Development of a Syzygium aromaticum, L. essential oil/ hydroxypropyl-β-cyclodextrin inclusion complex: Preparation, characterization, and evaluation

Clove essential oil (CEO) is known for its versatile biological activities, such as antibacterial, antioxidant, and insecticidal properties. However, its poor aqueous solubility and high volatility limit its widespread applications. Thus, to solve the above shortcomings, this study aimed to encapsulate CEO with hydroxypropyl-beta-cyclodextrin (HP-beta-CD) to obtain an inclusion complex (IC) via ultrasound-assisted coprecipitation. The optimal preparation parameters were 90 W ultrasonic power, 13:1 g/mL wall-to-core ratio, 38 degree celsius ultrasonication temperature, and 56 min ultrasonication time, resulting in an encapsulation efficiency of 81.38%. The formation of the IC was validated through various means of characterization. No significant differences were observed in the compositions of unencapsulated and encapsulated CEO. Moreover, the results of molecular docking displayed that the eugenol molecule entered the HP-beta-CD cavity from the wide side through its methoxy end. Furthermore, the release of the CEO from IC was controlled through the adjustment of the temperature and relative humidity. The aqueous solubility of CEO was evidently improved by complexation with HP-beta-CD. The inhibition of tyrosinase activity of IC was similar to that of CEO. These findings, which provide useful information for the potential application of CEO, suggest ultrasound-assisted coprecipitation as a practical approach for the preparation of CEO/HP-beta-CD IC. In addition, the complexation with HP-beta-CD is an effective strategy for controlling the release of CEO and improving its aqueous solubility.