Category: Formulation and Quality
Purpose: Hispolon (6-(3,4-dihydroxy-phenyl)-4-hydroxy-hexa-3,5-dien- 2-one;), a yellow pigment, is isolated from a mushroom species Phellinus igniarius (1). It is a phenolic compound, a structural analog of well-established curcumin and has garnered lot of attention due to its similar pharmacological activity. Recent research on hispolon has shown it to possess anti-inflammatory (2), anticancer (3) and antioxidant properties but no any formulation approaches are reported yet. The poor aqueous solubility of hispolon limits the oral absorption and thus confines the possibilities of utilization of this molecule for therapeutic significance. In this study, we have attempted to use sulfobutylether-β-cyclodextrin (SBEβCD) to enhance the aqueous solubility of hispolon. We assumed that SBEβCD would provide ample amount of space for entrapment of hydrophobic drug like hispolon and give highly soluble inclusion complexes.
Methods: An excess amount of hispolon was added to water of MilliQ water containing various concentrations of CD (0-100 mM) and the samples were allowed to shake at 24 h followed by equilibration at room temperature overnight. The samples were filtered through 0.45 µm filters and analyzed by HPLC at 424 nm. The phase solubility curve was plotted against concentration of SBEβCD. Equimolar concentrations of hispolon and SBEβCD was dissolved in mixture of methanol-water under sonication. After removal of methanol under 45˚C, the samples were stored at -80˚C for 48 hours before being freeze dried using lyophilizer for another 48 h. The solid material collected, passed through sieve 120 and stored in desiccator for analysis. The solid state characterization of the complexes was performed using Differential Scanning Calorimetry (DSC), Fourier Transform Infrared (FTIR) Spectroscopy, Nuclear Magnetic Resonance (NMR) and Scanning Electron Microscopy (SEM). Intrinsic dissolution rate of tablets containing hispolon complexes with anhydrous lactose as diluent was carried out using modified die assembly in dissolution apparatus (4,5). The physical mixture of hispolon and SBEβCD was taken as control for comparison in all above techniques.
Results: The phase solubility data (Figure 1) showed that the hispolon solubility is enhanced by the presence of SBEβCD by 15 fold (0.45 to 6.5 mg/ml). The complexation efficiency was found to be 0.4703 whereas the apparent stability constant as 340.05 M-1. The solid state characterization techniques (Figure 2) demonstrated the successful complexation of hispolon in SBEβCD. The DSC thermograms showed disappearance of hispolon peak in the complex. The FTIR spectra of the lyophilized complex lacked the characteristics absorption bands of hispolon. Both of these results indicate the formation of drug complex between drug and cyclodextrin. The Proton NMR has shown deshielding of drug protons indicating the encapsulation of drug inside SBEβCD. The SEM images confirmed the complexation as the surface of the complex showed very less amorphous deposits in comparison to the crystalline cluster of physical mixture. The intrinsic dissolution rate of hispolon was higher (80.43 µgcm-2min-1) as compared to its physical mixture with SBEβCD (55.76 µgcm-2min-1) as shown in Figure 3.
Conclusion: This study successfully utilized sulfobutyl ether β-cyclodextrin (SBE βCD) to form an inclusion complexes with hispolon to increase the water solubility and dissolution rate for improved permeability across GI tract. The findings provided a new possibility to utilize hispolon for enhanced oral absorption and bioavailability. We plan to utilize the complex formed in various formulation designs and investigate its potential benefits in coming future.
Ahmed Al Saqr– Auburn, Alabama
Oladiran Fasina– Auburn, Alabama
Brian Via– Auburn, Alabama
Jayachandra Babu Ramapuram– Professor, Auburn University, Harrison School of Pharmacy, Department of Drug Discovery and Development, Auburn, Alabama