Rajeev Singh

Spectral and thermal studies with anti-fungal aspects of some organotin(IV) complexes with nitrogen and sulphur donor ligands derived from 2-phenylethylamine

Some complexes of 2-phenylethyl dithiocarbamate, thiohydrazides and thiodiamines with dibenzyltin(IV) chloride, tribenzyltin(IV) chloride and di(para-chlorobenzyl)tin(IV) dichloride have been synthesized and investigated in 1:2 and 1:1 molar ratio. The dithiocarbamate ligand act as monoanionic bidentate and thiohydrazide, thiodiamines act as neutral bidentate ligand. The synthesized complexes have been characterized by elemental analysis and molecular weight determination studies and their bonding pattern suggested on the basis of electronic, infrared, 1H and 13C NMR spectroscopy. Using thermogravimetric (TG) and differential thermal analysis (DTA) various thermodynamic and kinetic parameters viz. reaction order (n), apparent activation energy (Ea), apparent activation entropy (S#) and heat of reaction (DeltaH) have been calculated and correlated with the structural aspects for solid-state decomposition of complexes. The ligands and their tin complexes have also been screened for their fungitoxicity activity against Rhizoctonia solanii and Sclerotium rolfsii and their ED50 values calculated.

Diurnal variation in phagocytic activity of splenic phagocytes in freshwater teleost Channa punctatus: melatonin and its signaling mechanism

The aim of the present study was to understand the rhythmic changes in innate immune response in freshwater fish Channa punctatus. Furthermore, the putative role of melatonin as the zeitgeber was explored. The phagocytic activity of splenic phagocytes assessed at 6-h intervals showed higher phagocytic activity during light phase than dark phase. The increased phagocytic activity during light phase was diminished by melatonin administration at 09:00 h. Implication of melatonin in control of diurnal variation in phagocytic activity was substantiated by administering irreversible tryptophan hydroxylase inhibitor, para-chlorophenylalanine (pCPA) at 18:00 h. pCPA abrogated the decrease of phagocytosis observed during dark phase, and the same was restored after melatonin administration. The direct involvement of melatonin in modulation of phagocytosis was demonstrated following in vitro experiments. Melatonin suppressed the phagocytic activity in a concentration-dependent manner without affecting the viability of phagocytes. The existence of functional membrane-bound melatonin receptors on fish phagocytes was pharmacologically demonstrated. Luzindole, melatonin membrane receptor antagonist, completely blocked the inhibitory effect of melatonin on phagocytosis. Further receptor-coupled adenylate cyclase-protein kinase A (PKA) pathway was implicated in transducing the melatonin effect as both adenylate cyclase and PKA inhibitor completely nullified the melatonin-induced suppression. An increased intracellular cAMP level in response to melatonin ascertained the second messenger status of cAMP for downstream signaling. However, manipulation of phospholipase C/PKC failed to influence the effect of melatonin on phagocytic activity. These observations in C. punctatus evidenced the diurnal rhythmicity in phagocytic activity that is regulated by melatonin following membrane-bound receptor-coupled cAMP-PKA pathway.

Synthesis, characterization & thermal studies of some dithiocarbazate schiff bases- organotin(IV), organozinc(II) complexes

The reactions of tribenzyltin chloride, di(para-chlorobenzyl)tin dichloride, methylzinc iodide with Schiff base ligands having nitrogen and sulphur donor atoms have been synthesized by the interaction of the suitable organometallic halide with respective ligands in THF. The synthesized complexes were found to be pure and have been characterized by elemental analysis, electronic, infrared, HNMR spectroscopy. Various thermodynamic parameters viz. activation energy (Ea), apparent activation entropy (S) and heat of reaction (ΔΗ) are reported. Mathematical analysis of TG and DTA data using Horowitz-Metzger method shows that the first order kinetics is applicable to all the complexes. It was observed that these complexes are stable and the thermal degradation of these complexes is a spontaneous process. The analysis has revealed that the ligand co-ordinates with the metal ion through the azomethine nitrogen and thioketo sulphur atoms.

Synthesis, spectral, thermal and anti-fungal studies of organotin(IV) thiohydrazone complexes.

The reaction of tribenzyltin(IV) chloride and di(para-chlorobenzyl)tin(IV) dichloride with thiohydrazones derived by condensation of 2-phenylethyl N-thiohydrazide with benzaldehyde, salicaldehyde, p-methylacetophenone and cinnamaldehyde have been investigated in 1:1 molar ratio. These ligands act as neutral, bidentate species and coordinate to the central tin (IV) atom through the thiosulphur and azomethine nitrogen. The newly synthesized complexes have been characterized by elemental analysis and molecular weight determination. The mode of bonding of the complexes has been suggested on the basis of infrared, electronic and (1)H NMR spectroscopy, and probable structures have been assigned to these complexes. Phenomenological and kinetic parameters have been calculated using thermogravimetric (TG) and differential thermal analytical (DTA) curves and their variations have been correlated with some structural parameters of the complexes. The ligands and their tin(IV) complexes have been screened in vitro for their fungicidal activity against Rhizoctonia solanii and Sclerotium rolfsii and found to be quite active in this respect.

Kappa-opioid receptor-mediated modulation of innate immune response by dynorphin in teleost Channa punctatus.

The immunomodulatory role of endogenous opioid peptides released during stress has been extensively studied in mammals, but least explored in lower vertebrates. The present in vitro study for the first time reports the specific opioid receptor-mediated immunomodulatory role of dynorphin-A((1-17)) in ectotherms. Dynorphin-A((1-17)) had pleiotropic effects on phagocyte functions, stimulatory on phagocytosis and superoxide production while inhibitory on the nitrite release. However, the effect of dynorphin-A((1-17)), whether stimulatory or inhibitory, markedly declined at high (10(-5)M) concentration. Dynorphin-A((1-17)) seems to mediate its action through opioid receptors since non-selective opioid receptor antagonist, naltrexone, completely blocked the effect of dynorphin-A((1-17)) on phagocytosis, superoxide production and nitrite release. Moreover, among specific opioid receptors antagonists, only selective kappa (kappa)-opioid receptor antagonist norbinaltorphimine was capable to antagonize the pleiotropic effects on phagocyte functions. The present study provides the direct evidence of immunomodulatory role of dynorphin-A((1-17)) via kappa-opioid receptor in freshwater teleost Channa punctatus.

1H NMR and FT-IR dataset based structural investigation of poly(amic acid)s and polyimides from 4,4′-diaminostilbene

Structural investigation of polymers by various available analytical methods is important in order to correlate the structure with polymer properties for which understanding of polymer structure is very important factor. The data presented here in this article shows the 1H NMR spectra used for the characterization of prepared poly(amic acid)s (PAAs). It is often difficult to assigns the peak in NMR of polymers due to its complexity. Data presented here helps in assigning the proton peak in complex NMR of PAAs prepared from aromatic diamines. Further functionality in polymer chains can be confirmed by FT-IR spectra. Change in functionality during some reaction or process can be monitored by disappearance or appearance of peaks in FT-IR. The complete imidization of PAAs to Polyimides (PIs) is difficult to analyze because of the chemical stability i.e. insolubility of PIs in most of the solvent therefore the completion of imidization process was confirmed using FTIR.

Immunomodulatory role of urotensins in teleost Channa punctatus

The present study, for the first time in ectothermic vertebrates, reports the immunoregulatory role of urotensins I and II (UI and UII). Urotensins decreased the phagocytosis and nitrite production by splenic phagocytes. On superoxide production, UI had stimulatory while UII showed inhibitory effect. UI exerted its effect on phagocytes through corticotrophin-releasing factor (CRF) receptor as its non-specific antagonist astressin completely blocked the effect of UI on phagocytosis, nitrite release and superoxide production. Among the antagonists for specific CRF receptor 1 and 2, only CRF receptor 1 antagonist NBI 27914 abolished the effect of urotensin I. On the other hand, UII mediated its effect through urotensin receptor (UT receptor) since its antagonist urantide antagonized the effect of UII on phagocytosis, superoxide and nitrite release. These findings provide the direct evidence on physiological role of UI and UII through CRF receptor 1 and UT receptor, respectively in control of fish immune responses.

Delta opioid receptor-mediated immunoregulatory role of methionine-enkephalin in freshwater teleost Channa punctatus (Bloch.).

The immunoregulatory role of methionine-enkephalin (Met-enk) is well studied in mammals, but has not been explored in ectotherms despite the fact that this peptide is highly conserved in vertebrates. The present study demonstrates the diverse effects of Met-enk depending on its concentration and specific function of splenic phagocytes in the freshwater fish Channa punctatus. Although Met-enk increased both phagocytic as well as respiratory burst activity, the concentration-related response was opposite to each other. It had the maximum stimulatory effect on phagocytosis at 10(-9)M, while the same concentration was least effective in increasing superoxide production. Similarly, Met-enk at concentrations lower or higher than 10(-9)M was either ineffective or less effective in case of phagocytosis, while highly effective in stimulating superoxide production. On the other hand, concentration-independent inhibitory effect of Met-enk was observed in case of nitrite production. Nonetheless, Met-enk regulated all the functions of phagocyte through opioid receptors since non-specific opioid receptor antagonist naltrexone completely blocked the effect of Met-enk on phagocytosis, superoxide and nitrite production by splenic phagocytes of C. punctatus. Among selective opioid receptor antagonists, delta-opioid receptor antagonist naltrindole completely antagonized the effect of Met-enk on phagocytosis, superoxide and nitrite production, while mu- and kappa-opioid receptor antagonist, CTAP and norbinaltorphimine, respectively, were ineffective in influencing any of the functions. This suggests that Met-enk modulates splenic phagocyte functions in the fish C. punctatus via delta-opioid receptor. This is further substantiated by using highly selective delta-opioid receptor agonist, SNC80.

A REVIEW: ORGANOTIN COMPOUNDS IN CORROSION INHIBITION

This review presents a brief overview of some of the major commercial organotin chemicals, their applications and substitutes. As the world of organotin chemicals is quite extensive and diverse, this will briefly discuss some of the major types of organotin compounds, concentrating on those derived from carboxylic acids, phosphoric acids, N, S-donating groups, organotin polymers and organotin compounds used for porous materials. In the end there is a short description of triorganotin compounds and their effects.

Synthesis, Characterization, and Thermal and Antimicrobial Activities of Some Novel Organotin(IV): Purine Base Complexes

A new series of organotin(IV) complexes with purine bases theophylline (HL1) and theobromine (L2) of the types R3Sn(L1), R2Sn(L1)Cl, R3Sn(L2)Cl, and R2Sn(L2)Cl2 (R = C6H5CH2–; p-ClC6H4CH2–) have been synthesized in anhydrous THF. The complexes were characterized by elemental analysis, conductance measurements, molecular weight determinations, UV-vis, IR, 1H, 13C NMR, and mass spectral studies. Various kinetic and thermodynamic parameters of these complexes have also been determined using TG/DTA technique. The thermal decomposition techniques indicate the formation of SnO2 as a residue. The results show that the ligands act as bidentate, forming a five-member chelate ring. All the complexes are 1u2009:u20091 metal-ligand complexes. In order to assess their antimicrobial activity, the ligands and their corresponding complexes have also been tested in vitro against bacteria (E. coli, S. aureus, and P. pyocyanea) and fungi (Rhizopus oryzae and Aspergillus flavus). All the complexes exhibit remarkable activity, and the results provide evidence that the studied complexes might indeed be a potential source of antimicrobial agents.