Saponins from Dolichos lablab seeds with anti-inflammatory activity.

As one of a traditional Chinese medicine with dual applications in both medicinal treatment and dietary consumption, the mature seeds of D. lablab were reported to be rich in saponins and have a good effect on inflammatory related diseases. However, the substance basis for its anti-inflammatory activity remains unclear. Thus, a comprehensive phytochemical investigation on triterpenoid saponins from D. lablab seeds was carried out, resulting in the isolation and identification of twenty-one new triterpenoid saponins including dolilabsaponins A1-A4, B, C, D1-D3, E-M, N1, N2 and O (1-21) along with thirteen known analogs (22-34). Notably, the known saponins, 31, 32, and 34 were obtained from Leguminosae family for the first time. The 1H and 13C NMR data of saponins 24 and 28 were firstly reported here. Additionally, lipopolysaccharide (LPS)-stimulated RAW264.7 cells model was utilized to assess inhibitory activities of compounds 1-34 on nitric oxide (NO) production. The results revealed that compounds 1-3, 9, 10, 13-15, 18, 22, 23 and 28-34 significantly suppressed the elevation of NO levels in LPS-induced RAW264.7 cells at the concentration of 30 μM, exhibiting a concentration-dependent manner at 3, 10, and 30 μM. The results suggested that compounds 1-3, 9, 10, 13-15, 18, 22, 23, and 28-34 possessed potential anti-inflammatory activity. Further western blot assay demonstrated that 1, 9, 10, 13, 14, and 18 suppressed inflammatory response via down-regulated the expression levels of inflammatory factors, tumor necrosis factor-alpha and interleukin-6.