Improvement of galangin solubility using native and derivative cyclodextrins. An UV-Vis and NMR study

The slightly water-soluble flavonoid galangin (G) and its inclusion with either β-cyclodextrin (βCD), hydroxypropyl-β-cyclodextrin (HPβCD) or Heptakis-2,6-O-di methyl-β-cyclodextrin (DMβCD) were investigated. The stoichiometric ratios and stability constants describing the extent of the formation of the complexes have been determined by phase-solubility measurements; in all cases type-AL diagrams have been obtained (soluble 1:1 complexes). The results showed that the complex efficiency of βCD and its derivatives was the order: DMβCD > HPβCD > βCD. The NMR study indicate that the inclusion of galangin in the cyclodextrin nano-cavity is different depending on the type of cyclodextrin used