Abstract: A marine bacterium, Pseudoalteromonas rubra QD1-2,was isolated from the Qingdao sea in China.The crude culture of QD1-2 was highly active against human tumor cells.In order to confirm chemical structure of the antitumor compound,The crude metabolites of QD1-2 was isolated and purified by using column chromatography with Diaion HP20 macroporous resin and then purified it by preparative HPLC.The chemical structure of the active compound finally obtained was achieved with spectroscopy methods,including high resolution mass spectrometry and1D and 2D nuclear magnetic resonance.According to the analysis results,we identified the active compound as a ubiquinone derivative with the molecular weight of 320,the molecular formula C₁₈H₂₄O₅.Finally antitumor activity was tested by the MTT method,showing very strong.The results revealed the huge potential of discovering novel antitumor compounds from Pseudoalteromonas, providing new sources for antitumor natural compounds.

Key words: Pseudoalteromonas, structure elucidation, coenzyme Q₂, antitumor activity