The Triterpenoids from Munronia pinnata and Their Anti-Proliferative Effects

Six new tirucallane-type triterpenoids, named munropenes A–F (1–6), were extracted from the whole plants of Munronia pinnata using a water extraction method. Their chemical structures were determined based on detailed spectroscopic data. The relative configurations of the acyclic structures at C-17 of munropenes A–F (1–6) were established using carbon–proton spin-coupling constants ((2,3)J(C,H)) and inter-proton spin-coupling constants ((3)J(H,H)). Furthermore, the absolute configurations of munropenes A–F (1–6) were determined through high-performance liquid chromatography (HPLC), single-crystal X-ray diffraction, and electronic circular dichroism (ECD) analyses. The antiproliferative effects of munropenes A–F were evaluated in five tumor cell lines: HCT116, A549, HepG2, MCF7, and MDAMB. Munropenes A, B, D, and F (1, 2, 4, and 6) inhibited proliferation in the HCT116 cell line with IC(50) values of 40.90, 19.13, 17.66, and 32.62 µM, respectively.