Preparation and characterisation of solid dispersions of tanshinone IIA, cryptotanshinone and total tanshinones

Total tanshinones are lipophilic active constituents extracted from Salvia miltiorrhiza Bge. Tanshinone IIA and cryptotanshinone are the major components in total tanshinones. However, the bioavailability of both compounds is low due to poor water solubility. To enhance the solubility and dissolution rate of tanshinone IIA, cryptotanshinone and total tanshinones, three common used hydrophilic carriers including PEG 6000, poloxamer 188 and PVP K30 were used to prepare the solid dispersions at different ratios, respectively. The solid dispersions were characterised by scanning electron microscopy (SEM), differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The results of powder X-ray diffraction confirmed the microcrystal state of total tanshinones in solid dispersions and no chemical interaction between total tanshinones and carriers was observed in FTIR spectra. The solubility and dissolution rate of tanshinone IIA and cryptotanshinone were significantly increased in all solid dispersions. Regarding tanshinone IIA, the solubility and dissolution rate of in solid dispersions prepared with poloxamer 188 were significantly higher than that with PEG 6000 and PVP K30. The higher solubility and dissolution rate of cryptotanshinone were obtained in solid dispersion of PVP K30 than that of PEG 6000 solid dispersions but no significant difference from poloxamer 188 solid dispersions. The results indicate that the superior carrier for preparation of tanshinone IIA and total tanshinones solid dispersions is poloxamer 188, and that for cryptotanshinone is PVP K30.