Comparative Evaluation of β-Cyclodextrin Inclusion Complexes with Eugenol, Eucalyptol, and Clove Essential Oil: Characterisation and Antimicrobial Activity Assessment for Pharmaceutical Applications

Clove essential oil (<i>Eugenia caryophyllata</i> essential oil, ECEO) is known for its high eugenol content and notable antimicrobial properties. However, the volatility and instability of its active compounds hinder broader pharmaceutical applications. <b>Methods:</b> This study characterised the chemical composition of ECEO and comparatively evaluated four <i>β</i>-cyclodextrin (<i>β</i>-CD) encapsulation methods: kneading, co-precipitation, lyophilisation, and co-precipitation-lyophilisation for eugenol, eucalyptol, and ECEO. Encapsulation efficiency, physicochemical properties, and antimicrobial potential were assessed. Analytical techniques included Gas Chromatography-Mass Spectrometry (GC-MS), Headspace GC-MS (HS-GC-MS), Differential Scanning Calorimetry (DSC), Job's method, and Dynamic Light Scattering (DLS). <b>Results:</b> GC-MS identified eugenol (90.67%), eugenyl acetate (4.77%), and (E)-<i>β</i>-caryophyllene (3.98%) as major components of ECEO, while HS-GC-MS indicated a slightly reduced eugenol content (86.46%). The kneading method yielded the highest encapsulation efficiency for eugenol, whereas the co-precipitation-lyophilisation method was optimal for eucalyptol. DSC thermograms confirmed complex formation, and DLS analysis revealed nanostructures averaging 186.4 nm in diameter (PDI = 0.298). Antimicrobial assays showed MIC values ranging from 0.039 mg/mL to 10,000 mg/mL. Notably, ECEO and its <i>β</i>-CD complex displayed enhanced efficacy against <i>Escherichia coli</i> (0.039 mg/mL), surpassing the reference antibiotic gentamicin (0.049 mg/mL). <b>Conclusions:</b><i>β</i>-Cyclodextrin encapsulation significantly enhances the stability and bioactivity of volatile antimicrobial compounds, thereby supporting their potential integration into advanced essential oil-based pharmaceutical formulations.