Complexation of Vinpocetine with Cyclodextrins in the Presence or Absence of Polymers. Binary and Ternary Complexes Preparation and Characterization

Abstract

Inclusion complexation between ß-cyclodextrin (ß-CD),hydroxypropyl-ß-cyclodextrin (HP-ß-CD), water-solublepolymers (PVP and HPMC) and vinpocetine was studied in aqueous solution and in the solid state.Phase solubility studies were used to evaluate the complexation in aqueous solution at roomtemperature. Stability constants (Kc) of binary and ternary complexes were determined spectrophotometrically. Differential scanning calorimetry (DSC)was used to characterize kneaded, co-evaporated and lyophilised binary and ternary systems.The Kc values obtained were 70.14 M-1 and 35.01 M-1 for vinpocetine-ß-CD and vinpocetine-HP-ß-CD and increased in a range of 17% to 94%by addition of water-soluble polymers. Some preliminary evidences ofinclusion complexation were obtained from DSC suggesting that co-evaporated and lyophilised binary andternary systems were truly inclusion complexes.