New cyclic C-geranylflavanones isolated from Paulownia fortunei fruits with their anti-proliferative effects on three cancer cell lines

Seven new C-geranylated flavanones, fortunones F - L (1–7), were isolated from the fresh mature fruits of Paulownia fortunei (Seem.) Hemsl. Their structures were determined by extensive spectroscopic data interpretation (UV, IR, HRMS, NMR, and CD). These new isolated compounds were all with a cyclic side chain modified from the geranyl group. Among them, compounds 1–3 all possessed a dicyclic geranyl modification, which was described firstly for Paulownia C-geranylated flavonoids. All the isolated compounds were subjected to the cytotoxic assay on human lung cancer cell A549, mouse prostate cancer cell RM1 and human bladder cancer cell T24, respectively. Results indicated A549 cell line was more sensitive to C-geranylated flavanones than the other two cancer cell lines and compounds 1, 7 and 8 exhibited potential anti-tumor effects (IC50 ˂ 10 μM). Further research revealed the effective C-geranylated flavanones could exert their anti-proliferative activity on A549 cells by inducing apoptosis and blocking cells in G1 phase.