Rilton Alves de Freitas

Amylose contents, rheological properties and gelatinization kinetics of yam (Dioscorea alata) and cassava (Manihot utilissima) starches

Abstract After defatting yam and cassava starches have amylose contents of 36.2 and 24.2%, respectively. Suspensions of these starches in water were analysed, in an oscillatory rheometer, using a heating rate of 4.0 °C min−1, deformation of 1% and a frequency of 1 Hz, the initial temperatures of gelatinization being 71 and 62 °C for yam and cassava, respectively. A gelatinization study was also carried out by differential scanning calorimetry with different heating rates (2.5, 3.0, 4.0 and 5.0 °C min−1), to give, by the Arrhenius equation, the activation Energy (Ea) of the process. Yam starch showed a more energetic gelatinization process of when compared to cassava starch and also had a lower rate constant (s−1), indicating a relatively slow gelatinization process of at higher temperatures. Yam gels formed by autoclaving a suspension (50 g l−1) showed after 24 h of refrigeration, a stronger structure than for a cassava gel.

Electrospinning of commercial guar-gum: Effects of purification and filtration

Guar gums of two different commercial sources were successfully electrospun on both mica and copper tape at several concentrations starting from 1% (w/w). The electrospun fibers formed with the raw materials were not uniform and presented aggregates and beads within the fibers. Two different purification procedures and a filtration sequence with different pore size membranes were applied to enhance galactomannan solution homogeneity and solubility. The consequence was improved fiber morphology. We observed that the precipitation step, within the purification procedure, produced changes in the molar mass distribution and yielded different fiber diameter. Furthermore, spherical aggregates between fibers and within them disappeared after the sequential filtration. The resulting electrospun fiber diameter decreased with membrane pore diameter reduction. We conclude that the filtration process is responsible for molecular disentanglement, as well as disaggregation, which leads to improved electrospun galactomannan fiber morphology.

Sesquiterpene lactones from Vernonia scorpioides and their in vitro cytotoxicity

Fresh leaves of Vernonia scorpioides are widely used in Brazil to treat a variety of skin disorders. Previous in vivo studies with extracts of this species had also demonstrated a high antitumor potential. This paper reports isolation of four sesquiterpene lactones (hirsutinolides and glaucolides), together with diacetylpiptocarphol, 8-acetyl-13-etoxypiptocarphol, luteolin, apigenin, and ethyl caffeate from fresh leaves and flowers of Vernonia scorpioides. The hypothesis that hirsutinolide 3 is formed during extraction was verified theoretically using Density Functional Theory. The effects of isolated compounds on in vitro tumor cells were investigated, as well as their genotoxicity by means of an in vitro comet assay. The results indicate that glaucolide 2 and hirsutinolide 4 are toxic to HeLa cells. These compounds were genotoxic in vitro, a property that appears to be related to the presence of their epoxy groups, which has been a more reliable indication of toxicity than substitution on C-13 or the presence of alpha,beta-unsaturated keto-groups. These results need to be replicated in vivo in order to ascertain their toxicity.

Antioxidant idebenone-loaded nanoparticles based on chitosan and N-carboxymethylchitosan

Nanoparticles based on chitosan (Ch) and N-carboxymethylchitosan (N-CMCh) cross-linked with tripolyphosphate (TPP) were developed by co-drying with idebenone in different polymer-to-drug ratios (1.3:1 to 16:1) with 20% (wt/wt) colloidal silicon dioxide and tripolyphosphate (0.2 mg/mL). At high ratios (8:1 and 16:1) the spray-dried powder showed spherical and dense particles with a size close to 1 μm, allowing almost complete drug coating by the polymeric system and a high efficiency of drug incorporation (>90% and >80%, for Ch and N-CMCh, respectively). The nanoparticles showed a 10-fold increase of drug stability in comparison with free drug and preserved antioxidant activity in vitro. Compared with the severely irritative free form of idebenone, the nanoparticle formulation showed decreased mucous membrane irritation. These results revealed the potential of Ch and N-CMCh nanoparticles as carriers for a hydrophobic and irritative drug such as idebenone for topical or nasal use.

Adsorption behavior of oxidized galactomannans onto amino-terminated surfaces and their interaction with bovine serum albumin

Galactomannans extracted from Cassia fastuosa (CF) and Leucaena leucocephala (LL) seeds were purified and oxidized with 2,2,6,6-tetramethylpiperidine-1-oxyl (TEMPO) to form the uronic acid-containing polysaccharides CFOX with a degree of oxidation (DO) of 0.22 and LLOX with DO of 0.66, respectively. The adsorption behavior of CFOX and LLOX onto amino-terminated surfaces was studied by means of ellipsometric measurements. The influence of pH and ionic strength on the adsorption was investigated. A strong dependence of pH on the adsorbed amount of CFOX and LLOX was observed. At pH 4, there was a maximum in the adsorbed amount caused by strong electrostatic attraction between the substrate and the oxidized galactomannans. On the other hand, no ionic strength effect on the adsorption of CFOX and LLOX was observed. The immobilization of bovine serum albumin onto LLOX and CFOX was studied as a function of pH. LLOX proved to be a more attractive substrate for BSA than CFOX, indicating that the favorable interactions between the carboxylate groups and the BSA segments have driven the adsorption process. At the isoelectric point of BSA a maximum in the adsorbed amount was found for both surfaces.

Bacterial cellulose in biomedical applications: A review

Bacterial cellulose (BC) derived materials represents major advances to the current regenerative and diagnostic medicine. BC is a highly pure, biocompatible and versatile material that can be utilized in several applications - individually or in the combination with different components (e.g. biopolymers and nanoparticles) - to provide structural organization and flexible matrixes to distinct finalities. The wide application and importance of BC is described by its common utilization as skin repair treatments in cases of burns, wounds and ulcers. BC membranes accelerate the process of epithelialization and avoid infections. Furthermore, BC biocomposites exhibit the potential to regulate cell adhesion, an important characteristic to scaffolds and grafts; ultra-thin films of BC might be also utilized in the development of diagnostic sensors for its capability in immobilizing several antigens. Therefore, the growing interest in BC derived materials establishes it as a great promise to enhance the quality and functionalities of the current generation of biomedical materials.

Layer-by-layer polysaccharide-coated liposomes for sustained delivery of epidermal growth factor

A three-dimensional layer-by-layer (LbL) structure composed by xanthan and galactomannan biopolymers over dioctadecyldimethylammonium bromide (DODAB) liposome template was proposed and characterized for protein drug delivery. The polymers and the surfactant interaction were sufficiently strong to create a LbL structure up to 8 layers, evaluated using quartz crystal microbalance (QCM) and zeta potential analysis. The polymer-liposome binding enthalpy was determined by isothermal titration calorimetry (ITC). The bilayer of biopolymer-coated liposomes with diameters of 165 (±15)nm, measured by dynamic light scattering (DLS), and ζ-potential of -4 (±13)mV. These bilayer-coated nanoparticles increased up to 5 times the sustained release of epidermal growth factor (EGF) at a first order rate of 0.005min(-1). This system could be useful for improving the release profile of low-stability drugs like EGF.

Topical curcumin-loaded hydrogels obtained using galactomannan from Schizolobium parahybae and xanthan.

The curcumin (CUR)-loaded binary hydrogel was formulated using xanthan and galactomannan from Schizolobium parahybae (guapuruvu). The binary hydrogels presented gel characteristics, stable pH values and mechanical stress resistance even after 45 days of heat exposure (45 °C). The CUR-loaded hydrogel content was 98.6% for XGMC (xanthan and galactomannan with CUR-microemulsion) after the stability test. The in vitro cytotoxicity analysis suggested non-cutaneous membrane irritation, and the in vitro skin permeation analysis indicated 2.15 to 2.50 μg mL(-1) CUR at the stratum corneum, epidermal and dermal levels. The XGEC (xanthan and galactomannan with CUR solubilized in ethanol) and XGMC hydrogels presented 76.8 and 63.2% inhibition of topical inflammation, respectively. Chemical stability and non-cytotoxicity analysis confirm the safety of prolonged exposure of the skin during the topical treatment, offering long-lasting XGEC and XGMC action.

Physico–chemical aspects of galactoxyloglucan from the seeds of Hymenaea courbaril and its tetraborate complex

A galactoxyloglucan hydrocolloid (HXGRP) (Glu:Xyl:Gal molar ratio, ∼4:3:1) was obtained from cotyledons of seeds of Hymenaea courbaril by aqueous extraction and then purified (33% yield). Rheological measurements showed that HXGRP, in aqueous systems, interacts with tetraborate ions increasing both, viscosity and G′ values, also increasing the viscoelasticity of the system, but not forming a gel, as shown by Cox-Merz experiments. This interaction dependent of the amount of sodium tetraborate and the pH, and was analyzed in terms of hindered reptation. A temperature sweep of the HXGRP-tetraborate complex showed a characteristic cleavage of cross-links between polysaccharide and borate ions at high temperatures. An aqueous solution of HXGRP after heating at 85 °C for 2 h showed a decrease in its absolute viscosity.

Microencapsulation of Juçara (Euterpe edulis M.) Pulp by Spray Drying Using Different Carriers and Drying Temperatures

Juçara pulp was microencapsulated using three different carrier agents—gelatin, gum arabic, and maltodextrin—by spray drying. Response surface methodology based on a two-factor-five-level central composite design was applied to determine the effect of inlet temperature (140–190°C) and carrier agent concentration (5–55%) on anthocyanin retention. Significant retention of anthocyanin content (>83%) was observed at the treatment conditions of 165°C inlet temperature and 5% of carrier agent. Anthocyanin retention was affected by temperature, due to its high sensitivity, and by carrier agent concentration, which is related to the interaction between the juçara pulp compounds and the carrier agent.