The biological activity of Zeise's salt and its derivatives.

With the aim to design new biologically active bioinorganic drugs of aspirin, whose mode of action is based on the inhibition of the cyclooxygenase(COX) enzymes, derivatives of Zeise's salt were synthesized in this structure-activity relationship study. Surprisingly, not only these Zeise-aspirin compounds but also Zeise's salt itself showed high inhibitory potency against COX enzymes in in vitro assays. In contrast, potassium tetrachloroplatinate and cisplatin did not influence the enzyme activity at equimolar concentrations. It was demonstrated by LC-ESI tandem-mass spectrometry that Zeise's salt platinates the essential amino acids Tyr385 (active site of the enzyme) and Ser516 (will be acetylated by aspirin) of COX-1, thereby strongly impairing the function of the enzyme. This finding demonstrates for the first time that Zeise's salt is pharmacologically active and is a potent enzyme inhibitor.

Synthesis, characterisation and biological evaluation of copper and silver complexes based on acetylsalicylic acid.

Metalcarbonyl complexes with ligands derived from acetylsalicylic acid demonstrated high cytotoxic potential against various tumor cell lines and strong inhibition of the cyclooxygenase enzymes COX-1 and 2. In this study we tried to achieve comparable effects with [alkyne]silver or copper trifluoromethanesulfonate complexes which are more hydrophilic then the uncharged metalcarbonyl derivatives. All compounds were evaluated for growth inhibition against breast (MCF-7, MDA-MB 231) and colon cancer (HT-29) cell lines and for COX-1 and COX-2 inhibitory effects at isolated isoenzymes. Pure ligands showed neither cytotoxic nor COX-inhibitory effects. While the silver complexes of (but-2-ynyl)-2-acetoxybenzoate (But-ASS-Ag) and (but-2-yne-1,4-diyl)-bis(2-acetoxybenzoate) (Di-ASS-But-Ag) were strong cytostatics, only the copper complex Di-ASS-But-Cu was active. At the COX enzymes the complexes were more effective than their ligands and aspirin.

Investigations on cytotoxicity and anti-inflammatory potency of licofelone derivatives.

A series of C5-substituted licofelone ([2,2-dimethyl-6-(4-chlorophenyl)-7-phenyl-2,3-dihydro-1H-pyrrolizin-5-yl]acetic acid) derivatives were developed by a parallel synthesis approach and investigated for cytotoxicity against MCF-7 and MDA-MB-231 cells as well as for anti-inflammatory potency in vitro and in vivo. Dependent on the C5-substituent, the compounds showed high selectivity for MCF-7 cells. Especially 2-oxoethyl benzoate derivatives were inactive at the MDA-MB-231 cell line and as active as 5-FU at MCF-7 cells. C5-acetyl (8a), -2-oxoethyl formiate (8e), -2-oxoethyl acetate (8f) and -2-oxoethyl propionate (8g) derivatives showed growth inhibition at both cell lines, comparable with cisplatin. Modifications significantly reduced the inhibitory potency at COX-1 and COX-2 in vitro and in the xylene-induced ear swelling assay in mice. Only compound 8a was equipotent to licofelone, ibuprofen and celecoxibe in vivo.

[Cyclopentadienyl]metalcarbonyl complexes of acetylsalicylic acid as neo-anticancer agents.

[(Prop-2-ynyl)-2-acetoxybenzoate]dicobalthexacarbonyl (Co-ASS), a derivative of the nonsteroidal anti-inflammatory drug aspirin(®) (ASS), demonstrated high cytotoxic potential against various tumor cells. The [acetylene]Co(2)(CO)(6) cluster strongly increased the biological effects compared to aspirin(®). In this study we evaluated the use of [cyclopentadienyl]metalcarbonyl as cytotoxic moiety with a broader series of metals: molybdenum, manganese, cobalt and rhodium. All compounds were tested for cytotoxicity against breast (MCF-7, MDA-MB-231) and colon cancer (HT-29) cell lines. Their COX-1 and COX-2 inhibitory effects were evaluated at isolated isoenzymes. Additionally, the influence on the level of the major COX metabolite prostaglandin E(2) (PGE(2)) was quantified in MDA-MB-231 breast cancer cells. Whereas the pure ligands or ASS did not show any cytotoxic effect, all metal complexes inhibited the tumor cell growth. The inhibitory effects at COX-1 and COX-2 enzymes were low. Only the Prop-Cp-ASS-Rh complex (10 µM) caused an important inhibition of COX-1 by 60% and COX-2 by 30%. ASS showed at the same concentration only a marginal repression of COX-1 activity (30%) and no effect on COX-2.

Synthesis and biological activities of transition metal complexes based on acetylsalicylic acid as neo-anticancer agents.

[(µ(4)-η(2))-(Prop-2-ynyl)-2-acetoxybenzoate]dicobalthexacarbonyl (Co-ASS), a derivative of aspirin (ASS), demonstrated high growth-inhibitory potential against various tumor cells with interference in the arachidonic acid cascade as probable mode of action. The significance of the kind of metal and cluster was verified in this structure-activity study: Co(2)(CO)(6) was respectively exchanged by a tetrameric cobalt-, trimeric ruthenium-, or trimeric ironcarbonyl cluster. Furthermore, the metal binding motif was changed from alkyne to 1,3-butadiene. Compounds were evaluated for growth inhibition, antiproliferative effects, and apoptosis induction in breast (MCF-7, MDA-MB 231) and colon cancer (HT-29) cell lines and for COX-1/2 inhibitory effects at isolated isoenzymes. Additionally, the major COX metabolite prostaglandin E2 (PGE(2)) was quantified in arachidonic acid-stimulated MDA-MB 231 breast tumor cells. It was demonstrated that the metal cluster was of minor importance for effects on cellular activity if an alkyne was used as ligand. Generally, no correlation existed between growth inhibition and COX activity. Cellular growth inhibition and antiproliferative activity at higher concentrations of the most active compounds Prop-ASS-Co(4) and Prop-ASS-Ru(3) correlated well with apoptosis induction.