therefore the relation between
current
density and concentration for
themushroom
extracts
will differs from that of gallic and ascorbic acid. The difference between the slopes of the two standards in Table 3, reflects the difference between their
diffusion
coefficients.
However, when compared with the extracts slopes, the enormous discrepancy cannot be explained on the basis of their different diffusion coefficients (species belong to a chemically comparable family of phenol compounds), but to the amount of effective electroactive mass in the mushroom extract composition. Based on the
similarity in the cyclic voltamograms of Agaricus sp,
it can be
assumed
that the species responsible for the electrochemical
activity are chemically similar as well as their diffusion coefficient.
In this context and based on the slopes values of peak current density vs. extract concentration plots, it can be concluded that the amount of electroactive phenolic compounds in A. bisporus, A. silvaticus and A. silvicola are almost double of that present in the extract of A. arvensis and A. romagnesii. In order to express the ‘‘antioxidant power” of the mushrooms
extracts in equivalent terms we compared the results with that of the standards. We must mention that at very low and high concentrations of extract there are significant deviations in linearity of j vs. mass, most probably due to adsorption phenomena on the electrode. The values are presented in Table 3, and are expressed in terms of either gallic or ascorbic acid. These results show that A. silvicola and A. silvaticus exhibit the highest ‘‘antioxidant power” in agreement with the results obtained in the biochemical assays. The values obtained from the electrochemical experiment are lower than those resulting from Folin Ciocalteu ´ s assay. This outcome is frequently observed when comparing the colorimetric method
with others and is attributed to the overestimation of the ‘‘total polyphenolic” content due to the interferences of other
non-phenolic species like reduction sugars (Blasco et al., 2005).Overall, all the species proved to have antioxidant properties,namely radical scavenging activity and lipid peroxidation inhibition capacity. By using electrochemical techniques, it was also proved that mushroom extracts have a similar composition on the electroactive species, which exhibit oxidation potentials more positive than the standards. A. silvaticus was the most efficient species presenting the lowest EC50 values in the chemical and biochemical assays, and the highest ‘‘antioxidant power” in the electrochemical assays. Finally, the work described in this study showed that cyclic voltammetry and differential pulse voltammetry can be considered as important techniques for the evaluation of mushrooms antioxidant properties.