Voltammetric determination of total antioxidant capacity of Bunchosia glandulifera tree extracts

Optimization of electrochemical methods for total antioxidant capacity (TAC) determination of Bunchosia glandulifera (Jacq.) Kunth (Malpighiaceae) extracts was performed. Other methods for antioxidant studies were also used for comparison with the results obtained by electrochemical assays. The extracts exhibited good solubility in the aprotic solvent dimethylsulfoxide. Hence, two electrochemical methods, namely cyclic (C) and differential pulse (DP) voltammetry (V) were optimized for TAC determination in this medium and by using ascorbic acid. The CV presented better linearity than DPV in the optimum conditions. TAC values determined by ABTS, FRAP and DPPH increased in the order seed < pulp < bark < leaf < root extract, in generally the same order observed by CV, indicating the applicability of the method in these conditions. The phenolic compounds contents were 302 ± 10, 327 ± 11, 1008 ± 71, 4003 ± 13 and 7502 ± 30 mg gallic acid/100 g extract, respectively, increasing in the same order as observed for TAC. On the other hand, such order disagreed with the amounts of major antioxidant vitamins, carotenoids and ascorbic acid, estimated in these extracts, which corresponded, by comparison with the contents of phenolic compounds, to 0.62, 34, 9.9, 0.39 and 0.86%, respectively. Thus, it can be inferred that specially in the case of roots and leaves, the contents of phenolic compounds may have greater contribution for their TAC values.