[Quenching of ethidium-DNA fluorescence by novel acridines with antitumor activities. II. The structure-activity relationship in acridines with fluorescence quenching of ethidium-DNA].

In order to elucidate the structure-activity relationship between the antitumor activity and the molecular structure of novel DNA-intercalator acridine derivatives (1a-g and 2a-i in Chart 1), DNA-binding properties (intercalation) of these acridines were examined by quenching in the fluorescence of the ethidium-DNA complex. The mechanism of quenching is caused by the displacement of DNA-bound ethidium by a second DNA binding ligand, acridines. The concentration (C50 value) of acridine necessary to reduce the initial fluorescence of DNA-bound ethidium by 50% showed a good correlation with their antitumor activities. The quenching of fluorescence for acridines was examined using amsacrine (AMSA) as a typical standard of the second DNA-bound ligand, and calf thymus DNA with an apparent site size of two base pair. Some of the acridine derivatives showed more potent quenching of fluorescence than amsacrine (AMSA).

Acridine derivatives. III. Preparation and antitumor activity of the novel acridinyl-substituted uracils.

In an investigation of a new class of deoxyribonucleic acid (DNA)-intercalating antitumor agents, novel acridinyl-substituted uracils have been synthesized and evaluated for activity against L1210 leukemia in vivo, and against bacteria and fungus. These compounds were prepared by the novel enamine reaction between 9-chloroacridines and 6-aminouracils. The positional effects of substituents on the acridine ring showed that compounds bearing electron-withdrawing groups at the 3- or 6-position of the acridine ring were the most active.