Constituents from Dolichos lablab L. Flowers and Their Anti-Inflammatory Effects via Inhibition of IL-1β Release

The occurrence of inflammation is closely related to the activation of the NLRP3 inflammasome. IL-1 beta produced during the activation of the NLRP3 inflammasome has strong pro-inflammatory activity and can also promote the release of inflammatory factors by other immune cells, exacerbating inflammatory damage to tissues. Utilizing IL-1 beta as the detection index to find small-molecule inhibitors targeting NLRP3 from natural products will benefit the search for drugs for inflammation-related diseases. During the exploration of anti-inflammatory active components derived from the flowers of Dolichos lablab L., an ingredient in traditional Chinese medicine with dual applications in both medicinal treatment and dietary consumption, fourteen compounds (1-14), including seven previously unreported ones, named flosdolilabnitrogenousols A-D (1-4) and flosdolilabsaponins A-C (5-7), were found. Their structures were established through extensive NMR spectra determination, HR-ESI-MS analysis, ECD calculations, and chemical reactions. Flosdolilabsaponin A (5) stands out as an exceptionally rare tetracyclic lactone oleane-type saponin. Additionally, the inhibitory activity on IL-1 beta release of all compounds, without cytotoxicity, was evaluated using BMDMs stimulated with LPS/Nigericin. An Elisa assay revealed that compounds 1, 8, 9, and 11-14 exhibited significant inhibition of IL-1 beta release at a concentration of 30 mu M. Structure-activity relationships were also discussed. This study indicates that D. lablab flowers possess anti-inflammatory activity, which might exert its effect by suppressing the activation of the NLRP3 inflammasome.