Isolation, structural elucidation, and insights into the anti-inflammatory effects of triterpene saponins from the leaves of Stauntonia hexaphylla

Abstract

Using various chromatographic techniques, 23 triterpene saponins (1-23) were isolated from an ethanol extract of Stauntonia hexaphylla, including two new compounds (12 and 15). Their chemical structures were established by comprehensive spectroscopic methods such as 1D- and 2D-NMR, and HR-ESI-MS, and chemical reactions. The anti-inflammatory activities of the isolated saponins were determined using the nitric oxide (NO) assay. Compound 13 exhibited the greatest inhibitory effect (IC₅₀ = 0.59 μM). In addition to NO, compound 13 suppressed the secretion of PGE₂, IL-1β, and IL-6, but not TNF-α, and inhibited the protein expression of iNOS and COX-2 in LPS-activated RAW264.7 cells. The chemical derivatives of the isolated compounds were studied using structure-activity relationships. The results suggested that compound 13 isolated from S. hexaphylla might be useful for treating inflammation. This is the first comprehensive study of saponins from the leaves of S. hexaphylla based on anti-inflammatory extract screening guidelines.

Keywords: Anti-inflammatory effect; NO; Stauntonia hexaphylla; Stauntonoside A; Stauntonoside B; Triterpenoid saponins.