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.
Keywords: MAPK; Mesona procumbens; NF-κB; anti-inflammatory; mesonaic acid.