Kaempferol Complexation in Cyclodextrins at Basic pH

The complexation of kaempferol with cyclodextrins (CDs) (beta, G(2)-beta-, and HP-beta-CDs) in basic medium was studied, and the complexation constants (K-c) were calculated by using enzymatic, solubility, and fluorometric methods. This is the first time that a decrease in fluorescence has been observed as result of the analyte complexation by CDs. The highest K-c value for kaempferol complexation was obtained for HP-beta-CDs. To establish the validity of the fluorometric method for determining the K-c between kaempferol and CDs, the same parameters were also determined by enzymatic and solubility methods. The enzymatic method was carried out by using horseradish peroxidase as oxidative enzyme, and the K-c values obtained were similar to those obtained by using the solubility method. However, the fluorometric method underestimated the K-c value by about 1.2-fold with respect to the other methods used. In all cases HP-beta-CDs showed the highest K-c value, indicating that they are more efficient in the formation of inclusion complexes with kaempferol.