Coumarin derivatives from Gerbera saxatilis.

Phytochemical investigation of Gerbera saxatilis (Astraceae) afforded three new coumarin derivatives 1- 3 and a known coumarin 4. Compounds 1 and 2 represent the first examples of the natural occurrence of the novel polycyclic pyrano[3-2c]coumarin carbon skeleton. The structures of compounds 1- 4 were characterized based on extensive spectroscopic analyses as well as comparison to the spectroscopic data reported. The structures of compounds 1 and 3 were further confirmed by X-ray data analyses. The cytotoxic activity of compounds 1- 4 was evaluated against selected cancer cell lines, including human leukemia cell (HL-60), human hepatoma cell (SMMC-7721), and human cervical carcinoma cell (HeLa) lines.