Five podophyllotoxin derivatives (1-5), two diterpenoids (6 and 7), three diterpenoid xylosides (8-10), a flavanonol glycoside (11), flavonol (12), and biflavonoid (13) were isolated from the leaves of Thujopsis dolabrata (Cupressaceae). Compounds 1, 6, and 8 were named (-)-β-isopeltatin, epi-nootkastatin 2, and acetoxyanticopalol 15-O-β-D-xylopyranoside, respectively. The structures of the isolated compounds were determined based on a detailed analysis of NMR spectroscopic data and through chromatographic and spectroscopic analyses following specific chemical transformations. The isolated compounds (1-5 and 7-11) were evaluated for their cytotoxicity toward HL-60 human promyelocytic leukemia cells and Caki-1 human kidney carcinoma cells. The podophyllotoxin derivatives (1-5) exhibited cytotoxicity against both HL-60 and Caki-1 cells with IC50 values ranging from 0.00069 to 5.4 µM, and the diterpenoid derivatives (7-10) demonstrated cytotoxicity against HL-60 cells with IC50 values ranging from 4.5 to 11 µM. HL-60 cells treated with 8 exhibited apoptosis characteristics, such as accumulation of sub-G1 cells and nuclear chromatin condensation.
Keywords: Cupressaceae; Thujopsis dolabrata; apoptosis; cytotoxicity; diterpene; podophyllotoxin.