Role of 3-O-sulfated heparan sulfate in virus-induced polykaryocyte formation

One way herpes simplex virus type-1 (HSV-1) spreads in vivo is by polykaryocytes formation. Here we demonstrate that polykaryocyte production during HSV-1 spread in cultured human corneal fibroblasts (CF) required heparan sulfate (HS) and more specifically 3-O sulfated HS (3-OS HS). The polykaryocyte formation heavily depended on the expression of HS on target (CF) cells but not on glycoprotein expressing effector cells. Furthermore, we provide the first visual evidence of 3-OS HS and HSV-1 gD colocalization during the membrane fusion process. Taken together our results provide novel insight into the significance of HS in polykaryocyte formation.     

Semisynthetic lysogalactolipids of plant origin

Starting from the natural mono- and digalactosyl diglycerides, 1′-O-acyl-3′-O-β-d-galactopyranosyl-sn-glycerol and 1′-O-acyl-3′-O-(6-O-α-d-galactopyranosyl-β-d-galactopyranosyl)-sn-glycerol were synthesized. In an attempt to prepare the 2′-O-acyl-isomer, only a mixture of the 1′-and 2′-O-acyl-isomers was obtained.     

Ericifolin: an eugenol 5-O-galloylglucoside and other phenolics from Melaleuca ericifolia

Ericifolin, an eugenol 5-O-beta-(6'-O-galloylglucopyranoside) possessing the naturally unknown phenolic moiety, 5-hydroxyeugenol, together with the two new phenolics, 2-O-p-hydroxybenzoyl-6-O-galloyl-(alpha/beta)-4C1-glucopyranose and 3-methoxyellagic acid 4-O-rhamnopyranoside have been isolated from the antibacterial leaves extract of Melaleuca ericifolia. In addition, 19 known phenolics were also separated and characterized. All structures were elucidated on the basis of analysis of 1H, 13C NMR, HMQC, HMBC and FTMS spectral data.     

Anthocyanin 3-galactosides from Cornus alba 'Sibirica' with glucosidation of the B-ring

The three anthocyanins, delphinidin 3-O-beta-galactopyranoside-3',5'-di-O-beta-glucopyranoside (1), delphinidin 3-O-beta-galactopyranoside-3'-O-beta-glucopyranoside (2) and cyanidin 3-O-beta-galactopyranoside-3'-O-beta-glucopyranoside (3), and the 3-O-beta-galactopyranosides of delphinidin (4) and cyanidin (5) were isolated from the bluish white berries and compound umbel of Siberian dogwood, Cornus alba 'Sibirica'. The ornamental autumn leaves and the characteristic purplish red bark of this variety were found to contain only pigment 5.     

Synthesis and membrane behavior of a new class of unnatural phospholipid analogs useful as phospholipase A2 degradable liposomal drug carriers

A new and unnatural type of lipid analogs with the phosphocholine and phosphoglycerol head groups linked to the C-2 position of the glycerol moiety have been synthesized and the thermodynamic lipid membrane behavior has been investigated using differential scanning calorimetry. From the heat capacity measurements, it was observed that the pre-transition was abolished most likely due to the central position of the head groups providing better packing properties in the low temperature ordered gel phase. Activity measurements of secretory phospholipase A2 (PLA2) on unilamellar liposomal membranes revealed that the unnatural phospholipids are excellent substrates for PLA2 catalyzed hydrolysis. This was manifested as a minimum in the PLA2 lag time in the main phase transition temperature regime and a high degree of lipid hydrolysis over a broad temperature range. The obtained results provide new information about the interplay between the molecular structure of phospholipids and the lipid membrane packing constrains that govern the pre-transition. In addition, the PLA2 activity measurements are useful for obtaining deeper insight into the molecular details of the catalytic site of PLA2. The combined results also suggest new approaches to rationally design liposomal drug carries that can undergo a triggered activation in diseased tissue by overexpressed PLA2.     

A first total synthesis of a novel sulfated ganglioside, 3'-O-sulfo-GM1b

A first total synthesis of a novel sulfated ganglioside, 3'-O-sulfo-GM1b, is described. The suitably protected gangliotriose (GgOSe3) derivative, 2-(trimethylsilyl)ethyl (2-acetamido-4,6-O-benzylidene-2-deoxy-beta-D-galactopyranosyl)-(1-->4)-(2,6-di-O-benzyl-3-O-p-methoxybenzyl-beta-D-galactopyranosyl)-(1-->4)-2,3,6-tri-O-benzyl-beta-D-glucopyranoside was glycosylated with the alpha-NeuAc-(2-->3)-galactose donor to give the protected GM1b oligosaccharide (95%). After proper manipulation of the protecting groups, the oligosaccharide was converted into the target ganglioside by the successive introduction of the ceramide and sulfo groups, followed by complete deprotection.     

Alkaloids from Galanthus nivalis

Phytochemical studies on Galanthus nivalis of Bulgarian origin resulted in the isolation of five compounds: 11-O-(3'-hydroxybutanoyl)hamayne, 3,11-O-(3',3'-dihydroxybutanoyl)hamayne, 3-O-(2'-butenoyl)-11-O-(3'-hydroxybutanoyl)hamayne, 3,11,3'-O-(3',3',3'-trihydroxybutanoyl)hamayne, and 2-O-(3'-acetoxybutanoyl)lycorine, together with five known alkaloids: ungeremine, lycorine, tazettine, hamayne, and ismine. Their structures were determined by (1)H and (13)C NMR spectroscopy and two-dimensional (1)H-(1)H and (1)H-(13)C chemical shift correlation experiments.     

Iridoid glucosides from Kickxia abhaica D.A. Sutton from Scrophulariaceae

Two iridoid glucosides namely; 6-acetylantirrinoside (1), 6'-O-p-hydroxybenzoylantirrinoside (2) were isolated from the aerial parts of Kickxia abhaica. Beside that, three known iridoid glucosides, antirrinoside (3), antirride (4) and mussaenosidic acid (5), one flavone glycoside (6) and a hexitol, d-mannitol (7) were isolated. The structures of the iridoid glucosides 1-2 were established by 1D and 2D NMR spectral data, including COSY, HMQC and HMBC experiments, as well as HRMS.     

Malonylated flavonol glycosides from the petals of Clitoria ternatea

Three flavonol glycosides, kaempferol 3-O-(2"-O-alpha-rhamnosyl-6"-O-malonyl)-beta-glucoside, quercetin 3-O-(2"-O-alpha-rhamnosyl-6"-O-malonyl)-beta-glucoside, and myricetin 3-O-(2",6"-di-O-alpha-rhamnosyl)-beta-glucoside were isolated from the petals of Clitoria ternatea cv. Double Blue, together with eleven known flavonol glycosides. Their structures were identified using UV, MS, and NMR spectroscopy. They were characterized as kaempferol and quercetin 3-(2(G)- rhamnosylrutinoside)s, kaempferol, quercetin, and myricetin 3-neohesperidosides, 3-rutinosides, and 3-glucosides in the same tissue. In addition, the presence of myricetin 3-O-(2"-O-alpha-rhamnosyl-6"-O-malonyl)-beta-glucoside was inferred from LC/MS/MS data for crude petal extracts. The flavonol compounds identified in the petals of C. ternatea differed from those reported in previous studies.     

Xanthones from Swertia punctata

Isolation of 1-O-primeverosyl-3,8-dihydroxy-5-methoxyxanthone and 1-O-gentiobiosyl-3,7-dimethoxy-8-hydroxyxanthone, along with five known xanthones, isobellidifolin, methylbellidifolin, isoswertianin, methylswertianin and norswertianin-1-O-beta-D-glucoside, from the roots of Swertia punctata is reported. In the aerial parts four xanthones, bellidifolin, methylbellidifolin, swertianolin and mangiferin, and flavone-C-glucoside, isoorientin were identified. The chemotaxonomic and pharmacological significance of these results is discussed.     

Isolation and characterization of 27-O-demethylrifamycin SV methyltransferase provides new insights into the post-PKS modification steps during the biosynthesis of the antitubercular drug rifamycin B by Amycolatopsis mediterranei S699

The gene rif orf14 in the rifamycin biosynthetic gene cluster of Amycolatopsis mediterranei S699, producer of the antitubercular drug rifamycin B, encodes a protein of 272 amino acids identified as an AdoMet: 27-O-demethylrifamycin SV methyltransferase. Frameshift inactivation of rif orf14 generated a mutant of A. mediterranei S699 that produces no rifamycin B, but accumulates 27-O-demethylrifamycin SV (DMRSV) as the major new metabolite, together with a small quantity of 27-O-demethyl-25-O-desacetylrifamycin SV (DMDARSV). Heterologous expression of rif orf14 in Escherichia coli yielded a 33.8-kDa polyhistidine-tagged polypeptide, which efficiently catalyzes the methylation of DMRSV to rifamycin SV, but not that of DMDARSV or rifamycin W. 27-O-Demethylrifamycin S was methylated poorly, if at all, by the enzyme to produce rifamycin S. The purified enzyme does not require a divalent cation for catalytic activity. While Ca(2+) or Mg(2+) inhibits the enzyme activity slightly, Zn(2+), Ni(2+), and Co(2+) are strongly inhibitory. The K(m) values for DMRSV and S-adenosyl-L-methionine (AdoMet) are 18.0 and 19.3 microM, respectively, and the K(cat) is 87s(-1). The results indicate that DMRSV is a direct precursor of rifamycin SV and that acetylation of the C-25 hydroxyl group must precede the methylation reaction. They also suggest that rifamycin S is not the precursor of rifamycin SV in rifamycin B biosynthesis, but rather an oxidative shunt-product.     

Six naphthylisoquinoline alkaloids and a related benzopyranone from a Congolese Ancistrocladus species related to Ancistrocladus congolensis

From the roots of a recently discovered Ancistrocladus taxon, with close affinities to Ancistrocladus congolensis regarding molecular ITS sequence data, six naphthylisoquinoline alkaloids, 5'-O-demethylhamatine (2), 5'-O-demethylhamatinine (3), 6-O-demethylancistroealaine A (4), 6,5'-O,O-didemethylancistroealaine A (5), 5-epi-6-O-methylancistrobertsonine A (6), and 5-epi-4'-O-demethylancistrobertsonine C (7), have been isolated, along with a likewise benzopyranone carboxylic acid, 8. The structural elucidation succeeded by chemical, spectroscopic, and chiroptical methods. Their bioactivities were tested against protozoan parasites causing severe tropical diseases. Furthermore, eight known related alkaloids were identified.     

Degraded limonoids from Melia azedarach and biogenetic implications

The unique series of C-2'-acylated C-glycosylflavones is extended by the discovery of the C-8-glucosyl derivatives 2'-O-galloylvitexin and 2'-O-galloylorientin and their C-6 analogues 2'-O-galloylisovitexin and 2'-O-galloylisoorientin, representing the first described O-galloyl-C-glycosylflavones. They are accompanied in the aerial parts of Pelargonium reniforme by the known non-galloylated parent analogues vitexin, orientin, isovitexin and isoorientin, as well as several known flavonoid-O-glycosides. The structures of these compounds were established from spectroscopic studies. Differentiation between C-glycosylation at C-6 and C-8 is discussed on the basis of the effects of dynamic rotational isomerism.     

Distribution of reaction products in phospholipase A2 hydrolysis

We have monitored the composition of supported phospholipid bilayers during phospholipase A₂ hydrolysis using specular neutron reflection and ellipsometry. Porcine pancreatic PLA₂ shows a long lag phase of several hours during which the enzyme binds to the bilayer surface, but only 5 ± 3% of the lipids react before the onset of rapid hydrolysis. The amount of PLA₂, which resides in a 21 ± 1 Å thick layer at the water-bilayer interface, as well as its depth of penetration into the membrane, increase during the lag phase, the length of which is also proportional to the enzyme concentration. Hydrolysis of a single-chain deuterium labelled d₃₁-POPC reveals for the first time that there is a significant asymmetry in the distribution of the reaction products between the membrane and the aqueous environment. The lyso-lipid leaves the membrane while the number of PLA₂ molecules bound to the interface increases with increasing fatty acid content. These results constitute the first direct measurement of the membrane structure and composition, including the location and amount of the enzyme during hydrolysis. These are discussed in terms of a model of fatty-acid mediated activation of PLA₂.     

The occurrence of 1-O-methyl-2-demethyl-phytylplastoquinol in Euglena gracilis

The isolation and characterization of 1-O-methyl-2-demethylphytylplastoquinol from photoheterotrophic cells of Euglena gracilis is described.     

A role for 3-O-sulfotransferase isoform-4 in assisting HSV-1 entry and spread

Many heparan sulfate (HS) 3-O-sulfotransferase (3-OST) isoforms generate cellular receptors for herpes simplex virus type-1 (HSV-1) glycoprotein D (gD). Interestingly, the ability of 3-OST-4 to mediate HSV-1 entry and cell-to-cell fusion has not been determined, although it is predominantly expressed in the brain, a primary target of HSV-1 infections. We report that expression of 3-OST-4 can render Chinese hamster ovary K1 (CHO-K1) cells susceptible to entry of wild-type and a mutant (Rid1) strain of HSV-1. Evidence for generation of gD receptors by 3-OST-4 was suggested by gD-mediated interference assay and the ability of 3-OST-4 expressing CHO-K1 cells to preferentially bind HSV-1 gD, which could be reversed by prior treatment of cells with HS lyases (heparinases-II/III). In addition, 3-OST-4 expressing CHO-K1 cells acquired the ability to fuse with cells-expressing HSV-1 glycoproteins. Demonstrating specificity, the cell fusion was inhibited by soluble 3-O-sulfated forms of HS, but not unmodified HS. Taken together our results suggest a role of 3-OST-4 in HSV-1 pathogenesis.     

Regioselective sulfonylation at O-2 of cyclomaltoheptaose with 1-(p-tolylsulfonyl)-(1H)-1,2,4-triazole

2(I)-O-p-Tolylsulfonylcyclomaltoheptaose was obtained in 42% yield by reaction of 1-(p-tolylsulfonyl)-(1H)-1,2,4-triazole on NaH-deprotonated cyclomaltoheptaose in DMF and further converted into the corresponding mono-2(I),3(I)-manno-epoxide.