Synthesis and biological evaluation of disubstituted amidoxanthones as potential telomeric G-quadruplex DNA-binding and apoptosis-inducing agents

A series of disubstituted xanthones was obtained by cationic modification of xanthone’s C2 and C7 with amine groups of different pKa values. Modified structures by using moieties with high pKa values had good antitumor activity according to the MTT assay, AO/EB staining and flow cytometry assay, especially bis-dimethylamine derivative (5a). Further study indicated that compound 5a had good binding activity to telomeric G-quadruplex DNA, as detected by using spectroscopy methods, melting profiles, polymerase chain reaction stop assay and molecular modeling study. The results suggested that the antitumor activity of 5a might be associated with its stabilization of G-quadruplex DNA, which could be developed as new G-quadruplex DNA stabilizer and potent antitumor agents.