Maria-Rita Sierakowski

In vitro and in vivo antiviral properties of sulfated galactomannans against yellow fever virus (BeH111 strain) and dengue 1 virus (Hawaii strain).

Two galactomannans, one extracted from seeds of Mimosa scabrella, having a mannose to galactose ratio of 1.1, and another with a 1.4 ratio from seeds of Leucaena leucocephala, were sulfated. The products from M. scabrella (BRS) and L. leucocephala (LLS) had a degree of sulfation of 0.62 and 0.50, and an average molecular weight of 620x10(3) and 574x10(3) gmol(-1), respectively. Their activities against yellow fever virus (YFV; BeH111 strain) and dengue 1 virus (DEN-1; Hawaii strain) were evaluated. This was carried out in young mice following intraperitoneal infection with YFV. At a dose of 49 mgkg(-1), BRS and LLS gave protection against death in 87.7 and 96.5% of the mice, respectively. When challenged with 37.5 LD50 of YFV, mice previously inoculated with BRS+virus or LLS+virus, showed 93.3 and 100% resistance, respectively, with neutralization titers similar to mice injected with 25 LD50 of formaldehyde-inactivated YFV. In vitro experiments with YFV and DEN-1 in C6/36 cell culture assays in 24-well microplates showed that concentrations that produced a 100-fold decrease in virus titer of YFV were 586 and 385 mgl(-1) for BRS and LLS, respectively. For DEN-1 they were 347 and 37 mgl(-1), respectively. Sulfated galactomannans, thus demonstrate in vitro and in vivo activity against flaviviruses.

Galactomannans and arabinans from seeds of caesalpiniaceae

Abstract Schizolobium amazonicum and S. parahybae galactomannans yielded the same pattern of oligosaccharides on partial acid hydrolysis. Seed coats of both species furnished unusual linear arabinans providing chemotyping evidence supporting the suggestion that they are not different species. Schizolobium parahybae and S. amazonicum seeds yielded galactomannans with identical 3.0:1 Man:Gal ratios and with the same d -galactose distribution along the main chain. Although the galactomannan from seeds of Cassia fastuosa showed the same Man:Gal ratio, its fine structure differed significantly from that of the two Schizolobium species as shown by the analysis of oligosaccharides (DP 2 to 6) obtained by partial acid hydrolysis. Seed coasts of S. parahybae and S. amazonicum furnished similar unusual neutral linear α- l -arabinofuranan (1 → 5) linked, as determined by methylation analysis, optical rotation and 13 C NMR spectroscopy. On the other hand, C. fastuosa seed coats furnished two acidic arabinans. These results in terms of using galactomannans and arabinans in chemotyping, support the suggestion of Rizzini that S. parahybae and S. amazonicum are not different species.

Structural Studies on Galactomannans From Brazilian Seeds

Abstract Chemical structures of galactomannans from the native Brazilian species, M. scabrella, S. barbatiman and S. parahy-bum were studied. Their seeds, on aqueous extraction, furnished high yields of viscous galactomannans, whose mannose to galactose ratios were 1.1:1, 1.5:1, and 3.0:1, respectively. The polysaccharides were analysed by methylation, periodate oxidation and chromium trioxide oxidation. The results, confirmed by 13C NMR spectroscopy, indicated expected structures of legume galactomannans, namely a polymeric main chain of (l→4) -linked β-D-mannopyranosyl residues substituted at 0–6 by single unit α-D-galactopyranosyl side-chains. 13C NMR spectra showed clear splitting of the O-substituted resonances of C-4 of the β-D-mannosyl residues depending on the nearest-neighbour probabilities, indicating a random arrangement of the D-galactosyl groups in all of the three galactomannans.

Rheological Properties of Butia Pulp

Rheological parameters of Butia pulp were determined at different temperatures using a concentric cylinder Haake Rotovisco rheometer, model RV-20, with measurement system ZA-30. Butia pulp was found to exhibit non-Newtonian, pseudoplastic behavior at all temperatures and the rheological parameters were adequately described by the Herschel-Bulkley model. Yield stress, flow behavior index, and consistency coefficient were significantly affected by temperature. The yield stress decreased exponentially with process temperature and ranged between 36.60 and 21.70 Pa. Apparent viscosity calculated through the Herschel-Bulkley model decreased with an increase in temperature. The Arrhenius model gave a good description of temperature effect on apparent viscosity of the pulp.

Some structural features of a heteropolysaccharide from the leaves of the cactus Pereskia aculeata

Abstract A homogenous water-soluble mucilaginous heteropolysaccharide containing 3.5 % protein was isolated from the leaves of Pereskia aculeata . It contains arabinose, galactose, rhamnose and galacturonic acid in a molar ratio of 5.1:8.2:1.8:1.0 and, based on conventional polysaccharide analysis techniques, has a (1→4)-linked β- D -galactopyranosyl main chain partially substituted at O-3 by β- L -arabinopyranosyl units, which are, in turn, di- O -substituted at O-2 and O-4 by non-reducing end-groups of α- L -arabinofuranose. Also present are O -substituted units of galactopyranosyluronic acid, which are also present as non-reducing end-groups. They are then linked (1→2) to rhamnopyranosyl units. Aqueous solutions of the heteropolymer had a maximum viscosity at pH 4.5 and viscosity was reduced in the presence of salts over a wide range of pHs. The 13 C NMR spectrum of the polysaccharide in DMSO indicated a great difference between the elevated segmental motion of the arabinosyl side chains and that of the core, since signals of the former were sharp and those of the latter extremely broad.

Propriedades reológicas da polpa de manga (Mangifera indica L. cv. Keitt) centrifugada

Objetivou-se com este trabalho estudar experimentalmente o comportamento reologico da polpa de manga centrifugada na faixa de temperatura de 10°C a 60°C. As medidas reologicas foram feitas no reometro Haake Rotovisco modelo RV 20, utilizando o sistema de medida de cilindros concentricos. A polpa integral foi produzida em uma despolpadeira com tela de 1,6 mm, congelada em um congelador de placas e armazenada a -15oC e centrifugada a 15000 rpm (29000 G), durante 40 minutos. O comportamento reologico da polpa de manga centrifugada (reogramas) foi ajustado pelo modelo de Ostwald de Waelle (Lei da Potencia) e as curvas de viscosidade aparente ajustadas pelo modelo de Mizrahi-Berk. Observou-se um comportamento pseudoplastico para a polpa de manga centriguda (n<1) e uma diminuicao na viscosidade aparente com o aumento da taxa de deformacao e temperatura, sendo que a viscosidade aparente da polpa de manga centrifugada tendeu a ficar constante a partir 200s-1.

Highly uneven distribution of O-acetyl groups in the acidic d-xylan of Mimosa scabrella (bracatinga)

Abstract The acidic O -acetyl- d -xylan of Mimosa scabrella contains xylose, 4- O -methylglucuronic acid, and O -acetyl groups in the molar ratios of 60:7:33 and, when subjected to controlled Smith degradation, provided xylosyl-, xylobiosyl-, xylotriosyl-, and xylotetraosyl-glycerol, as well as glycerol. Their proportions differed greatly from that which would arise from xylopyranosyl units substituted regularly with O -acetyl groups. In order to avoid ambiguities arising from resistance of some of the xylosyl units by substitution with 4- O -methylglucuronic acid, the O -acetylxylan was converted into a partly O -methylated polysaccharide having O -methyl groups with similar positions of substitution. Two successive Smith degradations were carried out, and the two sets of partly O -methylated derivatives resulting were identified by f.a.b.-m.s. The highly uneven distribution of O -acetyl groups along the xylan main-chain was confirmed, with the highest number of consecutive O -acetyl and 4- O -methylglucuronic acid substituents being six, and five O -acetyl substituents alone. 4- O -Methylglucuronic acid units were not substituted.

Location of O-acetyl groups in the heteropolysaccharide of the cactus Pereskia aculeata

Abstract The complex polysaccharide of the leaves of Pereskia aculeata is highly branched, containing units of arabinofuranose, arabinopyranose, galactopyranose, galactopyranosyluronic acid, and rhamnopyranose. Glucopyranose units are also present. The location of 25 molar % of acetate ester groups was determined using modified Bouveng procedures, one of the changes being the use of refluxing methanolic sodium methoxide for the removal of N -methyl- N -phenylcarbamoyl groups. With the aid of g.l.c.-m.s. on a capillary column of DB-210, which separated the various isomeric mono-, di-, and tri- O -methyl arabinitol acetates, and by examination of e.i. fragmentation patterns of various derivatives deuterated at C-1, the O -acetyl groups were located. They were found mainly as monosubstituents at O-2 and O-3 of nonreducing arabinofuranosyl end-groups and at O-2 of 4- O -substituted galacto- and gluco-pyranosyl units.

Wettability effect of graphene-based surfaces on silicon carbide and their influence on hydrophobicity of nanocrystalline cerium oxide films.

We investigate the water-repellent ability of graphene-based surfaces stabilized on silicon carbide (SiC) and the nanocrystalline cerium oxide (CeO2) films electrodeposited on them. Water contact angle is revealed strongly dependent on the number of graphene monolayers on SiC, indicating partial permeability of graphene on SiC. Fluctuations in the roughness of textured surfaces as well as variations of oxygen vacancy content in CeO2 electrodeposits are determinant for the hydrophobicity of the interaction between water droplets and nanocrystalline CeO2 electrodeposits on monolayers graphene on SiC.

Comportamento reológico de sistemas pécticos de polpas de frutas vermelhas

In this work, the rheological behavior of pectic systems formulated with pectins extracted from strawberry, blackberry, and raspberry pulps was investigated by means of oscillatory rheological tests. In addition, the chemical properties of these pectins were studied. The pectic systems from those red fruit pulps showed a strong gel character according to the rheological tests showing that the strawberry pectin presented the strongest gel character, which was confirmed by the Cox-Merz experiment, degree of esterification, and average molecular weight data. The galacturonic acid is directly related to the formation of the pectin network. Besides, the difference between the strength of the three pectic gels can be attributed to the esterification degree values and the average molecular weight of these biopolymers. The pectins extracted from the red fruits studied in this work can be classified as high methoxy pectins with a degree of esterification higher than 50%. The pectic gels exhibit good stability with an increase in temperature and in the shear-oscillatory constant time.