Perspectives on antimicrobial properties of Paulownia tomentosa Steud. fruit products in the control of Staphylococcus aureus infections

Abstract

Ethnopharmacological relevancePaulownia tomentosa Steud. (P. tomentosa) is a medium-sized tree traditionally used in Chinese folk medicine for the treatment of infectious diseases. It is a rich source of prenylated phenolic compounds that have been extensively studied for their promising biological activities. Aim of the studyDue to the increasing development of antibiotic resistance, our study investigated plant-derived natural products from the fruits of P. tomentosa that could control Staphylococcus aureus infections with novel targets/modes of action and reduce antimicrobial resistance. Materials and methodsThe ethanolic extract was fractionated and detected by liquid chromatography. The antistaphylococcal effects of the plant formulations were studied in detail in vitro by various biological methods, including microdilution methods for minimum inhibitory concentration (MIC), the checkerboard titration technique for synergy assay, fluorescence measurements for membrane disruption experiments, autoinducer-2-mediated bioassay for quorum sensing inhibition, and counting of colony-forming units for relative adhesion. Morphology was examined by transmission electron microscopy. ResultsTotal ethanolic extract and chloroform fraction showed MICs of 128 and 32 μg/mL, respectively. Diplacol, diplacone, and 3′-O-methyl-5′-hydroxydiplacone inhibited S. aureus growth in the range of 8–16 μg/mL. Synergistic potential was shown in combination with mupirocin and fusidic acid. The ethanolic extract and the chloroform fraction destroyed the cell membranes by 91.61% and 79.46%, respectively, while the pure compounds were less active. The ethanolic extract and the pure compounds reduced the number of adhered cells to 47.33–10.26% compared to the untreated control. All tested plant formulations, except diplacone, inhibited quorum sensing of S. aureus. Transmission electron microscopy showed deformation of S. aureus cells. ConclusionsThe products from the fruit of P. tomentosa showed antimicrobial properties against S. aureus alone and in combination with antibiotics. By affecting intracellular targets, geranylated flavonoids proposed novel approaches in the control of staphylococcal infections.