Structurally diverse coumarin derivatives from the buds of Edgeworthia gardneri and their cytotoxic activities

Five new coumarins, including three phenypropaninized coumarins edgegardnerols A-C (1-3), two bicoumarins edgegardnerols D and E (4 and 5), along with eight known analogues, were isolated and identified from the dried buds of E. gardneri. Their structures were elucidated by comprehensive analysis of their NMR, IR, UV, HR-ESI-MS, and ECD data. Furthermore, the absolute configurations of the glucose moiety were confirmed by HPLC analysis after acidic hydrolysis and chemical derivatization. The cytotoxic activities of all isolated compounds were evaluated against A549 and SMMC-7721 cell lines. Among the tested isolates, compound 12 showed the most potent cytotoxicity with IC₅₀ values of 22.65 μM and 25.83 μM in these two cell lines, respectively. Compared with cisplatin (29.78 μM), compound 12 exhibited stronger cytotoxic activity in A549 cell line. The preliminary structure-activity relationship showed that 7-hydroxy group on coumarin skeleton was structurally required for the cytotoxity against the A-549 and SMMC-7721 cell lines.