Phytotoxicity of Secondary Metabolites from Aptenia cordifolia

From the fresh leaves or twigs of Aptenia cordifolia, a total of 29 compounds were isolated, including the new tetranoroxyneolignan 18, the new dilignan 19, and the beta-ionone derivative 27, previously only known as a synthetic compound, together with 26 known compounds. The structures of the new products were determined by (1)H-, (13)C-, and 2D-NMR, as well as HR-MS analyses. The phytotoxic effects of the isolates on the germination and growth of the dicotyledon Lactuca sativa L. (lettuce) were studied in the concentration range 10(-4) to 10(-7) M. Several constituents of A. cordifolia were found to be equally active as or superior to 4-hydroxybenzoic acid (HBA) used as positive control.