title: Determination of total antioxidant capacity by a new spectrofluorometric method based on Ce(IV) reduction: Ce(III) fluorescence probe for CERAC assay.
abstract: A Ce(IV)-based reducing capacity (CERAC) assay was developed to measure the total antioxidant capacity (TAC) of foods, in which Ce(IV) would selectively oxidize antioxidant compounds but not citric acid and reducing sugars which are not classified as antioxidants. The method is based on the electron-transfer (ET) reaction between Ce(IV) ion and antioxidants in optimized acidic sulphate medium (i.e., 0.3 M H(2)SO(4) and 0.7 M Na(2)SO(4)) and subsequent determination of the produced Ce(III) ions by a fluorometric method. The fluorescent product, Ce(III), exhibited strong fluorescence at 360 nm with an excitation wavelength of 256 nm, the fluorescence intensity being correlated to antioxidant power of the original sample. The linear concentration range for most antioxidants was quite wide, e.g., 5.0 × 10(-7)-1.0 × 10(-5) M for quercetin. The developed procedure was successfully applied to the TAC assay of antioxidant compounds such as trolox, quercetin, gallic acid, ascorbic acid, catechin, naringin, naringenin, caffeic acid, ferulic acid, glutathione, and cysteine. The proposed method was reproducible, additive in terms of TAC values of constituents of complex mixtures, and the trolox equivalent antioxidant capacities (TEAC coefficients) of the tested antioxidant compounds gave good correlations with those found by reference methods such as ABTS and CUPRAC.
authors: Department of Chemistry, Faculty of Science and Letters, Istanbul Technical University, Ayazaga Campus, Maslak, 34469 Istanbul, Turkey.
authors: Dilek
authors: D
authors: Ozyurt
authors: Birsen
authors: B
authors: Demirata
authors: Resat
authors: R
authors: Apak
references: Talanta. 2001 May 30;54(4):715-25
references: 18968294
references: Free Radic Res. 2000 Nov;33 Suppl:S59-66
references: 11191277
references: J Agric Food Chem. 1999 Feb;47(2):633-6
references: 10563944
references: J Agric Food Chem. 2005 Mar 23;53(6):1841-56
references: 15769103
references: Free Radic Biol Med. 1999 May;26(9-10):1231-7
references: 10381194
references: Free Radic Res. 2005 Sep;39(9):949-61
references: 16087476
references: J Agric Food Chem. 2003 May 21;51(11):3273-9
references: 12744654
references: Clin Sci (Lond). 1993 Apr;84(4):407-12
references: 8482045
references: J Agric Food Chem. 2004 Dec 29;52(26):7970-81
references: 15612784
references: Anal Biochem. 1996 Jul 15;239(1):70-6
references: 8660627
references: Talanta. 2007 Feb 28;71(3):1155-65
references: 19071427
references: Clin Chem. 1998 Jun;44(6 Pt 1):1309-15
references: 9625058
references: Molecules. 2007 Jul 19;12(7):1496-547
references: 17909504
references: J Agric Food Chem. 2000 Aug;48(8):3396-402
references: 10956123
references: Biol Res. 2001;34(2):51-73
references: 11715209