Abstract: Using β-cyclodextrin (β-CD) as raw material, the host molecule of diethylenetriamine-β-cyclodextrin (DETA-β-CD) was synthesized to encapsulate betulinic acid (BA). Saturated water solution method and freeze drying technique were used to prepare the solid state powder of BA/DETA-β-CD complex. IR, ¹H NMR and SEM were used to illustrate the molecule recognition mechanism and host-guest interaction mode. MS and UPLC were employed to determine the BA content encapsulated in the complex. The results show that the hydrophobic of BA can penetrate into the DETA-β-CD cavity from the narrow side due to the hydrogen-bond interaction between the tether amino group and BA carboxyl group. The water solubility of BA was remarkably increased from 4.7×10^-5 mmol/L to approximately 15.33 mmol/L due to the multiple identification effect on BA from the hydrophobic cavity of DETA-β-CD and low polyvinyl amine side chain.

Key words: betulinic acid, cyclodextrin, complex, water solubility