Development and characterization of the zeolite imidazolate framework for a modified release of the drug scopoletin

Abstract Scopoletin (7-hydroxy-6-methoxychromen-2-one, SC) is a phenolic coumarin commonly found in some medicinal plants. This compound presents relevant literature data demonstrating its anti-inflammatory, antioxidant, antitumor, hypocholesterolemic and hypoglycemic activities. SC was loaded in situ into the Zeolitic Imidazolate Framework-8 (ZIF-8), a slow-releasing material with pharmaceutical application. Both ZIF-8 and SC:ZIF-8 drug delivery systems (DDS) were characterized by x-ray diffraction (XRD), scanning electron microscopy (SEM), nuclear magnetic resonance (NMR), thermogravimetry (TG), differential scanning calorimetry (DSC) and Fourier transform infrared (FTIR). The quantification of SC in the solution was performed by high-performance liquid chromatography with diode-array detection (HPLC-DAD) and the release profile at pHs 4.5 and 6.5 was compared under non-sink conditions of SC and SC:ZIF-8 DDS. Expectorant activity was also evaluated. The SC:ZIF-8 DDS showed an encapsulation efficiency of 22.5%. A pH-dependent release profile of SC present in the DDS was observed when compared to the pure SC. The most suitable kinetic model for pure SC at both pHs 4.5 and 6.5 was the Korsmeyer-Peppas model. For SC:ZIF-8 DDS at pH 4.5, the best model was the Korsmeyer-Peppas, but at pH 6.5 it was Peppas-Sahlin. SC also presented expectorant activity at 30 and 100 mg/kg doses, but the system did not show expectorant activity at 10 mg/kg dose.