Study On Synthesis And Anti-tumor Activities Of The Transition Metal Complexes With Emodin

Medicinal plants provides many pharmacological compounds. As the leadingcompounds, the structural modification of active compounds is a way to enhance thepharmacological activities, and become one of the important rasearch directions for newefficient drugs.Emodin, anthraquinone compound, is an active component contained in the root andrhizome of Giant Knotweed and Rhem palmatum L.(Polygonaceae). Several latestobservations have shown that emodin has the effects of anti-bacterial, anti-inflammatory,hepatoprotective, etc. The antiproliferative effects of emodin have been reported inmany cancer cell lines, including cell lines of HER2/neu-overexpressing breast cancer,lung cancer, leukemia, hepatocellular carcinoma, cervical cancer, prostate cancermultiple myeloma, and neuroblastoma. However, the antiproliferative activity ofemodin is usually of low potency, detectable only at relative high level (30-80μmol/L).As a leadingcompound, it would be significant important to study the structuralmodification of emodin in order to obtain theexcellent new antitumor activitycompounds. Because the electronic properties of metal and the structure effects ofnatural compounds can produce synergistic effect, and have stronger pharmacologicalactivity than natural compounds, we synthesized the transition metal complexes ofemodin, and discussed the mechanism of cell apoptosis using the approaches forbiochemistry, cell biology and molecular biology. The main results are listed:(1) To synthesis the metal [metal=Cu (II), Co (II), Ni (II), Zn (II) and Mn (II)]complexes of Emodin,the structure of the complexes were characterized by elementalanalyses, IR, UV-Vis, atomic absorption spectroscopy, TG-DSC, MS,1H-NMRand13C-NMR. The results showed that the9-carbonyl group and the1-phenolichydroxyl group of emodin coordinated to M(II), and formed six-membered ring. Thestoichiometric ratio of Emodin and Mn(II) is2:1. The structure of metal complexes is M(II)(Emodin)2.(2) Using the ultraviolet-visible spectrophotometer to analyze the free radicalscavenging activity of Emodin and its metal complexes. The results indicated that thecompounds exhibited antioxidant activity in a concentration-dependent manner. TheIC50values of five metal complexes were18.85-34.98μmol/L, and were lower than(Emodin)2and Vc. The results indicated that the antioxidant activity of emodin could be improved by coordinated with metal, and the metal also infulenced the antioxidantactivity of metal complexes. The metal complexes of emodin had excellent antioxidantactivity, and could prevent or treat diseases associated with oxidative stress, such as thecancer.(3) The interaction of Emodin metal complexes (metal: Cu(II), Co(II), Ni(II), Zn(II),Mn(II)) with DNA was investigated using UV-Vis spectra, fluorescence measurements,and viscosity measurements assay. The results showed that these complexes couldintercalate into the pairs of DNA. Comparing with the Kb and Kq constant, the metalcomplexes had stronger binding affinity than emodin with the order of Zn(II)(Emodin)2>Ni(II)(Emodin)2> Cu(II)(Emodin)2> Co(II)(Emodin)2> Mn(II)(Emodin)2>(Emodin)2.By coordinated with metal elements, the conjugated system of metal complexes isbigger than that of emodin, so the binding affinity of metal complexes is stronger thanemodin. In addition, the metal elements influenced the planar structure of complexes, sothe binding affinity is different from each other.(4) The anticancer activity and apoptosis mechanism of emodin metal complexesagainst the human cancer cells (Hep G2, HeLa, MCF-7, F10-B16, and MDA-MB-231)was tested by MTT assay, microscope observation, flow cytometry, and the molecularbiology technology. The results are listed as follows:I. It was found that emodin metal complexes had a significant inhibition to growthand proliferation of Hep G2, HeLa, MCF-7, MDA-MB-21and F10-B16human cancercell lines in a concentration-and time-dependent manner. The IC50values of the metalcomplexes against five cancer cells decreased approximately2-3times comparing withthose of (emodin)2and cisplatin, which meant that the anti-proliferative activity ofemodin metal complexes was stronger than that of emodin and cisplatin. Therein, HepG2, HeLa, and MCF-7cells were sensitive to complexes. The antitumor activity ofcomplexes was related to their DNA binding ability, and the order of the cytotoxicactivity of metal complexes in accordance with the binding affinity with DNA,II. After treatment with emodin metal complexes, morphological changes of cancercell lines were observed with microscope. The cells shrank and cell volumereducedwere observed, a decrease cell density was noticed and the apoptotic bodyappeared. As a result, emodin metal complexes could induce tumor cell apoptosis.III. Using flow cytometric analysis, the further studies was investigated on theinfluence of cancer cell cycles(HepG2, HeLa, MCF-7, and F10-B16cell lines) andapoptosis which were induced by emodin metal complexes. The results suggested that the cancer cells were arrested at G1phase in a concentration-dependent manner. Thecomplexes could extend the cell cycle. And then, the number of cells at S phase wasdecreased, which inhibited the proliferation of cancer cells. The deregulation of cellcycle had been reported to correlate with the induction of apoptosis. With the increasingconcentration of metal complexes, the number of early apoptotic cells also increased,which indicated that the metal complexes could induce the apoptosis cancer cells.IV. To discuss the molecular mechanisms of apoptosis, the effects of emodin metalcomplexes on expression of p53, p21, caspase-3, bcl-2, bax in Hep G2and MCF-7wereexamined by RT-PCR. The results exhibited that the metal complexes could activate p53gene, increase the expression of p21and bax gene, and decrease the expression of bcl-2,which reduce the ability of protection from apoptosis. The activation of caspase-3alsoinduced the cells apoptosis. Moreover, the complexes had serious influence on theexpression of p53, p21, caspase-3, bcl-2, bax in Hep G2, this result indicated that thecomplexes had stronger apoptosis function in Hep G2than that in MCF-7, which agreedwith MTT method.In this dissertation, we synthesized the metal complexes of emodin, andcharacterized the structure of complexes through comprehensive spectroscopic analysis.Moreover, we studied the antioxidant activity, the DNA-binding mode and anticanceractivity of the metal complexes, discussed the molecular mechanisms of anti-tumoractivity induced by metal complexes, which lay the foundation of development of newefficient antitumor drug, and provide a new consideration for novel drug design.