Baicalein solid dispersion prepared by solvent evaporation enhances oral bioavailability and alleviates ulcerative colitis.

Baicalein (BAC) is a flavonoid compound known for its effectiveness in treating ulcerative colitis (UC). However, its clinical application is limited by poor water solubility, low stability, and low oral bioavailability. In this study, a baicalein solid dispersion (BAC-SD) was prepared using Polyvinylpyrrolidone (PVP) and hydroxypropyl methylcellulose (HPMC) as carriers via the solvent evaporation method. Scanning Electron Microscope (SEM), Powder X-Ray Diffraction 6000 diffractometer (PXRD), Differential Scanning Calorimetry (DSC), and Fourier Transform Infrared Spectroscopy (FT-IR) analyses confirmed the transition of BAC from a crystalline to an amorphous state. This transformation significantly improved the solubility, dissolution rate, and permeability of BAC. The in vitro dissolution results showed that the cumulative dissolution rate of BAC-SD reached 86.86% at 240 min, representing a 10.09-fold increase in solubility compared to BAC. In Caco-2 and MDCK cell models, the apparent permeability coefficient (Papp) of BAC-SD increased by 2.7- and 3.1-fold, respectively. Pharmacokinetic studies in rats demonstrated that the relative bioavailability of BAC-SD was 236.4% compared to BAC. In the DSS-induced UC mouse model, BAC-SD treatment alleviated UC by increasing colon length, improving pathological damage, and reducing both the Disease Activity Index (DAI) score and levels of inflammatory factors, including TNF-α, IL-1β, and IL-6. In conclusion, we successfully prepared BAC-SD and demonstrated that its therapeutic effect on UC is achieved by enhancing solubility, permeability, and oral bioavailability.