Polypunctosides E-K: seven new steroidal saponins from Polygonatum punctatum Royle ex Kunth and their nitric oxide production inhibitory activities

Polygonatum punctatum Royle ex Kunth is a high-value medicinal plant found in old natural forests . A phytochemical study on the roots of this plant led to the isolation of seven new steroidal saponins including four furostans ( 1 – 4 ) and three furospirostans ( 5 – 7 ). Their structures were elucidated as (25 R )-26 -O- ( β - d- glucopyranosyl)-furost-5-ene-3 β ,17 α ,22 α ,26-tetraol 3 -O-α - l -arabinopyranosyl-(1 → 2)- β - d- glucopyranosyl-(1 → 4)- β - d- galactopyranoside ( 1 ), (25 R )-26 -O- ( β - d- glucopyranosyl)-furost-5-ene-3 β ,14 α ,17 α ,22 α ,26-pentaol 3 -O-α - l -arabinopyranosyl-(1 → 2)- β - d- glucopyranosyl-(1 → 4)- β - d -galactopyranoside ( 2 ), (25 R )-26 -O- ( β - d -glucopyranosyl)-furost-5-ene-22 α -methoxy-3 β ,17 α ,26-triol 3 -O-α - l -arabinopyranosyl-(1 → 2)- β - d -glucopyranosyl-(1 → 4)- β - d -galactopyranoside ( 3 ), (25 R )-26 -O- ( β - d -glucopyranosyl)-furost-5-ene-22 α -methoxy-3 β ,17 α ,26-triol 3 -O- [ α - l -arabinopyranosyl-(1 → 2)- β - d -glucopyranosyl-(1 → 4)]-[acetoxy-(→ 6)]- β - d -galactopyranoside ( 4 ), 26 -O- ( β - d -glucopyranosyl)-14 α, 17 α -dihydroxynuatigenin 3 -O-α - l -arabinopyranosyl-(1 → 2)- β - d -glucopyranosyl-(1 → 4)- β - d -galactopyranoside ( 5 ), 26 -O- ( β - d -glucopyranosyl)-17 α -hydroxynuatigenin 3 -O-α - l -arabinopyranosyl-(1 → 2)- β - d -glucopyranosyl-(1 → 4)- β - d -galactopyranoside ( 6 ), and 26 -O- ( β - d -glucopyranosyl)-14 α -hydroxynuatigenin 3 -O-α - l -arabinopyranosyl-(1 → 2)- β - d -glucopyranosyl-(1 → 4)- β - d -galactopyranoside ( 7 ) by extensive spectroscopic analyses, including infrared, high-resolution electrospray ionization mass spectrometry, and one- and two-dimensional nuclear magnetic resonance spectroscopy. Compounds 1 – 7 inhibited nitric oxide production in lipopolysaccharide activated RAW264.7 cells with IC 50 values ranging from 41.5 ± 3.2 to 62.2 ± 3.7 µM, compared to 33.8 ± 2.6 µM for the positive control compound l -NMMA. Graphical Abstract