Evaluation of Antibacterial Activity Expression of the Hinokitiol/Cyclodextrin Complex Against Bacteria

The purpose of this study was to assess the antimicrobial activity of a solid dispersion prepared by mixing and grinding hinokitiol (HT) with α-cyclodextrin (αCD), β-cyclodextrin (βCD), or γ-cyclodextrin (γCD). Antimicrobial activity was evaluated by calculating the minimum inhibitory concentration (MIC) and evaluating the change in the number of bacteria over time. The test microbes used were two Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and two fungi (Candida albicans and Aspergillus brasiliensis). Calculation of the MIC value of HT using the agar dilution method revealed that the MIC of HT/CD inclusion complexes was lower than that of HT alone. HT irreversibly inhibited the growth of microorganisms in a short amount of time. HT/CD complexes retained the antimicrobial activity of HT as a result of including HT in a CD complex. These results suggest that inclusion of HT, an antimicrobial component, using CDs could lead to appropriate control of the drug release rate and efficient display of antimicrobial activity.