A convenient synthesis of novel pyranosyl homo-C-nucleosides and their antidiabetic activities

A series of pyranosyl homo-C-nucleosides have been synthesized by reaction of butenonyl C-glycosides (5a–5j, and 8) and cyanoacetamide in presence of t-BuOK followed by further modifications. The reaction proceeds by Michael addition of cyanoacetamide to the butenonyl C-glycosides and subsequent dehydrative cyclization and oxidative aromatization to give glycosylmethyl pyridones (6a–6j, 7a–7j, 9, and 10). The glycosylmethyl pyridones (6a–6e) on reaction with POCl₃ under reflux gave respective glycosylmethyl pyridines (11a–11e and 12a–12e) in good yields. The synthesized compounds were screened for their in vitro α-glucosidase, glucose-6-phosphatase and glycogen phosphorylase inhibitory activities. One of the pyridylmethyl homo-C-nucleoside, compound 11d, displayed 52% inhibition of glucose-6-phosphatase as compared to the standard drug sodium orthovanadate while compound 12a showed a significant antihyperglycemic effect of 17.1% in the diabetic rats as compared to the standard drug metformin.     

Physiological evidence indicates microcystin-LR to be a part of quantitative chemical defense system

The functional role of microcystins (MC) is poorly understood. Here, we investigated the effect of pure MC-LR recovered from the freshwater planktonic cyanobacterium Nostoc sp. BHU001 on five closely related cyanobacteria (Nostoc muscorum, Nostoc commune, Anabaena fertilissima, Anabaena doliolum, and Cylinderospermum majus) isolated from different habitats as well as on the producer itself (Nostoc sp. BHU001). MC-LR was found to be a general growth inhibitor active at nanomolar range (25–100 μg L^?1). It inhibited the growth of all cyanobacterial strains in a concentration-dependent manner, except the producer. A. fertilissima was the most sensitive species. MC-LR affected vital metabolic processes such as photosynthesis, respiration, and nitrogen fixation. Nitrogenase activity showed maximum sensitivity, followed by respiration, photosynthesis, and general growth. The photosynthetic electron transport activity was maximally inhibited at PSI, followed by whole chain and PSII activities. Thus, MC-LR is active at multiple sites causing energy constraint to the vital metabolic processes of the target organisms. However, its requirement at high concentration, which is environmentally irrelevant, and lack of quantitative information on the extracellular release of MC-LR suggest that MC-LR has no allelopathic function and could be a part of a quantitative chemical defense system.     

Development of phoH as a novel signature gene for assessing marine phage diversity

Phages play a key role in the marine environment by regulating the transfer of energy between trophic levels and influencing global carbon and nutrient cycles. The diversity of marine phage communities remains difficult to characterize because of the lack of a signature gene common to all phages. Recent studies have demonstrated the presence of host-derived auxiliary metabolic genes in phage genomes, such as those belonging to the Pho regulon, which regulates phosphate uptake and metabolism under low-phosphate conditions. Among the completely sequenced phage genomes in GenBank, this study identified Pho regulon genes in nearly 40% of the marine phage genomes, while only 4% of nonmarine phage genomes contained these genes. While several Pho regulon genes were identified, phoH was the most prevalent, appearing in 42 out of 602 completely sequenced phage genomes. Phylogenetic analysis demonstrated that phage phoH sequences formed a cluster distinct from those of their bacterial hosts. PCR primers designed to amplify a region of the phoH gene were used to determine the diversity of phage phoH sequences throughout a depth profile in the Sargasso Sea and at six locations worldwide. phoH was present at all sites examined, and a high diversity of phoH sequences was recovered. Most phoH sequences belonged to clusters without any cultured representatives. Each depth and geographic location had a distinct phoH composition, although most phoH clusters were recovered from multiple sites. Overall, phoH is an effective signature gene for examining phage diversity in the marine environment.     

Combined 2D electrophoretic approaches for the study of white lupin mature seed storage proteome

Seed proteome analysis by 2D IEF/SDS-PAGE techniques is challenging for the intrinsic difficulties related to quantitative disparity of the seed proteins, i.e. storage and non-storage proteins, their polymorphic nature, the extensive post-translational modifications and the paucity of deposited primary structures available. Conversely, 2D maps of seed proteomes can be extremely useful for a number of fundamental and applied investigations. In this work, we have used a combination of two experimental approaches to identify the main protein components of an emerging protein-rich legume seed, that is white lupin seed (Lupinus albus, L.). One is the canonical proteomic approach including 2D electrophoretic separation and mass spectrometry of selected trypsin-digested polypeptides; the other approach is a group comparative 2D electrophoretic analysis of cotyledonary protein families. To this second purpose, the three main families of lupin seed proteins, namely alpha-conglutins, the 11S globulin fraction, beta-conglutins, the 7S globulin fraction, and gamma-conglutin, a basic 7S protein, were isolated by conventional biochemical techniques and their 2D reference maps were compared with the total protein map. With the first approach 37 out of 40 spots, making up about 35% of total spot volumes in the 2D map, were found to belong to the main seed protein families. Thanks to cDNA-deduced lupin storage protein sequences, determined on purpose and deposited, most of the identification statistical parameters were very good. Moreover, it was possible to identify several endogenously proteolysed subunits in the map. The second comparative approach, beside confirming these attributions, allowed to allocate 124 polypeptides within the three main lupin protein families. These two approaches proved to be mutually validating and their combined use was effective for the establishment of a seed proteome map even in the case of sequence and protein post-translational processing lack of information. The results obtained also extend our knowledge of the seed storage protein polymorphism of white lupin.     

Synthesis and evaluation of novel benzimidazole derivative [Bz-Im] and its radio/biological studies

Two different benzimidazole analogues act as multimodal agent, first one as novel non-peptidic CCK-B receptor antagonist and similarly as potent anti-fungal agent, designated as [Bz-Im]. These compounds were synthesized and characterized by spectroscopic techniques such as FT-IR, NMR, EI-MS and also evaluated for specific radiopharmaceuticals. Preliminary radiolabeling results with (99m)Tc and biological evaluation studies showed promising results for further evaluation in vivo. The efficiency of labeling was more than 97% and complex was stable for about 12h at 30 degrees C in the presence of serum. Both ligands showed binding to most of the organs, known to express CCK receptors in biodistribution studies. Cholecystokinin (CCK(1) andCCK(2)) receptor binding affinities of these analogues are, IC(50), 0.942+/-0.107 for compound C and 0.665+/-0.211 for compound D in rat pancreatic acini. The anti-fungal activity has shown inhibitory activity against Aspergillus flavus and Aspergillus niger. These studies have provided a new template for further development of non-peptidic ligands for diagnostic and therapeutic purposes of diseases related with CCK receptors as well as anti-microbes.     

In Silico Modeling-based Identification of Glucose Transporter 4 (GLUT4)-selective Inhibitors for Cancer Therapy

Tumor cells rely on elevated glucose consumption and metabolism for survival and proliferation. Glucose transporters mediating glucose entry are key proximal rate-limiting checkpoints. Unlike GLUT1 that is highly expressed in cancer and more ubiquitously expressed in normal tissues, GLUT4 exhibits more limited normal expression profiles. We have previously determined that insulin-responsive GLUT4 is constitutively localized on the plasma membrane of myeloma cells. Consequently, suppression of GLUT4 or inhibition of glucose transport with the HIV protease inhibitor ritonavir elicited growth arrest and/or apoptosis in multiple myeloma. GLUT4 inhibition also caused sensitization to metformin in multiple myeloma and chronic lymphocytic leukemia and a number of solid tumors suggesting the broader therapeutic utility of targeting GLUT4. This study sought to identify selective inhibitors of GLUT4 to develop a more potent cancer chemotherapeutic with fewer potential off-target effects. Recently, the crystal structure of GLUT1 in an inward open conformation was reported. Although this is an important achievement, a full understanding of the structural biology of facilitative glucose transport remains elusive. To date, there is no three-dimensional structure for GLUT4. We have generated a homology model for GLUT4 that we utilized to screen for drug-like compounds from a library of 18 million compounds. Despite 68% homology between GLUT1 and GLUT4, our virtual screen identified two potent compounds that were shown to target GLUT4 preferentially over GLUT1 and block glucose transport. Our results strongly bolster the utility of developing GLUT4-selective inhibitors as anti-cancer therapeutics.