Characterization and antioxidant activity of Amazonian woods

The heartwood and sapwood characteristics of 11 Amazonian trees were investigated. Whereas 7 of the specimens had densities greater than 0.7 g/cm³, the heartwood density of ipê amarelo (Tabebuia serratifolia), maçaranduba (Manilkara huberi), cumaru-ferro (Dipteryx odorata), and guarita (Astronium lecointei) exceeded 1.0 g/cm³. Jatobá contained small amounts of Klason lignin and α-cellulose, and large amounts of holocellulose and alkali extract, suggesting that it has a high polysaccharide content that can be dissolved in an alkaline medium. The difference in the syringyl/guaiacyl (S/G) ratios of the samples before and after alkali extraction suggests that alkali extracts contain syringyl-type polyphenols. In all of the samples, the heart-wood methanol extracts were larger in volume than the sapwood methanol extracts, and the sapwood alkali extracts were larger in volume than the heartwood alkali extracts. The antioxidant activities of the methanol and alkali extracts were assayed by measuring the levels of 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging activity and super oxide dismutase (SOD)-like activity, respectively. The heart-wood methanol extract of jatobá (Hymenaea courbaril) exhibited the highest level of activity (EC₅₀ = 44 mg/l), which exceeded that of α-tocopherol (EC₅₀ = 48 mg/l), and the heartwood alkali extracts of jatobá and ipê amarelo had high SOD-like activity comparable with red wine.