Assessment of synergistic and/ or prooxidant activity of mixtures of standard antioxidants at different molar ratios: the case of catechin and ascorbic acid.
2012
Mahmoud, M. A. A.
The behavior of two known antioxidants (Catechin and Ascorbic Acid) and their mixtures at different ratios and in the presence of various citric acid concentrations (0.5, 1, and 2mM) was studied with a view to elaborating predictions over an eventual prooxidant or synergistic activity. The measurements were carried out using Luminol Chemiluminescence and the DPPH radical scavenging test. The Co(II)-EDTA Luminol Chemiluminescence showed that the ratio of 1:3 at final concentrations of 100, 150, and 200 had the highest Io/I value, while that of the ratio 1:2 at a final concentration of 20uM had the lowest Io/I value. The DPPH radical scavenging test showed that all citric acid concentrations have enhanced the antioxidant activity of the equimolar mixture. The concentration of 0.5mM of citric acid has been selected due to its remarkable synergistic effect on the Ca:AA mixture for further examination on the pure antioxidants (Catechin and Ascorbic Acid). In both cases, their EC50 values were lower than the EC50 values of pure antioxidants. The LC-MS analysis for the two mixtures revealed that the presence of AA accounts for the good antioxidant behaviour of catechin, supported by the formation of Structure I (m/z 183). As its concentration is diminished vis-a-vis catechin, the antioxidant activity drops and this is attributed to the formation of structure II (m/z 255).
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