Phytotoxic compounds from Flourensia cernua.

Bioassay-directed fractionation of a CH(2)Cl(2)-MeOH (1:1) extract of the aerial parts of Flourensia cernua led to the isolation of three phytotoxic compounds, namely, dehydroflourensic acid (1), flourensadiol (2) and methyl orsellinate (3). Dehydroflourensic acid is a new natural product whose structure was established by spectral means. In addition, the known flavonoid ermanin and seven hitherto unknown gamma-lactones were obtained, these being tetracosan-4-olide, pentacosan-4-olide, hexacosan-4-olide, heptacosan-4-olide, octacosan-4-olide, nonacosan-4-olide, and triacontan-4-olide. Compounds 1-3 caused significant inhibition of radicle growth of Amaranthus hypochondriacus and Echinochloa crus-galli, interacted with bovine-brain calmodulin and inhibited the activation of the calmodulin-dependent enzyme cAMP phosphodiesterase.