Flavones from Struthiola argentea with anthelmintic activity in vitro.

Parasitic diseases caused by helminthes lead to significant health hazards to animals resulting in enormous economic impact. While a number of anthelmintics are currently available, all are encountering resistance and ones with a mode of action are needed. We report herein bioassay-guided isolation of three anthelmintic flavones 1-3, including the flavone, 5,6,2',5',6'-pentamethoxy-3',4'-methylenedioxyflavone (3) from the methanol extract of Struthiola argentea (Thymelaeaceae). The structure of 3 was elucidated by analysis of its 1D and 2D NMR and MS data. The two major flavones produced by this plant were also isolated and identified as yuankanin (4) and amentoflavone (5). A number of flavones related to the compounds isolated from S. argentea were acquired and tested to ascertain structure activity relationships. The isolation, structure, anthelmintic activity and structure activity relationships of the flavones are described. Compound 3 exhibited the most potent in vitro activity with 90% inhibition of larval motility at 3.1 microg/mL and compound 15 showed modest in vivo activity.