The Influence of Selected Factors on the Aqueous Cryptotanshinone Solubility

The application of cryptotanshinone (CT), a diterpenoid obtained from the root of Salviae miltiorrhiza, is significantly hindered due to its poor aqueous solubility. The aim of the present research was to develop an optimal solvent for analytical and preparative procedures of prospective dermal hydrogel formulations with CT. The influence of pH, temperature, and cosolvent presence on the solubility of CT was examined. Various components were applied to increase CT solubility, i.e., ethanol, 2-amino-2-methyl-1,3-propanediol, 2-amino-2-(hydroxymethyl)-1,3-propanediol, 2,2′,2″-nitrilotriethanol, and triisopropanoloamine. The concentration of CT was analyzed by spectral and chromatographic methods, including UV–vis and HPLC methods. The increased solubility of CT was demonstrated in alkaline solvents with ethanol as a cosolvent. CT solutions doped with alcoholamines are more stable compared to CT solutions doped with NaOH.