CONICET | Buscador de Institutos y Recursos Humanos

The antioxidant properties of extracts of the Brazilian fruits acerola and açai, were analyzed by spectroscopic protocols as a function of the degree of purification of the fruit extracts. The extracts were obtained from the frozen açai and acerola pulps with 1% HCl methanolic solution, to yield the crude extract (CE) followed by purification on an open column of Amberlit XAD-7 to obtain the partially pure extracts (PPE). The PPE was further purified by paper chromatography to give the pure extracts (PE). The bleaching kinetic of the dye radical ABTS of the extracts was monitored up to 6 min after reaction zero time and the percentage of radical scavenging (%RS) was determined by the absorption change at 734 nm. This value was calibrated with Trolox to yield TEAC values of the extracts. For açai extracts, the TEAC values were almost 50% lower than the respective acerola extracts, mainly due to the presence of high ascorbic acid (AA) levels only in acerola. In addition, the TEAC value decreased with the purification procedure for both extracts fruits, e.g. CE > PPE > PE, due to the diminution of the concentration of phenolic compounds. The kinetic of the methylene blue (MB) photosensitized degradation of 9,10-dimethylanthracene (DMA) by singlet oxygen (1O2) was used for monitoring the percentage of 1O2 quenching efficiency (%QE) by the different extracts. These values were similar for CE and PPE of both açai and acerola. However, a strong reduction of %QE for PE of açai as compared to acerola was observed due to the presence of AA in the PE of acerola. In conclusion, since the amounts of phenolic compounds are similar in both extracts, the better antioxidant capacity of acerola than açai extracts against free radicals and singlet oxygen can assigned to the presence of AA in acerola. Keywords: oxygen singlet quenching, free radical scavenging, tropical fruits. Acknowledgments: FAPESP (Brasil) CONICET (Argentina)

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