Two novel cytotoxic benzofuran derivatives from Brazilian propolis

Two novel benzofuran derivatives, propolis-benzofurans A (1) and B (2), were isolated from the MeOH extract of Brazilian propolis, together with two known isoprenylated compounds (E)-3-[2,3-dihydro-2-(1-methylethenyl)-7-prenyl-5-benzofuranyl]-2-propenoic acid and (E)-3-{4-hydroxy-3-[(E)-4-(2,3-dihydrocin-namoyloxy)-3-methyl-2-butenyl]-5-prenylphenyl}-2-propenoic acid. The structures of these compounds were elucidated on the basis of spectral analysis. Both the new compounds exhibited mild cytotoxicity toward highly liver-metastatic murine colon 26-L5 carcinoma and human HT-1080 fibrosarcoma cells.