Four new polyketide derivatives, pestalotiopols A-D (1-4), together with seven known compounds (5-11), were isolated from a chemical-epigenetic culture of Pestalotiopsis sp. The structures and absolute configurations of the new compounds (1-4) were determined by spectroscopic analyses, Mo2-induced CD, and electronic circular dichroism (ECD) calculations. All the isolated compounds (1-11) were tested for their cytotoxic activities. Among these compounds, compounds 1, 2, 6 and 7 exhibited cytotoxicity against four human cancer cell lines with IC50 values of 16.5-56.5 μM. The structure-activity relationships of compounds (1-11) were examined. The results indicated that both the diol system of the side chain and the aldehyde group might contribute to the cytotoxic activity. The possible biosynthetic pathways for compounds (1-4) were also postulated.
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