Beneficial anti-inflammatory effect of paeonol self-microemulsion-loaded colon-specific capsules on experimental ulcerative colitis rats

Paeonol, as the main phenolic compound isolated from the Chinese herbs, has been confirmed to present anti-inflammatory effects on ulcerative colitis (UC) in our previous study. However, its poor solubility has hindered its development of being a favourable pharmaceutical product in treating colon diseases. In this study, we prepared the colon-specific delivery system (Pae-SME-CSC) with paeonol-loaded self-microemulsion (Pae-SMEDDS), and evaluated its in vitro and in vivo properties, especially the anti-inflammatory effects on UC rats. The anti-inflammatory effects were evaluated by the disease activity index, colon weight/length ratio, and macroscopic damage and microscopic damage scores. IL-17, IL-6, and TGF-1 levels were also determined by enzyme-linked immunosorbent assay. The results showed that Pae-SME-CSC had good colon-targeting property in vivo and in vitro, with favourable stability. Efficacy evaluation showed that the dose of the paeonol group (100mg/kg) exhibited no significant effect on UC (p>.05, compared with the model group), while the Pae-SME-CSC group (100mg/kg) showed better anti-UC effects (p<.01 or p<.05), and its anti-inflammatory effect was close to that of the paeonol group (200mg/kg) (p>.05). These results indicated that the developed Pae-SME-CSC was suitable for colon-specific drug delivery.