Inhibitory activities against topoisomerase I & II by polyhydroxybenzoyl amide derivatives and their structure–activity relationship

o-, m-, p-Phenylenediamines having 2,3,4-trihydroxy, 3,4 dihydroxy, and 4-hydroxybenzoyl moieties were prepared and their inhibitory activities were measured against topoisomerase I and II. More hydroxy groups on two aromatic rings increased the activities. Bis(trihydroxybenzoyl)-o-phenylenediamide showed IC50=0.90 and 0.09 μM against topoisomerase I and II, respectively. Compounds with hydroxy groups protected by acetyl moiety still had the activities. Less hydroxy groups decreased their activities. Benzothiazole derivatives also indicated the activities.