Release characteristics of endogenous constituents by exposure of small intestine to modified beta-cyclodextrins

The aim of the present research is to characterize the leakage of intestinal constituents induced by beta-cyclodextrin (beta-CyD) derivatives using an in situ perfusion and an in vitro everted sac. The efficacy of 6-O-alpha-D-glucosyl (G1)- and 6-O-alpha-D-maltosyl (G2)-beta-CyDs as oral carriers was also compared with that of 2-hydroxypropyl-(HP1; average molar degree of substitution, 0.9) and 2,6-di-O-methyl (DM)-beta-CyDs. In the in situ studies, phenol red (PR) penetration and the release profiles of intestinal constituents for G2-beta-CyD were fairly close to those for HP1-beta-CyD. However, the ability of G2-beta-CyD to include cholesterol was greater than that of HP1-beta-CyD. To characterize the release of intestinal constituents induced by modified beta-CyDs, the capability of including cholesterol was held constant between DM- and branched beta-CyDs. The everted sac study showed that the amount of DM-beta-CyD transferred to the serosal side was not significantly different from the branched beta-CyDs. On the serosal side, the amount of cholesterols released was approximately 3 times higher for DM-beta-CyD than for the branched beta-CyDs at 60 min. The cumulative amounts of cholesterols for DM-beta-CyD increased approximately 6 times at 60 min compared with at 30 min, predominating over the leakage (average 2.6-fold) on the mucosal side. In contrast, the exposure of the branched beta-CyDs resulted in an insignificant increase over the period of this experiment. The present study suggests that permeable beta-CyD derivatives play an important role in the leakage of intestinal components. G2-beta-CyD is preferably recommended as a drug solubilizer in oral formulations as well as HP1-beta-CyD, based on the lower release of intestinal constituents.