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During our search for bioactive natural products from tropical plants, we investigated the chemical constituents of Curcuma parviflora Wall. (Zingiberaceae) collected in north-east Thailand. This plant is a perennial herb widely distributed over a forest area of the northern part of Thailand, and is used as an ornamental plant, and is edible, and also it has been said to be used for detoxification of scorpion bites in certain areas. Extensive investigation of extracts of the underground part of this plant led to the isolation of cytotoxic sesquiterpene-dimers, parviflorenes A-I (1-9), and their structures were elucidated by spectroscopic studies including X-ray crystal analylsis. Parviflorene A (1) and compounds 2,4,6, and 7 possess an unprecedented unsymmetrical bis-cadinane skeleton, while compound 3 is a dimer of cadinane and iso-cadinane, and compound 5 possesses another novel carbon framework consisting of two cadinanes with different bond-connection. Studies on determination of absolute stereochemistry of parviflorenes A (1), B (2), D (4), F (6), and G (7) were also described here. These new compounds showed cytotoxicity against P388 murine leukemia cells and other tumor cell lines. Parviflorenes A (1) and F (6) were cytotoxic against all tested tumor cell lines in the human cancer cell line panel assay, and DNA microarray and real time PCR studies revealed that parviflorene F (6) enhanced the gene expression of TRAIL-R2 by 4.9 times at the concentreation of 8μg/mL.