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

The in vitro antioxidant acid free radical scavenging properties of bark ex tracts of Anadenanthera macrocarpa Brenan (Fabaceae), Astronium urundeuva E ngl. (Anacardiaceae), Mimosa verrucosa Benth. (Fabaceae) and Sideroxylon ob tusifolium T.D. Penn. (Sapotaceae), four trees used as anti-inflammatory ag ents in the Brazilian state of Bahia, were studied using different bioassay s. The total reactive antioxidant potential (TRAP) of the aqueous and metha nolic extracts was determined by monitoring the intensity of luminol-enhanc ed chemiluminescence (CL), using 2,2'-azo-bis(2-amidinopropane) as a peroxy l radical source. All the extracts studied were active in this method. The highest activity, measured as equivalents of Trolox concentration, was obse rved in the methanolic extract of A. macrocarpa (TRAP = 3028 +/- 95 mu M). Lipid peroxidation was assessed by means of the production of thiobarbituri c acid reactive substances (TBARS) and hydroperoxide-initiated CL in rat li ver homogenates. As in the case of luminol-enhanced CL, all the extracts te sted were effective in reducing the production of TEARS, The highest activi ty was observed in the aqueous extract of A. macrocarpa (IC50= 54 mu g/ml). Extracts of A. macrocarpa and S. obtusifolium also reduced hydroperoxide-i nitiated CL, the methanolic extract of the former being the most active, sh owing an IC50 2.0 mu g/ml. DNA-sugar damage induced by Fe(II) salts was als o used to determine the capacity of the extracts to suppress hydroxyl radic al-mediated degradation of DNA. All extracts tested were highly effective i n reducing oxidation of DNA, The highest activity was observed in the metha nolic extract of A. urundeuva, showing an IC50 = 37 mu g/ml. The results ob tained suggest that the antioxidant activity described could play an import ant role in the anti-inflammatory activity claimed for the plants under stu dy. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.