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Spectroscopic Study and Antioxidant Properties of the Inclusion Complexes of Rosmarinic Acid With Natural and Derivative Cyclodextrins

Spectroscopic Study and Antioxidant Properties of the Inclusion Complexes of Rosmarinic Acid With Natural and Derivative Cyclodextrins

Saliha Esin Celik, Mustafa Ozyürek, Ayşe Nur Tufan, Kubilay Güçlü, Reşat Apak

Spectrochim Acta A Mol Biomol Spectrosc. 2011 May;78(5):1615-24.

PMID: 21377406

Abstract:

Measurement of total antioxidant activity/capacity of polyphenols in various solvent media necessitates the use of cyclodextrins to solubilize lipophilic antioxidants of poor aqueous solubility. The inclusion complexes of the slightly water soluble antioxidant, rosmarinic acid (RA), with α-cyclodextrin (α-CD), β-cyclodextrin (β-CD), 2-hydroxypropyl-β-cyclodextrin (HP-β-CD), 2-hydroxyethyl-β-cyclodextrin (HE-β-CD), and methyl-β-cyclodextrin (M-β-CD) were investigated for the first time. The effect of cyclodextrins (CDs) on the spectral features of RA was measured in aqueous medium using UV-vis and steady-state fluorescence techniques by varying the concentrations of CDs. The molar stoichiometry of RA-CD inclusion complexes was verified as 1:1, and the formation constants of the complexes were determined from Benesi-Hildebrand equation using fluorescence spectroscopic data. Among the CDs, maximum inclusion ability was measured in the case of M-β-CD followed by HP-β-CD, HE-β-CD, β-CD and α-CD. Solid inclusion complexes were prepared by freeze drying, and their functional groups were analyzed by IR spectroscopy. Antioxidant capacity of CD-complexed rosmarinic acid was measured to be higher than that of the lone hydroxycinnamic acid by the CUPric Reducing Antioxidant Capacity (CUPRAC) method. The mechanism of the TAC increase was interpreted as the stabilization of the 1-e oxidized o-catechol moiety of RA by enhanced intramolecular H-bonding in a hydrophobic environment provided by CDs, mostly by M-β-CD.

Chemicals Related in the Paper:

Catalog Number	Product Name	Structure	CAS Number	Price
AP128446322	(2-Hydroxyethyl)-β-cyclodextrin		128446-32-2	Price

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