ABSTRACT
Objective: To study betulin-3,28-diphosphate (BDP) water solubility improved by forming salt complexes with hydrophilic amino alcohols: meglumine as acidosis corrector and xymedon as the water-soluble antioxidant. Methods: We used 13C-, 31P-NMR, UV-spectroscopy and potentiometric titration to study the BDP-amine salt complexes formation and their solubility using HPLC-analysis. Results: The participation of xymedon in the proton transfer reaction with BDP in aqueous solutions was confirmed by the bathochromic shift of the carbonyl band from 299.1 nm to 304.2 nm, and by a hyperchromic effect (molar extinction ε from 8508 to 10 441 l·mol-1·cm-1) in UV-spectra. BDP complexation with meglumine was estimated by UV-spectral molar ratio method at 256 nm. Molar ratio of BDP-amine complexes (1:4) was proved by 31P-NMR. The chemical shift of phosphorus at C-3 atom of BDP (δ =-0.58 ppm) changed to+3.39 ppm, and at C-28 atom (δ =+0.28 ppm)–to+4.60 ppm. BDP solubility increased 100-600 fold according to HPLC-analysis. Conclusion: BDP interaction with amine in an aqueous solution was shown to proceed via a proton transfer due to relatively weak forces such as London forces, hydrogen bonding, electrostatic and hydrophobic interactions. In general, the formation of BDP salt complexes with amines in solution determines BDP water solubility. Water-soluble BDP enables to develop hydrophilic dosage forms.