Biphenylyl acetic acid was selectively conjugated to one of the primary hydroxyl groups of β-cyclodextrin through an ester- or amide-linkage, and the physicochemical properties (aqueous solubility and hydrolysis) were investigated.
Aqueous solubility of the conjugates was lower than those of either drug or parent β-cyclodextrin. The amide conjugate was stable in aqueous solution and in rat biological fluids and gastrointestinal contents. The ester conjugate was hydrolysed to β-cyclodextrin and biphenylyl acetic acid at moderate rates resulting in a V-shaped rate-pH profile in aqueous solution. The ester conjugate released the drug preferentially when incubated with the contents of caecum or colon, whereas no appreciable drug release was observed on incubation with contents of stomach or intestine, nor on incubation with intestinal or liver homogenates, nor on incubation with rat blood.
The present results suggest that the ester-type drug conjugate of β-cyclodextrin may serve as a colon-targeting prodrug.
苯基乙酸通过酯或酰胺键与β-环糊精的一个原始羟基选择性结合,研究了其物理化学性质(水溶性和水解)。
这些结合物的水溶性低于药物或原始的β-环糊精。酰胺结合物在水溶液和大鼠生物液和胃肠内容物中稳定。酯结合物在水溶液中呈V形速率-pH曲线,以适度的速率水解为β-环糊精和苯基乙酸。当与盲肠或结肠的内容物孵育时,酯结合物优先释放药物,而在胃或肠的内容物孵育,肠或肝脏匀浆孵育以及大鼠血液孵育中均未观察到明显的药物释放。
这些结果表明,β-环糊精的酯型药物结合物可能作为结肠靶向前药。