Bioactivity of Meliaceae, Amaryllidaceae, Solanaceae and Amaranthaceae plant aqueous extracts against the cattle tick Rhipicephalus microplus.

Commercial synthetic acaricides have selected resistant populations of Rhipicephalus microplus, and generate residues in the environment or in milk/cattle products. In this study, aqueous extracts (AE) from Melia azedarach (Maz), Allium sativum, Capsicum chinense, Nicotiana tabacum (Nta) and Dysphania ambrosioides were evaluated for the bioactivity against the cattle tick. The treatment using Nta or Maz AE resulted in the lowest egg hatching rate (34.0 ± 11% and 25.0 ± 19%), and in the values of reproduction inhibition ranging from 89.0% to 85.3%. Phytochemical screening associated to RP-HPLC/DAD analysis suggested the presence of alkaloids for Nta and gallic acid derivatives and catechins, for Maz. Such results highlighted that the use of Nta and Maz AE can be a promising source of bioactive compounds for the control of infections caused by the cattle tick.

Aqueous solutions of glycolic, propionic, or lactic acid in substitution of acetic acid to prepare chitosan dispersions: a study based on rheological and physicochemical properties.

Chitosan (CH) is a biopolymer derived from chitin, which is the second most abundant polysaccharide in nature, after cellulose. Their functional groups -NH2 and -OH can form intermolecular interactions with water and other molecules, enabling a variety of applications for CH. -NH2 groups become protonated in acidic solutions, causing an increase in electrostatic repulsion between CH chains, which facilitates their dispersion in aqueous media. Aqueous solutions of acetic acid and/or acetates buffers have been used to disperse CH, but may not be adequate for technological applications, espeacially because of the strong flavor this acid confers to formulations. In this study, 0.125; 0.250; 0.500; 0.750 and 1.000 g (100 g)-1 CH dispersions were prepared in acidic aqueous media (50 mmol L-1), not only with acetic (AA), but also with glycolic (GA), propionic (PA), or lactic (LA), acid aiming to evaluate the effects of biopolymer concentration and type of organic acid on: electrical conductivity, pH, density and rheological characteristics of dispersions. Moreover, ζ potential values of CH chains dispersed in these acidic aqueous media were assessed. pH, density and consistency index were influenced by the biopolymer concentration, but not by the acid type. At a given biopolymer concentration, ζ potential signs (+) and values suggested that electrostatic interactions between CH chains and counter-anions occurred, regardless of the type of the organic acid. Thus, at least from a physicochemical point of view, GA, PA or LA showed to be suitable to replace AA when preparing dispersions containing from 0.125 to 1.000 g (100 g)-1 CH for technological purposes, such as thickening or stabilizer in formulated food products.

Mixed starch/chitosan hydrogels: elastic properties as modelled through simulated annealing algorithm and their ability to strongly reduce yellow sunset (INS 110) release.

Biopolymers mixtures appear as a strategy to improve sensorial/technological characteristics of gel-like products. Thus, self-sustaining starch (S100/C0) hydrogels were prepared with a partial replacement of the gelling agent by 5.0 % (S95/C5), 7.5 % (S92.5/C7.5), or 10.0 % chitosan (S90/C10), and containing yellow sunset (INS 110). Major visual changes or significant differences on L*a*b* parameters were not observed for starch/chitosan hydrogels. Creep-recovery data was modeled using the simulated annealing algorithm, and relative recovery results showed an increase for S95/C5 (82.6 %), when compared to S100/C0 (72.9 %). After 312 h, chitosan strongly reduced the INS 110 release from hydrogels to an ethanolic solution (3.1∙10-4 and 4.1∙10-3 g/100 mL for S95/C5 and S100/C0, respectively) or to a sucrose solution (1.1∙10-3 and 6.5∙10-3 g/100 mL for S95/C5 and S100/C0, respectively). Such results highlighted that chitosan not only presented a techno-functionality on starch hydrogels by improving their elasticity but also by hindering the release of yellow sunset.

Chitosan dispersed in aqueous solutions of acetic, glycolic, propionic or lactic acid as a thickener/stabilizer agent of O/W emulsions produced by ultrasonic homogenization.

Chitosan is a natural polycationic polysaccharide with several known biotechnological functionalities, but its application in food products as ingredient or additive remains nowadays unusual. Additionally, ultrasonic production of food-grade emulsions is still an open research field, so ultrasound applicability for such purpose must be evaluated case by case. In this study, chitosan was dispersed in acid aqueous media containing acetic, glycolic, propionic or lactic acid (50 mmol·L-1), then added of the emulsifier Tween 20, and finally mixed to sunflower oil, through ultrasonic homogenization (20 kHz, 500 W, 4 min), in order to prepare O/W emulsions (oil fraction = 0.25). In all studied systems, oil droplets with average hydrodynamic diameter < 600 nm were obtained. The increase of chitosan concentration promoted the augment in consistency and the elastic character of the emulsions. Emulsions containing more than 0.500 g·(100 g)-1 of chitosan presented a minor increase of both oil droplets average hydrodynamic diameter and PDI, during storage for 28 days. Furthermore, such systems showed no phase separation when exposed to centrifugation, freeze-thawing, and freeze-thaw-heating cycles. Two main findings may be highlighted from this study: i) ultrasound processing is a promising approach to produce food-grade emulsified systems containing chitosan, and ii) chitosan is a suitable alternative as thickener/stabilizer for acidic emulsions, being its performance influenced by the biopolymer concentration and not by the organic acid present in the medium.

Insights on physicochemical aspects of chitosan dispersion in aqueous solutions of acetic, glycolic, propionic or lactic acid.

Chitosan is a polysaccharide well-known for its applicability as a biocompatible, biodegradable, and non-toxic material to produce drugs excipients and food coatings. Acidic media are required to disperse chitosan, and aqueous solutions of acetic acid have been typically used for this purpose. However, this acid has several sensory drawbacks. In this study, chitosan was dispersed [0.1 g·(100 mL)-1] in aqueous media containing acetic (AA), glycolic (GA), propionic (PA), or lactic (LA) acid, at 10, 20, 30, 40, or 50 mmol·L-1. The increase of acid concentration reduced pH and viscosity of the dispersions, and |ζ potential| of dispersed particles. Conversely, it increased electrical conductivity and density of the dispersions, and hydrodynamic diameter of dispersed particles. At a given concentration, these effects were slightly more pronounced for dispersions formed with GA or LA, compared to AA or PA. FT-IR data suggested more intense attractive interactions of chitosan chains with glycolate and lactate anions, than with acetate and propionate. Chitosan chains interacted more strongly with hydroxylated acids counter-anions than with their non-hydroxylated counterparts, leading to slight quantitative changes of physicochemical properties of these systems. Then, in physicochemical terms, GA, LA or PA are suitable to replace AA when preparing aqueous chitosan dispersions for technological applications.