L. (Kagawa et al., 1993) (17),13E-dien-15-oic acid HOOC OR ...

Three new labdane diterpenes from leaves and twigs of Juniperus pseudosabina Hook and 2D-NMR studies of 3-acetoxymanool
  • Citing Article
  • January 1990

... Elemental analyses were done in Central Analytical Service (CAS) at RuCer Bošković Institute. Gram-scale samples of 1,[10][11][12][19][20][21] were prepared by modified Hantzsch method employing 2 equiv of corresponding aminocrotonate esters 42 and aliphatic or aromatic aldehyde. 43 Compounds 13 and 14 were efficiently prepared by a method developed in our laboratory employing tetraethyl orthosilicate as a water scavenging agent, 44 whilst 1,[15][16][17][18]22,23 and 33) by modification of classical literature methods. ...

Synthesis of Hantzsch pyridines by tin tetrachloride induced oxidation of substituted 4-aryl-1, 4-dihydropyridines
  • Citing Article
  • June 1990

ChemInform

... The two compounds of this class reported by us in this study are reported for the first time against the E. coli MurA enzyme, validated by search engine Sci-Finder. Though, the synthesis of compound IN00152 and closely related structures to IN00156 are reported (Koul et al. 1990) In summary we can conclude that by applying ligand-based approach (pharmacophore screening), we found two novel inhibitors showing anti-MurA activity for E.coli. These molecules could provide a starting point for structure activity relationship studies and can be chemically optimized and design new molecules for development of novel E.coli MurA inhibitors. ...

Synthesis of antitubercular compounds bases on isoniazid model
  • Citing Article
  • January 1990

... 85%), elemicin (35%) and of its derivatives: (E)-isoelemicin (60%), hydroxyelemicin (75%) and (E)-methoxyisoelemicin (50%). At least two studies mentioned the formation of dimers of phenylpropanoids from eugenol and methyl eugenol in the presence of H 3 PO 4 [33] or palladium chloride in acetic acid [34] . Thus, and although this may be fortuitous, the disappearance of these compounds could explain about 57% of the observed decay of the total analyzed VOCs (Fig. 4B). ...

Anomalous behaviour of Pd(II) on phenylpropanoids
  • Citing Article
  • July 1996

... Several Juniperus species are used in traditional medicine as antitussive [1,2] as remedies for tuberculosis [3], fever, and as an insect repellent [4,5]. Phytochemical studies reveal that J phoenicea leaves contain a large variety of compounds, mainly abietane and pimarane diterpenoids [6], phenylpropanoids, and lignans [7][8][9]. ...

Seven new labdane diterpenes from Juniperus pseudosabina Hook
  • Citing Article
  • January 1987

Indian Journal of Chemistry

... Vasicine is a major alkaloid obtained from the leaves of Adhatoda vasica Nees, a wellknown medicinal plant used in Ayurvedic and Unani medicine [1] . TAZQ has been extensively studied as bronchodilator [2][3][4][5][6][7] . It inhibited lung phosphodiesterase activity, lipooxygenase activity, histamine release and antigen-induced mast cell degranulation [8] . ...

Studies on Some Biologically Active Azepinoquinazolines: Part I - An Approach to Potent Bronchodilatory Compounds
  • Citing Article
  • January 1988

Indian Journal of Chemistry