Antioxidant and free radical scavenging activities in extracts from medicinal trees used in the 'Caatinga' region in northeastern Brazil.

The in vitro antioxidant and free radical scavenging properties of bark extracts of Anadenanthera macrocarpa Brenan (Fabaceae), Astronium urundeuva Engl. (Anacardiaceae), Mimosa verrucosa Benth. (Fabaceae) and Sideroxylon obtusifolium T.D. Penn. (Sapotaceae), four trees used as anti-inflammatory agents in the Brazilian state of Bahia, were studied using different bioassays. The total reactive antioxidant potential (TRAP) of the aqueous and methanolic extracts was determined by monitoring the intensity of luminol-enhanced chemiluminescence (CL), using 2,2'-azo-bis(2-amidinopropane) as a peroxyl radical source. All the extracts studied were active in this method. The highest activity, measured as equivalents of Trolox concentration, was observed in the methanolic extract of A. macrocarpa (TRAP = 3028 +/- 95 microM). Lipid peroxidation was assessed by means of the production of thiobarbituric acid reactive substances (TBARS) and hydroperoxide-initiated CL in rat liver homogenates. As in the case of luminol-enhanced CL, all the extracts tested were effective in reducing the production of TBARS. The highest activity was observed in the aqueous extract of A. macrocarpa (IC50 = 54 microg/ml). Extracts of A. macrocarpa and S. obtusifolium also reduced hydroperoxide-initiated CL, the methanolic extract of the former being the most active, showing an IC50 = 2.0 microg/ml. DNA-sugar damage induced by Fe(II) salts was also used to determine the capacity of the extracts to suppress hydroxyl radical-mediated degradation of DNA. All extracts tested were highly effective in reducing oxidation of DNA. The highest activity was observed in the methanolic extract of A. urundeuva, showing an IC50 = 37 microg/ml. The results obtained suggest that the antioxidant activity described could play an important role in the anti-inflammatory activity claimed for the plants under study.