Antibacterial activity and modulatory effects of Bowdichia virgilioides ethanolic extract and its β-cyclodextrin inclusion complex against multidrug-resistant bacteria

Abstract

Cyclodextrins are known for forming inclusion complexes with natural compounds, which can protect these compounds and enhance their solubility and bioavailability, showing promising applications in the food and pharmaceutical industries. Bowdichia virgilioides Kunth, commonly known as “sucupira-preta,” has been described in the literature as having various biological properties, including antimicrobial, antioxidant, and anti-inflammatory activities. This study aimed to evaluate the antibacterial effect and the potential for modulation in association with the antibiotics gentamicin, ciprofloxacin, and meropenem of the ethanolic extract of Bowdichia virgilioides leaves (EEBv). It's complex with β-cyclodextrin (EEBv/βCD) against multidrug-resistant strains of Pseudomonas aeruginosa (PA-24), Escherichia coli (EC-06), and Staphylococcus aureus (SA-10). The complex was obtained using the co-evaporation method. Phase solubility studies and physicochemical characterizations were performed using UV–Vis spectroscopy, Fourier-transform infrared (FTIR) spectroscopy, thermogravimetric analysis (TG), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM) to confirm complex formation. The broth microdilution assay and fluorescence assays with SYTOX Green dye assessed the antibacterial activity and membrane permeability. The results did not demonstrate clinically relevant antibacterial activity for EEBv or EEBv/βCD; however, both demonstrated synergistic effects when combined with gentamicin and ciprofloxacin against SA-10 and PA-24. However, against the Gram-negative bacterial strain EC-06, only EEBv showed a significant effect when combined with ciprofloxacin and meropenem. An antagonistic effect was also observed between EEBv/βCD associated with meropenem, which may be explained by the interactions with β-cyclodextrin, reducing the bioavailability of this antibiotic. Both EEBv and EEBv/βCD improved membrane permeability, facilitating antibiotic influx in the tested strains. For the first time, these findings highlight the antimicrobial potential of Bowdichia virgilioides againts a multidrug-resistant bacterium clinically and demonstrate the feasibility of its complexation with β-cyclodextrin. This novel approach suggests a promising strategy for combating antibiotic-resistant bacterial infections. Nevertheless, in vivo studies are still necessary to validate its therapeutic applicability.