title: pH-dependent long-term radical scavenging activity of AA-2G and 6-Octa-AA-2G against 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation.
abstract: The 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS (radical +)) decolorization assay was applied to evaluate the stoichiometric radical scavenging activity of ascorbic acid (AA) and two AA derivatives, 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) and 2-O-alpha-D-glucopyranosyl-6-O-octanoyl-L-ascorbic acid (6-Octa-AA-2G). AA rapidly reacted with ABTS (radical +), and the reaction was completed within 10 min. In contrast, AA-2G and 6-Octa-AA-2G continuously reacted with ABTS (radical +), and the reaction was not completed after 2 h. The radical scavenging activity of AA-2G and 6-Octa-AA-2G in aqueous solutions at pH 4.0 and above was higher than that at pH 3.0, whereas AA showed no difference in the pH range 3 to 6. The amounts of ABTS (radical +) scavenged by one molecule of AA, AA-2G and 6-Octa-AA-2G after 2 h of reaction at pH 6.0 were approximately 2.0, 3.4 or 3.9 molecules, respectively. This study demonstrates that the quantity of ABTS (radical +) quenched by AA-2G and 6-Octa-AA-2G is superior to that of AA in a long-term reaction.
authors.affiliation: Department of Immunochemistry, Faculty of Pharmaceutical Sciences, Okayama University, Okayama, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Takebayashi
authors.forename: Akihiro
authors.initials: A
authors.lastname: Tai
authors.forename: Itaru
authors.initials: I
authors.lastname: Yamamoto
mesh_terms: D001205:Ascorbic Acid / Q000031:analogs & derivatives* / Q000494:pharmacology*; D052160:Benzothiazoles; D002412:Cations / Q000737:chemistry; D016166:Free Radical Scavengers / Q000494:pharmacology*; D005609:Free Radicals / Q000737:chemistry; D006863:Hydrogen-Ion Concentration; D013451:Sulfonic Acids / Q000037:antagonists & inhibitors* / Q000633:toxicity*
chemical_list: D052160:Benzothiazoles; D002412:Cations; D016166:Free Radical Scavengers; D005609:Free Radicals; D013451:Sulfonic Acids; C470083:octanoyl-6-O-ascorbic acid; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; C065378:ascorbic acid 2-O-glucoside; D001205:Ascorbic Acid