Browsing by Author "Shailja Singh"

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2-(4-Chlorophenyl)chromen-4-one
(2011) Shailja Singh; Manavendra K. Singh; Alka Agarwal; Satish K. Awasthi
The title compound, C15H9ClO2, is a synthetic flavonoid obtained by the cyclization of 3-(4-chloro-phen-yl)-1-(2-hy- droxy-phen-yl)prop-2-en-1-one. The 4-chloro-phenyl ring is twisted at an angle of 11.54°with respect to the chromen-4-one skeleton. In the crystal, pairs of molecules are interconnected by weak Cl⋯Cl interactions [3.3089 (10) Å] forming dimmers which are further peripherally connected through intermolecular C-H⋯O hydrogen bonds..
(2E)-1-(4-Amino-phen-yl)-3-(2,4-dichloro-phen-yl)prop-2-en-1-one
(2011) Shailja Singh; Manavendra K. Singh; Alka Agarwal; Firasat Hussain; Satish K. Awasthi
The title compound, C 15H 11C l2NO, is approximately planar (r.m.s. deviation = 0.062 Å) and contains a single C=C double bond in a trans (E) configuration. The crystal packing is stabilized by intermolecular N - H⋯N and N - H⋯O inter-molecular hydrogen bonding. © Singh et al. 2011.
A small bioactive glycoside inhibits epsilon toxin and prevents cell death
(Company of Biologists Ltd, 2019) Abhishek Shivappagowdar; Soumya Pati; Chintam Narayana; Rajagopal Ayana; Himani Kaushik; Raj Sah; Swati Garg; Ashish Khanna; Jyoti Kumari; Lalit Garg; Ram Sagar; Shailja Singh
Clostridium perfringens epsilon toxin (Etx) is categorized as the third most lethal bioterrorism agent by the Centers for Disease Control and Prevention (CDC), with no therapeutic counter measures available for humans. Here, we have developed a high-affinity inhibitory compound by synthesizing and evaluating the structure activity relationship (SAR) of a library of diverse glycosides (numbered 1-12). SAR of glycoside-Etx heptamers revealed exceptionally strong H-bond interactions of glycoside-4 with a druggable pocket in the oligomerization and β-hairpin region of Etx. Analysis of its structure suggested that glycoside-4 might self-aggregate to form a robust micelle-like supra-molecular complex due to its linear side-chain architecture, which was authenticated by fluorescence spectroscopy. Further, this micelle hinders the Etx monomer-monomer interaction required for oligomerization, validated by both surface plasmon resonance (SPR) and immunoblotting. This phenomenon in turn leads to blockage of pore formation. Downstream evaluation revealed that glycoside-4 effectively blocked cell death of Etx-treated cultured primary cells and maintained cellular homeostasis via disrupting oligomerization, blocking pore formation, restoring calcium homeostasis, stabilizing the mitochondrial membrane and impairing high mobility group box 1 (HMGB1) translocation from nucleus to cytoplasm. Furthermore, a single dosage of glycoside-4 protected the Etx-challenged mice and restored normal function to multiple organs. This work reports for the first time a potent, nontoxic glycoside with strong ability to occlude toxin lethality, representing it as a bio-arm therapeutic against Etx-based biological threat. © 2019. Published by The Company of Biologists Ltd
Enhanced uptake, high selective and microtubule disrupting activity of carbohydrate fused pyrano-pyranones derived from natural coumarins attributes to its anti-malarial potential
(BioMed Central, 2019) Sonal Gupta; Juveria Khan; Priti Kumari; Chintam Narayana; R. Ayana; Malabika Chakrabarti; Ram Sagar; Shailja Singh
Background: Malaria is one of the deadliest infectious diseases caused by protozoan parasite of Plasmodium spp. Increasing resistance to anti-malarials has become global threat in control of the disease and demands for novel anti-malarial interventions. Naturally-occurring coumarins, which belong to a class of benzo-α-pyrones, found in higher plants and some essential oils, exhibit therapeutic potential against various diseases. However, their limited uptake and non-specificity has restricted their wide spread use as potential drug candidates. Methods: Two series of carbohydrate fused pyrano[3,2-c]pyranone carbohybrids which were synthesized by combination of 2-C-formyl galactal and 2-C-formyl glucal, with various freshly prepared 4-hydroxycoumarins were screened against Plasmodium falciparum. The anti-malarial activity of these carbohybrids was determined by growth inhibition assay on P. falciparum 3D7 strain using SYBR green based fluorescence assay. Haemolytic activity of carbohybrid 12, which showed maximal anti-malarial activity, was determined by haemocompatibility assay. The uptake of the carbohybrid 12 by parasitized erythrocytes was determined using confocal microscopy. Growth progression assays were performed to determine the stage specific effect of carbohybrid 12 treatment on Pf3D7. In silico studies were conducted to explore the mechanism of action of carbohybrid 12 on parasite microtubule dynamics. These findings were further validated by immunofluorescence assay and drug combination assay. Results: 2-C-formyl galactal fused pyrano[3,2-c]pyranone carbohybrid 12 exhibited maximum growth inhibitory potential against Plasmodium with IC50 value of 5.861 μM and no toxicity on HepG2 cells as well as no haemolysis of erythrocytes. An enhanced uptake of this carbohybrid compound was observed by parasitized erythrocytes as compared to uninfected erythrocytes. Further study revealed that carbohybrid 12 arrests the growth of parasite at trophozoite and schizonts stage during course of progression through asexual blood stages. Mechanistically, it was shown that the carbohybrid 12 binds to α,β-heterodimer of tubulin and affects microtubule dynamics. Conclusion: These findings show carbohydrate group fusion to 4-hydroxycoumarin precursor resulted in pyrano-pyranones derivatives with better solubility, enhanced uptake and improved selectivity. This data confirms that, carbohydrate fused pyrano[3,2-c]pyranones carbohybrids are effective candidates for anti-malarial interventions against P. falciparum. © 2019 The Author(s).
Erratum: Enhanced uptake, high selective and microtubule disrupting activity of carbohydrate fused pyrano-pyranones derived from natural coumarins attributes to its anti-malarial potential (Malaria Journal (2019) 18 (346) DOI: 10.1186/s12936-019-2971-z)
(BioMed Central Ltd., 2020) Sonal Gupta; Juveria Khan; Priti Kumari; Chintam Narayana; R. Ayana; Malabika Chakrabarti; Ram Sagar; Shailja Singh
Please note, following publication of the original article [1], the authors have advised of three errors that are present in the published article. Firstly, the two instances of 'Albumax II' in the 'Methods' section of the article are incorrect: the reagent 'Albumax I' should be referred to instead. Secondly, 'giemsa' (also referred to in the 'Methods' section) should be capitalized, as 'Giemsa'. Finally, an incorrect version of Fig. 4 has been incorporated in the article; please find the correct version of Fig. 4 in this article, for reference. © 2020 The Author(s).
Metalloprotease Gp63-Targeting Novel Glycoside Exhibits Potential Antileishmanial Activity
(Frontiers Media S.A., 2022) Amrita Chakrabarti; Chintam Narayana; Nishant Joshi; Swati Garg; Lalit C. Garg; Anand Ranganathan; Ram Sagar; Soumya Pati; Shailja Singh
Visceral leishmaniasis (VL) and post kala-azar dermal leishmaniasis (PKDL) affect most of the poor populations worldwide. The current treatment modalities include liposomal formulation or deoxycholate salt of amphotericin B, which has been associated with various complications and severe side effects. Encouraged from the recent marked antimalarial effects from plant-derived glycosides, in this study, we have exploited a green chemistry-based approach to chemically synthesize a library of diverse glycoside derivatives (Gly1–12) and evaluated their inhibitory efficacy against the AG83 strain of Leishmania donovani. Among the synthesized glycosides, the in vitro inhibitory activity of Glycoside-2 (Gly2) (1.13 µM IC50 value) on L. donovani promastigote demonstrated maximum cytotoxicity with ~94% promastigote death as compared to amphotericin B that was taken as a positive control. The antiproliferative effect of Gly2 on promastigote encouraged us to analyze the structure–activity relationship of Gly2 with Gp63, a zinc metalloprotease that majorly localizes at the surface of the promastigote and has a role in its development and multiplication. The result demonstrated the exceptional binding affinity of Gly2 toward the catalytic domain of Gp63. These data were thereafter validated through cellular thermal shift assay in a physiologically relevant cellular environment. Mechanistically, reduced multiplication of promastigotes on treatment with Gly2 induces the destabilization of redox homeostasis in promastigotes by enhancing reactive oxygen species (ROS), coupled with depolarization of the mitochondrial membrane. Additionally, Gly2 displayed strong lethal effects on infectivity and multiplication of amastigote inside the macrophage in the amastigote–macrophage infection model in vitro as compared to amphotericin B treatment. Gp63 is also known to bestow protection against complement-mediated lysis of parasites. Interestingly, Gly2 treatment enhances the complement-mediated lysis of L. donovani promastigotes in serum physiological conditions. In addition, Gly2 was found to be equally effective against the clinical promastigote forms of PKDL strain (IC50 value of 1.97 µM); hence, it could target both VL and PKDL simultaneously. Taken together, this study reports the serendipitous discovery of Gly2 with potent antileishmanial activity and proves to be a novel chemotherapeutic prototype against VL and PKDL. Copyright © 2022 Chakrabarti, Narayana, Joshi, Garg, Garg, Ranganathan, Sagar, Pati and Singh.
Pathogen induced subversion of NAD+ metabolism mediating host cell death: a target for development of chemotherapeutics
(Springer Nature, 2021) Ayushi Chaurasiya; Swati Garg; Ashish Khanna; Chintam Narayana; Ved Prakash Dwivedi; Nishant Joshi; Zill e Anam; Niharika Singh; Jhalak Singhal; Shikha Kaushik; Amandeep Kaur Kahlon; Pallavi Srivastava; Manisha Marothia; Mukesh Kumar; Santosh Kumar; Geeta Kumari; Akshay Munjal; Sonal Gupta; Preeti Singh; Soumya Pati; Gobardhan Das; Ram Sagar; Anand Ranganathan; Shailja Singh
Hijacking of host metabolic status by a pathogen for its regulated dissemination from the host is prerequisite for the propagation of infection. M. tuberculosis secretes an NAD+-glycohydrolase, TNT, to induce host necroptosis by hydrolyzing Nicotinamide adenine dinucleotide (NAD+). Herein, we expressed TNT in macrophages and erythrocytes; the host cells for M. tuberculosis and the malaria parasite respectively, and found that it reduced the NAD+ levels and thereby induced necroptosis and eryptosis resulting in premature dissemination of pathogen. Targeting TNT in M. tuberculosis or induced eryptosis in malaria parasite interferes with pathogen dissemination and reduction in the propagation of infection. Building upon our discovery that inhibition of pathogen-mediated host NAD+ modulation is a way forward for regulation of infection, we synthesized and screened some novel compounds that showed inhibition of NAD+-glycohydrolase activity and pathogen infection in the nanomolar range. Overall this study highlights the fundamental importance of pathogen-mediated modulation of host NAD+ homeostasis for its infection propagation and novel inhibitors as leads for host-targeted therapeutics. © 2021, The Author(s).
Prevalence of autoantibodies and HLA DR, DQ in type 1 diabetes mellitus
(Journal of Clinical and Diagnostic Research, 2016) Shailja Singh; Usha; Gyanendra Singh; Neeraj Kumar Agrawal; Rana Gopal Singh; Shashi Bhushan Kumar
Introduction: Type I diabetes Mellitus (T1DM) is caused by autoimmune destruction of β-cells of pancreas. Two forms of T1DM are known called as 1A (autoimmune) and 1B (idiopathic). Aim: Aim was to study the prevalence of Anti-TTG IgA, Anti-TPO, GADA, ZnT8 and IA-2 autoantibodies and HLA DR and DQ genes and its diagnostic value in T1DM.Materials and Methods: Thirty four T1DM patients, 59 type 2 diabetes mellitus (T2DM) patients and 28 healthy controls were included in study. Antibodies levels were estimated by ELISA and HLA typing was performed by SSP-PCR method.Result: The prevalence of various autoantibodies in T1DM were Anti-TTG 14.7%, Anti-TPO 17.65%, GADA 38.23%, ZnT8 11.76% and IA-2 5.88%. Only GADA and ZnT8 were significantly positive in T1DM. GADA (66.67%) and ZnT8 (33.33%) positivity was more in patients below 15 years age while levels of other antibodies were higher after 15 years age. All autoantibodies were detected in higher frequency in T1DM than in T2DM and controls.HLA DR and DQ typing showed highly significant increase in DRB1*0301 (61.76%, p=0.00) and DQB1*0201 (64.71%, p=0.00) in T1DM. Subjects with HLA DRB1*0301 and DQB1*0201 had 80-100% positive prevalence of GADA, ZnT8, IA-2, Anti-TTG and Anti-TPO autoantibodies.Conclusion: Combination of GADA antibody with DRB1 and DQB1 estimation improved diagnosis of T1A than insulin antigen specific antibodies alone. © 2016, Journal of Clinical and Diagnostic Research. All rights reserved.
Role of HLA alleles polymorphism in systemic lupus erythematosus: A prospective study from North India
(Wolters Kluwer Medknow Publications, 2023) Ranjan Rana; Bitan Naik; Mahima Yadav; Usha Singh; Anup Singh; Shailja Singh
Background: Systemic lupus erythematosus (SLE) is a chronic autoimmune disorder and has complex etiopathogenesis. The most appropriate hypothesis states that genetic susceptibility in the presence of environmental risk factors predisposes to SLE. HLA class II alleles are critical to immune response and are highly polymorphic. Various alleles in HLA-DR and -DQ regions were analyzed in SLE patients and healthy controls to see their role in susceptibility or protection to SLE. Materials and Methods: This was a prospective observational study, in which a total of 100 SLE patients and 100 controls were analyzed. HLA typing was done by polymerase chain reaction (PCR)-sequence-specific oligonucleotide (SSO) method (SSO probe). Results: DRβ1∗0301 was significantly increased in SLE patients when compared to controls and had the highest odds ratio. Other risk factor alleles found to be increased were DRβ1∗0701, DQβ1∗0202, and DQβ1∗0301, which had a significant positive association with SLE, suggesting their role in susceptibility to SLE. In contrast, DRβ1∗0401, DRβ1∗1401, DRβ1∗1404, DRβ1∗1501, DQβ1∗0501, and DQα1∗0201 showed statistically significant reduction in SLE patients, while these were much more common in controls, suggesting their protective role. Conclusion: This study is only the second study in patients from North India and it determines the role of DRβ1∗0301, DRβ1∗0701, DQβ1∗0202, and DQβ1∗0301 alleles as risk factors in SLE patients. © 2023 Wolters Kluwer Medknow Publications. All rights reserved.
Stereoselective synthesis of carbohydrate fused pyrano[3,2-c]pyranones as anticancer agents
(Royal Society of Chemistry, 2018) Priti Kumari; Sonal Gupta; Chintam Narayana; Shakeel Ahmad; Nidhi Vishnoi; Shailja Singh; Ram Sagar
Pyrano[3,2-c]pyranone is an important structural motif present in many natural products exhibiting diverse biological activities. Two series of carbohydrate fused pyrano[3,2-c]pyranone derivatives (n = 20) were efficiently synthesized starting from 2-C-formyl galactal and 2-C-formyl glucal, reacting with various 4-hydroxycoumarins in a very short reaction time (10 min) under microwave assisted conditions. The anticancer activity of these synthesized pyrano[3,2-c]pyranones was determined in detail through cellular assays against MCF-7 (breast), MDA-MB-231 (breast) and HepG2 (liver) cancer cell lines. The newly synthesized pyrano[3,2-c]pyranones were screened for their cell-viability and anti-proliferative activity against MCF-7, MDA-MB-231 and HepG2 cell lines. Compounds 12, 13 and 14 exhibited high growth inhibitory potencies selectively against MCF-7 cells with half-maximal inhibitory concentration (IC50) values of 19.9, 14.5 and 10.9 μM respectively. Compounds 12, 13, 14, 15 and 19 inhibited the growth of MDA-MB-231 cells (breast) by 43, 44, 37, 31 and 45% respectively. However, no inhibitory effect was observed for these compounds in the human liver cancer cell line (HepG2) and normal cell lines (HEK293, human embryonic kidney cells). Mechanistic studies showed that these compounds alter the cell morphology and cause G2/M arrest in MCF-7. Further studies showed that compounds 12, 13 and 14 significantly inhibited cell migration which was accompanied by altered microtubule distribution. An enhanced accumulation of these compounds in cells was observed as compared to the 4-hydroxycoumarins precursor in the intracellular uptake assay. These findings confirm that carbohydrate fused pyrano[3,2-c]pyranones are better candidates for anticancer activity. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Synthesis and in vitro antiplasmodial activities of fluoroquinolone analogs
(2012) Sandeep K. Dixit; Nidhi Mishra; Manish Sharma; Shailja Singh; Alka Agarwal; Satish K. Awasthi; V.K. Bhasin
Fluoroquinolone analogs were synthesized by simple alkylation followed by click chemistry and evaluated for their antimalarial in vitro against chloroquine sensitive strain of Plasmodium falciparum while ciprofloxacin was used as standard. Our results showed that the compound 12 was found most active with IC 50 value of 1.33 μg/mL while ciprofloxacin showed IC 50 = 8.81 μg/mL. Therefore, screening of either known or unknown quinolone/fluoroquinolone analogs are worthwhile to find more potent antimalarial drugs which might prove useful in the treatment of mild or severe malaria in human either alone or in combination with existing antimalarial drugs. © 2012 Elsevier Masson SAS. All rights reserved.