Prenylated indole alkaloids and lignans from the flower buds of Tussilago farfara

Six new compounds including four prenylated indole alkaloids ( 1 – 4 ) and two lignans ( 5 – 6 ), along with eight known cometabolites ( 7 – 14 ), were isolated from the flower buds of Tussilago farfara . Structures of the new compounds were elucidated by comparison with structurally related known analogues and also by comprehensive spectroscopic analyses. Their absolute configurations were determined by a variety of means including Mosher's method, Marfey's analysis, electronic circular dichroism (ECD) exciton chirality method and ECD calculations. Our bioassays have established that compounds 1 and 2 showed potent α -glucosidase inhibitory activity with IC 50 values of 105 ± 4.7 and 35.2 ± 3.2 μM, respectively, while the known 13 and 14 exerted moderate DPPH radical scavenging activity with IC 50 values of 45.2 ± 2.9 and 29.2 ± 2.0 μM, respectively.