Antimutagens in the Brazilian folk medicinal carqueja (Baccharis trimera Less.)

Antimutagens from carqueja (Baccharis trimera Less., Compositae), a Brazilian folk medicinal plant used to treat liver disease and rheumatism, were examined; The methanol extract prepared from aerial parts of this plant strongly reduced the mutagenicity of 3-amino-1-methyl-5H-pyrido[4,3-b]-indole, when Salmonella typhimurium TA98 was used in the presence of rat liver microsomal fraction. The antimutagens were purified with chromatography. Antimutagenic activities were detected with a modified Ames test. Four active substances were identified in the methanol extract, 5,4'-dihydroxy-7-methoxyflavone (genkwanin), 5,4'-dihydroxy-6,7-dimethoxyflavone (cirsimaritin), 5,7,4'-trihydroxy-6-methoxyflavone (hispidulin), and 5,7,4'-trihydroxyflavone (apigenin). It is thought that these flavones are major active substances in carqueja. As for the structure-activity relationships, a decreasing tendency of the antimutagenic activity was found when the moiety of the hydroxy group of flavones was replaced by the methoxy group, except for cirsimaritin.