Desenvolvimento de nanoemulsões contendo líquido da casca da castanha do caju do tipo técnico (LCCt) /quitosana com atividade antimicrobiana

Abstract

The Chitosan is a biopolymer widely investigated for its biological properties, especially its antimicrobial and healing action, and as a result, many researchers have produced antimicrobial formulations of this biopolymer combined with natural bioactives such as plant extracts and essential oils, in order to enhance its activities. biological, especially antimicrobial. The cashew nut shell liquid (CNSL) is a by-product of the cashew agroindustry with low added value, rich in phenolic compounds, and has drawn the attention of the scientific community as a current focus of investigation, due to its broad spectrum of biological action for pharmaceutical applications. In this sense, nanoemulsion formulations produced from the technical CNSL (CNSLt) combined with chitosan were prepared with the aim of developing formulations with antimicrobial action in a sustainable way from renewable, biodegradable and abundant resources in nature. The nanoemulsions were formulated with different concentrations of CNSLt (0.5, 1 and 2% m/m) with and without chitosan (1% m/m) and Tween 80 (16% m/m) using mechanical agitation. These formulations were characterized to study their physical stability and potential antimicrobial activity, and CNSLt was characterized to investigate their chemical composition. From the results, it was possible to identify in the CNSLt the presence of chemical groups characteristic of the oil itself, as well as the presence of a mixture of cardanols and cardols and the di-unsaturated 2-methylcardol. The data obtained classified all formulations as nanoemulsions, with the exception of the sample containing only chitosan (NP), whose average diameter was ~500nm. The formulations without chitosan had a lower mean droplet diameter (from 25.60 to 101.32 nm) than those with chitosan (from 182.30 nm to 225.2 nm). The Zeta potential of the formulations without chitosan showed negative values (-5.20 to -5.40), while the dispersions with chitosan showed positive and higher values (30.90 to 42.00). In the macroscopic evaluation, all nanoemulsions behaved stably throughout the evaluation period (120 days), with the exception of sample N0.5, which showed signs of flocculation in the last analysis. The pH values were slightly acidic for the formulations without chitosan (6.28 to 6.96), while the formulations containing chitosan showed very acidic values (3.51 to 3.81). Through the optical microscopy images, it was possible to show the encapsulation of the CNSLt in the formulations containing chitosan, whose droplets presented morphologies similar to liposomes. In the rheological test, all formulations showed non-Newtonian, pseudoplastic and anti-thixotropic behavior. Finally, CNSLt showed antimicrobial activity only against the Staphylococcus aureus strain, while formulations containing chitosan and CNSLt exhibited strong inhibition against Staphylococcus aureus, Salmonella enterica and Candida albicans. Thus, it can be concluded that nanoemulsions based on chitosan and CNSLt are antimicrobial emulsified formulations with potential for use in pharmaceutical purposes.