A new mixed ligand–silver(I) complex of formula [Ag(tpp)2(p-Hbza)] (1) (p-HbzaH = 4-hydroxybenzoic acid and tpp = triphenylphosphine) has been synthesized and characterized by elemental analysis, mp, vibrational spectroscopy (mid- and far-FT-IR), 1H-NMR, UV-vis, ESI-MS spectroscopic techniques and X-ray crystallography. Complex 1 and the already known mixed ligand–silver(I) complexes of formulae [Ag(tpp)2(salH)] (2) (salH2 = salicylic acid or 2-hydroxy-benzoic acid) and {[Ag(tpp)3(asp)](dmf)} (3) (aspH = o-acetylsalicylic acid) were used for the clarification of the cytostatic activity mechanism. Thus, 1–3 were tested for their in vitro cytotoxic activity against leiomyosarcoma (LMS) and human breast adenocarcinoma (MCF-7) cells with trypan blue and Thiazolyl Blue Tetrazolium Bromide (MTT) assays. For both cell lines, complexes 1–3 were found to be more active than cisplatin. Due to the morphology of the LMS cells after incubation with 1–3, the type of cell death was evaluated by flow cytometry assay and DNA fragmentation. The results show that LMS cells undergo programmed cell death (apoptosis). DNA binding tests indicate the ability of complexes 1–3 to modify the activity of the cells. The binding constants of 1–3 towards calf-thymus DNA (CT-DNA) ((27.7 ± 7.9) × 104 (1), (13.3 ± 6.5) × 104 (2) and (11 ± 2.8) × 104 (3) M−1) indicate strong interaction. Moreover, the influence of complexes 1–3 on the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX) was kinetically studied. Finally, docking studies on DNA binding interactions were performed.

Mixed ligand-silver(I) complexes with anti-inflammatory agents which can bind to lipoxygenase and calf-thymus DNA, modulating their function and inducing apoptosis.

Lipoxygenase activity associated to isolated soybean plasma membranes

Crystals of Ph3SnCl (1) were grown from a methanol/acetonitrile solution. Compounds [Ph3SnOH]n (2) and [(Ph2Sn)4Cl2O2(OH)2] (3) were crystallized from diethyl ether/methanol/acetonitrile and hot acetone/water solutions respectively, of the white precipitation, formed by adding KOH to solutions of 1 and [Ph2SnCl2] in 1 : 1 and 1 : 2 molar ratios respectively. Complex 1 was characterized by X-ray crystallography. X-ray structure determination of compounds 2 and 3 confirmed the previously reported identities. The molecular structure of 1, reported here, is a new polymorphic form of the known one for Ph3SnCl. Four independent [Ph3SnCl] molecules constitute the crystal structure of 1. The moieties are packed in two pairs in a tail-to-tail arrangement. Complexes 1–3 were evaluated for their in vitro cytotoxic activity (cell viability) against human cancer cell lines: HeLa (human cervical), MCF-7 (breast, estrogen receptor (ER) positive), MDA-MB-231 (breast, ER negative), A549 (lung), Caki-1 (kidney carcinoma), 786-O (renal adenocarcinoma), K1 (thyroid carcinoma), and the normal human lung cell line MRC-5 (normal human fetal lung fibroblast cells) versus, the normal immortalized human mammary gland epithelial cell line MTSV17 with a sulforhodamine B (SRB) assay. The results show potent cytotoxic activity of the complexes against all cell lines used, which was superior to that of cisplatin (CDDP). Compounds 1–3 showed higher activity against breast cancer cells MCF-7 (ER positive) than against of MDA-MB-231 (ER negative). These findings prompted us to search for possible interaction of these complexes with other cellular elements of fundamental importance in cell proliferation. The influence of these complexes 1–3 upon the catalytic peroxidation of linoleic acid to hydroperoxylinoleic acid by the enzyme lipoxygenase (LOX), as well as their binding affinity towards calf thymus-DNA, were kinetically and theoretically studied.

Structural and In Vitro Biological Studies of Organotin(IV) Precursors; Selective Inhibitory Activity Against Human Breast Cancer Cells, Positive to Estrogen Receptors

O2 uptake by tissue extracts in the presence of linoleic acid is generally ascribed to lipoxygenase. Such an O2 uptake can be observed not only with mitochondria of Solanum tuberosum L. and Arum maculatum L. and pure lipoxygenase but also with cytochrome c. However, the rate of oxidation is highly dependent on the procedure used to prepare the solutions of linoleic acid. Unless special care is taken to prevent contact between linoleic acid and O2, it appears that linoleic acid hydroperoxide is readily formed. This derivative can be readily oxidized by mitochondria or cytochrome c. On the other hand, the use of a rapid and specific enzymic procedure to estimate the disappearance of linoleic acid demonstrates that linoleic acid itself is not consumed at any appreciable rate by mitochondria or cytochrome c, the true substrate being linoleic acid hydroperoxide. During the reaction, the heme nucleus of added cytochrome c or of mitochondrial cytochromes undergoes deep alterations. Therefore, caution should be exerted when equating an O2 uptake observed in the presence of linoleic acid to a lipoxygenase activity. The same holds true for the similarity of reaction towards specific inhibitors between lipoxygenase and the cyanide-insensitive pathway oxidase.

I.G. Borisova

Papers

Investigation of lipoxygenase functions in chloroplasts and mitochondria from Pisum sativum seedlings