Novel hydroxy lignans from the heartwood of gmelina arborea

The structures of six new lignans isolated from the heartwood of Gmelina arborea have been determined. They are 6“ - bromo - isoarboreol, 4 - hydroxysesamin, 4,8 - dihydroxysesamin, 1,4 - dihydroxysesamin (gummadiol), 2 - piperonyl - 3 - hydroxymethyl - 4 - (α - hydroxy - 3,4 - methylenedioxybenzyl) - 4 - hydroxytetrahydrofuran, and the 4 - O - glucoside of 4 - epigummadiol. The ¹H and ¹³C NMR and mass spectra of these compounds and their derivatives are discussed, and the structure previously assigned to a germination inhibitor from Aegilops ovata is questioned.     

Pacharin: a new dibenzo(2,3-6,7)oxepin derivative from bauhinia racemosa lamk

The isolation of resveratrol and a new dibenzoxepin derivative, pacharin, from the heartwood of $\text{Bauhinia}$$\text{racemosa}$ Lank is reported. The structure of pacharin has been established as l,7-dlhydroxy-3-methoxy-2-methyl-dibenzo(2,3-6,7) oxepin (Va) by a study of its chemical and spectroscopic properties, including X-ray analysis.     

The methanol-induced conformational transitions of β-lactoglobulin, cytochrome c, and ubiquitin at low pH: A study by electrospray ionization mass spectrometry

The methanol-induced conformational transitions under acidic conditions for beta-lactoglobulin, cytochrome c, and ubiquitin, representing three different classes of proteins with beta-sheets, alpha-helices, and both alpha-helices and beta-sheets, respectively, are studied under equilibrium conditions by electrospray ionization mass spectrometry (ESI-MS). The folding states of proteins in solution are monitored by the charge state distributions that they produce during ESI and by hydrogen/deuterium (H/D) exchange followed by ESI-MS. The changes in charge state distributions are correlated with earlier studies by optical and other methods which have shown that, in methanol, these proteins form partially unfolded intermediates with induced alpha-helix structure. Intermediate states formed at about 35% methanol concentration are found to give bimodal charge state distributions. The same rate of H/D exchange is shown by the two contributions to the bimodal distributions. This suggests the intermediates are highly flexible and may consist of a mixture of two or more rapidly interconverting conformers. H/D exchange of proteins followed by ESI-MS shows that helical denatured states, populated at around 50% methanol concentration, transform into more protected structures with further increases in methanol concentration, consistent with previous circular dicroism studies. These more protected structures still produce high charge states in ESI, similar to those of the fully denatured proteins.     

Rhizophorin A, a novel secolabdane diterpenoid from the Indian mangrove plant Rhizophora mucronata

The ethyl acetate extract of Rhizophora mucronata furnished rhizophorin A, a novel secolabdane diterpenoid, (6R,11S,13S)-6,11,13-trihydroxy-2,3-seco-14-labden-2,8-olide-3-oic acid (1).     

Organelle‐Specific Activity‐Based Protein Profiling in Living Cells

A multimodal activity‐based probe for targeting acidic organelles was developed to measure subcellular native enzymatic activity in cells by fluorescence microscopy and mass spectrometry. A cathepsin‐reactive warhead conjugated to a weakly basic amine and a clickable alkyne, for subsequent appendage of a fluorophore or biotin reporter tag, accumulated in lysosomes as observed by structured illumination microscopy (SIM) in J774 mouse macrophage cells. Analysis of in vivo labeled J774 cells by mass spectrometry showed that the probe was very selective for cathepsins B and Z, two lysosomal cysteine proteases. Analysis of starvation‐induced autophagy, a catabolic pathway involving lysosomes, showed a large increase in the number of tagged proteins and an increase in cathepsin activity. The organelle‐targeting of activity‐based probes holds great promise for the characterization of enzyme activities in the myriad diseases linked to specific subcellular locations, particularly the lysosome.     

Direct interaction of a vancomycin derivative with bacterial enzymes involved in cell wall biosynthesis.

BACKGROUND: The glycopeptide antibiotic vancomycin complexes DAla-DAla termini of bacterial cell walls and peptidoglycan precursors and interferes with enzymes involved in murein biosynthesis. Semisynthetic vancomycins incorporating hydrophobic sugar substituents exhibit efficacy against DAla-DLac-containing vancomycin-resistant enterococci, albeit by an undetermined mechanism. Contrasting models that invoke either cooperative dimerization and membrane anchoring or direct inhibition of bacterial transglycosylases have been proposed to explain the bioactivity of these glycopeptides. RESULTS: Affinity chromatography has revealed direct interactions between a semisynthetic hydrophobic vancomycin (DCB-PV), and select Escherichia coli membrane proteins, including at least six enzymes involved in peptidoglycan assembly. The N(4)-vancosamine substituent is critical for protein binding. DCB-PV inhibits transglycosylation in permeabilized E. coli, consistent with the observed binding of the PBP-1B transglycosylase-transpeptidase. CONCLUSIONS: Hydrophobic vancomycins interact directly with a select subset of bacterial membrane proteins, suggesting the existence of discrete protein targets. Transglycosylase inhibition may play a role in the enhanced bioactivity of semisynthetic glycopeptides.     

Non Solvent Reaction: Ammonium Acetate Catalyzed Highly Convenient Preparation of Trans-Cinnamic Acids

trans-Cinnamic acids were obtained in near quantitative yield when various aromatic aldehydes were heated with equimolar quantity of malonic acid in presence of ammonium acetate under solvent free conditions. Considerable enhancement in the rate of the reaction was observed when the decarboxylative condensation was carried out under microwave irradiation.

     

Formation of oleogels based on edible lipid materials

Oleogels may be defined as lipophilic liquid and solid mixtures, in which solid lipid materials (oleogelators) with lower concentrations (<10 wt.%) can entrap bulk liquid oil by ways of the formation of network of oleogelators in the bulk oil. The oelogelators can be grouped into two: self-assembly system and crystal particles system. This article reviewed recent work on the formation of oleogels using various types of oleogelators. The fundamental aspects of the formation of lipid network, kinetic and microscopic properties of oleogels are discussed with a special emphasis on crystal particle based oleogels. The potential applications of edible oil based-oleogels and their functionality are also described.