Preparation and activity evaluation of chrysin-ß-D-galactopyranoside.

Chrysin-ß-D-galactopyranoside was efficiently synthesized, evaluated for its inhibitory activities against H22 cell lines compared with chrysin, the scavenging of hydroxyl radical, DPPH radical and superoxide anion, inhibitory effect against bacteria and fungi. The structures of all compounds were fully characterized by spectroscopic data (NMR, MS). The anti-tumor, antioxidant and antimicrobial activities of chrysin-ß-D-galactopyranoside were proved to be enhanced significantly compared with chrysin.

Synthesis and solid-state study of supramolecular host-guest assemblies: Bis[6-O,6-O'-(1,2:3,4-diisopropylidene-alpha-D-galactopyranosyl)thiophosphoryl] dichalcogenides.

A complementary approach for studying structural details of complex solid materials formed by symmetrical and unsymmetrical dichalcogenides, which employs both X-ray diffraction (XRD) and solid-state NMR (SS NMR), is presented. The new diagnostic technique allows reversible crystallographic space group change and very subtle distortion of host geometry to be followed during guest migration in the crystal lattice. Bis[6-O,6-O'-(1,2:3,4-diisopropylidene-alpha-D-galactopyranosyl)]thiophosphoryl selenenyl sulfide, a representative of wheel-and-axle host (WAAH) molecules, can be synthesized in the solid state by grinding and gentle heating of disulfide 1 and diselenide 2. Full characterization of disulfide 1 in the solid phase has been reported (J. Org. Chem. 1995, 60, 2549). In the current work, the synthesis and both XRD and SS NMR studies of the isostructural diselenide substrate 2 are presented. A (31)P cross polarization magic angle spinning experiment is employed to follow the progress of synthesis of selenenyl sulfide 3 in the solid state. It is concluded that selenenyl sulfide exists in equilibrium with disulfide and diselenide in a 1:1:1 ratio in both the liquid and the powdered solid. A mixture of isostructural dichalcogenides crystallized from different solvents form three-component host-guest inclusion complexes with columnar architecture. In the host-guest complex of diselenide 2 with toluene (space group C2), columns of host molecules are in parallel orientations along all the axes, whereas in the structures of diselenide 2 with propan-2-ol and propan-1-ol (space group P3 2), the columns of host molecules lay along the 3-fold symmetry axis. Thermal processes effecting structural changes in the host lattice and the kinetics of reversible guest molecule diffusion were investigated using SS NMR spectroscopy. Finally, the Se/S scrambling phenomenon and limitations in the X-ray structure refinement of organic compounds containing selenium and sulfur in chains are discussed.

Biodistribution characteristics of galactosylated emulsions and incorporated probucol for hepatocyte-selective targeting of lipophilic drugs in mice.

PURPOSE: Galactosylated emulsions containing cholesten-5-yloxy-N-(4-((1-imino-2-D-thiogalactosylethyl)amino)butyl)formamide (Gal-C4-Chol) as a "homing device" were developed for hepatocyte-selective drug targeting. The targeting efficiency of galactosylated emulsions was evaluated by a distribution study in mice. METHODS: Soybean oil/EggPC/cholesterol (Chol) (weight ratio, 70:25: 5) (bare) emulsions and soybean oil/EggPC/Gal-C4-Chol (weight ratio, 70:25:5) (Gal) emulsions were prepared and labeled with [3H]cholesteryl hexadecyl ether (CHE). [14C]probucol as a model lipophilic drug was incorporated in the emulsions or EggPC/Chol/Gal-C4-Chol (Gal) liposomes. Their tissue and intrahepatic distribution were evaluated following intravenous injection in mice. RESULTS: After intravenous injection, Gal-emulsions were rapidly eliminated from the blood and accumulated in the liver, in contrast to the bare-emulsions. The liver uptake clearance of Gal-emulsions was 3.2- and 1.2-times greater than that of bare-emulsions and Gal-liposomes, respectively. The uptake ratio in liver parenchymal cells (PC) and nonparenchymal cells (NPC) of Gal-emulsions was higher than that of Gal-liposomes, being 7.4 and 3.0, suggesting that Gal-emulsions are an effective PC-selective carrier. The hepatic uptake of Gal-emulsions, but not that of bare-emulsions, was significantly inhibited by the pre-dosing of not only lactoferrin but also Gal-liposomes, suggesting asialoglycoprotein receptor-mediated endocytosis. Furthermore, [14C]probucol incorporated in Gal-emulsions was efficiently delivered to the liver compared with Gal-liposomes. CONCLUSION: Gal-emulsions have been proven to be an alternative carrier for hepatocyte-selective drug targeting.

Synthesis of hexasaccharide fragments of pectin.

Short syntheses of partially methyl-esterified hexagalacturonates 1-5 are described as part of the development of strategies for the preparation of larger pectic oligosaccharides. The methodology is based on the repeated coupling of galactose mono- and disaccharide donors onto a galactose acceptor until a hexagalactan is obtained. All glycosylations are carried out with n-pentenyl glycosides to provide good yields of the desired alpha anomers. Pentenyl disaccharide donors are prepared by the coupling of two pentenyl galactosides controlled by either the armed-disarmed effect or by converting one pentenyl galactoside into the corresponding galactosyl bromide or fluoride. Two orthogonal protecting groups are employed at C6, which makes it possible to oxidize these positions to either the carboxylic acid or to the methyl ester. Each hexagalactan is therefore able to bifurcate into two different hexagalacturonates with a reverse methyl-esterification pattern. The methyl ester distribution in the hexagalacturonates is confirmed by tandem mass spectrometry.

A new synthesis of galactose-poly(ethylene glycol)-polyethylenimine for gene delivery to hepatocytes.

A synthesis method of conjugating polyethylenimine (PEI) derivatives with terminally galactose-grafted poly(ethylene glycol) (PEG) was developed by using a bifunctional PEG derivative containing both an alpha-vinyl sulfone (VS) and an omega-N-hydroxysuccinimidyl (NHS) ester groups (VS-PEG-NHS). VS-PEG-NHS is commonly used as a crosslinker to modify proteins with ligands by first coupling amine groups to the NHS ester, followed by coupling sulfhydryl groups to the VS ester, because the reaction of VS groups with amine groups of proteins is suppressed below pH 8. However, the 1H-NMR determination of the conjugated products of branched PEI (M(w)=25 kDa) with VS-PEG-NHS at pH 6.0-8.0 indicated that the VS groups were completely bound to the amine groups of PEI as well as the NHS groups. At pH 7.0, all VS groups reacted with the primary, secondary, or tertiary amine groups of PEI in 2 h. Such different reaction behaviors would be due to a higher density of amine groups of PEI as compared with those of proteins. In contrast, the reactions with a small molecular monoamine, such as p-aminophenyl beta-D-galactopyranoside, showed that the NHS groups selectively coupled with the amine groups, and the VS groups remained completely intact. The NHS groups of VS-PEG-NHS were selectively conjugated to amine groups of p-aminophenyl beta-D-galactopyranoside (VS-PEG-Gal). Then, the VS groups of Gal-PEG unit were completely conjugated with the primary, secondary, or tertiary amine groups of PEI. Thus, the use of only two reaction steps could conveniently carry out the conjugation of terminally galactose-grafted PEG to 1 and 5 mol.% of amine functions in PEI. The gel retardation assay of the complexes between Gal-PEG-PEI and plasmid DNA indicated that these polymeric gene carriers possess the potent ability to condense plasmid DNA electrostatically as well as PEI. The transfection efficiency with 1% Gal-PEG-PEI in human hepatocyte-derived cell lines (HepG2), a model of parenchymal cells in liver (hepatocytes), was superior to that of PEI at their corresponding optimal ratios of polymer to plasmid DNA. In HepG2 cells, luciferase activity with 1% Gal-PEG-PEI at an N/P ratio of 20 was 2.1-fold greater than that of PEI at an N/P ratio of 5. In mouse fibroblasts (NIH3T3) that have no ASGP receptors, the transfection efficiency with 1% Gal-PEG-PEI drastically decreased to 1/40 of that with PEI. These data indicate that a new synthesis method can produce polyethylenimine derivatives with terminally galactose-grafted poly(ethylene glycol) for specific gene targeting to the liver.

The synthesis, testing and use of 5-fluoro-alpha-D-galactosyl fluoride to trap an intermediate on green coffee bean alpha-galactosidase and identify the catalytic nucleophile.

5-Fluoro-alpha-D-galactopyranosyl fluoride was synthesized and its interaction with the active site of an alpha-galactosidase from green coffee bean (Coffea arabica), a retaining glycosidase, characterized kinetically and structurally. The compound behaves as an apparently tight binding (Ki = 600 nM) competitive inhibitor, achieving this high affinity through reaction as a slow substrate that accumulates a high steady-state concentration of the glycosyl-enzyme intermediate, as evidenced by ESiMS. Proteolysis of the trapped enzyme coupled with HPLC/MS analysis allowed the localization of a labeled peptide that was subsequently sequenced. Comparison of this sequence information to that of other members of the same glycosidase family revealed the active site nucleophile to be Asp145 within the sequence LKYDNCNNN. The importance of this residue to catalysis has been confirmed by mutagenesis studies.