Aralianudasides C-E: three undescribed triterpenoid saponins from the buds of Aralia elata and its airway inflammation inhibitory activity

Aralia elata (Araliaceae), widely distributed in Asia, is traditionally used for treating arthritis, cardiovascular diseases, tumours and asthma. Phytochemical analysis of its buds led to the isolation of three previously undescribed triterpenoid saponins-Aralianudasides C-E (1-3). Aralianudaside C (1) represents the first taraxastane-type saponin identified in Araliaceae, featuring a β-D-glucose moiety at C-3. Aralianudaside D (2) contains a rare D-xylose unit linked to C-6' of C-3-O-glucose, while Aralianudaside E (3) possesses a unique trisaccharide chain with D-glucose attached to C-4'' of C-3'-O-glucose. Furthermore, compounds 2 and 3 significantly reduced IL-6 expression in LPS-induced 16HBE airway epithelial cells with the suppression rate of 31.63% and 37.27% (the suppression rate of positive control Dex was 79.04%).