Synthesis and antitumor activities of rare earth substituted phosphotungstates containing 5-fluorouracil

Two novel rare earth substituted phosphotungstates containing 5-fluorouracil, K₉(C₄H₄FN₂O ₂)₂Nd(PW₁₁O₃₉)₂25H ₂O (FNdPW) and K₉(C₄H₄FN ₂O₂)₂Ce(PW₁₁O₃₉) ₂23H₂O (FCePW), were synthesized and characterized by elementary analysis, FT-IR spectra, X-ray powder diffraction and ¹H NMR. The thermal analysis showed that FNdPW decomposed at 210 and 493 °C, and FCePW decomposed at 223 and 471 °C, both of which had good thermal stabilities. MTT tests were performed to study the antitumor activities against HeLa cells and HepG-2 cells of FNdPW, FCePW, 5-fluorouracil, C₄H ₄FN₂O₂H₂PW₁₂O ₄₀8H₂O and K₁₁Ln(PW₁₁O ₃₉)₂xH₂O (Ln=Nd, Ce), and their cytotoxicities against HEK 293 cells. The results showed that FNdPW and FCePW possessed higher antitumor activities and lower cytotoxicities than those of 5- fluorouracil and C₄H₄FN₂O₂H₂PW ₁₂O₄₀8H₂O, of which FNdPW exhibited the highest antitumor activates against HeLa cells (EC₅₀=3.41×10 ^-6 mol/L) and HepG-2 cells (EC₅₀=6.24×10 ^-6 mol/L). Thus the introduction of rare earth elements and 5-fluorouracil could significantly enhance antitumor effect of polyoxometalates.