Abstract: In this study, inclusion complexes of 5-heneicosylresorcinol (AR21) with α-, β-, and γ-cyclodextrin (CD) were prepared using the saturated aqueous solution method. The effect of varying molar ratio of AR21 to CD (1:1, 1:2, 1:3, and 1:4) on the encapsulation efficiency and structural characteristics of inclusion complexes was systematically investigated. The results demonstrated that all AR21/CD complexes exhibited favorable encapsulation performance, with encapsulation efficiencies exceeding 60%. Notably, the AR21/α-CD complex at a 1:4 molar ratio achieved the highest encapsulation efficiency of (92.35 ± 0.05)%. Structural characterization using Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), differential scanning calorimetry (DSC), 1H nuclear magnetic resonance (NMR), and density functional theory (DFT) calculations revealed significant structural differences between the inclusion complexes and their corresponding physical mixtures, confirming successful complex formation. Furthermore, the AR21/α-CD system demonstrated the best stability among all studied complexes.

Key words: alkylresorcinol; 5-heneicosylresorcinol; cyclodextrin; inclusion complexes