title: Re-evaluation of ABTS*+ Assay for Total Antioxidant Capacity of Natural Products.
abstract: 2,2'-Azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt radical cation (ABTS*+) is a stable free radical frequently used for estimating the total antioxidant capacity (TAC) of natural products. The existing methods for ABTS*+ radical-scavenging activity assays are diverse in pre-diluting solvents and reaction time, which lead to errors in the TAC estimations. To develop an effective and universal method for estimating the ABTS*+ capacity accurately and reasonably, five pre-dilution solvents [methanol, ethanol, phosphate buffer (Na2HPO4-NaH2PO4, 200 mM, pH = 7.4), PBS buffer (Na2HPO4-NaH2PO4- NaCl, 200 mM, pH = 7.4), and distilled water] and different reaction times were investigated in ABTS*+ assays of five typical antioxidants. The results showed that the solvent effects were very significant. When using different pre-diluting solvents, different detection wavelengths should be selected. ABTS*+ assay could be measured within 2-10 min to obtain a rough result, which was mostly 6 min in the literature. However, full and accurate evaluation of antioxidant reactivity rather than capacity requires recording ABTS*+ loss continuously during the whole reaction period. The present study makes a recommendation for estimating the ABTS*+ capacity accurately and reasonably.
authors.forename: Jian-Wei
authors.initials: JW
authors.lastname: Dong
authors.forename: Le
authors.initials: L
authors.lastname: Cai
authors.forename: Yun
authors.initials: Y
authors.lastname: Xing
authors.forename: Jing
authors.initials: J
authors.lastname: Yu
authors.forename: Zhong-Tao
authors.initials: ZT
authors.lastname: Ding
mesh_terms: D000975:Antioxidants / Q000737:chemistry*; D052160:Benzothiazoles / Q000737:chemistry*; D001688:Biological Products / Q000737:chemistry*; D015394:Molecular Structure; D013451:Sulfonic Acids / Q000737:chemistry*
chemical_list: D000975:Antioxidants; D052160:Benzothiazoles; D001688:Biological Products; D013451:Sulfonic Acids; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid