Abstract: Quercetin is of high interest in pharmaceutical industry due to its antioxidant activity and potential therapeutic effects on airway inflammation and cardiovascular diseases. However, the application of quercetin is limited due to its low water solubility and poor stability. Cyclodextrins (CDs) are macrocyclic molecules able to form inclusion complex with guest molecules, effectively enhancing their solubility, stability and bioavailability. In order to overcome the defect of quercetin, we prepared inclusion complexes of quercetin with three different cyclodextrins such as β-CD, G-β-CD and G2-β-CD. The phase solubility study showed that there was a linear relationship between the solubility of quercetin and the molality of CDs, and G-β-CD performed the best among three cyclodextrins in terms of increasing the solubility of quercetin. In order to confirm the formation of inclusion complex, some analytical techniques were applied, such as ultravioletvisible spectroscopy, Fourier transform infrared (FT-IR) spectroscopy, scanning electron microscopy, X-ray diffraction and thermogravimetric-differential scanning calorimetry. The results revealed that the inclusion complex was formed as expected and the thermal stability of the guest molecule was improved. Furthermore, molecular docking showed that the ring C of quercetin was inserted into the hydrophobic cavity of G-β-CD during the inclusion process.

Key words: quercetin, modified cyclodextrins, inclusion complex, characterisation, molecular docking