Incorporação de extrato de folhas de café (Coffea arabica L.) em filmes de quitosana: caracterização físico-química e avaliação das atividades antimicrobiana e cicatrizante in vitro

Abstract

Wound dressings containing natural polymers such as chitosan are applied to wound healing. In addition to its biological and structural advantages, this polymer allows the incorporation of bioactive compounds, potentiating a new approach to wound repair. Coffee leaves are considered by-products of the coffee industry, generated in significant amounts, and have numerous bioactive compounds with health benefits, such as antioxidant, antibacterial, and anti-inflammatory properties. In this way, the objective of the present study was to develop chitosan films incorporated with different concentrations of C. arabica L. leaf extract, with the perspective of combining the biological activities of the extract and chitosan, as well as improving the physicochemical properties of the film. The leaves were pulverized and subjected to ultrasound-assisted extraction in a 70% hydroalcoholic solution. 5-caffeoylquinic acid (5-CQA) and mangiferin were identified and quantified by high-performance liquid chromatography. Also, the extract's antioxidant activity, cytotoxicity, and antimicrobial activities were evaluated. The films were prepared by the solvent casting method, with 2% (w/v) of chitosan, in the absence (control) and the presence of different concentrations of hydroalcoholic extract of leaves of C. arabica L. (125 mg/cm3 - Q EFC1; 250 mg/cm3 - Q-EFC2 e 500 mg/cm3- Q-EFC3). The precursor solutions were characterized by zeta potential, dynamic light scattering, and rheological measurements to evaluate the existence of interactions between the extract components with chitosan, still in the liquid phase. After making the films, physicochemical parameters such as thickness, average weight, optical parameters, moisture content, degree of swelling, solubility, and in vitro release were determined. Furthermore, the films were characterized by vibrational spectroscopy in the infrared region, thermal analysis (TGA and DTA), and dynamic mechanical analysis (DMA) in axial and rotational modes to evaluate the existence of solid-state interactions as well as the thermal and mechanical properties of the films. Finally, the cytotoxicity, antimicrobial and healing activities in vitro were evaluated. The extract obtained an IC50 in the DPPH• assay of 13.52 ± 1.12 µg/mL, the reducing power of phosphomolybdenum was 17.08 ± 0.63 of AAR% to quercetin and 54.76 ± 1.91 of AAR% to rutin, and the percentage of inhibition of lipid peroxidation was 53.29 ± 2.98 %. The coffee leaf extract content was 2.05 ± 0.11 g/100g of 5-ACQ and 1.87 ± 0.30 g/100g of mangiferin. The chitosan films incorporated with coffee leaf extracts showed uniformity concerning weight and thickness. They also showed high moisture content, swelling, and solubilities favorable for the maintenance of skin wounds and good thermal resistance above body temperature but low mechanical resistance. Through the FTIR analysis, it was possible to verify the functional groups of chitosan and the extract and intermolecular interactions between the compounds. Regarding the biological assays, all films demonstrated antimicrobial activity against Staphylococcus aureus and Staphylococcus epidermidis and the absence of cytotoxicity in L929 cell line. Also, Q-EFC1 and Q-EFC2 films promoted promising cell migration in the in vitro healing assay. We concluded that the films added with extracts from the leaves of C. arabica L. showed satisfactory and promising physicochemical and biological properties for application in the treatment of skin wounds.