Variation in antioxidant activity of extracts of Acacia confusa of different ages

The antioxidant activity of extracts of Acacia confusa of different ages has been evaluated. Ethanolic extracts of bark, twigs, branches (2- and 5 cm-diameter branch-bark, 2- and 5 cm-diameter branch-wood), and leaves of 15-, 25-, and 35-year-old A. confusa were examined. Results indicate that the ethanolic extracts of 5 cm-diameter branch-bark and bark of A. confusa exhibited stronger antioxidant activities, and higher phenolic and proanthocyanidin contents than the other plant parts. Furthermore, twig, 2 cm-diameter branch-wood, 2 cm-diameter branch-bark, and 5 cm-diameter branch-wood extracts of 35-year-old specimens showed better antioxidant activities and higher phenolic contents, followed by the 25- and 15-year-old specimens tested. This reveals that the composition of extracts and their differential antioxidant activities are dependent on the age of A. confusa. In addition, the total phenolic content of A. confusa ethanolic extracts has a high positive correlation with the DPPH free-radical scavenging activity (R² = 0.83), superoxide radical-scavenging activity (R² = 0.66), ferrous ion-chelating effect (R² = 0.67), and reducing power (R² = 0.92).