Characterisation of C-β-Cyclodextrin-Thymol Inclusion Complexes as Delivery Systems for Antibacterial and Antioxidant Applications

Thymol (THY) is a natural antioxidant and antimicrobial; however, its biological activity and application in the food and pharmaceutical fields are limited due to its low water solubility and volatility. In this study, inclusion complexes of cationic-β-cyclodextrin-THY (C-β-CD-THY) were prepared by using the aqueous stirring method. Then UV–Vis spectra, FT-IR, NMR, DSC, XRD and SEM data were collected to characterise the structure and morphology of the inclusion complexes. Phase solubility experiments showed a better solubilisation effect of C-β-CD-THY than HP-β-CD-THY. At a concentration of 0.64 mmol/L for THY, the DPPH scavenging rate was 60.99% and 61.31% for HP-β-CD-THY and C-β-CD-THY, respectively, whereas that of THY in 10% ethanol was only 43.47%. The bacteriostatic activity was verified using a circle of inhibition and the live/dead bacterial double stain. C-β-CD-THY exhibited better antimicrobial activities against Escherichia coli and Staphylococcus aureus than HP-β-CD-THY. In conclusion, the C-β-CD-THY inclusion complexes have the potential to be applied as an effective bacteriostatic agent for food and pharmaceutical applications.