Browsing by Author "Manish K. Tiwari"

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Catalytic role of iron-superoxide dismutase in hydrogen abstraction by super oxide radical anion from ascorbic acid
(Royal Society of Chemistry, 2016) Manish K. Tiwari; Phool C. Mishra
The catalytic role of iron-superoxide dismutase (Fe-SOD) in the work of ascorbic acid (AA) as a superoxide radical anion scavenger has been studied by employing a model developed recently for the active site of the enzyme. All relevant molecular geometries were optimized at the M06-2X/6-311+G(d) level of density functional theory in the gas phase, which was followed by solvation in aqueous media, employing the integral equation formalism of the polarizable continuum model (IEF-PCM). It was found that single step double hydrogen transfer from each of four pairs of AA sites, and two separate single hydrogen transfers from each of two pairs of AA sites, are involved in scavenging the superoxide radical anions. Even in the absence of Fe-SOD, AA is shown to serve as a fairly good superoxide radical anion scavenger, in agreement with experiment; however, in the presence of Fe-SOD, its efficiency is highly enhanced as double hydrogen transfer from three pairs of sites of AA becomes barrierless. The barrier energy for the first step of the single hydrogen transfer from each of the two pairs of AA sites is very high, due to which this mechanism would practically be inoperative. Further, transformation of H2O2 into two water molecules, due to its dissociation into two OH radicals, followed by transfer of two hydrogen atoms from AA, with the process not involving Fe-SOD, would also not occur practically, as the corresponding barrier energies are very high. Thus, AA would not be able to scavenge H2O2. © The Royal Society of Chemistry 2016.
Experimental and theoretical exploration of molecular structure and anticancer properties of two N, N′–disubstituted thiocarbamide derivatives
(Elsevier B.V., 2019) Sunil K. Pandey; Seema Pratap; Manish K. Tiwari; Gaetano Marverti; Jerry P. Jasinski
Two new compounds N-(2-chloro-4-nitrophenyl)-N’-(phenoxycarbonyl) thiocarbamide (1) and N-(2-chloro-4-nitrophenyl)-N’-(4-nitrobenzoyl) thiocarbamide (2), have been derived by the reaction of phenoxycarbonyl isothiocyanate/4-nitrobenzoyl isothiocyanate with 2-chloro-4-nitroaniline. The structures of these compounds were determined by spectroscopic (FT-IR, 1H and 13C NMR, UV–Visible) and single crystal X-ray studies. Both the crystal structures are symmetrical and planar with anti-periplanar orientation of C[dbnd]O and C[dbnd]S group. The molecular structure and vibrational properties of the compounds studied at B3LYP/6-311G ++ (d, p) level of density functional theory further concrete the experimental results. These compounds were screened for their in vitro cytotoxicity activity against seven human cancer cell lines; cervical (2008 and C13*), colorectal (HT29 and HCT116) and ovarian carcinoma (A2780, A2780/CP and IGROV-1). Compound 2 exhibited significant activity against all the cell lines whereas compound 1 demonstrated appreciable activity only against ovarian carcinoma cell lines. © 2018
From ACQ to AIE: The CN(π)-(π)Ar interaction driven structural and photophysical properties of aromatic ring conjugated novel diaminomaleonitrile derivatives
(Elsevier B.V., 2022) Monika; Abhineet Verma; Manish K. Tiwari; Navin Subba; Satyen Saha
Studying solid and solution state photoluminescence properties are exclusive to understanding Aggregation Caused Quenching (ACQ) and Aggregation Induced Emission (AIE) behaviour of organic molecules to explore the mechanism of molecular luminescence in greater detail. A unique hydrogen-bonded dimer with imperative interaction (CN)π—π(Ar) was designed and synthesized by selecting diaminomaleonitrile (DMN) as stator and decorated with different aromatic rotors (phenyl to pyrene). Depending on the intermolecular interaction present in the molecular system, (AIE) or (ACQ) has been observed and found to be tunable. The single-crystal x-ray diffraction analysis of these derivatives shows that AIE characteristics could be seen where to (CN)π—π(Ar) intermolecular interactions between the aromatic rotors and stator, coupled with NH––NC intermolecular hydrogen bonding is present, while the absence of these interaction reflected in ACQ observation. The significant impacts of steric, conjugation and electronic effects on the ACQ / AIE properties are presented based on crystallography analysis, optical spectra measurements and theoretical calculations. © 2022 Elsevier B.V.
Inhibition Conversion of Aspirin into Salicylic Acid in Presence of Glycine
(Springer, 2024) Ranjana Singh; Manish K. Tiwari; Ranjan K. Singh
Aspirin (AS) is a common drug having anti-pyretic and anti-inflammatory properties which is widely used in diverse medical conditions. The intake of AS may cause adverse effects such as gastrointestinal ulcer, tinnitus and Reye’s syndrome. The adverse effects of AS arise due to conversion of AS into salicylic acid (SAL). Glycine (Gly) is a simplest non essential amino acid having anti-oxidative and anti-inflammatory effects. It also reduces the risk of obesity, hypertension, and diabetes mellitus. AS with Gly is well accepted form of the drug for the treatment of rheumatic conditions in comparisons to the bare AS. In the present work using UV-Visible absorption, fluorescence and DFT/ TD-DFT techniques confirmed that in presence of Gly inhibited the conversion of AS into SAL effectively. © The Author(s), under exclusive licence to Springer Science+Business Media, LLC, part of Springer Nature 2024.
Label-Free Fluorometric Detection of Adulterant Malachite Green Using Carbon Dots Derived from the Medicinal Plant Source Ocimum tenuiflorum
(Wiley-Blackwell, 2019) Devyani Shukla; Fanindra Pati Pandey; Puja Kumari; Nilanjan Basu; Manish K. Tiwari; Jayeeta Lahiri; Ravindra N. Kharwar; Avanish S. Parmar
Food adulteration is an alarming concern in developing countries causing an increased rate of cancer incidents. This study aims to address this concern by detecting adulteration in green vegetables. A facile green one-step and cost-effective strategy to synthesize carbon quantum dots derived from a herbal source has been utilized to design a fluorescence-based sensor for detecting malachite green (MG), a toxic carcinogenic dye, commonly used as an adulterant to give a fresh green look to green vegetables. The leaf-extract of Ocimum tenuiflorum has been used to synthesize highly photostable carbon dots for detecting MG with a limit of detection (LOD) as low as 18 nM. Further, this principle has been utilized to design a prototype calorimetric sensor. The mechanism of the interaction between malachite green and carbon dots has been probed using DFT by employing the SMD solvation model. In addition, CQDs also possess strong antioxidant activity and minimal cytotoxicity enabling their utilization in many biological and sensing applications. This shows the versatility of these easily scalable carbon dots. © 2019 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim
Spectroscopic Studies of CDPy Molecule in Different Protic and Aprotic Solvents and Investigation of Antioxidant Property
(Springer, 2020) Ranjana Singh; Manish K. Tiwari; Jyoti Goutam; Ranjan K. Singh
The properties of 3-Cyano-4, 6-Dimethyl-2-Pyridone (CDPy) were analyzed to study the antioxidant behavior. The UV-Visible absorption and fluorescence properties of CDPy have been studied in two protic (water and methanol) and two aprotic (acetonitrile and dimethyl sulfoxide) solvents. Its antioxidant properties were compared with well known antioxidant ascorbic acid. This compound, CDPy was found to exhibits moderate antioxidant properties. The experimental results were reproduced by theoretical density functional methods, which helped to understand the experimental result better. © 2020, Springer Science+Business Media, LLC, part of Springer Nature.