Electroanalytical Study of Macluraxanthone: A Natural Product with a Strong Antioxidant and Antimalarial Activity

Abstract

The electrochemical behaviour of macluraxanthone (McX), a natural compound with significant antioxidant and anti-malarial properties, is reported here for the first time. The anodic behaviour of McX is related with its chemical reducing power, and both redox properties are compared with the ones of osajaxanthone (OjX), a similar molecule with non-antioxidant activity. Based on cyclic voltammetric technique, it was observed that the electrooxidation of McX at a glassy carbon electrode (GCE) is quasireversible and pH dependent, occurring easily at pH ≥ 7. The anodic behaviour of McX correlates well with its antioxidant/reducing activity (evaluated by the DPPH method), being both redox processes attributed to the oxidation of the catechol moiety of McX. The electron transfer processes between the catechol/o-quinone redox function of McX and the GCE are simultaneously diffusion- and adsorption-controlled and blocked by the adsorption of some inactive products. The achieved results are very useful for understanding and predicting the oxidative behaviour of other xanthones with biological properties. The main anodic process of McX at GCE yields a well-defined and sensitive DPV response, which can be easily used for the analytical determination of this natural xanthone in real samples, namely in physiological infusions to be used in biological and clinical trials.