Ligation of the quinolone antibacterial agent pipemidic acid to Keggin polyoxotungstates

Three new drug molecules modifying Keggin polyoxometallate compounds have been synthesized under hydrothermal conditions and structurally characterized by routine techniques. Single-crystal X-ray diffraction analysis shows that compound 1 is constructed by a Keggin cluster and two [Cu(PPA)2] drug complexes, formulated as [Cu(PPA)2]2·[PW12O40]·6H2O. Compound 2 consists of a Cd substituted Keggin cluster [PW11CdO39] and five isolated HPPA drug molecules, formulated as [HPPA]5·[PW11CdO39]·2H2O. Compound 3 consists of a full oxidised Keggin [PW12O40] cluster and three isolated HPPA drug molecules, formulated as [HPPA]3·[PW12O40]·2H2O. Additionally, the antitumor activity of the three new compounds and their parent components in vitro were studied by a MTT experiment. The results show that introduction of TM-PPA/PPA into the polyoxoanion surface could increase their antitumor activity and make the compounds penetrate into the cells easily. Furthermore, the antitumor activity of the compounds can be modulated by their different structures.

Graphical abstractThe first examples of pipemidic acid drug molecules modifying Keggin polyoxometallate compounds are reported. The antitumor activities in vitro show that introduction of M-PPA/PPA into the POM surface may increase the antitumor activity, which can be modulated by their different structures.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Compounds 1–3 are the first examples that POMs are modified by drug molecules pipemidic acid. ► Due to the introduction of PPA-M/PPA, the antitumor activities of POMs are ameliorated. ► The antitumor activity of compounds 1–3 comes from the synergism of POMs and PPA/M-PPA.