Unravelling the interaction of ethyl cinnamate in 2-hydroxypropyl and methyl-β-cyclodextrin by spectroscopic and theoretical evaluation for enhanced antibacterial activities

Abstract

Essential oil components are the most common agents used to inhibit pathogens. Ethyl cinnamate (ECIN) is a hydrophobic essential oil component with well-known antibacterial properties but is poorly soluble in water, which limits its applications. In this study, inclusion complexes (ICs) were prepared by encapsulating ECIN in β-cyclodextrin (βCD), 2-hydroxypropyl-βCD, or methyl-βCD using an ultrasonication method to enhance water solubility and thermal and antibacterial properties. UV–Vis absorption and fluorescence spectral results indicated strong non-covalent interactions between ECIN and βCD derivatives in aqueous solution, and double reciprocal profiles revealed a guest:host stoichiometry of 1:1. Fourier-transform infrared and proton nuclear magnetic resonance spectroscopy investigations revealed that the phenyl ring of ECIN is located deeply in the CD nanocavities. X-ray diffraction, ultraviolet–visible diffuse reflectance spectroscopy, photoluminescence, and field emission scanning electron microscopy were performed to obtain crystalline, optical, and morphological information on solid ECIN-CDs. Thermogravimetric/differential thermal studies confirmed the improved stability of ECIN in solid CD-ICs by detecting an increase in the degradation temperature of ECIN from 50–140 °C to 310–410 °C. Further, the geometrical and frontier molecular orbital structures of the ECIN-CDs were theoretically evaluated using parametric method-3. Finally, antibacterial assays conducted against the foodborne pathogens Staphylococcus aureus and Escherichia coli revealed that encapsulated ECIN had a greater inhibitory effect, which suggested the devised nanocarriers promote the solubilization of essential oil components in aqueous solutions.