Rational Formulation Engineering of Fraxinellone Utilizing 6-O-α-d-maltosyl-β-cyclodextrin for Enhanced Oral Bioavailability and Hepatic Fibrosis Therapy

Although Fraxinellone (Frax) isolated from Dictamnus albus L. possessed excellent anti-hepatic fibrosis activity, oral administration of Frax suffered from the inefficient therapeutic outcome in vivo due to negligible oral absorption. At present, the oral formulation of Frax is rarely exploited. For rational formulation design, we evaluated preabsorption risks of Frax and found that Frax was rather stable while poorly dissolved in the gastrointestinal tract (78.88 mu g/mL), which predominantly limited its oral absorption. Further solubility test revealed the outstanding capacity of cyclodextrin derivatives (CDs) to solubilize Frax (6.8-12.8 mg/mL). This led us to study the inclusion complexes of Frax with a series of CDs and holistically explore their drug delivery performance. Characterization techniques involving H-1-NMR, FT-IR, DSC, PXRD, and molecular docking confirmed the most stable binding interactions when Frax complexed with 6-O-alpha-D-maltosyl-beta-cyclodextrin (G(2)-beta-CD-Frax). Notably, G(2)-beta-CD-Frax exhibited the highest solubilizing capacity, fast dissolution rate, and superior Caco-2 cell internalization with no obvious toxicity. Pharmacokinetic studies demonstrated markedly higher oral bioavailability of G(2)-beta-CD-Frax (5.8-fold that of free drug) than other Frax-CDs. Further, long-term administration of G(2)-beta-CD-Frax (5 mg/kg) efficiently inhibited CCl4-induced hepatic fibrosis in the mouse without inducing any toxicity. Our results will inspire the continued advancement of optimal oral Frax formulations for anti-fibrotic therapy.