Anti-Inflammatory Saponins From an Edible Aquatic Plant Nymphoides hydrophylla

The present investigation of Nymphoides hydrophylla is a Taiwan indigenous edible aquatic plant, belongs to the Menyanthaceae family, and has been used as a traditional food with potential medicinal values against fever, insect bites, ulcer, and skin diseases. Interestingly, we found that the plant extract showed a significant anti-inflammatory effect.

The aim is isolation, structure elucidation, and anti-inflammatory evaluation of secondary metabolites from N. hydrophylla.

This study involves the bioactive isolation and structural studies of the pure compounds determined by NMR, UV, IR spectroscopies, and HRMS. The anti-inflammatory activity of the pure compounds was evaluated in vitro. In addition, isolates showed remarkable anti-inflammatory activities to regulate superoxide anion generation and elastase release in fMLF/CB-induced human neutrophils.

This study conducted 10 oleanane-type saponins with oligoglycoside linkage, including two new (1 and 2) identified from the butanol extract of N. hydrophylla. As a result, Compounds 1 and 2, representing new triterpene saponins, have not been previously reported. In vitro anti-inflammatory tests revealed that Compounds 1, 5-7, 9, and 10 showed significant anti-inflammatory effects by inhibiting superoxide anion generation with IC₅₀ values of 1.62, 0.92, 0.28, 2.69, 0.29, and 0.15 μM, respectively, whereas compounds 1, 5, 6, 9, and 10 showed potential inhibition on elastase release in human neutrophils, with IC₅₀ values of 0.19, 1.12, 0.70, 0.68, and 0.51 μM, respectively.

Our findings suggested that the components of N. hydrophylla have the potential to develop anti-inflammatory agents.