Desenvolvimento, caracterização e avaliação antibacteriana do complexo de inclusão [6]-shogaol/ciclodextrina

Abstract

[6]-shogaol (6SH), an artifact of [6]-gingerol, is a substance present in ginger, responsible for several biological activities, including antimicrobial action. Due to its low water solubility, it is necessary to develop a pharmaceutical pre-formulation to make it more water soluble and consequently improve its bioavailability, such as inclusion complexes (CI) with cyclodextrins (CDs), which have been widely used in medicine, food and agriculture. Therefore, it is important to know the complexation and characterization techniques for the production of IC with high efficiency. Thus, the objectives of this study were: to compile evidence on the various methods of preparation and characterization of IC among substances isolated from medicinal plants and CDs, and to develop, characterize and evaluate the antimicrobial and antibiofilm properties of IC containing 6SH. Thus, a systematic review of publications was carried out, following the PRISMA writing guide. Twenty-seven articles that demonstrate the advantages and disadvantages of different IC preparation and characterization techniques were selected. In the experimental part of this work, 6SH was extracted from dried ginger using the Soxhlet technique and then isolated and purified by classical liquid chromatography and high performance liquid chromatography (HPLC). Following the methodology of Higuchi and Connors (1965), two phase solubility diagrams were constructed with 6SH, HP-β-CD and β-CD (in water, at 25°C, 72 h). HP-β-CD was chosen to develop the IC with 6SH through the co-evaporation/lyophilization method. The IC was characterized by spectrometric techniques (NMR and IR) and Molecular Modeling. A stability study of free and complexed 6SH was carried out in an aqueous solution at 40 °C for a period of 1 week. The determination of the minimum inhibitory concentration (MIC) of the ICs was carried out in a microdilution assay in a 96-well plate against Staphylococcus aureus and the anti-biofilm activity by the method of staining the biofilm biomass with crystal violet. Statistical treatment was performed using 2-way analysis of variance (ANOVA), followed by Tukey's test. From the solubility diagram it was possible to determine the intrinsic solubility of [6]-shogaol (0.76 µg/mL), as well as to visualize the significant increase in its solubility, especially with HP-β-CD. The spectroscopic analyzes demonstrated that the co-evaporation/lyophilization technique was effective in IC formation. In the stability test, free 6SH showed degradation (>50%) after 24 hours of incubation, while CI was highly stable (3.5 times greater). The CI containing 6SH did not show antimicrobial activity against S. aureus, however, it showed anti-biofilm activity. With these findings, it was possible to conclude that the methodologies employed in the development of the inclusion complex were appropriate to achieve the main pharmacokinetic objectives: increased water solubility and stability of 6SH. As a result of the improvement of the physicochemical properties of the generated product, it is hoped that the biological activity of IC in the management of clinical conditions is superior to that of the free substance.