Inclusion Complexation of Usnic Acid - Hydroxypropyl-β-cyclodextrin: Physicochemical Characterization and Dissolution Rate Studies

Abstract

With antiviral, antiproliferative, anti-inflammatory, and analgesic effects, usnic acid is an effective antimicrobial agent against human and plant diseases. The purpose of this study was to examine the physicochemical properties of usnic acid, a class II drug with high membrane permeability and poor solubility according to the Biopharmaceutical Classification System (BCS), by forming an inclusion complex with hydroxypropyl-β-cyclodextrin, in order to improve its solubility and rate of dissolution. In order to compare the two physical mixtures, this study used the co-grinding process with a molar ratio of 1:1 and 1:2. Physicochemical characteristics, solubility tests, and dissolution tests were used to evaluate the inclusion complexation and physical mixes. Differential scanning calorimeter (DSC), Fourier transform infrared (FT-IR), and X-ray diffraction (XRD) were used to evaluate the physicochemical characteristics of the samples. The dissolving experiments were conducted using phosphate buffer at pH 7.4, whereas the solubility tests were conducted with CO2-free aquadest. Solubility tests with 1:1 inclusion complexes showed a 9-fold increase and 1:2 complexes a 10-fold increase over pure usnic acid. A dissolving percentage of 13.35% was achieved in the 60th minute, surpassing the dissolution percentage of pure usnic acid (which is 3.05% in the dissolution test), indicating a greater dissolution rate compared to other formulae in the 1:2 mol inclusion complexation.