Eight new cadinene-sesquiterpenes (1-8), one eudesmane-sesquiterpene (9), and three known compounds (10-13) were isolated from an endophytic fungus, Aspergillus flavus, which was isolated from a toxic medicinal plant, Tylophora ovata. Their structures were elucidated by interpretation of spectroscopic data, and absolute configurations determined according to the specific rotation and electron circular dichroism methods. Compounds 4-8, 11, and 12 exhibited latent hepatic protection effects at 10 μM, and compound 12 selectively inhibited the proliferation of MCF-7 breast cancer cells with an IC50 values of 2.6 μM.