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

抄録

The 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS^·+) decolorization assay was applied to evaluate the stoichiometric radical scavenging activity of ascorbic acid (AA) and two AA derivatives, 2-O-α-D-glucopyranosyl-L-ascorbic acid (AA-2G) and 2-O-α-D-glucopyranosyl-6-O-octanoyl-L-ascorbic acid (6-Octa-AA-2G). AA rapidly reacted with ABTS^·+, and the reaction was completed within 10 min. In contrast, AA-2G and 6-Octa-AA-2G continuously reacted with ABTS^·+, 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^·+ 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^·+ quenched by AA-2G and 6-Octa-AA-2G is superior to that of AA in a long-term reaction.