Munropins G-J: Four New Prieurianin-Type Limonoids from Munronia pinnata and Their Structural and Molecular Characterization.

(Meliaceae), a medicinal plant used in Zhuang traditional medicine, is recognized as a rich source of structurally diverse limonoids. In our continuing investigation of bioactive constituents from Guangxi medicinal plants, four new prieurianin-type limonoids, munropins G-J (-), were isolated from their aerial parts. Their structures were determined through comprehensive spectroscopic analysis, including nuclear magnetic resonance and high-resolution mass spectrometry, and further supported by quantum chemical calculations for electronic circular dichroism and statistical probability analysis. Munropins G () and H () feature an unprecedented C-12 β-D-glucosylated α-methyl-2'-hydroxypentanoate side chain and a C-17 β-substituted furan ring, with being the 7-O-acetyl derivative of . Munropins I () and J () possess a formyl group at C-11, a 3-methyl-2-hydroxypentanoate ester at C-12, and a C-17 γ-hydroxy-α,β-unsaturated γ-lactone unit (21-hydroxy for 3, 23-hydroxy for ), each existing as an equilibrating mixture of C-21 epimers-a phenomenon observed for the first time within a prieurianin-type framework. The absolute configurations of and were established by quantum chemical electronic circular dichroism calculations, while those of and remain to be assigned. All compounds were evaluated for cytotoxicity against human lung (A549), liver (HepG2), breast (MCF-7), and colon (HCT116) cancer cell lines and for anti-inflammatory activity in lipopolysaccharide-induced RAW 264.7 murine macrophages, but none exhibited significant effects at a concentration of 80 μM. This study expands the chemical diversity of limonoids and provides new molecular scaffolds for future structure-activity relationship investigations and chemotaxonomic markers for the Meliaceae family.