Lignans and Flavonoids from Cajanus cajan (L.) Millsp. and Their α-Glucosidase Inhibitory Activities

A pair of new lignan conformers ( 1 – 2 ), one new flavonoid glycoside ( 3 ), as well as nineteen known compounds were purified from the twigs and leaves of Cajanus cajan (L.) Millsp.. The planar structures of the unknown compounds were determined via NMR and high-resolution mass spectrometry, while their absolute configurations were elucidated via comparison between their experimental and calculated electronic circular dichroism (ECD) values. All the isolated compounds were assayed for their α -glucosidase inhibitory activities. The results demonstrated that compounds 8 – 12 , 15 – 16 , 18 – 19 , 21 – 22 had strong inhibition activities, with compound 10 (IC 50 =0.4±0.21 μM) most active. The structure-activity relationships were preliminarily summarized. Enzyme kinetics showed that compounds 8 , 9 , 15 – 16 , 18 – 19 , 21 – 22 were non-competitive inhibitors and compounds 10 – 12 were anti-competitive ones. Graphical