Triterpenoids and Flavonoids from the Leaves of Astragalus membranaceus and Their Inhibitory Effects on Nitric Oxide Production

Four new cycloartane triterpenes, named huangqiyegenins V and VI and huangqiyenins K and L ( 1 – 4 , resp.), together with nine known triterpenoids, 5 – 13 , and eight flavonoids, 14 – 21 , were isolated from a 70%‐EtOH extract of Astragalus membranaceus leaves. The structures of the new compounds were elucidated by detailed spectroscopic analyses, and the compounds were identified as (9 β ,11 α ,16 β ,20 R ,24 S )‐11,16,25‐trihydroxy‐20,24‐epoxy‐9,19‐cyclolanostane‐3,6‐dione ( 1 ), (9 β ,16 β ,24 S )‐16,24,25‐trihydroxy‐9,19‐cyclolanostane‐3,6‐dione ( 2 ), (3 β ,6 α ,9 β ,16 β ,20 R ,24 R )‐16,25‐dihydroxy‐3‐( β ‐ D ‐xylopyranosyloxy)‐20,24‐epoxy‐9,19‐cyclolanostan‐6‐yl acetate ( 3 ), and (3 β ,6 α ,9 β ,16 β ,24 E )‐26‐( β ‐ D ‐glucopyranosyloxy)‐16‐hydroxy‐3‐( β ‐ D ‐xylopyranosyloxy)‐9,19‐cyclolanost‐24‐en‐6‐yl acetate ( 4 ). All isolated compounds were evaluated for their inhibitory activities against LPS‐induced NO production in RAW264.7 macrophage cells. Compounds 1 – 3, 14, 15 , and 18 exhibited strong inhibition on LPS‐induced NO release by macrophages with IC 50 values of 14.4–27.1 μ M .