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Oxygen radical absorbance capacity (ORAC) of cyclodextrin-solubilized flavonoids, resveratrol and astaxanthin as measured with the ORAC-EPR method.

Sueishi Y, Ishikawa M, Yoshioka D, Endoh N, Oowada S, Shimmei M, Fujii H, Kotake Y - J Clin Biochem Nutr (2011)

Bottom Line: The results indicated that the agreement between spin trapping-based and fluorescence-based values was only fair partly because of a large variation in the previous fluorescence-based data.Typical radical scavenging abilities in trolox equivalent unit are: catechin 0.96; epicatechin 0.94; epigallocatechin gallate 1.3; kaempferol 0.37; myricetin 3.2; resveratrol 0.64; and astaxanthin 0.28, indicating that myricetin possesses the highest antioxidant capacity among the compounds tested.We sorted out the possible causes of the deviation between the two methods.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.

ABSTRACT
Recently, we proposed an oxygen radical absorbance capacity method that directly quantifies the antioxidant's scavenging capacity against free radicals and evaluated the radical scavenging abilities for water soluble antioxidant compounds. In this study, we determined the radical scavenging abilities of lipophilic antioxidants which were solubilized by cyclodextrin in water. Commonly employed fluorescence-based method measures the antioxidant's protection capability for the fluorescent probe, while we directly quantify free-radical level using electron paramagnetic resonance spin trapping technique. In addition, the spin trapping-based method adopted controlled UV-photolysis of azo-initiator for free radical generation, but in fluorescence-based method, thermal decomposition of azo-initiator was utilized. We determined the radical scavenging abilities of seven well-known lipophilic antioxidants (five flavonoids, resveratrol and astaxanthin), using methylated β-cyclodextrin as a solubilizer. The results indicated that the agreement between spin trapping-based and fluorescence-based values was only fair partly because of a large variation in the previous fluorescence-based data. Typical radical scavenging abilities in trolox equivalent unit are: catechin 0.96; epicatechin 0.94; epigallocatechin gallate 1.3; kaempferol 0.37; myricetin 3.2; resveratrol 0.64; and astaxanthin 0.28, indicating that myricetin possesses the highest antioxidant capacity among the compounds tested. We sorted out the possible causes of the deviation between the two methods.

No MeSH data available.


EPR spectra of AAPH radical adduct (assigned to RO• radical adduct) of CYPMPO that was recorded after the UV-photolysis of phosphate buffer solution, containing AAPH (5 mM), CYPMPO (5 mM) and DM-β-CD solubilized CA: (a) [DM-β-CD] = 0.94 mM and (b) [DM-β-CD] = 0.94 mM plus [CA] = 22.0 µM. Horizontal broken lines in the spectra demonstrate the change in EPR signal height of the selected peak by the addition of the antioxidant CA.
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Figure 2: EPR spectra of AAPH radical adduct (assigned to RO• radical adduct) of CYPMPO that was recorded after the UV-photolysis of phosphate buffer solution, containing AAPH (5 mM), CYPMPO (5 mM) and DM-β-CD solubilized CA: (a) [DM-β-CD] = 0.94 mM and (b) [DM-β-CD] = 0.94 mM plus [CA] = 22.0 µM. Horizontal broken lines in the spectra demonstrate the change in EPR signal height of the selected peak by the addition of the antioxidant CA.

Mentions: Chemical compound called spin trap (CYPMPO is shown as an example in the above scheme) reacts with free radical R to form stable compound called spin adduct, that is also free radical. The spin adduct is relatively stable and can be readily identified and quantified with EPR spectrometer. In this study, free radicals were generated from AAPH with UV irradiation (5 s irradiation, 200 W mercury arc RUF-203s, Radical Research Inc.) to the sample solution that was set in the EPR resonant cavity. The sample solution contained AAPH and CYPMPO in sodium phosphate buffer (0.1 M, pH = 7.4). As a result, EPR spectra shown in Fig. 2 were obtained. The analysis of the EPR spectral pattern provides the identification of the free radical, and EPR-signal height is proportional to the free radical concentration. The spin trap and the antioxidant compete to react with AAPH radicals, from which the ORAC value of the antioxidant is calculated.(13) EPR signal intensity of the spin adduct in the presence and absence of antioxidant was measured to calculate ORAC-EPR values. The calculation method is described in the following section.


Oxygen radical absorbance capacity (ORAC) of cyclodextrin-solubilized flavonoids, resveratrol and astaxanthin as measured with the ORAC-EPR method.

Sueishi Y, Ishikawa M, Yoshioka D, Endoh N, Oowada S, Shimmei M, Fujii H, Kotake Y - J Clin Biochem Nutr (2011)

EPR spectra of AAPH radical adduct (assigned to RO• radical adduct) of CYPMPO that was recorded after the UV-photolysis of phosphate buffer solution, containing AAPH (5 mM), CYPMPO (5 mM) and DM-β-CD solubilized CA: (a) [DM-β-CD] = 0.94 mM and (b) [DM-β-CD] = 0.94 mM plus [CA] = 22.0 µM. Horizontal broken lines in the spectra demonstrate the change in EPR signal height of the selected peak by the addition of the antioxidant CA.
© Copyright Policy - open-access
Related In: Results  -  Collection

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Figure 2: EPR spectra of AAPH radical adduct (assigned to RO• radical adduct) of CYPMPO that was recorded after the UV-photolysis of phosphate buffer solution, containing AAPH (5 mM), CYPMPO (5 mM) and DM-β-CD solubilized CA: (a) [DM-β-CD] = 0.94 mM and (b) [DM-β-CD] = 0.94 mM plus [CA] = 22.0 µM. Horizontal broken lines in the spectra demonstrate the change in EPR signal height of the selected peak by the addition of the antioxidant CA.
Mentions: Chemical compound called spin trap (CYPMPO is shown as an example in the above scheme) reacts with free radical R to form stable compound called spin adduct, that is also free radical. The spin adduct is relatively stable and can be readily identified and quantified with EPR spectrometer. In this study, free radicals were generated from AAPH with UV irradiation (5 s irradiation, 200 W mercury arc RUF-203s, Radical Research Inc.) to the sample solution that was set in the EPR resonant cavity. The sample solution contained AAPH and CYPMPO in sodium phosphate buffer (0.1 M, pH = 7.4). As a result, EPR spectra shown in Fig. 2 were obtained. The analysis of the EPR spectral pattern provides the identification of the free radical, and EPR-signal height is proportional to the free radical concentration. The spin trap and the antioxidant compete to react with AAPH radicals, from which the ORAC value of the antioxidant is calculated.(13) EPR signal intensity of the spin adduct in the presence and absence of antioxidant was measured to calculate ORAC-EPR values. The calculation method is described in the following section.

Bottom Line: The results indicated that the agreement between spin trapping-based and fluorescence-based values was only fair partly because of a large variation in the previous fluorescence-based data.Typical radical scavenging abilities in trolox equivalent unit are: catechin 0.96; epicatechin 0.94; epigallocatechin gallate 1.3; kaempferol 0.37; myricetin 3.2; resveratrol 0.64; and astaxanthin 0.28, indicating that myricetin possesses the highest antioxidant capacity among the compounds tested.We sorted out the possible causes of the deviation between the two methods.

View Article: PubMed Central - PubMed

Affiliation: Department of Chemistry, Faculty of Science, Okayama University, 3-1-1 Tsushima-naka, Kita-ku, Okayama 700-8530, Japan.

ABSTRACT
Recently, we proposed an oxygen radical absorbance capacity method that directly quantifies the antioxidant's scavenging capacity against free radicals and evaluated the radical scavenging abilities for water soluble antioxidant compounds. In this study, we determined the radical scavenging abilities of lipophilic antioxidants which were solubilized by cyclodextrin in water. Commonly employed fluorescence-based method measures the antioxidant's protection capability for the fluorescent probe, while we directly quantify free-radical level using electron paramagnetic resonance spin trapping technique. In addition, the spin trapping-based method adopted controlled UV-photolysis of azo-initiator for free radical generation, but in fluorescence-based method, thermal decomposition of azo-initiator was utilized. We determined the radical scavenging abilities of seven well-known lipophilic antioxidants (five flavonoids, resveratrol and astaxanthin), using methylated β-cyclodextrin as a solubilizer. The results indicated that the agreement between spin trapping-based and fluorescence-based values was only fair partly because of a large variation in the previous fluorescence-based data. Typical radical scavenging abilities in trolox equivalent unit are: catechin 0.96; epicatechin 0.94; epigallocatechin gallate 1.3; kaempferol 0.37; myricetin 3.2; resveratrol 0.64; and astaxanthin 0.28, indicating that myricetin possesses the highest antioxidant capacity among the compounds tested. We sorted out the possible causes of the deviation between the two methods.

No MeSH data available.