Host-guest interaction and properties of cucurbit[n]uril (n=7,8) with chlorzoxazone

The interaction between cucurbit[n]uril (n = 7,8, Q[n]s) and chlorzoxazone (CHZ) was investigated using single-crystal X-ray diffraction spectroscopy, isothermal titration calorimetry (ITC), UV–vis spectroscopy and 1H NMR spectroscopy. The effects of cucurbit[n]uril (n = 7,8) on the stability, water solubility and CHZ in vitro release performance were also studied. The results showed that CHZ and Q[8] formed a 2:1 inclusion complex (CHZ2@Q[8]) with a binding constant of 6.971 × 104 L·mol−2 and CHZ and Q[7] formed a 1:1 inclusion complex (CHZ@Q[7]) with a binding constant of 9.546 × 104 L·mol−1. The intervention of cucurbit[n]uril (n = 7,8) prolonged the CHZ release time in artificial gastric and intestinal juices and increased the solubility of CHZ in aqueous solution while hardly affecting the stability.