Novel Flavonoids from the Fern Notholaena sulphurea

Abstract

The major constituent of the yellow frond exudate of the fern Notholaena sulphured was identified by spectroscopic methods as 3,5,2′-trihydroxy-7-methoxy-8-acetoxy flavone and its structure was confirmed by synthesis. This novel natural flavonoid was also detected in the frond exudate of five other Notholaena species. In the yellow form of N. sulphurea, the rare 5,2′- dihydroxy-7,8-dimethoxy flavone was also found, along with some trivial flavonoids. The white form of N. sulphurea produces three dihydrochalcones that are accompanied by some kaempferol methyl ethers and apigenin-7-methyl ether. The 3-acetoxy as well as the 3-butyroxy and the 4′- butyroxy derivatives of 7-methyl aromadendrin were also identified in this material. One of them was shown to belong to the extremely rare group of 3-cis-dihydroflavonols.