Ebracpenes A and B, Unusual Ring C-seco and Ring D‑aromatic Nor-Triterpenoids, from Euphorbia ebracteolata and Lipase Inhibitory Evaluation

Two unusual ring C-seco and ring D-aromatic nor-triterpenoids, ebracpenes A (1) and B (2), were obtained from Euphorbia ebracteolata roots and elucidated by widely spectroscopic data analyses, such as 1D, 2D NMR, HRESIMS, and X-ray crystallography analysis. Compound 2 showed a significant inhibitory activity on lipase (IC50 = 0.89 μM as well as the Ki determined to be 0.69 μM). Enzyme kinetics analysis and molecular docking experiments revealed that compound 2 was a competitive inhibitor, binding to the active site of lipase.本研究从无苞大戟（Euphorbia ebracteolata）的根部中分离得到2个罕见的C环开裂型、D环芳香化降三萜类化合物——埃巴菌素A（1）与B（2），并通过一维（1D）、二维（2D）核磁共振波谱（NMR）、高分辨电喷雾电离质谱（HRESIMS）以及X射线晶体衍射分析等多种光谱学手段完成结构解析。化合物2对脂肪酶表现出显著的抑制活性，其半最大抑制浓度（IC50）为0.89 μM，抑制常数（Ki）为0.69 μM。酶动力学分析与分子对接实验结果表明，化合物2属于竞争性抑制剂，可结合至脂肪酶的活性位点。