Synthesis, characterization and antitumor activity of rare earth (Y, La) substituted phosphotungstates containing 5-fluorouracil

Two rare earth substituted Keggin-type phosphotungstates containing 5-fluorouracil, K10C4H4FN2O2Y(PW11O39)210H2O (FYPW) and K9(C4H4FN2O2)2La(PW11O39)218H2O (FLaPW) were synthesized in aqueous solution, and the structures were characterized by Fourier transform infrared spectroscopy (FT-IR), element analysis, inductively coupled plasma spectrometry (ICP), X-ray powder diffraction (XRD) and 1H nuclear magnetic resonance (NMR). Thermal analysis showed that the decomposition processes of the two compounds could be divided into three steps, the loss of crystal water, the decomposition of 5-fluorouracil unit and the decomposition of Keggin-type polyanions. The in vitro cytotoxicities against HEK 293, HeLa and HepG-2 cells were studied by methyl thiazolyl tetrazolium (MTT) assay. The results showed that FYPW and FLaPW had higher antitumor activities than 5-fluorouracil, C4H4FN2O2H2PW12O408H2O and rare earth substituted polyoxometalates K11Ln(PW11O39)2nH2O (Ln=Y, La). It was concluded that introducing 5-fluorouracil and rare earth (Y or La) into its structure was a considerable way to enhance antitumor activities of polyoxometalates.