RESUMO
To determine the relative ranking of autoxidative potential of various sugars the fluorescence of phycoerythrin was monitored in the presence of various concentrations of sugars incubated at 37 degrees C with or without CuSO4. The antioxidative properties of these sugars was assayed in the presence of a peroxy radical generator 2,2' azobis(2 amidinopropane) AAPH. The results indicate that 25 mM D-glucose, but not 5 mM D-glucose solution can significantly potentiate CuSO4-induced free radical damage after 32 h of incubation. This weak effect was comparable to that seen with lactose or maltose and was in contrast to the high potency of fructose and ribose in potentiating phycoerythrin damage through oxidation. 2-Deoxyribose had an antioxidant effect in this assay. In the presence of AAPH, 25 mM D-glucose, and to a lesser extent, 5 mM D-glucose, had statistically significant free radical quenching effect (61.5 +/- 0.7% and 44.9 +/- 2.4% inhibition of oxidation, respectively). The corresponding free radical quenching effect expressed as percentage inhibition of oxidation for 5 mM fructose, maltose, lactose, ribose, and deoxyribose and ascorbate were 30.2 +/- 1.9%, 49.1 +/- 1.2%, 53.5 +/- 1.6%, 64.7 +/- 1.8%, 68.8 +/- 1.7%, and 69.5 +/- 1.0%, respectively. It is concluded that autoxidative potential of simple sugars is highly diverse. Whereas some sugars have no oxidative potential, others are potent prooxidants in the presence of Cu++, and some can have antioxidant properties. However, the autoxidative potential of reducing sugars is extremely weak compared with that of the free copper ions. All sugars tested have antioxidant effect in the presence of peroxy radical generator. In this assay, the antioxidant potency of deoxyribose was comparable to that of ascorbate.
