The interaction between cucurbit(7)uril (Q[7]) and 5-aminosalicylic acid (5-ASA) at different pH was studied by fluorescence spectroscopy and ¹ H NMR technique. The results revealed that Q[7] bound 5-ASA with a ratio of 1∶1 stoichiometry at pH＜6.0, while no obvious interaction between Q[7] and 5-ASA was observed at pH＞6.0. The inclusion complex of Q[7]-5-ASA was dominant in acidic aqueous solution, while free 5-ASA drug molecules were released at pH＞6.0 due to the decomposition of the inclusion complex, indicating that the interaction between Q[7] and 5-ASA was dependent on the value of pH. The thermodynamics study revealed that the formation of the complex between Q[7] and 5-ASA was favored by an enthalpic factor. The solid inclusion complex prepared by a co-evaporation method was further characterized by Fourier transformation-infrared spectroscopy, differential scanning calorimetry and thermal gravity to assess the formation of the inclusion complex. Thus, Q[7] could be used as a potential 5-ASA colon-specific drug delivery.

Key words: cucurbit(7)uril, 5-aminosalicylic acid, inclusion complex, pH influence