Analysis of the electrochemical parameters of the tested xanthones showed a similar behavior at pH 11.0, in comparison to those discussed at pH 7.4 (Scheme 1). The defined oxidation peak of compound XH2 presented a similar (although lower) potential value (Ep2a = 0.38 V) than the analogue XH4 (Ep2a = 0.40 V), and derivative XH5 presented a lower anodic peak at 0.37 V. The low intensity current peaks (from 0.08 to 0.04 V) presented in the cyclic voltammograms of compounds XH3, XH6–XH9 may be ascribed to the catechol unit oxidation, at pH 11.0 versus Ag/AgCl (Fig. 1). Indeed, the electrochemical studies of quercetin and catechin referred anodic potentials at 0.07 and 0.23 V, respectively, at pH 8.0.17 At the same pH, other authors observed a lower anodic potential of catechin at 0.16 V.23 On the other hand and as expected,the oxidation peak of quercetin is shifted toward a less positive potential at 0.10 V, raising the pH at 9.0.27 The second anodic peak is less pronounced and attributed to the oxidation of the paraphenol group of compounds XH6 and XH8 (Fig. 1). At pH 11.0, the highest catechol group oxidation peak was observed for compound XH9 at 0.12 V.8 Curiously, this compound exhibited two oxidation peaks, while hematoxylin, an important bioactive flavonoid having also two catechol units, presented only one anodic peak, both in acidic and basic pH values.1