Verubulin (Azixa) Analogues with Increased Saturation: Synthesis, SAR and Encapsulation in Biocompatible Nanocontainers Based on Ca2+ or Mg2+ Cross-Linked Alginate

Tubulin-targeting agents attract undiminished attention as promising compounds for the design of anti-cancer drugs. Verubulin is a potent tubulin polymerization inhibitor, binding to colchicine-binding sites. In the present work, a series of verubulin analogues containing a cyclohexane or cycloheptane ring 1,2-annulated with pyrimidine moiety and various substituents in positions 2 and 4 of pyrimidine were obtained and their cytotoxicity towards cancer and non-cancerous cell lines was estimated. The investigated compounds revealed activity against various cancer cell lines with IC50 down to 1-4 nM. According to fluorescent microscopy data, compounds that showed cytotoxicity in the MTT test disrupt the normal cytoskeleton of the cell in a pattern similar to that for combretastatin A-4. The hit compound (N-(4-methoxyphenyl)-N,2-dimethyl-5,6,7,8-tetrahydroquinazolin-4-amine) was encapsulated in biocompatible nanocontainers based on Ca2+ or Mg2+ cross-linked alginate and it was demonstrated that its cytotoxic activity was preserved after encapsulation.

New Organometallic Ru(II) Compounds with Lonidamine Motif as Antitumor Agents

The combination of one molecule of organic and metal-based fragments that exhibit antitumor activity is a modern approach in the search for new promising drugs. In this work, biologically active ligands based on lonidamine (a selective inhibitor of aerobic glycolysis used in clinical practice) were introduced into the structure of an antitumor organometallic ruthenium scaffold. Resistant to ligand exchange reactions, compounds were prepared by replacing labile ligands with stable ones. Moreover, cationic complexes containing two lonidamine-based ligands were obtained. Antiproliferative activity was studied in vitro by MTT assays. It was shown that the increase in the stability in ligand exchange reactions does not influence cytotoxicity. At the same time, the introduction of the second lonidamine fragment approximately doubles the cytotoxicity of studied complexes. The ability to induce apoptosis and caspase activation in tumour cell MCF7 was studied by employing flow cytometry.

Biological Activity of Novel Organotin Compounds with a Schiff Base Containing an Antioxidant Fragment

A series of novel organotin(IV) complexes on the base of 2-(N-3',5'-di-tert-butyl-4'-hydroxyphenyl)-iminomethylphenol (L) of formulae Me₂SnBr₂(L)₂ (1), Bu₂SnCl₂(L)₂(2), Ph₂SnCl₂(L) (3), Ph₂SnCl₂(L)₂ (4) Ph₃SnBr(L)₂ (5) were synthesized and characterized by ¹H, ¹³C, ¹¹⁹Sn NMR, IR, ESI-MS and elemental analysis. The crystal structures of initial L and complex 2 were determined by XRD method. It was found that L crystallizes in the orthorhombic syngony. The distorted octahedron geometry around Sn center is observed in the structure of complex 2. Intra- and inter-molecular hydrogen bonds were found in both structures. The antioxidant activity of new complexes as reducing agents, radical scavengers and lipoxygenase inhibitors was estimated spectrophotometrically in CUPRAC and DPPH tests (compounds 1 and 5 were found to be the most active in both methods), and in the process of enzymatic oxidation in vitro of linoleic acid under the action of lipoxygenase LOX 1-B (EC₅₀ > 33.3 μM for complex 2). Furthermore, compounds 1-5 have been investigated for their antiproliferative activity in vitro towards HCT-116, MCF-7 and A-549 and non-malignant WI-38 human cell lines. Complexes 2 and 5 demonstrated the highest activity. The plausible mechanisms of the antiproliferative activity of compounds, including the influence on the polymerization of Tb+MAP, are discussed. Some of the synthesized compounds have also actively induced apoptosis and blocked proliferation in the cell cycle G2/M phase.

Is antitumor Pt(IV) complex containing two axial lonidamine ligands a true dual- or multi-action prodrug?

This work studied the mechanism of action of a Pt(IV) complex 2 bearing two axial lonidamine ligands, which are selective inhibitors of aerobic glycolysis. The presence of two lonidamine ligands in 2 compared to the parent Pt(II) complex increased its antiproliferative activity, cellular accumulation, and changed its cell cycle profile and mechanism of cell death. In 3D cell culture, 2 showed exceptional antiproliferative activity with IC50 values as low as 1.6 μM in MCF7 cells. The study on the influence of the lonidamine ligands in the Pt complex on glycolysis showed only low potency of ligands to affect metabolic processes in cancer cells, making the investigated complex, not a dual- or multi-action prodrug. However, the Pt(IV) prodrug effectively delivers the cytotoxic Pt(II) complex into cancer cells.

Bicyclic Isoxazoline Derivatives: Synthesis and Evaluation of Biological Activity

The application of non-planar scaffolds in drug design allows for the enlargement of the chemical space, and for the construction of molecules that have more effective target-ligand interactions or are less prone to the development of resistance. Among the works of the last decade, a literature search revealed spirothiazamenthane, which has served as a lead in the development of derivatives active against resistant viral strains. In this work, we studied the novel molecular scaffold, which resembles spirothiazamenthane, but combines isoxazoline as a heterocycle and cyclooctane ring as a hydrophobic part of the structure. The synthesis of new 3-nitro- and 3-aminoisoxazolines containing spiro-fused or 1,2-annelated cyclooctane fragments was achieved by employing 1,3-dipolar cycloaddition of 3-nitro-4,5-dihydroisoxazol-4-ol 2-oxide or tetranitromethane-derived alkyl nitronates with non-activated alkenes. A series of spiro-sulfonamides was obtained by the reaction of 3-aminoisoxazoline containing a spiro-fused cyclooctane residue with sulfonyl chlorides. Preliminary screening of the compounds for antiviral, antibacterial, antifungal and antiproliferative properties in vitro revealed 1-oxa-2-azaspiro[4.7]dodec-2-en-3-amine and 3a,4,5,6,7,8,9,9a-octahydrocycloocta[d]isoxazol-3-amine with activity against the influenza A/Puerto Rico/8/34 (H1N1) virus in the submicromolar range, and high values of selectivity index. Further study of the mechanism of the antiviral action of these compounds, and the synthesis of their analogues, is likely to identify new agents against resistant viral strains.

Effect of Hybrid Organotin Compound on Activity of LPO and Antioxidant Protection of the Liver Tissues in Animals with Melanoma B16

The central element of the "metastatic organotropism" is a shift of the pro/antioxidant balance in cells and activation of oxidative stress and protective antioxidant systems. We studied the effects of bis(3,5-di-tert-butyl-4-hydroxyphenylthiolate)dimethylol (Me-3) in the maximum effective and toxic total doses on the level of markers of oxidative stress and antioxidant protection in the liver of mice with melanoma B16 before the appearance of macroscopic metastases. In 48 h after tumor inoculation, Me-3 was administered intraperitoneally once a day for 5 days in total doses of 375 and 500 mg/kg according to the classical method. Administration of the hybrid organotin compound Me-3 produced different effects on the pro/antioxidant state of the microenvironment of liver tissue as the target of melanoma B16 metastasis. The results suggest that inversion of the anti/prooxidant profile of Me-3 is determined by its dose.

Evaluation of the pharmacological activity of hybrid organotin compounds in a B16 melanoma model in the classical and metronomic administration modes

Introduction: In modern medical chemistry, much attention is paid to the search for new antimetastatic agents based on metal compounds. Organotin compounds promise to be good candidates as the treatment of malignant neoplasms. In order to reduce a possible nonspecific toxic effect of tin compounds and to expand the intended therapeutic use, the paper presents hybrid tin (IV) complexes with Sn-S bond containing a fragment of 2,6-di-tert-butylphenol. The aim of the study was to evaluate the antitumor and antimetastatic effects of bis (3,5-di-tert-butyl-4-hydroxyphenylthiolate) dimethylolol (Me3) and (3,5-di-tert-butyl-4-hydroxyphenylthiolate) triphenylolol (Me5) in a model of transplanted melanoma tumor in B16 mice in classical and metronomic administration mode.

Materials and methods: The efficacy of organotin compounds was studied in a model of a transplanted tumor with spontaneous metastasis of C57Bl/6 (female) melanoma B16 mice using the following indicators: average life expectancy, inhibition of tumor growth by weight, tumor mass, and metastasis inhibition index.

Results and discussion: The most pronounced antimetastatic effect (54% and 36%) is achieved with a five-fold intraperitoneal injection of Me3 and Me5 at the total doses of 375 mg/kg and 250 mg/kg. The comparable results of the efficacy were obtained in the classical and metronomic modes of the injection of hybrid organotin compounds. With an increase in the injected dose, there is an effect of activating the tumor process with the generalized metastasis.

Conclusion: Bis dimethylolol (Me3) and triphenylolol (Me5) compounds demonstrate both a pronounced antimetastatic activity and a multidirectional effect on the growth of the primary focus and the metastasis in lungs, depending on an injected dose.

Novel substituted 5-methyl-4-acylaminoisoxazoles as antimitotic agents: Evaluation of selectivity to LNCaP cancer cells

A series of novel antimitotic agents was designed using the replacement of heterocyclic cores in two tubulin-targeting lead molecules with the acylated 4-aminoisoxazole moiety. Target compounds were synthesized via heterocyclization of β-aryl-substituted vinylketones by tert-butyl nitrite in the presence of water as a key step. 4-Methyl-N-[5-methyl-3-(3,4,5-trimethoxyphenyl)isoxazol-4-yl]benzamide (1aa) was found to stimulate partial depolymerization of microtubules of human lung carcinoma A549 cells at a high concentration of 100 µM and to totally inhibit cell growth (IC₅₀  = 0.99 µM) and cell viability (IC₅₀  = 0.271 µM) in the nanomolar to submicromolar concentration range. These data provide evidence of the multitarget profile of the cytotoxic action of compound 1aa. The SAR study demonstrated that the 3,4,5-trimethoxyphenyl residue is the key structural parameter determining the efficiency both towards tubulin and other molecular targets. The cytotoxicity of 3-methyl-N-[5-methyl-3-(3,4,5-trimethoxyphenyl)isoxazol-4-yl]benzamide (1ab) to the androgen-sensitive human prostate adenocarcinoma cancer cell line LNCaP (IC₅₀  = 0.301 µM) was approximately one order of magnitude higher than that to the conditionally normal cells lines WI-26 VA4 (IC₅₀  = 2.26 µM) and human umbilical vein endothelial cells (IC₅₀  = 5.58 µM) and significantly higher than that to primary fibroblasts (IC₅₀  > 75 µM).

Metallodrug Profiling against SARS-CoV-2 Target Proteins Identifies Highly Potent Inhibitors of the S/ACE2 interaction and the Papain-like Protease PLpro

The global spread of the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has called for an urgent need for dedicated antiviral therapeutics. Metal complexes are commonly underrepresented in compound libraries that are used for screening in drug discovery campaigns, however, there is growing evidence for their role in medicinal chemistry. Based on previous results, we have selected more than 100 structurally diverse metal complexes for profiling as inhibitors of two relevant SARS-CoV-2 replication mechanisms, namely the interaction of the spike (S) protein with the ACE2 receptor and the papain-like protease PLpro . In addition to many well-established types of mononuclear experimental metallodrugs, the pool of compounds tested was extended to approved metal-based therapeutics such as silver sulfadiazine and thiomersal, as well as polyoxometalates (POMs). Among the mononuclear metal complexes, only a small number of active inhibitors of the S/ACE2 interaction was identified, with titanocene dichloride as the only strong inhibitor. However, among the gold and silver containing complexes many turned out to be very potent inhibitors of PLpro activity. Highly promising activity against both targets was noted for many POMs. Selected complexes were evaluated in antiviral SARS-CoV-2 assays confirming activity for gold complexes with N-heterocyclic carbene (NHC) or dithiocarbamato ligands, a silver NHC complex, titanocene dichloride as well as a POM compound. These studies might provide starting points for the design of metal-based SARS-CoV-2 antiviral agents.

Impact of organotin compounds on the growth of epidermoid Lewis carcinoma

Introduction: Search for new compounds with a broad antitumor and antimetastatic potency due to multiple targeting remains important in medicinal chemistry, pharmacology and oncology. We report the efficacy of hybrid organotin agents bis-(3,5-di-tert-butyl-4-hydroxyphenylthiolate) dimethyltin (Ме3) and (3,5-di-tert-butyl-4-hydroxyphenylthiolate) triphenyltin (Ме5).

Materials and methods: The compounds were administered to mice bearing the spontaneously metastatic epidermoid Lewis lung carcinoma (LLC). The efficacy of the treatment was evaluated by mean life span, percentage of tumor growth inhibition, number of lung metastases, frequency of metastasis, tumor weight 21 days after tumor cell inoculation, and a degree of lung damage according to the method of D. Tarin and J.E. Price.

Results and discussion: For new organotin compounds containing an antioxidant protective fragment of 2,6-di-tert-butylphenol, moderate antitumor and pronounced antimetastatic effects were revealed in the Lewis model of epidermoid lung carcinoma; more active for Me5. Some features of the development of the process of metastasis were recorded with the introduction of various doses of hybrid organotin compounds.

Conclusion: Substances Ме3 and Ме5 possess specific activity on the model under investigation, which allows one to suggest these organotins as promising series of antitumor and antimetastatic agents with multiple targeting mode of action.

Ru(III) Complexes with Lonidamine-Modified Ligands

A series of bifunctional Ru(III) complexes with lonidamine-modified ligands (lonidamine is a selective inhibitor of aerobic glycolysis in cancer cells) was described. Redox properties of Ru(III) complexes were characterized by cyclic voltammetry. An easy reduction suggested a perspective for these agents as their whole mechanism of action seems to be based on activation by metal atom reduction. New compounds demonstrated a more pronounced antiproliferative potency than the parental drug; individual new agents were more cytotoxic than cisplatin. Stability studies showed an increase in the stability of complexes along with the linker length. A similar trend was noted for antiproliferative activity, cellular uptake, apoptosis induction, and thioredoxin reductase inhibition. Finally, at concentrations that did not alter water solubility, the selected new complex evoked no acute toxicity in Balb/c mice.

[Conjugate of podophyllotoxin with chlorambucil: synthesis, biological testing and molecular modeling]

In the present work we have studied a novel conjugate of the DNA alkylating agent chlorambucil with podophyllotoxin, a ligand of the colchicine binding site in tubulin. The target compound was obtained by Steglich esterification of podophyllotoxin with the percentage yield of 41%. Results of biotesting carried out on the carcinoma A549 cell line revealed that at a concentration of 2 μM the conjugate caused full depolymerization of microtubules without any other effect on free tubulin. The conjugate inhibited proliferation (IC50=135±30 nM) and growth (EC50=240±30 nM) of A549 cells. The data of computer molecular docking of the novel compound into the 3D model of the colchicine binding site in α,β-tubulin and molecular dynamics modelling allowed to explain the observed difference in effects of chlorambucil-podophyllotoxin and chlorambucil-colchicine conjugates on microtubules.

Cryoprotective activity of phosphorus-containing phenol

The antioxidant and cryoprotective efficiencies of a 3,5-di-tert-butyl-4-hydroxyphenyl)methylenediphosphonic acid (MDPA) differ significantly for sperm cells of various species of sturgeon fish (Russian sturgeon, beluga and Stellate sturgeon). The ability of phosphorus-containing phenol MDPA to decrease the level of lipid peroxidation of sperm, beneficial effect on the activity indicators of the sperm of native sturgeon and of the defrosted one after deep freezing as well as on the fertility of sperm cells was shown.

Novel selective anticancer agents based on Sn and Au complexes. Mini-review

Cancer is one of the most common causes of death in modern medicine. Molecular design of novel substances with pharmacological activity is one of the goals of medicinal inorganic chemistry. Platinum complexes are widely used in the treatment of cancer, despite high efficacy their use is limited by side effects, as well as primary or acquired resistance. In this regard, the search for novel metal-containing antitumor compounds is underway. Organotins and gold compounds are promising pharmacological agents with anti-cancer properties. The introduction of protective antioxidant fragments into inorganic compounds molecules is a way to reduce the side effects of anti-cancer drugs on healthy cells. 2,6-dialkylphenols belonging to vitamin E (α-tocopherol) mimetics are widely used as antioxidants and stabilizers. The properties of Ph3SnCl (Sn-I), Ph3PAuCl (Au-I) and complexes Ph3SnSR (Sn-II) and Ph3PAuSR (Au-II) based on 2,6-di-tert-butyl-4-mercaptophenol (RSH) as radical scavengers and reducing agents were studied in model reactions. For Sn-II and Au-II the comparative study of cytotoxic action was made and the IC50 values on different cancer cell lines were found to be depended on the nature of metal. In general, Sn(IV) complexes possessed higher cytotoxicity than Au(I) complexes. In order to clarify the mechanism of cytotoxic mode of action the effect of compounds on Fe3+-induced lipid peroxidation, mitochondrial potential and mitochondrial permeability, cell cycle and induction of apoptosis was studied. Organotin compounds can bind tubulin SH-groups and inhibit its polymerization by a dose-dependent mechanism, whereas gold compounds inhibit Thioredoxin reductase (TrxR). In vivo experiments on acute toxicity of Sn-II and Au-II proved their moderate toxic action that opens prospects for the further study as antitumor agents.

New Derivatives of Bacteriopurpurin with Thiolated Au (I) Complexes: Dual Darkand Light Activated Antitumor Potency

BACKGROUND

Conventional antitumor Photosensitizers (PS) are normally low toxic in the dark whereas light activation triggers massive cell death (photodynamic therapy, PDT).

OBJECTIVE

To expand the therapeutic potential of PS to dual potency cytocidal agents, taking advantage of the use of bacteriopurpurin for a deeper tissue penetration of light, and suitability of the tetrapyrrolic macrocycle for chemical modifications at its periphery.

METHODS

Conjugation of a pro-oxidant thiolate Au (I) moiety to the bacteriopurpurin core and evaluation of cytotoxicity in cell culture and in vivo.

RESULTS

New water-soluble derivatives showed micromolar cytotoxicity for cultured human tumor cell lines in the dark, including the subline with an altered drug response due to p53 inactivation. Cellular PDT with the selected conjugate, thiolate Au (I)-dipropoxybacteriopurpurinimide (compound 6) with two triphenylphosphine Au fragments, triggered rapid (within minutes) cell death. Damage to the plasma membrane (necrosis) was a hallmark of cell death by compound 6 both in the dark and upon light activation. Furthermore, one single i.v. injection of compound 6 caused retardation of transplanted syngeneic tumors at the tolerable dose. Illumination of tumors that accumulated compound 6 significantly synergized with the effect of 6 in the dark.

CONCLUSION

Complexes of virtually non-toxic, photoactivatable bacteriopurpurin with the gold-containing organic moiety are considered the dual potency antitumor agents, tentatively applicable for intractable tumors.

The antioxidant 2,6-di-tert-butylphenol moiety attenuates the pro-oxidant properties of the auranofin analogue

Metal-based drugs are gaining momentum as a rapidly developing area of medicinal inorganic chemistry. Among gold pharmaceuticals, auranofin is a well known antirheumatic drug. The efficacy of gold-organic complexes largely depends on their pro-oxidant properties since auranofin targets the redox enzyme thioredoxin reductase (TrxR). However, an uncontrollable oxygen burst may be harmful for healthy cells; therefore, the search for chemical modifications to attenuate oxidation-related general toxicity of gold containing anti-inflammatory drugs is justified. In this study, we demonstrate that the incorporation of a specific antioxidant phenol fragment can counterbalance the pro-oxidative potential of the Au containing complex molecule. The electrochemical studies of AuPPh₃SR (1, R= 3,5-di-tert-butyl-4-hydroxyphenyl) and its precursors AuPPh₃Cl (2) and RSH (3) showed that complex 1 and phenol 3 efficiently scavenged the radicals (as detected by cyclic voltammetry) whereas 2 had no effect. Compound 1 inhibited TrxR in vitro with IC₅₀ 0.57 ± 0.15 μM, a value one order of magnitude bigger than the potency reported for auranofin. Compound 1 (5 mg kg^-1 daily gavage for 14 days) caused a decrease in ex vivo spontaneous and ascorbate-induced lipid peroxidation in the homogenates of rat lung, heart muscle, spleen, liver, kidneys, testicles and brain as assessed by the thiobarbituric acid reactive substances. Importantly, in animals fed with 1, no discernible general toxicity was registered suggesting that this compound is well tolerated. Our results provide evidence for an efficient synthetic route to obtain gold containing anti-inflammatory drug candidates with balanced pro/anti-oxidative properties.

Hybrid metal complexes with opposed biological modes of action – promising selective drug candidates

The oxidative stress is considered to be involved in the pathogenesis of many diseases. The antioxidative defense system in the living organism regulates the toxic impact of ROS and there is strong evidence that the antioxidants prevent some pathologies including cancer. The specific chemical properties of metal-based drugs impart innovative pharmacological profiles to this type of therapeutic agents, most likely in relation to novel biomolecular mechanisms. This review will focus on a novel approach to design polyfunctional metal-based physiollogically active compounds with opposed modes of action – prooxidant metal center and antioxidant 2,6-dialkylphenol group. The synthesis and anti/prooxidant activity and cytotoxicity studies of novel organometallic/coordination compounds (ferrocenes, complexes with di-(2-picolyl)amine ligand, porphyrins, pyridines, thiols, carboxylates) based on either biogenic metals (Fe, Mn, Co, Cu, Zn, Ni) or exogenic metals (Sn, Au, Rh) are presented and discussed. The results allow us to conclude that combining in one molecule a redox active metal center and cytoprotective functional organic moiety with antioxidative function is a promising way to rational metallodrug design in modern medicinal chemistry.

Synthesis and biological evaluation of novel 5-hydroxylaminoisoxazole derivatives as lipoxygenase inhibitors and metabolism enhancing agents

A versatile synthesis of novel 5-hydroxylaminoisoxazoles bearing adamantane moieties has been accomplished using the heterocyclization reactions of readily available unsaturated esters by the treatment with tetranitromethane in the presence of triethylamine and subsequent reduction of resulting 5-nitroisoxazoles by SnCl2 with the participation of THF. A number of obtained isoxazole derivatives were evaluated for their antioxidative activity, inhibition of lipoxygenases and impact on the rat liver mitochondria. The majority of tested compounds demonstrated moderate antiradical activity in DPPH test (up to EC50 16μM). The same compounds strongly inhibited soybean lipoxygenase (up to IC50 0.4μM) and Fe(2+)- and Fe(3+)-induced lipid peroxidation (LP) of rat brain cortex homogenate (up to IC50 0.3μM). All tested isoxazole derivatives promoted the phosphorylating respiratory activity simultaneously with maximal stimulated respiratory activity of mitochondria and do not reveal any toxicity towards the primary culture of rat cortex neurons.

Protein ruthenation and DNA alkylation: chlorambucil-functionalized RAPTA complexes and their anticancer activity

The conjugation of chlorambucil to the RAPTA scaffold results in an anticancer active agent capable of cross-linking DNA and proteins.

Metal-based antioxidants--potential therapeutic candidates for prevention the oxidative stress-related carcinogenesis: mini-review

The oxidative stress that is associated with the abnormal level of reactive oxygen species (ROS) is considered to be involved in the carcinogenesis process. The antioxidative defense system in the living organism regulates the toxic impact of ROS and there is strong evidence that the antioxidants prevent carcinogenesis. This review will focus on a novel approach to design synthetic metal-based antioxidants and to study their in vitro, ex vivo and in vivo activities in the cellular oxidation processes that might be involved in promotion of carcinogenesis. The antioxidants are divided into several groups depending on the nature of the ligands used: 2,6-dialkylphenols, flavonoids, polyphenols, peptides, purines, pyridines and their derivatives. Some currently achieved results in testing metal complexes as antioxidants show that they could potentially facilitate the scavenging of excess ROS, and thus restore redox balance in the damaged cells and organs. Therefore there is a strong need of the design of novel potential therapeutic candidates for prevention the oxidative stress-related carcinogenesis based on metal complexes.

Oleic acid peroxidation in the presence of metallo-porphyrins

The influence of free bases of meso-tetrakis(3,5-di-tert-butyl-4-hydroxy-phenyl)porphyrins and meso-tetraphenylporphyrins and their complexes of Co , Ni , Cu , Pt upon the radical chain oxidation of oleic acid as model substrates for lipid peroxidation has been studied. It was shown that the introduction of the antioxidative phenolic fragment into the porphyrin ring leads to the dual activity of phenolic porphyrins when compared with their tetraphenyl substituted analogues in substrate oxidation. Free base phenolic porphyrins and their nickel, copper, platinum complexes demonstrate acute inhibitory effect upon oleic acid peroxidation due to the key role of 2,6-di-tert-butylphenol moities, whereas cobalt porphyrin exhibits dual activity associated with the presence of both the redox active metal center and phenolic group.

Biological studies of new organotin(IV) complexes of thioamide ligands

New organotin(IV) complexes with heterocyclic thioamides 2-mercapto-benzothiazole (Hmbzt), 5-chloro-2-mercapto-benzothiazole (Hcmbzt) and 2-mercapto-benzoxazole (Hmbzo) of formulae [(C(6)H(5))(3)Sn(mbzt)] (1), [(C(6)H(5))(3)Sn(cmbzt)] (3) and [(C(6)H(5))(2)Sn(cmbzt)(2)] (4), together with the already known [(C(6)H(5))(3)Sn(mbzo)] (2), [(n-C(4)H(9))(2)Sn(cmbzt)(2)] (5) and [(CH(3))(2)Sn(cmbzt)(2)] (6) were used to study their influence on the peroxidation of oleic acid. The influence of complexes (3)-(6) upon peroxidation of oleic acid showed that the formation of reactive radicals caused the initiation of the chain radical oxidation of the substrate. The influence of complexes (1)-(6) upon the catalytic peroxidation of linoleic acid by the enzyme lipoxygenase (LOX) was also studied and compared to those of cisplatin. Compounds (1)-(6) were finally tested for in vitro cytotoxicity against leiomyosarcoma cells.

The role of radical reactions in organomercurials impact on lipid peroxidation

The organomercury compounds RHgX and R(2)Hg are broad-spectrum biocidal agents acting via diverse mechanisms in biological systems. Despite the enormous amount of studies carried out in last decades to elucidate the detailed mechanisms of organomercurials toxicity their biomolecular mode of action is still under debate. Among various toxicity mechanisms the action of RHgX and R(2)Hg at the membrane level due to the lipophilic properties of their molecules is discussed. Organomercurials are supposed to induce membrane associated oxidative stress in living organism through different mechanisms including the enhancement of the lipid peroxidation and intracellular generation of reactive oxygen species (ROS), H(2)O(2), O(2)(-), HO(). The perturbation of antioxidative defense system and the peroxidation of unsaturated fatty acids in membrane lipid bilayer are consequences of this impact. On the other hand, the involvement of organomercurials in radical and redox biochemical processes is manifested in carbon to metal bond cleavage that leads to the generation of reactive organic radicals R(). This pathway is discussed as one of the multiple mechanisms of organomercurials toxicity. The goal of this review is to present recent results in the studies oriented towards the role of organomercurials in the xenobiotic-mediated enhancement of radical production and hence in the promotion of lipids peroxidation. The application of natural and synthetic antioxidants as detoxification agents is presented.