New saikosaponins from the roots of Bupleurum chinense

Abstract

Seven new saikosaponins (1−7), together with four known ones (8−11), were isolated from the roots of Bupleurum chinense. Their structures were elucidated by comprehensive spectroscopic analysis and chemical methods. All obtained saikosaponins were oleanane-type, except for compound 11, which was the first lupane–type saikosaponin isolated from the genus Bupleurum. Compound 1 represented the first example of saikosaponins bearing a hydroxyl group at C-15, while compound 4 was a saikosaponin containing acetoxy group at C-23 rarely found in genus Bupleurum. Compounds 6 and 7, bearing an n-butoxy moiety at C-11, were confirmed to be artifacts by LC–MS experiment. All the isolates were evaluated for their inhibitory effects towards nitric oxide production induced by lipopolysaccharide in BV-2 microglial cells, and saikosaponins A (9) and D (10) exhibited the most potent activity, which were comparable to the positive control dexamethasone.