Synthesis and Biological Evaluation of Gold(III) Substituted Tetraarylporphyrin Chlorides as Anticancer Reagents

Synthesis and Anticancer Activity of Gold Porphyrin Linked to Malonate Diamine Platinum Complexes

Recently, gold(III) porphyrins have gained great interest as anticancer drugs not only for the stability of gold(III) but also for the functionalization of the porphyrin to allow bridging with another metal such as platinum(II). We report here, for the first time, the synthesis of three new bimetal compounds containing a gold(III) porphyrin conjugated to a platinum diamine moiety through malonate bridging to obtain enhanced cytotoxicity from both metals combined with the phototoxicity of the porphyrin. The three complexes differ in the type of diamine ligand around platinum(II): ammonia (NH₃), cyclohexanediamine (CyDA), and pyridylmethylamine (Py). The synthesis was carried out using the complexation of activated malonic acid derivatives with aquadiaminoplatinum(II) complexes, and the products were characterized by IR, NMR, mass spectra, and elementary analysis. The cytotoxic activity of the conjugates was screened in both healthy cell lines and cancer cell lines, human fibroblast cells (FS-68) and human breast cancer cells (MCF-7), and was compared to that of the corresponding platinum(II) complexes. The cyclohexyldiamine (CyDA) derivative exhibited the greatest cytotoxic effect among the series. The results showed that Au(III)/Pt(II) conjugates are more potent by 2-5.6-fold than the corresponding platinum complexes. Moreover, the dyad AuP-PtCyDA is 18% more potent and also more selective toward cancer cells than the parent gold porphyrin substituted with malonic acid. On the other hand, the IC₅₀ of the dyad AuP-PtCyDA is 43% lower than that of AuTPP but is more selective toward healthy cells. Singlet oxygen measurements indicated that gold(III) porphyrin derivatives are poor oxygen sensitizers and cell death occurred potentially due to generation of other reactive oxygen species (ROS) upon reductive quenching of the gold porphyrin excited state. In addition, the increase in cancer cell death obtained after light irradiation is totally absent in healthy cells, demonstrating the specificity of this PDT treatment on cancer cells. Our findings imply that the incorporation of two different cytotoxic metals in the same molecule represents a remarkable cytotoxic effect in comparison to traditional homometallic Pt(II) drugs.

Gold(III) complexes in medicinal chemistry

A number of gold(III) compounds has been designed with the objective of overcoming the disadvantages associated with the platinum-based drugs for cancer treatment. Compounds of a remarkable structural manifold show significant antiproliferative effects in vitro against a number of cancer cells, including cisplatin resistant ones. The target of most of them is, unlike that of cisplatin, not the DNA. Although the mechanisms of action displayed by the gold compounds in biological media are still under investigation, many studies show evidence that the cellular targets are mitochondria-based. Recent advances in gold(III) medicinal chemistry also recommend such compounds for other pharmacological applications such as the treatment of viral or parasitic diseases. The radioactive isotopes 198Au and 199Au present potential in radiotherapy.

Gold(III) Tetraarylporphyrin Phosphonate Derivatives as Potential Anticancer Agents

5-[4-(Dialkyoxyphosphorylamino)]phenyl-10,15,20- triphenylporphyrinato gold(III)chlorides have been synthesised and evaluated for their in vitro cytotoxic activity against SMMC-7721 human hepatic and sarcoma 180 mouse cancer cell line panels. 5-[4-(Diisopropoxyphosphorylamino)]phenyl-10,15,20- triphenylporphyrinato gold(III)chloride exhibited significant growth inhibitory properties against sarcoma 180 mouse cancer cells (IC50 value = 2.60 μM) and 5-[4-(dipropoxyphosphorylamino)]phenyl-10,15,20-triphenylporphyrinato gold(III)chloride showed significant growth inhibitory properties against SMMC-7721 human hepatic cancer cells (IC50 value = 5.10 μM).

Synthesis and Cancer Cell Cytotoxicity of Gold(III) Tetraarylporphyrins with a C5-Carboxylate Substituent

Gold(III) tetraarylporphyrins with a C5-carboxylate substituent have been synthesised and their in vitro cytotoxic activity against SGC-7901 human gastric cancer cell line panel evaluated. The compound 5-[4-(4-ethoxycarbonylbut oxy)phenyl]-10,15,20-tri(4-methoxyphenyl)porphyrinatogold(III) chloride exhibited significant growth inhibitory properties against SGC-7901 human gastric cancer cells and afforded an IC50 value of 29 μM for 69.73% of the cell lines in the panel.