The melibiose-derived glycation product mimics a unique epitope present in human and animal tissues.

Non-enzymatic modification of proteins by carbohydrates, known as glycation, leads to generation of advanced glycation end-products (AGEs). In our study we used in vitro generated AGEs to model glycation in vivo. We discovered in vivo analogs of unusual melibiose-adducts designated MAGEs (mel-derived AGEs) synthesized in vitro under anhydrous conditions with bovine serum albumin and myoglobin. Using nuclear magnetic resonance spectroscopy we have identified MAGEs as a set of isomers, with open-chain and cyclic structures, of the fructosamine moiety. We generated a mouse anti-MAGE monoclonal antibody and show for the first time that the native and previously undescribed analogous glycation product exists in living organisms and is naturally present in tissues of both invertebrates and vertebrates, including humans. We also report MAGE cross-reactive auto-antibodies in patients with diabetes. We anticipate our approach for modeling glycation in vivo will be a foundational methodology in cell biology. Further studies relevant to the discovery of MAGE may contribute to clarifying disease mechanisms and to the development of novel therapeutic options for diabetic complications, neuropathology, and cancer.

New N-substituted hydrazones, derivatives of uridyl aldehyde.

N-substituted isomeric hydrazones of uridyl aldehyde have been synthesized. The occurrence of the dominant E isomers with respect to the azomethine group was confirmed by means of NMR spectroscopy. Synthesized hydrazones feature an acetonide moiety as a protection of two hydroxyl groups on the ribose part. The attempt to remove the protecting group resulted in an azo-hydrazone tautomeric mixture. The described compounds may be valuable chiral ligands for metal chelation. Assessment of manganese(II) ion affinity to one selected hydrazone was performed.

Thermoresponsive microgels containing trehalose as soft matrices for 3D cell culture.

A series of thermoresponsive glycomicrogels with trehalose in the cross-links or with trehalose in the cross-links and as pending moieties was synthesized. These materials were obtained by surfactant-free precipitation copolymerization of N-isopropylacrylamide and various amounts of trehalose monomers. The resultant particles showed a spherical shape and a submicrometer hydrodynamic size with a narrow size distribution. At 25 °C, glycomicrogels in solutions with physiological ionic strength formed stable colloids, which further gelled upon heating to physiological temperature forming a macroscopic hydrogel with an interconnected porous structure. These extremely soft matrices with dynamic storage modulus in the range of 9-70 Pa were examined in 3D culture systems for HeLa cell culture in comparison to traditional 2D mode. They showed relatively low syneresis over time, especially when glycomicrogels with a high content of hydrophilic trehalose were used as building blocks. An incorporated pending trehalose composed of two α,α'-1,1'-linked d-glucose moieties was used with the intention of providing multivalent interactions with glucose transporters (GLUTs) expressed on the cell surface. A better cell viability was observed when a soft hydrogel with the highest content of trehalose and the lowest syneresis was used as a matrix compared to a 2D control assay.

New monomeric and dimeric uridinyl derivatives as inhibitors of chitin synthase.

This study described the synthesis and in vitro evaluation of eight new derivatives of uridine as antifungal agents and inhibitors of chitin synthase. Dimeric uridinyl derivatives synthesized by us did not exhibit significant activity. One of the studied monomeric derivative, 5'-(N-succinyl)-5'-amino-5'-deoxyuridine methyl ester (compound 7) showed activities against several fungal strains (MIC range 0.06-1.00 mg/mL) and inhibited chitin synthase from Saccharomyces cerevisiae (IC50=0.8mM). Moreover compound 7 exhibited synergistic interaction with caspofungin against Candida albicans (FIC index=0.28).

Synthesis and biological evaluation of 5'-glycyl derivatives of uridine as inhibitors of 1,4-ß-galactosyltransferase.

New 5'-glycyl derivatives of uridine containing fragments of varying lipophilicity were synthesized as analogues of natural peptidyl antibiotics. One of the studied compounds, 5'-O-(N-succinylglycyl)-2',3'-O-isopropylideneuridine (A4), showed moderate inhibition against 1,4-ß-galactosyltransferase. However, additional studies showed that the observed inhibitory effect was due to binding to bovine serum albumin, which was used in assays as a stabilizer.

Synthesis and cytotoxicity of 2,3-enopyranosyl C-linked conjugates of genistein.

A series of glycoconjugates, derivatives of genistein containing a C-glycosylated carbohydrate moiety, were synthesized and their anticancer activity was tested in vitro in the human cell lines HCT 116 and DU 145. The target compounds 15-17 were synthesized by treating ω-bromoalkyl C-glycosides derived from L-rhamnal (1) with a tetrabutylammonium salt of genistein. The new, metabolically stable analogs of previously studied O-glycosidic genistein derivatives inhibited proliferation of cancer cell lines through inhibition of the cell cycle.

Synthesis and preliminary biological evaluations of 5'-substituted derivatives of uridine as glycosyltransferase inhibitors.

New derivatives of uridine which contain a b-ketoenol motif were synthesized, characterized and biologically tested. Synthesized compounds 1-4 showed no activity against bovine milk ß-1,4-galactosyltransferase I at concentrations up to 2.0 mM and were not active against Candida albicans and Aspergilus fumigatus up to the maximum tested concentration of 1,000 µg/mL.

Synthesis of 2-deoxy-hexopyranosyl derivatives of uridine as donor substrate analogues for glycosyltransferases.

A series of 2-deoxy-hexopyranosyl derivatives of uridine have been synthesized as analogues of UDP-sugar. These compounds were tested as inhibitors against bovine beta-1,4-galactosyltransferase I in fluorescent assays and showed no significant inhibition.

5-Amino-2-pyridyl 1-thioglycosides in synthesis of analogs of glycosyltransferases substrates.

We present the synthesis of 1-thioglycosyl derivatives of uridine, which were designed to act as potential donor substrates for glycosyltransferases. We constructed such analogs using 5-amino-2-pyridyl 1-thioglycosides as glycosyl units which were connected to uridine via succinic linker. For preparation of the amide bonds we applied different condensation procedures.

Simultaneous removal of benzyl and benzyloxycarbonyl protective groups in 5'-O-(2-deoxy-alpha-D-glucopyranosyl)uridine by catalytic transfer hydrogenolysis.

Synthesis of N(3),2',3'-O-tris-(benzyloxycarbonyl)uridine and its use in the synthesis of 5'-O-(2-deoxy-alpha-d-glucopyranosyl)uridine is described. Simultaneous removal of benzyl and benzyloxycarbonyl groups was accomplished by catalytic transfer hydrogenolysis in the presence of Pearlman's catalyst without competing side reactions.

Adducts of uridine and glycals as potential substrates for glycosyltransferases.

We report on the synthesis of 2-deoxyglycosyl derivatives of uridine as potential donor substrates for glycosyltransferases. The totally stereoselective synthesis is accomplished by two sequential addition reactions of uridine derivatives to glycals promoted by triphenylphosphine-hydrogen bromide.

4-O-Acetyl-3-O-tert-butyldimethylsilyl-L-rhamnal: a building block in the stereoselective synthesis of 2-deoxy-alpha-L-rhamnopyranosides.

The stereoselective synthesis of 2-deoxy-alpha-L-glycosides by addition of various acceptors to 4-O-acetyl-3-O-tert-butyldimethylsilyl-L-rhamnal promoted by triphenylphosphine-hydrogen bromide is developed.