Schmeda-Hirschmann, G. Laboratorio de Química de Productos Naturales, Instituto de Química de Recursos Naturales, Universidad de Talca, Casilla 747, Talca, Chile.The methanolic extract of the aerial parts of Lobelia bridgesii and L. tupa (Lobeliaceae) showed activity in the DNA binding assay. Bioassay-guided isolation led to the alkaloids norlobelanidine and norlelobanidine as the main bioactive constituents of othe plant. At 0.50 mg/mL, the percentual DNA binding of both compounds were 79% and 71%, respectively