Synthesis, DNA-binding and antiproliferative activity of N-(Nitrogen heterocyclic) norcantharidin acylamide acid

Two novel norcantharidin acylamide acids (HL¹=N-pyrimidine norcantharidin acylamide acid, C₁₂H₁₃N₃O₄; HL²=N-pyridine norcantharidin acylamide acid, C₁₃H₁₄N₂O₄) were synthesized by a reaction of norcantharidin(NCTD) with 2-aminopyrimidine and 2-aminopyridine, respectively. Their structures were characterized by elemental analysis, IR, UV and 1 H NMR. Fluorescence titration and viscosity measurements indicated that HL¹, HL² and HL³ (HL³=N-phenyl norcantharidin acylamide acid, C₁₄H₁₅NO₄) can bind calf thymus DNA via partial intercalation. The liner Stern-Volmer quenching constant K_sv values for HL¹, HL² and HL³ were 2.05 × 10⁴ L mol⁻¹, 1.15 × 10⁴ L mol⁻¹ and 8.30×10³ L mol⁻¹, respectively. Two compounds containing heterocycle of HL¹ and HL² have been found to cleave pBR322 plasmid DNA at physiological pH and temperature. The test of antiproliferation activity showed that the compounds had moderate to strong antiproliferative ability against the tested cell lines except of HL³ against the SMMC7721 cell line. The results indicated that the heterocycle attached to the norcantharidin was favorable to antiproliferative activity. This result was consistent with the DNA binding experiment.