Cytotoxic polyoxygenated isopimarane diterpenoids from the edible rhizomes of Kaempferia galanga (kencur)

Kaempferia galanga (Family Zingiberaceae) is a widely distributed Asian medicinal plant and cultured crop. Several traditional uses of the rhizomes of this plant have been reported with widely using as flavors and spice in cooking. The present work concerned the isolation and identification as well as antiproliferative activity of metabolites of the rhizomes of K. galanga. Three new polyoxygenated isopimarane diterpenoids, kaemgalangols B-D (1-3), were isolated and identified in addition to 20 knowns (4-27), one monoterpene (28), and five known phenolic compounds (29-33). The chemical structures of the isolated compounds were established mainly based upon the spectroscopic analysis such as FT-IR, 1D and 2D NMR, and HRMS. The antiproliferative activity of all isolates was screened against CCRF-CEM leukemia cells using a fixed concentration of 30 mu M. Dose response curve of compounds 19 and 20 showed IC50 values of <= 50 mu M against CCRF-CEM, MDAMB-231-pcDNA and HCT116 (p53(+/+)). Compound 20 showed the most potent activity against three tested cell lines with IC50 values of 35.28, 61.60, and 42.77 mu M, respectively.