Fusion of Michael-acceptors enhances the anti-inflammatory activity of ginsenosides as potential modulators of the NLRP3 signaling pathway

Ginsenosides are a promising group of secondary metabolites for developing anti-inflammatory agents. In this study, Michael acceptor was fused into the aglycone A-ring of protopanoxadiol (PPD)-type ginsenosides (MAAG), the main pharmacophore of ginseng, and its liver metabolites to produce novel derivatives and assess their anti-inflammatory activity in vitro. The structure-activity relationship of MAAG derivatives was assessed based on their NO-inhibition activities. Of these, a 4-nitrobenzylidene derivative of PPD (2a) was the most effective and dose-dependently inhibited the release of proinflammatory cytokines. Further studies indicated that 2a-induced downregulation on lipopolysaccharide (LPS)-induced iNOS protein expression and cytokine release may be related to its inhibitory effect on MAPK and NF -KB signaling pathways. Importantly, 2a almost completely inhibited LPS-induced production of mitochondrial reactive oxygen species (mtROS) and LPS-induced NLRP3 upregulation. This inhibition was higher than that by hydrocortisone sodium succinate, a glucocorticoid drug. Overall, the fusion of Michael acceptors into the aglycone of ginsenosides greatly enhanced the anti-inflammatory activities of the derivatives, and 2a alleviated inflammation considerably. These findings could be attributed to the inhibition of LPS-induced mtROS to block abnormal activation of the NLRP3 pathway.

Automated summary

Ginsenoside derivatives with Michael acceptor fused into the aglycone A-ring were synthesized and evaluated for their anti-inflammatory activity. The 4-nitrobenzylidene derivative of PPD (2a) showed the most effective inhibition of proinflammatory cytokine release. Further studies revealed that 2a downregulated iNOS protein expression and cytokine release through inhibition of the MAPK and NF-KB signaling pathways. Additionally, 2a almost completely inhibited LPS-induced production of mtROS and NLRP3 upregulation. These findings suggest that the fusion of Michael acceptors into ginsenosides greatly enhances their anti-inflammatory activity, with 2a showing significant anti-inflammatory effects by inhibiting mtROS-mediated activation of the NLRP3 pathway.