Sesquiterpenes from Streptomyces qinglanensis and Their Cytotoxic Activity.

Nine sesquiterpenes, including eight pentalenenes ( 1 - 8 ) and one bolinane derivative ( 9 ), were isolated from the culture broth of a marine-derived actinobacterium Streptomyces qinglanensis 213DD-006. Among them, 1 , 4 , 7 , and 9 were new compounds. Their planar structures were determined by spectroscopic methods (HRMS, 1D, and 2D NMR), and the absolute configuration was established by biosynthesis consideration and electronic-circular-dichroism (ECD) calculations. All the isolated compounds were screened for their cytotoxicity against six solid and seven blood cancer cell lines. Compounds 4 - 6 and 8 showed a moderate activity against all of the tested solid cell lines, with GI 50 values ranging from 1.97 to 3.46 µM.