Bioactive constituents of Conyza albida

The bioactivity-guided fractionation of an active chloroform extract of Con yza albida led to the isolation of three alkenynes, deca-4,6-diyn-2-(Z)-eno ic methyl ester (1), deca-4,6-diyn-2 -(Z)-enoic ethyl ester (2) and deca-2, 4-diene-4-hydroxy-6-yn-1,4-olide (3), and the terpenoid spathulenol (4), as the active toxic metabolites in the Artemia sp. lethality test. When teste d in the KB cell cytotoxicity assay, compounds 1-4 demonstrated IC50 values of 52.2, 38.4, 117.9, and 83.8 muM, respectively. All compounds studied we re inactive in the DNA methyl green and DNA strand scission assays, while c ompounds 3 and 4 showed moderate activity as inhibitors of human topoisomer ase I. Compound 2 is reported here for the first time.