This work describes the evaluation of the antioxidant activity in the system b-carotene / linoleic acid and radical scavenging effects of the substances 2',4'-dihydroxychalcone, 2',3,4,4'-tetrahydroxychalcone (butein), 4-methoxy-2',3,4'-trihydroxychalcone, 7-hydroxyflavanone, 3',4',7-trihydroxyflavanone (butin), 7,4'-dihydroxyflavanone (liquiritigenin), 6-methoxy-7- hydroxydihydroflavonol and lasiodiplodin isolated of the extract CHCl3 of the stem of Dioclea violacea and 3',4',5,7-tetrahydroxyflavanol (quercetin), 4',7- dimethoxy-3',5-dihydroxyflavanol and epicatechin isolated of the Erythroxylum nummularia leaves. These compounds were evaluated and compared with the antioxidant standards n-propyl gallate, BHT and á α-tocoferol.