Neoamphimedine: a new pyridoacridine topoisomerase II inhibitor which catenates DNA

The pyridoacridines neoamphimedine and amphimedine were isolated from Xestospongia sp. from the Philippines and Xestospongia cf. carbonaria from Micronesia. The chemical formula, chemical shifts and proton coupling pattern for amphimedine is the same as for amphimedine isolated by Schmitz and colleagues. Neoamphimedine was found to be cytotoxic to normal CHO AAS cells. It was also observed that neoamphimedine stimulates topoisomerase II dependent cleavage 3% above controls compared to etoposide, which stimulates 38% cleavage at the same concentration.