Antioxidant flavonoid glycosides from aerial parts of the fern Abacopteris penangiana.

Five new flavan-4-ol glycosides, abacopterins E-I ( 5- 9), and seven known flavonoid glycosides ( 3 and 10- 15) were isolated from the aerial parts of the fern Abacopteris penangiana. Their structures were elucidated on the basis of extensive spectroscopic analysis, including HSQC, HMBC, (1)H- (1)H COSY, and ROESY, and chemical evidence. The isolated glycosides were evaluated for their antioxidant activity using the TEAC assay, and compounds 3, 5- 8, 10, 11, 14, and 15 showed TEAC values of 1.03-1.91 mM.