Haroldo C.B. Paula

Chitosan/cashew gum nanogels for essential oil encapsulation

Nanogels based on chitosan and cashew gum were prepared and loaded with Lippia sidoides oil. Several parameters such as cashew gum concentration and relative oil content in the matrix had their influence on nanogel properties investigated. Nanogels were characterized regarding their morphologies, particle size distributions, zeta potential, Fourier transform infrared spectroscopy and essential oil contents. The release profile was investigated by UV/vis spectroscopy and its efficacy was determined through bioassays. Results showed that samples designed using relative ratios matrix:oil 10:2, gum:chitosan 1:1 and 5% gum concentration showed high loading (11.8%) and encapsulation efficiency (70%). Nanogels were found to exhibit average sizes in the range 335-558 nm. In vitro release profiles showed that nanoparticles presented slower and sustained release. Bioassays showed that larval mortality was related mainly to oil loading, with samples presenting more effective larvicide efficacies than the pure L. sidoides oil.

Alginate/cashew gum nanoparticles for essential oil encapsulation.

Alginate/cashew gum nanoparticles were prepared via spray-drying, aiming at the development of a biopolymer blend for encapsulation of an essential oil. Nanoparticles were characterized regarding to their hydrodynamic volume, surface charge, Lippia sidoides essential oil content and release profile, in addition to being analyzed by infrared spectroscopy (FT-IR), thermal analysis (TGA/DSC) and X-ray diffractometry. Nanoparticles in solution were found to have averaged sizes in the range 223-399 nm, and zeta potential values ranging from -30 to -36 mV. Encapsulated oil levels varied from 1.9 to 4.4% with an encapsulation efficiency of up to 55%. The in vitro release profile showed that between 45 and 95% of oil was released within 30-50h. Kinetic studies revealed that release pattern follow a Korsmeyer-Peppas mechanism.

Effect of mono and divalent salts on gelation of native, Na and deacetylated Sterculia striata and Sterculia urens polysaccharide gels

The effects of purification and salt addition on gelation of Sterculia striata and Sterculia urens (karaya) gels were investigated. Both gums form thermoreversible and ‘true’ gels. Melting transition temperature (Tm) of Na-polysaccharide sample was lower than that of the native gum. A gel-like mechanical spectrum is observed for two Sterculia gums with G′>G″ and little frequency dependence. The presence of acetyl groups in both gums seems to stabilize the gel. The Tm decreases and the critical gelation concentration increases after deacetylation. The addition of monovalent salts (LiCl, NaCl, KCl) to native S. striata polysaccharide decreases the Tm. However, the gel becomes stronger when monovalent salts are added to Na- and deacetylated gum. The gel strength of Na- S. striata polysaccharide in the presence of divalent salt follows the order: Mg2+>Ca2+>Sr2+>Ba2+, i.e. inversely proportional to the cationic radius. Addition of divalent salts to S. urens polysaccharide promotes a Tm decrease. A model for the gelation was proposed that includes ionic interactions and hydrogen bonding.

Activity of chitosan-encapsulated Eucalyptus staigeriana essential oil on Haemonchus contortus

Phytotherapy has been described as an alternative method for the control of gastrointestinal nematodes in small ruminants. Goal of the encapsulation of essential oils in biopolymer matrices is to optimize the biological effects of these oils. The aim of the present study was to evaluate the in vitro and in vivo anthelmintic activity of encapsulated Eucalyptus staigeriana essential oil (EncEs) on the eggs and larvae of Haemonchus contortus. Therefore, the egg hatching test (EHT), larval development test (LDT) and worm load evaluation were performed to evaluate Meriones unguiculatus experimentally infected with H. contortus. The chemical constituents of E. staigeriana essential oil (EsEO) and the in vitro oil release profile from the chitosan matrix at a pH of 1.2 and 7.0 were also characterized. EncEs and EsEO inhibited larval hatching by 97.19% and 99.96% at doses of 1.5 and 1.0 mg ml(-1), respectively. In the LDT, EncEs and EsEO induced a larvicidal effect greater than 95% at concentrations of 5.8 and 8 mg ml(-1), respectively. EncEs and EsEO decreased H. contortus load in M. unguiculatus by 40.51% and 46.44%, respectively. The major chemical constituents of EsEO were (+)-Limonene (72.9%), 1,8-Cineole (9.5%) and o-Cimene (4.6%). The release profile of EsEO was 30% in acid and 25% at neutral pH. The similar efficacy of EncEs and EsEO demonstrates that there was no optimization of anthelmintic action following the encapsulation process. Therefore, the use of new encapsulation matrices with controlled release in the pH of the abomasum should be investigated.

Swelling studies of chitosan/cashew nut gum physical gels

Abstract Gels from chitosan/cashew nut gum (CH/CNG) were prepared with different chitosan to cashew nut gum ratio and their swelling behaviour was investigated as a function of pH and salt. Infrared and Carbon-13 nuclear magnetic resonance spectroscopy were used to elucidate the gel structure. Swelling in water diminishes sharply when the ratio CH/CNG increases. In the presence of Na + counterions the degree of swelling ( Q ) remains fairly constant, whereas in presence of Ca 2+ counterions Q increases with the CH/CNG ratio. It was found that swelling is maximal at pH 2 and at pH 10, where the gel can absorb water up to 44 times its own weight. Chitosan amine and cashew nut carboxylate groups seem to play a major role in the swelling mechanism, being the polysaccharide gum the major factor responsible for water absorption.

Composition and effect of salt on rheological and gelation properties of Enterolobium contortisilliquum gum exudate

The composition, structure and rheological properties and metal ions interaction with Enterolobium contortisilliquum gum were investigated. This gum contains galactose, arabinose, rhamnose and glucuronic acid as main monosaccharide components. 13C nuclear magnetic resonance spectroscopy revealed that the anomeric composition is similar to the Enterolobium cyclocarpum exudate, however no 4-O-methylglucuronic acid was detected for E. contortisilliquum. The rheological experiment resulted in a very similar flow behaviour to that found for E. cyclocarpum gum. The empirical stiffness parameter, B was determined (B=0.090) and suggested that the polysaccharide possesses semi-flexible chains. Cation affinity of the gum aqueous solution was determined by intrinsic viscosity measurements and gelation. The melting temperature of gels pointed to a charge/ionic radius ratio dependence for metal ions. Thermodynamic parameters (enthalpy and entropy) at the melting temperature were also calculated.

Lippia sidoides essential oil encapsulation by angico gum/chitosan nanoparticles

Chitosan (CH) and angico gum (AG) nanoparticles were loaded with essential oil, Lippia sidoides (Ls), being characterized according to their composition, size distribution, Ls:polymer ratio, thermal stability and in vitro and in vivo controlled release. Nanoparticles prepared using Ls:AG ratios of 1:2 to 1:20 had loading values of 3.3 to 7.7%, with encapsulation efficiencies in the range of 16.0 to 77.8%. Particle sizes were in the range of 10-60 nm and size distributions were independent of Ls content, for different Ls:AG ratios. Infrared spectroscopy revealed the presence of thymol in the nanoparticles. TGA and DSC revealed that the degradation temperature of AG-CH nanoparticles decreased with an increase in Ls content. Controlled-release data showed a slower release profile for samples with Ls:AG = 1:10 than for the other samples. Bioassays showed that sample Ls:AG = 1:10 has a greater larvicidal effect, with 85 ± 3% mortality.

Comparative efficacy and toxic effects of carvacryl acetate and carvacrol on sheep gastrointestinal nematodes and mice

Carvacrol is a compound isolated from some essential oils. It has been reported to possess anthelmintic activity. Acetylation of this monoterpene has been proposed as a potential way to reduce the toxicity and enhance the pharmacological effects of carvacrol. This study aimed to evaluate the effect of carvacryl acetate (CA) using in vitro and in vivo assays with gastrointestinal nematodes of small ruminants. The egg hatching test (EHT), larval development test (LDT) and adult worm motility (AWM) assessment were conducted to evaluate the effect of the acetylated product and pure carvacrol on Haemonchus contortus eggs, larvae and adults. The structural changes induced in adult H. contortus were assessed using scanning electron microscopy (SEM). CA and carvacrol acute toxicity was evaluated in mice. Finally, the efficacy of 250 mg/kg CA and 2.5mg/kg monepantel (positive control) were evaluated in 30 sheep naturally infected with gastrointestinal nematodes by the fecal egg count reduction test (FECRT). In vitro tests were analyzed by analysis of variance (ANOVA) followed by comparison with Tukeys test. The efficacy was calculated by the Boot Street program using the arithmetic average. The number of eggs in feces (epg) of the groups were transformed to log (x+1) and subjected to ANOVA to compare differences among the groups by Tukeys test. The level of significance was P<0.05. CA and carvacrol inhibited larval hatching by 89.3 and 97.7% at doses of 8.0 and 1.0mg/ml, respectively. At the concentration of 2mg/ml, CA and carvacrol inhibited 100% of larval development. At a concentration of 200 μg/ml, CA and carvacrol inhibited the motility of adult worms by 100% and 58.3% at 24h post-exposure, respectively. CA caused cuticle and vulvar flap wrinkling and bubbles to emerge from the tegument. Carvacrol caused more discreet effects on the cuticle and vulvar flap. The LD10 and LD50 of CA were 566.7 mg/kg and 1544.5mg/kg, respectively. The LD10 and LD50 of carvacrol were 546.8 mg/kg and 919 mg/kg, respectively. CA and monepantel reduced the epg of sheep by 65.9 and 96.4%, respectively, at 16 days post-treatment. CA showed in vitro and in vivo anthelmintic activity and was less toxic than carvacrol.

Efficacy of free and nanoencapsulated Eucalyptus citriodora essential oils on sheep gastrointestinal nematodes and toxicity for mice.

Herbal medicines with anthelmintic effects are alternatives for the sustainable control and prevention of disease caused by gastrointestinal parasites. The nanoencapsulation of essential oils has been proposed to enhance the absorption of their constituents and improve their efficacy. The present study aimed to evaluate the efficacy of free and nanoencapsulated Eucalyptus citriodora essential oil (EcEO) on the control of gastrointestinal nematodes of small ruminants in vitro and in vivo. Chitosan was used as a matrix for the formulation of a nanoemulsion. Chromatographic and physico-chemical analyses of EcEO were performed. Egg hatch (EHT) and larval development (LDT) tests were conducted to evaluate the effectiveness of nanoencapsulated and free EcEO on the eggs and larvae of Haemonchus contortus. Acute toxicity of free and nanoencapsulated EcEO was evaluated using mice. Finally, nanoencapsulated EcEO efficacy on the control of gastrointestinal nematodes was calculated by fecal egg count reduction test (FECRT) treating 30 sheep naturally infected with 250 mg/kg of free and nanoencapsulated EcEO. In vitro tests were analyzed by an analysis of variance (ANOVA) followed by comparison with the Tukey test. The efficacy of FECRT was calculated by the BootStreet program through arithmetic average, using the formula 100 (1-XT/XC). To compare the differences between epg, the data were transformed to log(x+1) and subjected to an ANOVA to compare the significant differences between groups by Tukeys. The level of significance was P<0.05. The free (4 mg/ml concentration) and nanoencapsulated (2mg/ml concentration) EcEO inhibited larvae hatching by 97.2% and 92.8%, respectively. Free and nanoencapsulated EcEO at 8 mg/ml inhibited larval development by 99.8% and 98.1%, respectively. In the acute toxicity test, the LD10 and LD50 of free EcEO was 1999 and 2653 mg/kg, respectively, while the LD10 and LD50 of nanoencapsulated EcEO was 1121 and 1681 mg/kg, respectively. Nanoencapsulated and free EcEO reduced FEC similarly by 40.5% and 55.9%, respectively at 10 days post-treatment. Nanoencapsulated EcEO did not obtain the expected efficacy in vivo.

Self-assembled nanoparticles of acetylated cashew gum: Characterization and evaluation as potential drug carrier

Acetylated cashew gum (ACG) was synthesized and self-assembled nanoparticles were obtained through the dialysis of an organic solution (DMSO) against a non-solvent (water). The ACG was characterized by infrared spectroscopy. The degree of substitution was 2.8 as determined by NMR spectroscopy. The physicochemical properties of the self-assembled nanoparticles in aqueous media were characterized by DLS, SEM and fluorescence spectroscopy. The mean diameter of the self-assembled nanoparticles obtained was 179 nm and the critical aggregation concentration (CAC) in water was 2.1×10(-3) g/L. Indomethacin (IND) was used as a hydrophobic model drug and was incorporated into the hydrophobized polysaccharide. Both loaded and unloaded nanoparticles were found to be spherical with diameters in the ranges of 70-170 nm and 108-314 nm (determined by SEM), respectively. Controlled drug release was observed for up to 72 h.