Isolation,structural assignment and synthesis of (SE)-2-methyloctyl 3-(4-methoxyphenyl) propenoate from the marine soft coral Sarcophyton ehrenbergi

A new metabolite 1 has been isolated from the marine soft coral Sarcophyton ehrenbergi along with two known diterpenoids 2 and 3 and cholesterol 4. The structure of 1 was determined by means of detailed spectroscopic analysis and unambiguously confirmed to have the S configuration by the synthesis of both enantiomers using 4-benzyl-2-oxazolidinone auxiliaries. (S)- and (R)-1, 3 and some of the synthetic intermediates were evaluated for cytotoxic activity against human lung cancer (A549), prostate cancer (DU145), cervical cancer (HeLa) and breast cancer (MCF-7) cell lines in an in vitro bioassay.     

Elastic anomalies of La0.67Sr0.33−xBaxMnO3 in the vicinity of TC

With a view to understand the elastic behaviour of a material system, La_0.67Sr_0.33−xBa_xMnO₃ (where x=0, 0.1, 0.2, and 0.33) especially in the vicinity of their magnetic transition temperature T_C, a systematic investigation of ultrasonic velocity over a temperature range 300-400 K has been carried out. The materials prepared by citrate gel route, were characterized structurally by XRD and on analyzing the XRD patterns, it has been concluded that all the samples are having rhombohedral structure with space group of R3?c. The magnetic (T_C) transition temperatures determined by AC susceptibility measurements are found to decrease continuously with increasing barium concentration. Finally, the ultrasonic longitudinal velocities of all the samples are found to exhibit considerable softening in the vicinity of their magnetic transition temperatures, T_C and the observed behaviour is explained using mean field theory and Jahn-Teller theorem.     

Modeling of nonlinear boundary value problems in enzyme-catalyzed reaction diffusion processes

A mathematical model of steady state mono-layer potentiometric biosensor is developed. The model is based on non stationary diffusion equations containing a non linear term related to Michaelis-Menten kinetics of the enzymatic reaction. This paper presents a complex numerical method (He’s variational iteration method) to solve the non-linear differential equations that describe the diffusion coupled with a Michaelis-Menten kinetics law. Approximate analytical expressions for substrate concentration and corresponding current response have been derived for all values of saturation parameter α and reaction diffusion parameter K using variational iteration method. These results are compared with available limiting case results and are found to be in good agreement. The obtained results are valid for the whole solution domain.     

Spectrofluorometric studies on the binding interaction of bioactive imidazole with bovine serum albumin: a DFT based ESIPT process

Bioactive imidazole derivatives were synthesized and characterized by NMR spectra, mass and CHN analysis. An excited state intramolecular proton transfer (ESIPT) process in hydroxy imidazole has been studied using emission spectroscopy. In hydrocarbon solvent, the tautomer emission predominates over the normal emission and in alcoholic solvent like ethanol; a dramatic enhancement of normal emission is observed which was due to increased solvation. DFT calculation on energy, charge distribution of the rotamers in the ground and excited states of the imidazole derivative were performed and discussed. PES calculation indicates that the energy barrier for the interconversion of two rotamers is too high in the excited state than in the ground state. The interaction between bioactive imidazole derivative and bovine serum albumin (BSA) was investigated.     

Synthesis and physicochemical studies of some novel picrate derivatives

(1)H and (13)C NMR spectra were recorded for some novel picrate derivatives derived from some 3,3-methyl-2,6-diarylpiperidin-4-ones and 3-benzyl-2,6-diarylpiperidin-4-one. The difference in the chemical shift of equatorial methylene proton and axial methylene proton at C(5) [Δ = δ(eq)-δ(ax)] is highly negative which is in contrast to the value observed in the corresponding parent piperidin-4-ones and this is attributed to the syn 1,3-diaxial interaction between the axial N-H bond and axial hydrogen at C-5. The effect of protonation on the chemical shifts was studied in detail. The chemical shifts of the heterocyclic ring protons are influenced by the picrate anion. Solvatochromism of picrates were studied in detail. DFT calculations were carried out in order to find out the NBO analysis, HOMO-LUMO energies, MEP studies and hyperpolarisability behaviour. The electric dipole moment (μ) and the first-hyperpolarisability (β) value of the investigated molecules have been studied theoretically which reveal that the synthesized molecules have microscopic non-linear optical (NLO) behaviour with non-zero values.     

Solvatochromic analysis of some N-nitroso oxime derivatives--Taft and Catalan approach

Some novel N-nitroso oxime derivatives were synthesized and characterized by (1)H, (13)C, (1)H-(1)H and (1)H-(13)C COSY NMR spectra. The spectra of all these N-nitroso oximes reveal the presence of two isomers labelled as E (-NOH group is anti to N-N=O moiety) and Z (-NOH group is syn to N-N=O moiety) in solution and the coupling constants ruled out the possibility of normal chair conformation. From the theoretical studies and coupling constant values it was found that both E (major) and Z (minor) isomers of N-nitroso oximes exist as an equilibrium mixture of CA and boat conformation (B(1)) and this was also supported by DFT calculation. The photophysical properties of these oxime derivatives were studied and the observed lower fluorescence quantum yield may be due to an increase in the non-radiative deactivation rate constant. This is attributed due to the presence of non-chair conformation of N-nitroso oxime derivatives.     

Luminescent study on the binding interaction of bioactive imidazole with bovine serum albumin-A static quenching mechanism

Novel bioactive imidazole derivatives were synthesized and characterized by NMR spectra, mass and CHN analysis. The interaction between the imidazole derivative and bovine serum albumin (BSA) was investigated by fluorescence and UV-vis absorption spectroscopy. The fluorescence quenching of BSA by the imidazole derivatives may be due to the formation of imidazole-BSA complex. The fluorescence quenching mechanism of BSA by imidazole was analyzed and the binding constant has been calculated. The binding distance between imidazole and BSA was obtained based on Forester's non-radiation energy transfer (FRET). The effect of some common ions on the binding constant between imidazole and BSA was also examined.     

Interesting transformations of naturally occurring cassane diterpenoids and bioevaluation of the products

Two cassane diterpenoids, pulcharrin G (1) and 6β-cinnamoyl-7β-hydroxy-voucapen-5-α-ol (2), the constituents of Caesalpinia pulcherrima, were treated with BF₃·OEt₂ to furnish two olefinic products 3 and 4, respectively. The products were formed by elimination of water and migration of a methyl group from C-4 to C-5. The cytotoxic and antimicrobial activities of 3 and 4 were examined.     

Essential oil composition of two unique ginger (Zingiber officinale Roscoe) cultivars from Sikkim

Volatile oils from two most popular cultivars from Sikkim namely, Bhaisa and Majulay, were isolated, characterised by analytical GC and GC-MS. Sixty constituents accounting for 94.9% and 92.6% of the Bhaisa and Majulay oils were identified. The major compounds of Bhaisa oil were geranyl acetate (18.8%), zingiberene (16.3%) and geranial (8.2%) and those of Majulay oil were zingiberene (19.8%) and geranial (16.5%). Compared to other ginger cultivar oils, the Bhaisa oil had higher content of oxygenated compounds (43.1%). This is the first report on the essential oils from Sikkim ginger cultivars.     

Structural,electrical, magnetic,elastic, and internal friction studies of Nd1−xCaxMnO3 (x=0.2, 0.33, 0.4, and 0.5) manganites

A series of Nd_1?xCa_xMnO₃ (x=0.2, 0.33, 0.4, and 0.5) manganites was prepared by sol–gel route by sintering at 1300 °C, mainly to understand the correlation between electron, spin, and phonon couplings. The internal friction and longitudinal modulus along with electrical and magnetic properties have been measured. All the samples are found to exhibit anomalies at T_C, T_N, and T_CO transition temperatures. The anomalies in longitudinal modulus and the internal friction peak at T_CO are attributed to Jahn–Teller effect. A strong correlation between the temperature dependent elastic, anelastic, resistivity, and ac susceptibility properties has been observed and an effort has been made to explain the observed anomalous behavior by a qualitative model.