Studies on the Uptake of Glucose Derivatives by Red Blood Cells

Development and Characterization of Novel Chitosan-Coated Curcumin Nanophytosomes for Treating Drug-Resistant Malaria

This study aimed at enhancing the efficacy of curcumin (CR) by formulating and coating it with chitosan. In silico molecular docking studies revealed that CR exhibited almost similar and low binding energies when compared to artemisinin, indicating high stability at the target site. It can be confirmed that CR is effective in treating and reducing Plasmodium falciparum parasites. Fourier transform infrared studies confirmed that there was a shift and disappearance of some drug peaks in the formulation which revealed complexation with phospholipids. The F2EXT3-developed formulation exhibited greater solubility (24.31 ± 3.47 μg/mL) when compared to pure CR (7.99 ± 1.95 μg/mL). Proton nuclear magnetic resonance studies confirmed the formation of Curcumin-phospholipid hydrogen bonding in F2EXT3. The in vitro drug release studies revealed that the developed formulation F2EXT3 exhibited better drug release at 71.98% at 48 h; this might be due to the effective entrapment efficiency of the drug inside the phospholipid, presence of polyethylene glycol 4000 and chitosan further assisted in sustained release of the drug. Scanning electron microscopy studies revealed that optimized F2EXT3 CR nanophytosomes were nearly spherical with narrow size distribution and smooth surface. The zeta potential of the F2EXT3 showed -3.5 mV. Stability studies revealed that the formulation remained stable even after 6 months. It was observed from the hemin assay that CR and F2EXT3 exhibited (50 μg/mL curcumin) exhibited IC50 values of 47 ± 2.45 and 22 ± 1.58 μM, respectively. Further in vivo antimalarial activity on resistant and sensitive strains needs to be performed to evaluate the efficacy of the developed formulation.

Towards Selective Binding to the GLUT5 Transporter: Synthesis, Molecular Dynamics and In Vitro Evaluation of Novel C-3-Modified 2,5-Anhydro-D-mannitol Analogs

Deregulation and changes in energy metabolism are emergent and important biomarkers of cancer cells. The uptake of hexoses in cancer cells is mediated by a family of facilitative hexose membrane-transporter proteins known as Glucose Transporters (GLUTs). In the clinic, numerous breast cancers do not show elevated glucose metabolism (which is mediated mainly through the GLUT1 transporter) and may use fructose as an alternative energy source. The principal fructose transporter in most cancer cells is GLUT5, and its mRNA was shown to be elevated in human breast cancer. This offers an alternative strategy for early detection using fructose analogs. In order to selectively scout GLUT5 binding-pocket requirements, we designed, synthesized and screened a new class of fructose mimics based upon the 2,5-anhydromannitol scaffold. Several of these compounds display low millimolar IC50 values against the known high-affinity 18F-labeled fructose-based probe 6-deoxy-6-fluoro-D-fructose (6-FDF) in murine EMT6 breast cancer cells. In addition, this work used molecular docking and molecular dynamics simulations (MD) with previously reported GLUT5 structures to gain better insight into hexose-GLUT interactions with selected ligands governing their preference for GLUT5 compared to other GLUTs. The improved inhibition of these compounds, and the refined model for their binding, set the stage for the development of high-affinity molecular imaging probes targeting cancers that express the GLUT5 biomarker.

Fluorodesulfurization of Thionobenzodioxoles with Silver(I) Fluoride

Difluorobenzodioxole is an important functional group found in both pharmaceuticals and agrochemicals. The late-stage introduction of this functional group is challenged by typical fluorination conditions of HF and strong oxidants. Here, we demonstrate that a range of difluorobenzodioxoles can be prepared from catechols in two steps through conversion into thionobenzodioxoles, followed by desulfurative fluorination with silver(I) fluoride. These mild reaction conditions are compatible with a variety of functional groups and enable access to a range of functionalized difluorobenzodioxoles.

Diagnostic value of GLUT-1 in distinguishing malignant mesothelioma from reactive mesothelial cells: a meta-analysis

Background: Previous studies have demonstrated the diagnostic value of glucose transporter 1 (GLUT-1) to distinguish malignant mesothelioma (MM) from reactive mesothelial cells (RMC), but the results are inconsistent. The purpose of this meta-analysis is to investigate the diagnostic accuracy of GLUT-1 in distinguishing MM from RMC.Methods: A systematical search was conducted until May 2019 in PubMed, Medline, Embase and the Cochrane Library. The revised tool for the quality assessment of diagnostic accuracy studies (QUADAS-2) was used to assess the quality of the eligible studies. The Stata15 and Review Manager5.3 software programmes were used to perform the meta-analysis.Results: A total of 24 studies, including 969 MM patients and 1080 RMC individuals were explored in the meta-analysis. The summary assessments revealed that the pooled sensitivity was 0.73 (95% CI, 0.62-0.81) and the pooled specificity was 0.95 (95% CI, 0.91-0.98). The area under the summary ROC curve (AUC) was 0.93 (95% CI: 0.91-0.95).Conclusions: GLUT-1 is highly accurate to distinguish MM from RMC.

Molecular Tools for Facilitative Carbohydrate Transporters (Gluts)

Facilitative carbohydrate transporters-Gluts-have received wide attention over decades due to their essential role in nutrient uptake and links with various metabolic disorders, including diabetes, obesity, and cancer. Endeavors directed towards understanding the mechanisms of Glut-mediated nutrient uptake have resulted in a multidisciplinary research field spanning protein chemistry, chemical biology, organic synthesis, crystallography, and biomolecular modeling. Gluts became attractive targets for cancer research and medicinal chemistry, leading to the development of new approaches to cancer diagnostics and providing avenues for cancer-targeting therapeutics. In this review, the current state of knowledge of the molecular interactions behind Glut-mediated sugar uptake, Glut-targeting probes, therapeutics, and inhibitors are discussed.

Dehydroascorbate-derivatized chitosan particles for targeting antimalarial agents to infected erythrocytes

The mammalian glucose transporter GLUT-1 and Plasmodium falciparum hexose transporter PfHT1 are overexpressed on human RBC infected with the parasite (iRBC), presumably for enhanced glucose uptake. Dehydroascorbic acid (DHA) competes out glucose in GLUT-1 binding. We prepared particles containing chloroquine phosphate using novel derivatives of chitosan (CSN). CSN was either pre-derivatized with DHA (PRE) or particles made of CSN were derivatized by surface-grafting DHA (POST). The optimized formulations were analyzed for size (170-200nm) drug content (about 40%) entrapment efficiency (50-57%), in vitro drug release (80% in 72h, Higuchi's model), hemolysis on exposure to whole blood or RBC at 5% hematocrit, cytotoxicity towards cultured HEK 293T (kidney) and HepG2 (hepatic) cells, targeting iRBC and in vitro efficacy against P. falciparum. PRE particles were superior to POST CSN particles in terms of uptake and extent of preferential targeting to iRBCs than RBCs. Unlike starch particles reported earlier, dextrose did not competitively inhibit uptake of DHA-derivatized CSN particles. Both formulations significantly induced parasite inhibition at 1nM while free drug showed comparable activity at 100nM. Both PRE and POST particles were superior to free drug in efficacy. Targeting with high efficiency promises dose reduction and possibility of overcoming efflux-based drug resistance.

One-Pot UV-Triggered o-Nitrobenzyl Dopamine Polymerization and Coating for Surface Antibacterial Application

Dopamine (DA) protected by an o-nitrobenzyl functionality on its phenolic group was synthesized as a photolabile catecholamine derivative. This compound, o-nitrobenzyl dopamine (NBDA), was more stable than DA in basic solution at pH 8.5 and will not self-polymerize when protected from light. UV irradiation of a methanolic solution of NBDA at 365 nm for 40 min induced ca. 85% deprotection. Taking advantage of the stability of NBDA, a one-pot spray coating technique for modifying surfaces with polydopamine (PDA) was developed. Using ethylene glycol with Tris buffer (pH 8.5) as the solvent for this technique, stainless steel substrates can be coated with a robust PDA layer. Silver was deposited on the PDA-coated surface after treatment with silver nitrate solution, and >80% of the deposited silver remained on the surface after 1 week immersion in water. The NBDA-Ag surface was highly effective in inhibiting Staphylococcus aureus (S. aureus) biofilm formation.

Trienamine catalyzed asymmetric synthesis and biological investigation of a cytochalasin B-inspired compound collection

Due to their enhanced metabolic needs many cancers need a sufficient supply of glucose, and novel inhibitors of glucose import are in high demand. Cytochalasin B (CB) is a potent natural glucose import inhibitor which also impairs the actin cytoskeleton leading to undesired toxicity. With a view to identifying selective glucose import inhibitors we have developed an enantioselective trienamine catalyzed synthesis of a CB-inspired compound collection. Biological analysis revealed that indeed actin impairment can be distinguished from glucose import inhibition and led to the identification of the first selective glucose import inhibitor based on the basic structural architecture of cytochalasin B.

Small molecule ice recrystallization inhibitors enable freezing of human red blood cells with reduced glycerol concentrations

In North America, red blood cells (RBCs) are cryopreserved in a clinical setting using high glycerol concentrations (40% w/v) with slow cooling rates (~1°C/min) prior to storage at -80°C, while European protocols use reduced glycerol concentrations with rapid freezing rates. After thawing and prior to transfusion, glycerol must be removed to avoid intravascular hemolysis. This is a time consuming process requiring specialized equipment. Small molecule ice recrystallization inhibitors (IRIs) such as β-PMP-Glc and β-pBrPh-Glc have the ability to prevent ice recrystallization, a process that contributes to cellular injury and decreased cell viability after cryopreservation. Herein, we report that addition of 110 mM β-PMP-Glc or 30 mM β-pBrPh-Glc to a 15% glycerol solution increases post-thaw RBC integrity by 30-50% using slow cooling rates and emphasize the potential of small molecule IRIs for the preservation of cells.

Methylation and subsequent glycosylation of 7,8-dihydroxyflavone

An O-methyltransferase SpOMT2884, originating from Streptomyces peucetius ATCC 27952, was cloned, expressed, and applied for the production of target metabolite from Escherichia coli. Biochemical characterization of the 25kDa recombinant protein by in vitro and in vivo experiments showed that SpOMT2884 was an S-adenosyl-l-methionine-dependent O-methyltransferase. SpOMT2884 catalyzed O-methylation of different classes of flavonoids such as flavones (7,8-dihydroxyflavone (7,8-DHF), luteolin), flavonols (quercetin, rutin), flavanone (naringenin), and isoflavonoids (daidzein, formononetin). Biotransformation of 7,8-DHF, a preferred substrate of SpOMT2884, in a grown-induced culture of E. coli BL21 (DE3) harboring the recombinant pET-28a-SpOMT2884 stoichiometrically converted 7,8-DHF into 7-hydroxy-8-methoxyflavone, which was confirmed by liquid chromatography, mass spectrometry and various nuclear magnetic resonance (NMR) spectroscopy analyses. In order to improve the biotransformation substrate, time and media parameters were optimized and the production was scaled up using a 3-L fermentor. The maximum yield of 7-hydroxy-8-methoxyflavone was 192μM (52.57mg/L), representing almost 96% bioconversion within 12h, when 200μM of 7,8-DHF was supplemented in the culture. Further, the 7-hydroxy-8-methoxyflavone was purified in large scale and was used as a substrate separately for in vitro glycosylation to produce glucose, galactose and 2-deoxyglucose conjugated at 7th hydroxyl position of 7-hydroxy-8-methoxyflavone. Biological activity showed that 7-hydroxy-8-methoxyflavone had long term cytoprotective and antioxidant effects compared to 7,8-DHF suggesting that methylation enhances the stability of substrate and glycosylation has proved to increase the water solubility.

Synthesis of difluoroaryldioxoles using BrF3

A novel synthesis of different aromatic and heteroaromatic difluorodioxole derivatives has been developed. The starting materials were catechols, which, after treatment with thiophosgene, formed at 0 °C the respective thiodioxoles. The latter were reacted for a short time with commercially available bromine trifluoride, producing potentially biologically important difluoroaryldioxoles in moderate to high yields.