Triterpenoid saponins and phenylpropanoid glycosides from the roots of Polygala japonica Houtt. with anti-inflammatory activity

Abstract

Phytochemical study of the roots of Polygala japonica resulted in the isolation of a new triterpenoid saponin, polyjaposide A (1), a new phenylpropanoid glycoside, japonicaside A (6), and 10 known compounds: tenuifolin (2), polygalasaponin XXVIII (3), polygalasaponin XLVII (4), fallaxsaponin A (5), β-d-[(1-O-cinnamoyl)-(3-O-benzoyl)]-fructofuranosyl-(2 → 1)-α-d-glucopyranosyl-(2 → 1)-6-O-acetyl-β-d-glucopyranoside (7), tenuifolisides A (8) and B (9), (β-d-[3-O-(3,4,5-trimethoxycinnamoyl)]-fructofuranosyl-α-d-[6-O-(4-methoxybenzoyl)]-glucopyranoside (10), β-d-(3-O-sinapoyl)-fructofuranosyl-α-d-(6-O-sinapoyl)-glucopyranoside (11), and 6-acetyl-3,6′-diferuloylsucrose (12). Their structures were elucidated by extensive spectroscopic methods, including 1D and 2D NMR and MS spectra. Compounds 9 and 10 were shown to inhibit of nitrite and PGE2 production in LPS-stimulated BV2 microglial cells, with IC50 values ranging from 11.7 to 22.5 μM. These inhibitory effects were confirmed by decreases in iNOS and COX-2 expression levels in BV2 cells stimulated with LPS. Furthermore, compounds 9 and 10 significantly suppressed the release of pro-inflammatory cytokines, including TNF-α, IL-1β, IL-6 and IL-12 in LPS-stimulated BV2 cells. This data suggests that 9 and 10 might be potential therapeutic candidates for the treatment of neuro-inflammatory disorders.