Kaemgalangol A: Unusual seco-isopimarane diterpenoid from aromatic ginger Kaempferia galanga

Abstract A new unusual seco-isopimarane, kaemgalangol A ( 1 ) and 12 usual analogs ( 2−13 ) were isolated from the rhizomes of Kaempferia galanga (Family: Zingiberaceae). KaemgalangolA ( 1 ) represented a rarely isolated 9,10-seco-isopimarane skeleton. The chemical structures of the isolated compounds were mainlyinvestigated by spectroscopic techniques such as 1D, 2D NMR, and HRMS. The absolute configuration of 1 – 3 was studied by X-ray diffraction analysis as well as experimental and TDDFT-calculated electronic circular dichroism. Among the isolated diterpenoids, 5 , 6 and 9 exhibited cytotoxic activity against HeLa (IC 50 75.1, 74.2 and 76.5 μM, respectively) and HSC-2 (IC 50 69.9, 53.3 and 58.2 μM, respectively) cancer cells.