Synthesis and evaluation of the anti-mammary tumor activity and of the estrogenic side effects of [1,2-bis(2,6-dihalo-3-hydroxyphenyl)ethylenediamine]platinum(II) complexes

Investigating the antibacterial activity of salen/salophene metal complexes: Induction of ferroptosis as part of the mode of action

The continuous increase of resistant bacteria including Staphylococcus aureus and its methicillin-resistant phenotype (MRSA) is currently one of the major challenges in medicine. Therefore, the discovery of novel lead structures for the design of drugs to fight against infections caused by these bacteria is urgently needed. In this structure-activity relationship study, metal-based drugs were investigated for the treatment of resistant pathogens. The selected Ni(II), Cu(II), Zn(II), Mn(III), and Fe(II/III) complexes differ in their salen- and salophene-type Schiff base ligands. The in vitro activity was evaluated using gram-positive (S. aureus and MRSA) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa). Especially the iron(III) complexes displayed promising antimicrobial effects against gram-positive bacteria, with MIC₉₀ values ranging from 0.781 to 50 μg/mL. Among them, chlorido[(N,N'-bis(salicylidene)-1,2-phenylenediamine]iron(III) (6) showed the best MIC₉₀ value (0.781 μg/mL = 1.93 μmol/L) against S. aureus and MRSA. Complex 6 was comparably potent as ciprofloxacin against S. aureus (0.391 μg/mL = 1.18 μmol/L) and only marginally less active than tetracycline against MRSA (0.391 μg/mL = 0.88 μmol/L). As part of the mode of action, ferroptosis was identified. Applying compound 6 (10 μg/mL), both gram-positive strains grown in PBS were killed within 20 min. This efficacy basically documents that salophene iron(III) complexes represent possible lead structures for the further development of antibacterial metal complexes.

Synthesis, characterization, and evaluation of cis-diphenyl pyridineamine platinum(II) complexes as potential anti-breast cancer agents

Although cisplatin is considered as an effective anti-cancer agent, it has shown limitations and may produce toxicity in patients. Therefore, we synthesized two cis-dichlorideplatinum(II) compounds (13 and 14) composed of meta- and para-N,N-diphenyl pyridineamine ligands through a reaction of the amine precursors and PtCl2 with respective yields of 16 and 47 %. We hypothesized that compounds 13 and 14, with lipophilic ligands, should transport efficiently in cancer cells and demonstrate more effectiveness than cisplatin. When tested for biological activity, compounds 13 and 14 were found to inhibit the growth of MCF 7 and MDA-MB-231 cells (IC50s 1 ± 0.4 µM and 1 ± 0.2 µM for 13 and 14, respectively, and IC50 7.5 ± 1.3 µM for compound 13 and 1 ± 0.3 µM for compound 14). Incidentally, these doses were found to be lower than cisplatin doses (IC50 5 ± 0.7 µM for MCF 7 and 10 ± 1.1 µM for MDA-MB-231). Similar to cisplatin, 13 and 14 interacted with DNA and induced apoptosis. However, unlike cisplatin, they blocked the migration of MDA-MB-231 cells suggesting that in addition to apoptotic and DNA-binding capabilities, these compounds are useful in blocking the metastatic migration of breast cancer cells. To delineate the mechanism of action, computer-aided analyses (DFT calculations) were conducted for compound 13. Results indicate that in vivo, the pyridineamine ligands are likely to dissociate from the complex, forming a platinum DNA adduct with anti-proliferative activity. These results suggest that complexes 13 and 14 hold promise as potential anti-cancer agents.

Fluorescent chemodosimeter for selective detection of cyanide in water

A coumarin-based fluorescent chemodosimeter with a salicylaldehyde functionality as a binding site has been developed for selective detection of cyanide anions over other anions in water at biological pH.

Platinum(II) complexes interfering with testicular steroid biosynthesis: drugs for the therapy of advanced or recurrent prostate cancers? Preclinical studies

[Meso-1,2-bis(2,6-dihalo-3/4-hydroxyphenyl)ethylenediamine]platinum(II) complexes (meso-1-PtLL': 2,6-F(2),3-OH; meso-2-PtLL': 2,6-F(2),4-OH; meso-3-PtLL': 2,6-Cl(2),3-OH; meso-4-PtLL': 2,6-Cl(2),4-OH; L = OH(2), L' = OSO(3) or L,L' = Cl(2)) were designed with the aim to get drugs comprising both cytotoxic and testosterone level lowering potencies. It is assumed that such compounds are more efficient than the established endocrine therapeutic measures and can affect the development of hormone refractory prostate cancer (PC). With exception of meso-3-PtLL' all Pt-complexes and the comparison compound cisplatin significantly reduced the testosterone level in experiments on male rats. However, in the test on the Dunning R3327 PC of the rat only cisplatin and meso-4-PtLL' showed a significant anti-tumor activity at well-tolerated dose ranges. Meso-4-PtLL' also significantly extended the time to disease progression in comparison with orchiectomy in this tumor model. Interestingly, the relapsed tumor, too, responded to meso-4-PtLL' as demonstrated in a long-term study on orchiectomized rats bearing Dunning R3327 PC grafts. This effect cannot be ascribed to cytotoxic effects of meso-4-PtLL' because of its inactivity on the human LNCaP/FGC PC cell line. Therefore, the contribution of an additional mechanism to the anti-prostate cancer activity of meso-4-PtLL', presumably owing to its estrogenic potency, must be considered. This assumption was supported by test results with diethylstilbestrol (DES) (non-steroidal estrogen) on the Dunning R3327 PC of the rat relapsed after orchiectomy. This tumor model was strongly inhibited by DES. The possible mode of action of meso-4-PtLL' is thoroughly discussed.

Tumour-inhibiting platinum complexes--state of the art and future perspectives

Thirty years after the onset of the first clinical studies with cisplatin, the development of antineoplastic platinum drugs continues to be a productive field of research. This article reviews the current preclinical and clinical status, including a discussion of the molecular basis for the activity of the parent drug cisplatin and platinum drugs of the second and third generation, in particular their interaction with DNA. Further emphasis is laid on the development of third generation platinum drugs with activity in cisplatin-resistant tumours, particularly on chelates containing 1,2-diaminocyclohexane (DACH) and on the promising and more recently evolving field of non-classic ( trans- and multinuclear) platinum complexes. The development of oral platinum drugs and drug targeting strategies using liposomes, polymers or low-molecular-weight carriers in order to improve the therapeutic index of platinum chemotherapy are also covered.

Biphenyls as surrogates of the steroidal backbone. Part 1: synthesis and estrogen receptor affinity of an original series of polysubstituted biphenyls

In the course of a programme aimed at discovering new ligands of the estrogen receptor, we explored a series of substituted biphenyls. Their synthesis and binding affinity are described.

Effect of a diphenylethylenediamine platinum complex on steroidogenesis in rats

Although less cytotoxic, the new platinum complex [meso-1,2-bis(2,6-difluoro-4-hydroxyphenyl)-ethylenediamine]sulfatopl atinum (II) (2) is equipotent to cisplatin (1) in the oestrogen-dependent MXT mammary tumour of the mouse. As this may be due to oestrogen level-lowering properties, we compared the effect of 1 and 2 on steroidogenesis in the rat. A single dose of 1 and 2 (20 mumol/kg s.c.) decreased plasma testosterone level in male rats by 90% (1, day 3) and 80% (2, day 7). Luteinizing hormone level remained unchanged in intact and in ovariectomized rats. The activities of the following testicular enzymes were decreased (day 7): cholesterol side-chain cleavage enzyme (1: 33%; 2: 36%), 3 beta-hydroxysteroid dehydrogenase/delta 4,delta 5-isomerase (1: 31%; 2: 48%) and 17 alpha-hydroxylase/17,20-lyase (1: 21%; 2: 15%). Testicular microsomal cytochrome P450 content was also diminished (1: 60%; 2: 49%, day 7). Corticosterone level in plasma and biosynthesis in adrenal explants was not affected, indicating the selectivity of action at the gonadal level. In vitro, neither 1 nor 2 (2 and 20 microM) influenced binding of human chorionic gonadotropin to testis interstitial cells during an observation period up to 21 h. These results suggest that 1 and 2 act at the gonadal level by inhibiting the expression of the steroidogenic enzymes. They do not, however, inactivate the luteinizing hormone receptor.

Third generation antitumor platinum(II) complexes of the [1-(fluoro/difluorophenyl)-2-phenylethylenediamine]platinum(II) type

The diastereomeric 1-(fluoro/difluorophenyl)-2-phenylethylene-diamines (4-fluoro: erythro-1/threo-1; 2,4-difluoro: erythro-2/-threo-2; 2,6-difluoro: erythro-3/threo-3) and the diastereomeric 1-(4-fluorophenyl)-2-(3-hydroxyphenyl)ethylenediamines (erythro-4/-threo-4) were synthesized from appropriately substituted stilbenes by reaction with IN3 and subsequent LiAlH4 reduction. Coordination of the 1,2-diphenylethylenediamines to platinum was carried out by use of K2PtI4. The water-soluble aquasulfato-platinum(II) complexes (erythro/threo-1-PtSO4-erythro/threo-4-PtSO4) were obtained from the diiodoplatinum(II) complexes by reaction with Ag2SO4. Additionally erythro/threo-1-PtSO4 and erythro/threo-4-PtSO4 were transformed into the dichloroplatinum(II) complexes (erythro/threo-1-PtCl2, erythro/threo-4-PtCl2) by treatment with KCl. In contrast to the less effective erythro-configurated sulfatoplatinum(II) complexes the threo-analogues showed comparable or even superior activities to cisplatin on the human MDA-MB-231 breast cancer cell line. On the MXT-M-3.2 breast cancer of the mouse only erythro- and threo-4-PtSO4 caused similar effects like cisplatin. The strong inhibitory effect of the diastereomeric sulfatoplatinum(II) complexes on the P-388 leukemia of the mouse was equal to that of cisplatin. On the latter tumor threo-4-PtCl2 was the most active among the less toxic dichloroplatinum(II) derivatives.

Aqua[1,1-bis(4-hydroxyphenyl)-1,2-diamino-2-phenylethane]- sulfatoplatinum(II), a new compound for the treatment of the mammary carcinoma

The highly estrogen receptor(ER)-affinic compound 1,1-bis(4-hydroxyphenyl)-2-phenylethane (BHPE) was used as carrier ligand for a new cisplatin derivative, aqua[1,1-bis(4-hydroxyphenyl)-1,2-diamino-2-phenylethane]sulfatoplati num (II) (3-PtSO4) for the therapy of the ER-positive (i.e. hormone sensitive) breast cancer. The diamine ligand 1,1-bis(4-hydroxyphenyl)-1,2-diamino-2-phenylethane (3) was synthesized by transformation of the O-methyl ether derivative of BHPE into the 1,2-bisazido compound 3b with IN3/NaN3, reduction of both N3 residues into NH2 groups [3a] and subsequent ether cleavage with BBr3. From the diamine ligand 3 and K2PtI4 a five-membered chelate 3-PtI2 was obtained which was transformed into 3-PtSO4 with Ag2SO4. In comparison to BHPE the ER-affinity of 3-PtSO4 is markedly reduced. 3-PtSO4 possesses, however, weak cytotoxic activity (P388) and antiestrogenic, but no estrogenic properties. 3-PtSO4 is comparable with BHPE in terms of its activity on the hormone sensitive MXT-M 3.2 breast cancer of the mouse.