Potential new inorganic antitumour agents from combining the anticancer traditional Chinese medicine (TCM) matrine with Ga(III), Au(III), Sn(IV) ions, and DNA binding studies.

Three new compounds of Ga(III), Au(III), Sn(IV) with matrine (MT), [H-MT][GaCl(4)] (1), [H-MT][AuCl(4)] (2) and [Sn(H-MT)Cl(5)] (3), have been synthesized and characterized by elemental analysis, IR, ESI-MS and single crystal X-ray diffraction methods. The crystal structural analyses indicate that 1 and 2 are ionic compounds, whereas 3 is a tin(IV) complex formed by the monodentate MT via its carbonyl oxygen atom of MT coordinating to Sn(IV). Their in vitro cytotoxicity towards eight selected tumour cell lines has been evaluated by MTT (3-[4,5-Dimentylthiazole-2-yl]-2,5-diphenpyltetra-zolium bromide) method, and compounds 1 and 2 exhibit enhanced activity, such as 1 to SW480, 2 to HeLa, HepG2 and MCF-7, which exceeds matrine and cisplatin, and display synergistic contribution of their components. The cell cycle analyses show that compounds 1, 3 and MT exhibit cell cycle arrest at the G(2)/M phase. Interactions of these compounds with calf thymus DNA (ct-DNA) have been investigated by spectroscopic analyses. The planar extension of the intercalative metal-matrine compounds increases the interaction of the metal-matrine with DNA, indicating that the cationic metal ions and configuration of the intercalated metal-matrine will affect the extent of interaction. Compound 2, [H-MT][AuCl(4)], exhibits more intensive binding ability to DNA, which may correlate with intercalation and other action mode. The circular dichroism spectra of the ct-DNA bound with metal-MT compounds also suggest that ct-DNA interacted with 1, 2, 3 does not influence its secondary structure. Furthermore, both compounds 1 and 2 exhibit effective inhibition ability to topoisomerase (TOPO I) at concentration of 50 μM, while matrine and compound 3 do not.