Pyranicin, a non-classical annonaceous acetogenin, is a potent inhibitor of DNA polymerase, topoisomerase and human cancer cell growth.

This report describes the inhibitory activities of the natural and non-natural acetogenins [mucocin (compound 1), jimenezin (compound 2), 19-epi jimenezin (compound 3), muconin (compound 4), pyranicin (compound 5), pyragonicin (compound 6), 10-epi pyragonicin (compound 7), and a gamma-lactone (compound 8)], which were synthesized by us, against DNA polymerase (pol), DNA topoisomerase (topo), and human cancer cell growth. Among the compounds tested, compound 5 was revealed to be the strongest inhibitor of the animal pols and human topos tested, and the IC50 values for pols and topos were 2.3-15.8 and 5.0-7.5 microM, respectively. The compound also suppressed human cancer cell (promyelocytic leukemia cell line, HL-60) growth with the same tendency as the inhibition of pols and topos and the LD50 value was 9.4 microM. Compound 5 arrested the cells at G2/M and G1 phases, and prevented the incorporation of thymidine into the cells, indicating that it blocks DNA replication by inhibiting the activity of pols and topos. This compound also induced apoptosis of the cells. Based on these results, the action mode of compound 5 is discussed.