Biswajit Kumar Singh

Publications of Biswajit Kumar Singh

• Leishmania donovani: oral therapy with glycosyl 1,4-dihydropyridine analogue showing apoptosis like phenotypes targeting pteridine reductase 1 in intracellular amastigotes.

  Authors: Jaspreet Kaur, Nasib Singh, Biswajit Kumar Singh, Anuradha Dube, Rama Pati Tripathi, Prashant Singh, Neeloo Singh

  Experimental parasitology. 02/2010; 125(3):310-4.

  Glycosyl 1,4-dihydropyridine analogue (2,6-dimethyl-4-(3-O-benzyl-1,2-O-isopropylidene-beta-l-threo pentofuranos-4-yl)-1-phenyl-1,4-dihydro-pyridine-3,5-dicarboxylic acid diethyl ester) synthesizedGlycosyl 1,4-dihydropyridine analogue (2,6-dimethyl-4-(3-O-benzyl-1,2-O-isopropylidene-beta-l-threo pentofuranos-4-yl)-1-phenyl-1,4-dihydro-pyridine-3,5-dicarboxylic acid diethyl ester) synthesized in our laboratory, inhibited Leishmania donovani infection in vitro and in hamsters (Mesocricetus auratus) when administered orally. This analogue is nontoxic, cell-permeable and orally effective. This glycosyl dihydropyridine analogue functioned through arrest of cells in sub-G0/G1-phase, triggering mitochondrial membrane depolarization-mediated programmed cell death of the intracellular amastigotes.

• Leishmania donovani: A glycosyl dihydropyridine analogue induces apoptosis like cell death via targeting pteridine reductase 1 in promastigotes.

  Authors: Jaspreet Kaur, Biswajit Kumar Singh, Rama Pati Tripathi, Prashant Singh, Neeloo Singh

  Experimental parasitology. 08/2009;

  Targeting of pteridine reductase1 (PTR1) in Leishmania is essential for development of successful antifolate chemotherapy. In search for specific inhibitors of PTR1 we have previously reported phenylTargeting of pteridine reductase1 (PTR1) in Leishmania is essential for development of successful antifolate chemotherapy. In search for specific inhibitors of PTR1 we have previously reported phenyl 1, 4-dihydropyridine ring as the lead structure showing antileishmanial efficacy in vitro and by the oral route in vivo. In this study we present programmed cell death inducing potential of this glycosyl dihydropyridine analogue (2, 6-dimethyl-4-(3-O-benzyl-1, 2-O-isopropylidene-beta-L-threo-pentofuranos-4-yl)-1-phenyl-1, 4-dihydro-pyridine-3, 5-dicarboxylic acid diethyl ester). Flow cytometric analysis revealed that this analogue induces cell cycle arrest at G2/M phase with subsequent increase in sub-G1 peak. Incubation of Leishmania promastigotes with this analogue causes exposure of phosphatidylserine to the outer leaflet of plasma membrane, formation of reactive oxygen species, depolarization of mitochondrial membrane potential and concomitant nuclear alterations that included DNA fragmentation. The results from this study on promastigotes give important lead to investigate further in intracellular amastigotes, the biologically relevant parasite stage in host macrophages.

• Preparation and reactions of sugar azides with alkynes: synthesis of sugar triazoles as antitubercular agents.

  Authors: Biswajit Kumar Singh, Amit Kumar Yadav, Brijesh Kumar, A Gaikwad, Sudhir Kumar Sinha, Vinita Chaturvedi, Rama Pati Tripathi

  Carbohydrate research. 06/2008; 343(7):1153-62.

  5-azido-5-deoxy-xylo-, ribo-, and arabinofuranoses were prepared by the reaction of the respective 5-O-(methanesulfonyl) or p-toluenesulfonyl derivatives with NaN3 in DMF. The intermediate5-azido-5-deoxy-xylo-, ribo-, and arabinofuranoses were prepared by the reaction of the respective 5-O-(methanesulfonyl) or p-toluenesulfonyl derivatives with NaN3 in DMF. The intermediate 5-azido-5-deoxy glycofuranoses on 1,3-cycloaddition with different alkynes in the presence of CuSO4 and sodium ascorbate gave the corresponding sugar triazoles in very good yields. The synthesized sugar triazoles were evaluated for their antitubercular activity against Mycobacterium tuberculosis H37Rv, where one of the compounds displayed mild antitubercular activity in vitro with MIC 12.5 microg/mL.

• Leishmania donovani: A glycosyl dihydropyridine analogue induces apoptosis like cell death via targeting pteridine reductase 1 in promastigotes

  Authors: Jaspreet Kaur, Biswajit Kumar Singh, Rama Pati Tripathi, Prashant Singh, Neeloo Singh

  Experimental Parasitology.

  Targeting of pteridine reductase 1 (PTR1) in Leishmania is essential for development of successful antifolate chemotherapy. In search for specific inhibitors of PTR1 we have previously reportedTargeting of pteridine reductase 1 (PTR1) in Leishmania is essential for development of successful antifolate chemotherapy. In search for specific inhibitors of PTR1 we have previously reported phenyl 1,4-dihydropyridine ring as the lead structure showing antileishmanial efficacy in vitro and by the oral route in vivo. In this study, we present programmed cell death inducing potential of this glycosyl dihydropyridine analogue (2,6-dimethyl-4-(3-O-benzyl-1,2-O-isopropylidene-β-l-threo-pentofuranos-4-yl)-1-phenyl-1,4-dihydro-pyridine-3,5-dicarboxylic acid diethyl ester). Flow cytometric analysis revealed that this analogue induces cell cycle arrest at G2/M phase with subsequent increase in sub-G1 peak. Incubation of Leishmania promastigotes with this analogue causes exposure of phosphatidylserine to the outer leaflet of plasma membrane, formation of reactive oxygen species, depolarization of mitochondrial membrane potential and concomitant nuclear alterations that included DNA fragmentation. The results from this study on promastigotes give important lead to investigate further in intracellular amastigotes, the biologically relevant parasite stage in host macrophages.

• Leishmania donovani: Oral therapy with glycosyl 1,4-dihydropyridine analogue showing apoptosis like phenotypes targeting pteridine reductase 1 in intracellular amastigotes

  Authors: Jaspreet Kaur, Nasib Singh, Biswajit Kumar Singh, Anuradha Dube, Rama Pati Tripathi, Prashant Singh, Neeloo Singh

  Experimental Parasitology.

  Glycosyl 1,4-dihydropyridine analogue (2,6-dimethyl-4-(3-O-benzyl-1,2-O-isopropylidene-β-l-threo pentofuranos-4-yl)-1-phenyl-1,4-dihydro-pyridine-3,5-dicarboxylic acid diethyl ester) synthesized inGlycosyl 1,4-dihydropyridine analogue (2,6-dimethyl-4-(3-O-benzyl-1,2-O-isopropylidene-β-l-threo pentofuranos-4-yl)-1-phenyl-1,4-dihydro-pyridine-3,5-dicarboxylic acid diethyl ester) synthesized in our laboratory, inhibited Leishmania donovani infection in vitro and in hamsters (Mesocricetus auratus) when administered orally. This analogue is nontoxic, cell-permeable and orally effective. This glycosyl dihydropyridine analogue functioned through arrest of cells in sub-G0/G1-phase, triggering mitochondrial membrane depolarization-mediated programmed cell death of the intracellular amastigotes.