Browsing by Author "Sharma, S"

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Arsenic induced physiological changes in improved varieties of rice grown in Malwa region of Punjab
(Society for Advancement of Human and Nature (SADHNA), 2015) Kamboj, Ritu; Sharma, S; Vishwakarma, G.S.; Mittal, Sunil
Rice is a major staple food throughout the world. However metal contamination of rice has been recognized as a new disaster on large scale. Two rice cultivars viz PR 116 and PR 118 were grown in vitro to study the effect of increasing arsenic concentration (50, 100, 250 and 500 µM) on germination, root and shoot length, biomass dry weight, chlorophyll content and per cent cellular respiration. Results showed reduction in all these parameters thereby proving the toxic nature of arsenic. Arsenic accumulation in roots and shoots of both the varieties was monitored by atomic absorption spectrophotometer (AAS) and it was concluded that arsenic is translocated to above ground tissues and ultimately reaches the grain. The status of arsenic concentration of rice and its affect on human health need to be further investigated.
Cyclocondensation reactions of an electron deactivated 2-aminophenyl tethered imidazole with mono/1, 2-biselectrophiles: synthesis and DFT studies on the rationalisation of imidazo [1, 2-a] quinoxaline versus benzo [f] imidazo [1, 5-a][1, 3, 5] triazepine selectivity switches.
(Royal Society of Chemistry, 2018) Joshi, G.; Chauhan, M; Kumar, R; Thakur, A; Sharma, S; Singh, R.; Wani, A.A.; Sharon, A.; Bharatam, P.V; Kumar, R.
Microwave-promoted ring-closure reactions of 5-amino-1-(2-aminophenyl)-1H-imidazole-4-carbonitrile (7) with various mono/1,2-biselectrophiles are presented. The reaction of 7 with aldehydes, ketones and isocyanates produced the corresponding Pictet–Spengler (PS) products i.e. the imidazo[1,2-a]quinoxaline ring system via 6-endo-trig cyclisation. On the other hand, the reaction of 7 with CH(OEt)3, and CDI resulted in the formation of benzo[f]imidazo[1,5-a][1,3,5]triazepine scaffolds via a 7-exo-trig cyclisation process. The mechanistic aspects of these ring cyclisation processes have been analysed and studied to rationalise 6- versus 7-membered ring formation using density functional theory (DFT). DFT calculations revealed the involvement of N-Heterocyclic Carbene (NHC) in the PS reaction mechanism.
Nitric oxide induced modulations in adventitious root growth, lignin content and lignin synthesizing enzymes in the hypocotyls of Vigna radiata
(Elsevier, 2019) Sharma, S; Singh, H.P; Batish, D.R; Kohli, R.K.
The present study evaluated the role of nitric oxide (NO) in mediating adventitious root (AR) growth, lignification and related enzymatic changes in the hypocotyls of Vigna radiata. To meet the objectives, the changes in AR growth, lignin content, and the activities of enzymes−peroxidases, polyphenol oxidases, and phenylalanine ammonia lyases− with NO donor and its scavenger were monitored. Hypocotyls were cultivated in aqueous solution supplemented with different concentrations of SNP (sodium nitroprusside, NO donor compound) and its scavenging compound (2,4-carboxyphenyl-4,4,5,5-tetramethylimidazoline-1-oxyl-3-oxide; cPTIO). Specifically, at low concentrations, SNP induced AR growth, increased the total lignin content and altered the activities of related oxidoreductases- peroxidases, polyphenol oxidases and phenylalanine ammonia lyases- which are involved in lignin biosynthesis pathway. At higher concentrations, a decline in AR growth and lignification was noticed. We analysed the function of NO in AR formation by depleting the endogenous NO using scavenging compound cPTIO. Hypocotyls grown in a medium supplemented with scavenger cPTIO exhibited significant decline in AR growth and the activities of lignin synthesizing enzymes. Application of NO scavenger showed that stimulatory properties on root lignification may be owing to NO itself. In addition, changes in AR growth were significantly correlated with these modified biochemical activities. Our analysis revealed that NO supplementation induces prominent alterations in lignin level during AR formation and this might be due to an alteration in the activity of lignin biosynthetic enzymes, which further affected the polymerization of monolignols and AR growth. © 2019 Elsevier Masson SAS
Phytotoxic selectivity analysis of Eucalyptus tereticornis essential oil against rice, Oryza sativa and its weeds, Echinochloa crus-galli and Cyperus rotundus
(2015) Vishwakarma, G; Sharma, S; Mittal, Sunil
Relay tricyclic Pd (ii)/Ag (i) catalysis: design of a four-component reaction driven by nitrene-transfer on isocyanide yields inhibitors of EGFR.
(Royal Society of Chemistry, 2018) Sawant, D.M.; Sharma, S; Pathare, R.S; Joshi, G; Kalra, S; Sukanya, S; Maurya, A.K.; Metre, R.K; Agnihotri, V.K.; Khan, S.; Kumar, Raj; Pardasania, R. T.
Synthesis of pyrazolo[1,5-c]quinazolines from four easily available precursors is presented through a one-pot tricyclic Pd(II)/Ag(I) relay catalysis. The bimetallic relay cascade forges five new chemical bonds by concatenating six discrete chemical steps. The relay catalysis enables four-component assembly of pyrazolo[1,5-c]quinazolines that selectively inhibit EGFR, exhibit apoptosis through the ROS-induced mitochondrial-mediated pathway, and arrest the cell cycle at the G1 phase.
Synthetic versus Enzymatic Pictet-Spengler Reaction: An Overview.
(Bentham, 2018) Sharma, S; Kalra, S; Joshi, G; Singh, S; Kumar, R.
Pictet-Spengler reactions is an irreplaceable part of cyclization reaction leading to the formation of indispensable heterocyclic moieties including imidazole, benzoxazole, pyrrole, indole and others having immense biological and chemical significance. Researchers have explored this reaction using different types of catalysts and reactions conditions (including solvents, acids, etc.) to ensure the better selectivity, less reaction time and high product yields. A total of five Pictet-Spenglerases have been discovered from various sources including plants, animals, fungi, and microbes, and are responsible for the synthesis of various important alkaloids of biological medicinal importance. Objective: The present review is a strenuous effort to assemble information mainly focusing on synthetic as well as biological Pictet-Spengler reactions catalysed by enzymes called Pictet-Spenglerase. Conclusion: In the present review, the recent advances in the PS-mediated synthesis of diverse heterocycles such as tetrahydroisoquinoline, tetrahydro-β-carbolines, tetrahydroimidazopyridines and other fused heterocycles via chemical as well as enzymatic pathways have been covered. The compounds find their scope as medicinal agents for the treatment of cancer, tuberculosis, bacterial infection, leishmanial, etc. The compilation is expected to provide a mechanistic insight to chemists to enhance the reaction condition, yields and another parameter to ensure the safe and inexpensive reaction conditions considering the “Green-Concept” of chemistry.
TEQIP-II Sponsored,
(2015) Nag, S; Sharma, S; Mittal, Sunil; Kumar, R; Vishwakarma, G. S.
Unanticipated Cleavage of 2-Nitrophenyl-Substituted N-Formyl Pyrazolines under Bechamp Conditions: Unveiling the Synthesis of 2-Aryl Quinolines and Their Mechanistic Exploration via DFT Studies.
(ACS Publications, 2018) Joshi, G; Wani, A.A.; Sharma, S; Bhutani, P; Bharatam, P.V.; Paul, A.T.; Kumar, R.
We herein report for the first time an unusual decomposition of 2-nitrophenyl-substituted N-formyl pyrazolines under Bechamp reduction condition employed to yield 2-aryl quinolines exclusively instead of pyrazolo[1,5-c]quinazolines. The reaction investigation suggests acid-mediated cleavage of 1 followed by a retro-Michael addition, and a subsequent in situ intramolecular reductive cyclization through a modified Friedlander mechanism afforded 2-aryl quinolines (2) in good yields. The proposed mechanistic pathways were supported via experimental evidence and density functional theory studies. B3LYP/6-31+G(d) analysis indicated the involvement of trans-2-hydroxyaminochalcone as a key intermediate and its isomerization and cyclization, leading to unusual product formation.