CYCLODEXTRINS AS SECONDARY ANTIOXIDANTS - SYNERGISM WITH ASCORBIC ACID

摘要

The preservation of the antioxidant capacity of ascorbic acid by 2-hydroxypropyl-beta-cyclodextrins has been studied. For this, a model system consisting of ascorbic acid, H2O2, a phenolic compound, 2,2,5,7,8-pentamethylchroman-6-ol (PMC), and commercial soybean lipoxygenase was used. In this system, ascorbic acid was oxidized by PMC radicals generated by the hydroperoxidative activity of lipoxygenase, giving rise to a biphasic curve, in which the inflection point represents the time at which all the ascorbic acid has been consumed (t .(ip)). This t .(ip) depends on the enzyme, ascorbic acid, and PMC concentration. When 2-hydroxypropyl-beta-cyclodextrins were included in the system, the t .(ip), increased, indicating that these cyclodextrins were acting as secondary antioxidants, so preserving the antioxidant capacity of the system. A mathematical model to explain the effect of cyclodextrins on ascorbic acid oxidation in this experimental system is described, giving a constant, K-c, which represents the preservation capacity of a particular antioxidant system produced by cyclodextrins. [References: 43]