Triterpene Acids from Mesona procumbens Exert Anti-inflammatory Effects on LPS-Stimulated Murine Macrophages by Regulating the MAPK Signaling Pathway

Five new triterpene acids, mesonaic acids A–C (1–3), 2α,3α,19α-trihydroxy-24-nor-4(23),12-oleanadien-28-oic acid (4), and 3α,19α,22α-trihydroxy-2-oxo-12-ursen-28-oic acid (5), and 10 known triterpene acid compounds (6–15) were isolated from a methanolic extract of Mesona procumbens. Triterpenes 1–3 possess unusual hexacyclic skeletons with a 13α,27-cyclopropane ring. Regarding their anti-inflammatory activity, compounds 1–3, 6, and 7 inhibited NO production with EC₅₀ values lower than 15 μM, which were better than that of the positive control quercetin. Compounds 1–3, 6, and 7 markedly decreased levels of the inducible iNOS and COX-2 proteins in macrophages by inhibiting the activation of NF-κB through interference with the MAPK signaling pathway. Based on these data, compounds 1–3, 6, and 7 have great potential as NO inhibitors.