Vibrational spectroscopy and DFT calculations of di‐amino acid peptides: α‐ and β‐N‐acetyl‐L‐Asp‐L‐Glu in the solid state

Experimental vibrational spectroscopic studies and density functional theory (DFT) calculations of the di‐amino acid peptide derivatives α‐ and β‐N‐acetyl‐L‐Asp‐L‐Glu have been undertaken. Raman and infrared spectra have been recorded for samples in the solid state. DFT simulations were conducted using the B3‐LYP correlation functional and the cc‐pVDZ basis set to determine energy minimized/geometry optimized structures (based on a single isolated molecule in the gaseous state). Normal coordinate calculations have provided vibrational assignments for fundamental modes, including their potential energy distributions. Significant differences are observed between α‐ and β‐N‐acetyl‐L‐Asp‐L‐Glu both in the computed structures and in the vibrational spectra. The combination of experimental and calculated spectra provide an insight into the structural and vibrational spectroscopic properties of di‐amino acid peptide derivatives. Copyright © 2009 John Wiley & Sons, Ltd.     

Two new 3-C-carboxylated flavones from the rhizomes of Caragana conferta

Confertins A (1) and B (2), new 3-C-carboxylated flavones, have been isolated from the ethyl acetate soluble fraction of the rhizomes of Caragana conferta. Their structures have been assigned on the basis of spectroscopic studies.     

Microwave assisted synthesis,characterization and biological evaluation of palladium and platinum complexes with azomethines

Reactions of 3-acetyl-2,5-dimethylthiophene with thiosemicarbazide and semicarbazide hydrochloride resulted in the formation of new heterocyclic ketimines, 3-acetyl-2,5-dimethylthiophene thiosemicarbazone (C₉H₁₃N₃OS₂ or L¹H) and 3-acetyl-2,5- dimethylthiophene semicarbazone (C₉H₁₃N₃OS or L²H), respectively. The Pd(II) and Pt(II) complexes have been synthesized by mixing metal salts in 1:2 molar ratios with these ligands by using microwave as well as conventional heating method for comparison purposes. The authenticity of these ligands and their complexes has been established on the basis of elemental analysis, melting point determinations, molecular weight determinations, IR, ¹H NMR and UV spectral studies. These studies showed that the ligands coordinate to the metal atom in a monobasic bidentate manner and square planar environment around the metal atoms has been proposed to the complexes. Both the ligands and their complexes have been screened for their antimicrobial activities. The antiamoebic activity of both the ligands and their palladium compounds against the protozoan parasite Entamoeba histolytica has been tested.     

Chymotrypsin inhibitory triterpenoids from Silybum marianum

Marianine, the new lanostane triterpene (1) and marianosides A (2) and B (3) have been isolated from the whole plant of Silybum marianum. Their structures were elucidated on the basis of extensive analysis of their one dimensional and two dimensional nuclear magnetic resonance (1D, 2D-NMR) spectral data. All inhibited chymotrypsin in a concentration-dependent manner.     

Pregnane derivatives from Potentilla evestita

A new pregnane derivative, 2,6beta,7beta-trihydroxy-4-methyl-19-norpregna-1,3,5(10)-trien-17-one, has been isolated from the ethyl acetate soluble fraction of Potentilla evestita along with a pregnane derivative, 11alpha,17alpha,21-trihydroxypregna-4,16(22)-diene-3,20-dione, that is reported for the first time as a natural product. Their structures were elucidated with the aid of 1H and 13C NMR spectra and by COSY, HMQC, HMBC and NOESY experiments.     

Boronic acid functionalized fibrous cellulose for the selective enrichment of glycopeptides

Enrichment of glycoproteins has been important because of their dynamicity and role in biological systems. Study of glycoproteins is complex because of the simultaneous glycosylation and deglycosylation inside the body. Often employed affinities for glycopeptides are hydrazide, boronic acid, or physiosorbed lectin on support materials. Cellulose, a natural polysaccharide, has rich surface chemistry, stable structure, low cost and availability in different variants. In present study, fibrous cellulose is oxidized using periodate to modify with boronic acid. Attachment of boronic acid is confirmed by Fourier transform infrared spectroscopy. Particle size and morphology of boronic acid@fibrous cellulose is studied by scanning electron microscopy. The enrichment efficiency is evaluated by using horseradish peroxidase as model protein. Boronic acid@fibrous cellulose is selective up to 1:250 for spiked horseradish peroxidase in bovine serum albumin digest, sensitive down to 0.1 femtomol and recovering 88.15% glycopeptides. Moreover, protein binding capacity is determined as 213 mg/g and 41% sequence coverage of horseradish peroxidase protein with all eight glycosylation sites detected. Total of 18 glycopeptides are enriched from immunoglobulin digest showing ability of boronic acid@fibrous cellulose to enrich glycoproteins from multiglycoforms. Enrichment from human serum recovers 18% extracellular and 72% secreted glycoproteins via bottom‐up approach and online tools.     

Important Properties of Sulfur–Bonded Organoboron (III) Complexes with Biologically Potent Ligands

Abstract

Important properties of sulfur/oxygen and nitrogen bonded organoboron (III) complexes with biologically potent ligands viz., semicarbazone, thiosemicarbazone, and dithiocarbazate having the donor groups ONX and NS have been studied. The unimolar and bimolar reactions of phenylboronic acid with monobasic bidentate and dibasic tridentate ligands result in the formation of colored solids which have been characterized by the elemental analysis, molecular weight determinations, and conductance measurements. The UV, IR, and NMR ( ¹ H, ¹³ C, and ¹¹ B) spectral studies indicate tetracoordinated geometry for the resulting complexes. Both the ligands and their complexes have been screened for their fungicidal and bactericidal activities, and the results indicate that they exhibit significant antimicrobial properties.     

Sulfur-Bonded Coordination Compounds of Palladium(II) and Platinum(II) and Their Antimicrobial Activity

The synthetic, spectroscopic, and biological studies of some new palladium(II) and platinum(II) complexes derived from biologically active sulfur donor ligands 1H-indol-2,3-dione benzothiazoline (Bzt ₁ H) and 5-nitro-1H-indol-2,3-dione benzothiazoline (Bzt ₂ H) have been described. The reactions were carried out in 1:2 molar ratios. The authenticity of the benzothiazolines and their complexes has been established on the basis of elemental analyses; molecular weight determinations; and IR, ¹ H NMR, ¹³ C NMR, and UV spectral studies. Based on IR and ¹ H NMR spectral studies, a square-planar structure has been assigned to these complexes. Studies were conducted to assess the comparative growth inhibiting potential of the synthesized complexes against the benzothiazolines for a variety of fungal and bacterial strains. The studies demonstrate that the ligands and complexes possess antimicrobial properties. Further, it was noted that the growth-inhibiting potential of the complexes is greater than the parent benzothiazolines.     

Behavioural dynamics in the biological control of pests: role of silicon complexes

The complexes of silicon (IV) with Schiff base ligands (L₁H and L₂H of isatin derivatives) having a sulfur and oxygen donor system were prepared by the reactions in methanol environment. These were isolated and characterized by elemental analysis, molecular weight determinations and conductance measurements. On the basis of electronic, infrared, ¹H, ¹³C and ²⁹Si NMR spectral studies, trigonal bipyramidal geometry was suggested for the resulting complexes. These data support preferential binding of sulfur and oxygen atom to the silicon atom. The disease resistance activities of the ligands and their corresponding complexes were examined successfully in in vitro and in vivo experiments, against pathogenic fungi and bacteria. Results were quite encouraging and these were compared with the standard pesticides Bavistin and Streptomycin. Copyright © 2008 John Wiley & Sons, Ltd.     

Intramolecular phenylborane complexes with monobasic bidentate Schiff bases

A series of intramolecular complexes with Schiff base ligands having N∩S and N∩O donor systems were synthesized in an open vessel under microwave irradiation (MWI) using a domestic microwave oven. The reaction time has been brought down from hours to seconds with improved yield as compared with the conventional heating. The complexes have been characterized on the basis of elemental analysis, conductance measurements and spectroscopic analysis. Based on the IR, ¹H NMR, ¹¹B NMR and ¹³C NMR spectroscopic studies, a tetrahedral geometry has been proposed for the resulting complexes. The compounds have been screened in vitro against bacteria and fungi to test their antimicrobial property and in vivo in male albino rats to test their antifertility property. The testicular sperm density, motility and density of cauda epididymal spermatozoa along with biochemical parameters of reproductive organs have been examined and discussed. Copyright © 2007 John Wiley & Sons, Ltd.