NO Release Inhibitory Activity of Flavonoids from Aesculus Wilsonii Seeds through MAPK (P38), NF-κB, and STAT3 Cross-Talk Signaling Pathways

Abstract The flavonoid constituents of Aesculus wilsonii, a source of the Chinese medicinal drug Suo Luo Zi, and their in vitro anti-inflammatory effects were investigated. Fifteen flavonoids, including aeswilflavonosides IA-IC (1 – 3) and aeswilflavonosides IIA-IIE (4 – 8), along with seven known derivatives were isolated from a seed extract. Their structures were elucidated by extensive spectroscopic methods, acid and alkaline hydrolysis, and calculated electronic circular dichroism spectra. Among them, compounds 3 and 7 possess a 5-[2-(carboxymethyl)-5-oxocyclopent-yl]pent-3-enylate or oleuropeoylate substituent, respectively, which are rarely reported in flavonoids. Compounds 2, 3, 7, and 12 – 15 were found to inhibit lipopolysaccharide-induced nitric oxide production in RAW 264.7 cell lines. In a mechanistic assay, the flavonoid glycosides 2, 3, and 7 reduced the expressions of interleukin-6 and tumor necrosis factor-alpha induced by lipopolysaccharide. Further investigations suggest that 2 and 3 downregulated the protein expression of tumor necrosis factor-alpha and interleukin-6 by inhibiting the phosphorylation of p38. Compound 7 was found to reduce the production of inducible nitric oxide synthase, and the secretion of tumor necrosis factor-alpha and interleukin-6 through inhibiting nuclear factor kappa-light-chain-enhancer of activated B signaling pathway. Compounds 2, 3, and 7 possessed moderate inhibitory activity on the expression of signal transducer and activator of transcription-3. Taken together, the data indicate that the flavonoid glycosides of A. wilsonii seeds exhibit nitric oxide release inhibitory activity through mitogen-activated protein kinase (p38), nuclear factor kappa-light-chain-enhancer of activated B, and signal transducer and activator of transcription-3 cross-talk signaling pathways.