Inclusion complexes of rosmarinic acid and cyclodextrins: stoichiometry,association constants,and antioxidant potential |
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Authors: | Bruno Medronho Artur J M Valente Patrícia Costa Anabela Romano |
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Institution: | 1. IBB-CGB, Faculty of Sciences and Technology, University of Algarve, Campus de Gambelas, Ed. 8, Faro, 8005-139, Portugal 2. Department of Chemistry, University of Coimbra, Coimbra, 3004-535, Portugal
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Abstract: | The interaction between β-cyclodextrin (β-CD) and the polyphenol rosmarinic acid (RA) is here reported by 1H NMR titration experiments. The formation of an aqueous soluble inclusion complex is confirmed and valuable information regarding mode of penetration of guest into β-CD, stoichiometry, and stability of the complex is obtained. The analysis by the continuous variation method shows the undoubted formation of 1:1 β-CD/RA complex. Additionally, the estimated apparent association constants reveal the importance of the asymmetry of the RA in the complexation; the incorporation of the catechol moiety closer to the carboxylic group is more favorable (K?=?2,028 M?1) than from the other end of the RA molecule (K?=?1,184 M?1). Finally, we have also investigated the antioxidant activity and storage stability of the β-CD/RA complexed system; the presence of β-CD was found to produce a remarkable enhancement on the antioxidant activity. |
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