Determination of the inclusion complex constant between oleuropein and cyclodextrins by complexation theory
Oleuropein (OLE) is a major phenolic compound of olive leaf (Olea europaea) and has many therapeutic properties associated with olive leaf extracts. This work concerns the determination of the inclusion complex constant between OLE and cyclodextrins (CDs), based on the competition of two guests for the CD cavity, one being a dye and the other OLE. The dye used was methylorange (MO) and pH 3 was selected, since MO molar absorptivity at 500 nm is at maximum in this condition. A solution of MO, OLE, and α-CD or β-CD, with citrate buffer was used for determining the absorbance values. From these data and by appropriate mathematical modeling, the equilibrium constant for the formation of OLE:CD complexes were obtained: for OLE:α-CD K = 1,352.4 L mol−1 (R 2 = 0.9975) and for OLE:β-CD K = 1,827.9 L mol−1 (R 2 = 0.9991). The results show that OLE has a greater affinity for β-CD than for α-CD and given the relatively high constants, OLE:CD complexes have potential for giving longer shelf lives for OLE medicinal and food additive preparations.
KeywordsOleuropein Cyclodextrin Inclusion Complex
We are grateful to the supporting institutions: CAPES (Coordenação de Aperfeiçoamento de Pessoal de Nível Superior) and UEM (Universidade Estadual de Maringá).
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