Novel Flavonoids from the Fern Notholaena sulphurea

T he m ajo r constituent of the yellow frond exudate of the fern Notholaena sulphurea was iden tified by spectroscopic m ethods as 3 ,5 ,2 '-trihydroxy-7-m ethoxy-8-acetoxy flavone and its struc tu re was confirm ed by synthesis. This novel natural flavonoid was also de tected in the frond exudate of five o ther Notholaena species. In the yellow form of N. sulphurea, the rare 5 ,2 'dihydroxy-7,8-dim ethoxy flavone was also found, along with some trivial flavonoids. T he white form o f N. sulphurea produces three dihydrochalcones that are accom panied by som e kaem pferol m ethyl e thers and apigenin-7-m ethyl ether. The 3-acetoxy as well as the 3-butyroxy and the 4 'butyroxy derivatives of 7-m ethyl arom adendrin were also identified in this m ateria l. O ne of them was show n to belong to the extrem ely rare group of 3-c«-dihydroflavonols.