Characterization of inclusion complex of vitamin E compound with 2,6-di-O-methylated β-cyclodextrin as the solubility enhancer and its kinetic determination for radical scavenging ability

• Published in: Journal of Inclusion Phenomena and Macrocyclic Chemistry Vol. 72; no. 3-4; pp. 467 - 472
• Main Authors: Sueishi, Yoshimi, Hori, Masashi, Inazumi, Naoya
• Format: Journal Article
• Language: English
• Published: Dordrecht Springer Netherlands 01.04.2012
• Subjects: Chemistry; Chemistry and Materials Science; Crystallography and Scattering Methods; Food Science; Organic Chemistry; Original Article; Radical scavenging ability; NMR; Spin trap; Vitamin E; EPR; Inclusion complex
• ISSN: 0923-0750; 1573-1111
• DOI: 10.1007/s10847-011-0018-3

The structure of the inclusion complex of α-tocopherol (vitamin E compound) with 2,6-di- O -methylated β-cyclodextrin (DM-β-CD) was characterized by 2D ROESY NMR measurements, suggesting that DM-β-CD includes the side-chain moiety of α-tocopherol. The inclusion complexation of DM-β-CD showed the usefulness of water solubilizer for the radical scavenging assay of vitamin E compounds in aqueous solution. Using the electron paramagnetic resonance (EPR) competitive spin trapping method, we determined the oxygen radical (RO ∙ ) scavenging abilities of seven vitamin E compounds (tocopherols and tocotrienols), which were solubilized by DM-β-CD in water. The order of the RO ∙ radical scavenging abilities for vitamin E compounds solubilized by DM-β-CD are α- > β- ≈ γ- > δ-, which is in agreement with the oxidation potential values of antioxidants. It is noted that the RO ∙ radical scavenging abilities of tocotrienols are comparable to those of tocopherols. Based on the results, the mechanism of the antioxidant reaction of vitamin E compounds with the RO ∙ radical is discussed.