Structurally diverse triterpenes obtained from the fruits of Ziziphus jujuba Mill. as inflammation inhibitors by NF-κB signaling pathway.

Abstract

Twenty-nine triterpenes were obtained from the fruits of Ziziphus jujuba Mill. through various chromatography methods, and their stereo-structures were confirmed by spectroscopic methods. Among them, 2α,3β,20-trihydroxylupane-28-oic acid (1) was identified as a new compound, and the 1H and 13C NMR data of 7, 8 and 23, as well as the 13C NMR data of 17 are reported here for the first time. Meanwhile, the nitric oxide (NO) inhibitory activities of all compounds were examined in lipopolysaccharide (LPS)-stimulated RAW264.7 cells. As results, compounds 2, 7, 10-13, 15, 16, 18-21, 26-29 were found to play important roles in suppressing NO production at 5 μM. The structure-activity relationships (SARs) on NO inhibition indicated that the ursolic and oleanolic acid skeletons, p-coumaroyl group substitution, six-membered A ring, and deoxygenation (loss of C[double bond, length as m-dash]O) in the C ring showed a more positive effect on the NO inhibitory activity of triterpenes, while the reduction of the A ring C[double bond, length as m-dash]O to OH was a negative factor. Moreover, it was found that compounds 15 and 19 could suppress the phosphorylation of IκBα and NF-κB/p65 to prevent it from shifting into the nucleus and downregulate the expression of inflammatory factors, such as iNOS, IL-6 and TNF-α. Our investigations revealed that the NO inhibitory effects of the active triterpenes obtained from Z. jujuba were mediated, at least in part, through the NF-κB signaling pathway.