Mitochondrial toxicity of selective COX-2 inhibitors via inhibition of oxidative phosphorylation (ATP synthesis) in rat liver mitochondria

Cyclooxygenase-2 (COX-2) inhibitors (coxibs) are non-steroidal anti-inflammatory drugs (NSAIDs) designed to selectively inhibit COX-2. However, drugs of this therapeutic class are associated with drug induced liver injury (DILI) and mitochondrial injury is likely to play a role. The effects of selective COX-2 inhibitors on inhibition of oxidative phosphorylation (ATP synthesis) in rat liver mitochondria were investigated. The order of potency of inhibition of ATP synthesis was: lumiracoxib (IC₅₀: 6.48 ± 2.74 μM) > celecoxib (IC₅₀: 14.92 ± 6.40 μM) > valdecoxib (IC₅₀: 161.4 ± 28.6 μM) > rofecoxib (IC₅₀: 238.4 ± 79.2 μM) > etoricoxib (IC₅₀: 405.1 ± 116.3 μM). Mechanism based inhibition of ATP synthesis (K_inact 0.078 min^− 1 and K_I 21.46 μM and K_inact/K_I ratio 0.0036 min^− 1 μM^− 1) was shown by lumiracoxib and data suggest that the opening of the MPT pore may not be the mechanism of toxicity. A positive correlation (with r² = 0.921) was observed between the potency of inhibition of ATP synthesis and the log P values. The in vitro metabolism of coxibs in rat liver mitochondria yielded for each drug substance a major single metabolite and identified a hydroxy metabolite with each of the coxibs and these metabolites did not alter the inhibition profile of ATP synthesis of the parent compound. The results suggest that coxibs themselves could be involved in the hepatotoxic action through inhibition of ATP synthesis.     

Inhibitory effects of astaxanthin, β-cryptoxanthin,canthaxanthin, lutein,and zeaxanthin on cytochrome P450 enzyme activities

Astaxanthin, β-cryptoxanthin, canthaxanthin, lutein and zeaxanthin, the major xanthophylls, are widely used in food, medicine, and health care products. To date, no studies regarding the inhibitory effects of these xanthophylls on the nine CYPs isozymes have been reported. This study investigated the reversible and time-dependent inhibitory potentials of five xanthophylls on CYPs activities in vitro. The reversible inhibition results showed that the five compounds had only a weak inhibitory effect on the nine CYPs. Lutein did not inhibit the nine CYPs activities. Astaxanthin weakly inhibited CYP2C19, with an IC₅₀ of 16.2 μM; and β-cryptoxanthin weakly inhibited CYP2C8, with an IC₅₀ of 13.8 μM. In addition, canthaxanthin weakly inhibited CYP2C19 and CYP3A4/5, with IC₅₀ values of 10.9 and 13.9 μM, respectively. Zeaxanthin weakly inhibited CYP3A4/5, with an IC₅₀ of 15.5 μM. However, these IC₅₀ values were markedly greater than the C_max values reported in humans. No significant IC₅₀ shift was observed in the time-dependent inhibition screening. Based on these observations, it is unlikely that these five xanthophylls from the diet or nutritional supplements alter the pharmacokinetics of drugs metabolized by CYPs. These findings provide some useful information for the safe use of these five xanthophylls in clinical practice.     

Characterization of estrogenic and androgenic activity of phthalates by the XenoScreen YES/YAS in vitro assay

The presented study investigates and compares the estrogenic and androgenic activities of commonly used diesters of phthalic acid (phthalates) using the XenoScreen YES/YAS assay. Phthalates are commonly used plasticizers in polymers dedicated for i.e. food and drug containers. Since phthalates are not chemically bonded to the polymer, they can leach or migrate from the polymer. Therefore, phthalates are identified as contaminants in a variety of consumer products. Investigation of estrogenic and androgenic activities of phthalates (DEP, DBP, BBP, DEHP and DINP) showed no significant effect of tested substances either on hERα or hAR receptors. Phthalates exhibited strong anti-estrogenic (IC₅₀ for BBP = 8.66 μM, IC₅₀ for DEHP = 3.61 μM and IC₅₀ for DINP = 0.065 μM) and anti-androgenic (IC₅₀ for BBP = 5.30 μM, IC₅₀ for DEHP = 2.87 μM and IC₅₀ for DINP = 0.068 μM) activities.     

Cytotoxicity and genotoxicity of phenazine in two human cell lines

Phenazine was recently identified as a drinking water disinfection byproduct (DBP), but little is known of its toxic effects. We examined in vitro cytotoxicity and genotoxicity of phenazine (1.9–123 μM) in HepG2 and T24 cell lines. Cytotoxicity was determined by an impedance-based real-time cell analysis instrument. The BrdU (5-bromo-2′-deoxyuridine) proliferation and MTT ((3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide) viability assays were used to examine mechanisms of cytotoxicity. Genotoxicity was determined using the alkaline comet assay. Concentration-dependent cytotoxicity was observed in HepG2 cells, primarily due to an antiproliferative effect (BrdU 24 h IC₅₀: 11 μM; 48 h IC₅₀: 7.8 μM) observed as low as 1.9 μM. T24 cells experienced a minor antiproliferative effect (BrdU 24 h IC₅₀: 47 μM; 48 h IC₅₀: 17 μM). IC₅₀ values for HepG2 proliferation and viability were 54–77% lower compared to T24 cells. In both cell lines, IC₅₀ values for proliferation were 66–90% lower than those for viability. At phenazine concentrations producing equivalent cytotoxicity, HepG2 cells (1.9–30.8 μM) experienced no significant genotoxic effects, while T24 cells (7.7–123 μM) experienced significant genotoxicity at ⩾61.5 μM. While these effects were seen at phenazine concentrations above those found in disinfected water, the persistence of the antiproliferative effect and the differential toxicity in each cell line deserves further study.     

Preparation of Novel Analogues of the Nonredox-Type Non-Competitive Leukotriene Biosynthesis Inhibitor AKBA

AKBA (acetyl-11-keto-β-boswellic acid, 1 ) and KBA (11-keto-β-BA, 2 ) from Boswellia serrata Roxb. and Boswellia carterii Birdw. are direct, nonredox-type inhibitors of 5-lipoxygenase, the key enzyme for leukotriene biosynthesis (IC₅₀ = 1.5 and 3μM in intact neutrophils, respectively). In order to study the impact of the carboxyl function for enzyme inhibition, we synthesized novel analogues of boswellic acids. The C-4 alcohol derivative of KBA ( 4 ) still exerted 5-lipoxygenase inhibitory activity (IC₅₀ = 4.5 μM), whereas ( 8 ), the C-4 alcohol analogue of β-boswellic acid ( 7 ), the methyl ester analogue of KBA ( 5 ), and acetyl-11-keto-amyrin ( 9 ) possessed no inhibitory potential in concentrations up to 50 μM. These findings reveal that a hydrophilic group at C4 in combination with an 11-keto-function is essential for 5-lipoxygenase inhibition by boswellic acids.     

Discovery of soluble epoxide hydrolase inhibitors from natural products

With the goal of developing soluble epoxide hydrolase (sEH) inhibitors with novel chemical structures, the sEH inhibitory activities of 30 natural compounds were evaluated using both a fluorescent substrate, 3-phenyl-cyano(6-methoxy-2-naphthalenyl)methyl ester- 2-oxiraneacetic acid, and a physiological substrate, 14,15-epoxyeicosatrienoic acid. To evaluate the selectivity of sEH inhibition, the inhibition of microsomal epoxide hydrolase (mEH), which plays a critical role in detoxification of toxic epoxides, was determined using human liver microsomes. Honokiol and β-amyrin acetate, isolated from Magnolia officinalis and Acer mandshuricum, respectively, displayed strong inhibition of sEH activity, with respective IC₅₀ values of 0.57 μM and 3.4 μM determined using the fluorescent substrate, and 1.7 μM and 6.1 μM determined using 14,15-epoxyeicosatrienoic acid. mEH activity was decreased to 49% or 61% of control activity by 25 μM honokiol or β-amyrin acetate, respectively. These results suggest that β-amyrin acetate and honokiol exhibit sEH inhibitory activity, although their sEH selectivity should be improved.     

Selective inhibition of the cytochrome P450 isoform by hyperoside and its potent inhibition of CYP2D6

Hyperoside, quercetin-3-O-galactoside, is a flavonoid isolated from Oenanthe javanica. In the present study, we investigated potential herb-drug inhibitory effects of hyperoside on nine cytochrome P450 (CYP) isoforms in pooled human liver microsomes (HLMs) and human recombinant cDNA expressed CYP using a cocktail probe assay. Hyperoside strongly inhibited CYP2D6-catalyzed dextromethorphan O-demethylation, with IC₅₀ values of 1.2 and 0.81 μM after 0 and 15 min of preincubation, and a Ki value of 2.01 μM in HLMs, respectively. Hyperoside strongly decreased CYP2D6 activity dose-, but not time-, dependently in HLMs. In addition, the Lineweaver–Burk and Secondary plots for the inhibition of CYP2D6 in HLMs fitted a competitive inhibition mode. Furthermore, hyperoside decreased CYP2D6-catalyzed dextromethorphan O-demethylation activity of human recombinant cDNA-expressed CYP2D6, with an IC₅₀ value of 3.87 μM. However, other CYPs were not inhibited significantly by hyperoside. In conclusion, our data demonstrate that hyperoside is a potent selective CYP2D6 inhibitor in HLMs, and suggest that hyperoside might cause herb-drug interactions when co-administrated with CYP2D substrates.     

Toxic effects of xylazine on endothelial cells in combination with cocaine and 6-monoacetylmorphine

The use of xylazine as a drug of abuse has emerged worldwide in the last 7 years, including Puerto Rico. Clinical findings reported that xylazine users present greater physiological deterioration, than heroin users. The aim of this study was to assess the xylazine toxicity on endothelial cells, as this is one of the first tissues impact upon administration. Human umbilical vein endothelial cells in culture were treated with xylazine, cocaine, 6-monoacetylmorphine (heroin metabolite) and its combinations, at concentrations of 0.10–400 μM, for periods of 24, 48 and 72 h. IC₅₀ were calculated and the Annexin V assay implemented to determine the cell death mechanism. Results indicated IC₅₀ values at 24 h as follow: xylazine 62 μM, cocaine 210 μM, 6-monoacetylmorphine 300 μM. When these drugs were combined the IC₅₀ value was 57 μM. Annexin V results indicated cell death by an apoptosis mechanism in cells treated with xylazine or in combination. Results demonstrated that xylazine use inhibits the endothelial cell proliferation, at lower concentrations than cocaine and 6-monoacetylmorphine. These findings contribute to the understanding of the toxicity mechanisms induced by xylazine on endothelial cells.     

Development of novel N-linked aminopiperidine-based mycobacterial DNA gyrase B inhibitors: Scaffold hopping from known antibacterial leads

DNA gyrase of Mycobacterium tuberculosis (MTB) is a type II topoisomerase that ensures the regulation of DNA topology and has been genetically demonstrated to be a bactericidal drug target. We present the discovery and optimisation of a novel series of mycobacterial DNA gyrase inhibitors with a high degree of specificity towards the mycobacterial ATPase domain. Compound 5-fluoro-1-(2-(4-(4-(trifluoromethyl)benzylamino)piperidin-1-yl)ethyl)indoline-2,3-dione (17) emerged as the most potent lead, exhibiting inhibition of MTB DNA gyrase supercoiling assay with an IC₅₀ (50% inhibitory concentration) of 3.6 ± 0.16 μM, a Mycobacterium smegmatis GyrB IC₅₀ of 10.6 ± 0.6 μM, and MTB minimum inhibitory concentrations of 6.95 μM and 10 μM against drug-sensitive (MTB H37Rv) and extensively drug-resistant strains, respectively. Furthermore, the compounds did not show any signs of cardiotoxicity in zebrafish ether-à-go-go-related gene (zERG), and hence constitute a major breakthrough among the otherwise cardiotoxic N-linked aminopiperidine analogues.     

Synthesis and antiviral activities of a novel class of thioflavone and flavonoid analogues

A novel class of thioflavone and flavonoid derivatives has been prepared and their antiviral activities against enterovirus 71 (EV71) and the coxsackievirus B3 (CVB3) and B6 (CVB6) were evaluated. Compounds 7d and 9b showed potent antiviral activities against EV71 with IC₅₀ values of 8.27 and 5.48 μM, respectively. Compound 7f, which has been synthesized for the first time in this work, showed the highest level of inhibitory activity against both CVB3 and CVB6 with an IC₅₀ value of 0.62 and 0.87 μM. Compounds 4b, 7a, 9c and 9e also showed strong inhibitory activities against both the CVB3 and CVB6 at low concentrations (IC₅₀=1.42?7.15 μM), whereas compounds 4d, 7c, 7e and 7g showed strong activity against CVB6 (IC₅₀=2.91–3.77 μM) together with low levels of activity against CVB3. Compound 7d exhibited stronger inhibitory activity against CVB3 (IC₅₀=6.44 μM) than CVB6 (IC₅₀>8.29 μM). The thioflavone derivatives 7a, 7c, 7d, 7e, 7f and 7g, represent a new class of lead compounds for the development of novel antiviral agents.     

Old class but new dimethoxy analogue of benzimidazole: a bacterial topoisomerase I inhibitor

New antimicrobials are needed to combat drug resistance and have often been equated with the identification and exploitation of novel targets. This study focused on the synthesis of new benzimidazole analogues with improved DNA minor groove-binding affinity and having lower cytotoxicity to mammalian cells as well as selective targeting of bacterial DNA over host DNA. 5-(4-Methylpiperazin-1-yl)-2-[2′-(3,4-dimethoxyphenyl)-5′-benzimidazolyl]benzimidazole (DMA) cleared bacterial infections from mammalian cell culture without apparent cytotoxicity to mammalian cells. Moreover, DMA inhibited microbial topoisomerase over mammalian topoisomerase, with a 50% inhibitory concentration (IC₅₀) value for human topoisomerase I of >54 μM compared with an IC₅₀ of <10 μM for Escherichia coli topoisomerase I in vitro.     

Anti-leukemic effects of gallic acid on human leukemia K562 cells: Downregulation of COX-2, inhibition of BCR/ABL kinase and NF-κB inactivation

Gallic acid (GA) induces apoptosis in various cancer cell lines. In this study, we investigated the apoptotic activity induced by GA on chronic myeloid leukemia (CML) cell line-K562 and the underlying mechanism. GA reduced the viability of K562 cells in a dose and time dependent manner. GA led to G₀/G₁ phase arrest in K562 cells by promoting p21 and p27 and inhibiting the levels of cyclin D and cyclin E. Further studies indicated apoptosis with impaired mitochondrial function as a result of deranged Bcl-2/Bax ratio, leakage of cytochrome c and PARP cleavage along with DNA fragmentation and by up-regulating the expression of caspase-3. GA also activated the protein expressions of fatty acid synthase ligand and caspase-8. GA is more effective in imatinib resistant-K562 (IR-K562) cells (IC₅₀ 4 μM) than on K562 cells (IC₅₀ 33 μM). GA inhibited cyclooxygenase-2 (COX-2) in K562 as well as IR-K562 cells appears to be COX-2 involved in the suppression of growth. Interestingly, GA also inhibited BCR/ABL tyrosine kinase and NF-κB. In conclusion, GA induced apoptosis in K562 cells involves death receptor and mitochondrial-mediated pathways by inhibiting BCR/ABL kinase, NF-κB activity and COX-2.     

Identification and characterization of diarylimidazoles as hybrid inhibitors of butyrylcholinesterase and amyloid beta fibril formation

In this contribution, a chemical collection of aromatic compounds was screened for inhibition on butyrylcholinesterase (BChE)’s hydrolase activity using Ellman’s reaction. A set of diarylimidazoles was identified as highly selective inhibitors of BChE hydrolase activity and amyloid β (Aβ) fibril formation. New derivatives were synthesized resulting in several additional hits, from which the most active was 6c, 4-(3-ethylthiophenyl)-2-(3-thienyl)-1H-imidazole, an uncompetitive inhibitor of BChE hydrolase activity (IC₅₀ BChE = 0.10 μM; K_i = 0.073 ± 0.011 μM) acting also on Aβ fibril formation (IC₅₀ = 5.8 μM). With the aid of structure–activity relationship (SAR) studies, chemical motifs influencing the BChE inhibitory activity of these imidazoles were proposed. These bifunctional inhibitors represent good tools in basic studies of BChE and/or promising lead molecules for AD therapy.     

Anti-allergic activity of emodin on IgE-mediated activation in RBL-2H3 cells

BackgroundEmodin (1,3,8-trihydroxy-6-methylanthraquinone) is a Chinese herbal anthraquinone derivative from the rhizome of rhubarb (Rheum palmatum L.) that exhibits numerous biological activities, such as antitumor, antibacterial, antiinflammatory, and immunosuppressive. In the present studies, the anti-allergic activities of emodin were investigated to elucidate the underlying active mechanisms.MethodsThe inhibitory effects of emodin on the IgE-mediated allergic response in rat basophilic leukemia (RBL-2H3) cells were evaluated by measuring the release of granules and cytokines. The Ca²⁺ mobilization in RBL-2H3 cells loaded with the Ca²⁺-reactive fluorescent probe Fluo-4 AM was also measured by laser scanning confocal microscope.ResultsEmodin inhibited the release of β-hexosaminidase (β-HEX; IC₅₀ = 5.5 μM) and tumor necrosis factor (TNF)-α (IC₅₀ = 11.5 μM) from RBL-2H3 cells induced by 2,4-dinitrophenylated bovine serum albumin (DNP-BSA) and displayed stronger inhibition of β-HEX release than ketotifen fumarate salt (IC₅₀ = 63.8 μM). Emodin at a concentration of 12.5 μM also inhibited the DNP-BSA-induced influx of extracellular Ca²⁺ in RBL-2H3 cells.ConclusionsThese results suggested that emodin likely exhibits anti-allergic activities via increasing the stability of the cell membrane and inhibiting extracellular Ca²⁺ influx.     

Sub-anesthetic concentrations of (R,S)-ketamine metabolites inhibit acetylcholine-evoked currents in α7 nicotinic acetylcholine receptors

The effect of the (R,S)-ketamine metabolites (R,S)-norketamine, (R,S)-dehydronorketamine, (2S,6S)-hydroxynorketamine and (2R,6R)-hydroxynorketamine on the activity of α7 and α3β4 neuronal nicotinic acetylcholine receptors was investigated using patch-clamp techniques. The data indicated that (R,S)-dehydronorketamine inhibited acetylcholine-evoked currents in α7-nicotinic acetylcholine receptor, IC₅₀=55±6 nM, and that (2S,6S)-hydroxynorketamine, (2R,6R)-hydroxynorketamine and (R,S)-norketamine also inhibited α7-nicotinic acetylcholine receptor function at concentrations ≤1 μM, while (R,S)-ketamine was inactive at these concentrations. The inhibitory effect of (R,S)-dehydronorketamine was voltage-independent and the compound did not competitively displace selective α7-nicotinic acetylcholine receptor ligands [¹²⁵I]-α-bungarotoxin and [³H]-epibatidine indicating that (R,S)-dehydronorketamine is a negative allosteric modulator of the α7-nicotinic acetylcholine receptor. (R,S)-Ketamine and (R,S)-norketamine inhibited (S)-nicotine-induced whole-cell currents in cells expressing α3β4-nicotinic acetylcholine receptor, IC₅₀ 3.1 and 9.1 μM, respectively, while (R,S)-dehydronorketamine, (2S,6S)-hydroxynorketamine and (2R,6R)-hydroxynorketamine were weak inhibitors, IC₅₀ >100 μM. The binding affinities of (R,S)-dehydronorketamine, (2S,6S)-hydroxynorketamine and (2R,6R)-hydroxynorketamine at the NMDA receptor were also determined using rat brain membranes and the selective NMDA receptor antagonist [³H]-MK-801. The calculated K_i values were 38.95 μM for (S)-dehydronorketamine, 21.19 μM for (2S,6S)-hydroxynorketamine and>100 μM for (2R,6R)-hydroxynorketamine. The results suggest that the inhibitory activity of ketamine metabolites at the α7-nicotinic acetylcholine receptor may contribute to the clinical effect of the drug.     

Comparative in vitro and ex-vivo myelotoxicity of aflatoxins B1 and M1 on haematopoietic progenitors (BFU-E,CFU-E,and CFU-GM): Species-related susceptibility

Haemato- and myelotoxicity are adverse effects caused by mycotoxins. Due to the relevance of aflatoxins to human health, the present study, employing CFU-GM-, BFU-E- and CFU-E-clonogenic assays, aimed at (i) comparing, in vitro, the sensitivity of human vs. murine haematopoietic progenitors to AFB1 and AFM1 (0.001–50 μg/ml), (ii) assessing whether a single AFB1 in vivo treatment (0.3–3 mg/kg b.w.) alters the ability of murine bone marrow cells to form myeloid and erythroid colonies, and (iii) comparing the in vitro with the in vitro ex-vivo data.We demonstrated (i) species-related sensitivity to AFB1, showing higher susceptibility of human myeloid and erythroid progenitors (IC₅₀ values: about 4 times lower in human than in murine cells), (ii) higher sensitivity of CFU-GM and BFU-E colonies, both more markedly affected, particularly by AFB1 (IC₅₀: 2.45 ± 1.08 and 1.82 ± 0.8 μM for humans, and 11.08 ± 2.92 and 1.81 ± 0.20 μM for mice, respectively), than the mature CFU-E (AFB1 IC₅₀: 12.58 ± 5.4 and 40.27 ± 6.05 μM), irrespectively of animal species, (iii) regarding AFM1, a species- and lineage-related susceptibility similar to that observed for AFB1 and (iv) lack of effects after AFB1 in vivo treatment on the proliferation of haematopoietic colonies.     

Toxicity of the synthetic polymeric 3-alkylpyridinium salt (APS3) is due to specific block of nicotinic acetylcholine receptors

The in vivo and in vitro toxic effects of the synthetic polymeric 3-alkylpyridinium salt (APS3), from the Mediterranean marine sponge Reniera sarai, were evaluated on mammals, with emphasis to determine its mode of action. The median lethal doses of APS3 were 7.25 and higher that 20 mg/kg in mouse and rat, respectively. Intravenous administration of 7.25 and 20 mg/kg APS3 to rat caused a significant fall followed by an increase in mean arterial blood pressure accompanied by tachycardia. In addition, cumulative doses of APS3 (up to 60 mg/kg) inhibited rat nerve-evoked skeletal muscle contraction in vivo, with a median inhibitory dose (ID₅₀) of 37.25 mg/kg. When administrated locally by intramuscular injection to mouse, APS3 decreased the compound muscle action potential recorded in response to in vivo nerve stimulation, with an ID₅₀ of 0.5 mg/kg. In vitro experiments confirmed the inhibitory effect of APS3 on mouse hemidiaphragm nerve-evoked muscle contraction with a median inhibitory concentration (IC₅₀) of 20.3 μM, without affecting directly elicited muscle contraction. The compound inhibited also miniature endplate potentials and nerve-evoked endplate potentials with an IC₅₀ of 7.28 μM in mouse hemidiaphragm. Finally, APS3 efficiently blocked acetylcholine-activated membrane inward currents flowing through Torpedo nicotinic acetylcholine receptors (nAChRs) incorporated to Xenopus oocytes, with an IC₅₀ of 0.19 μM. In conclusion, our results strongly suggest that APS3 blocks muscle-type nAChRs, and show for the first time that in vivo toxicity of APS3 is likely to occur through an antagonist action of the compound on these receptors.     

The interactions of azure B,a metabolite of methylene blue,with acetylcholinesterase and butyrylcholinesterase

Methylene blue (MB) is reported to possess diverse pharmacological actions and is attracting increasing attention for the treatment of neurodegenerative disorders such as Alzheimer's disease. Among the pharmacological actions of MB, is the significant inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE). These activities may, at least in part, underlie MB's beneficial effects in Alzheimer's disease. MB is metabolized to yield N-demethylated products of which azure B, the monodemethyl metabolite, is the predominant species. Azure B has been shown to be pharmacologically active and also possesses a variety of biological actions. Azure B therefore may contribute to the pharmacological profile of MB. Based on these considerations, the present study investigates the possibility that azure B may, similar to MB, act as an inhibitor of human AChE and BuChE. The results document that azure B inhibits AChE and BuChE with IC₅₀ values of 0.486 μM and 1.99 μM, respectively. The results further show that azure B inhibits AChE and BuChE reversibly, and that the modes of inhibition are most likely competitive. Although the AChE and BuChE inhibitory activities of azure B are twofold and fivefold, respectively, less potent than those recorded for MB [IC₅₀(AChE) = 0.214 μM; IC₅₀(BuChE) = 0.389 μM] under identical conditions, azure B may be a contributor to MB's in vivo activation of the cholinergic system and beneficial effects in Alzheimer's disease.     

Synthetic polysulfane derivatives induce cell cycle arrest and apoptotic cell death in human hematopoietic cancer cells

Natural polysulfanes including diallyltrisulfide (DATS) and diallyltetrasulfide (DATTS) from garlic possess antimicrobial, chemopreventive and anticancer properties. However these compounds exhibit chemical instability and reduced solubility, which prevents their potential clinical applicability. We synthesized six DATS and DATTS derivatives, based on the polysulfane motif, expected to exhibit improved physical and chemical properties and verified their biological activity on human leukemia cells.We identified four novel cytotoxic compounds (IC₅₀ values: compound 1, 24.96 ± 12.37 μM; compound 2, 22.82 ± 4.20 μM; compound 3, 3.86 ± 1.64 μM and compound 5, 40.62 ± 10.07 μM, compared to DATTS: IC₅₀: 9.33 ± 3.86 μM). These polysulfanes possess excellent differential toxicity, as they did not affect proliferating mononuclear blood cells from healthy donors.We further demonstrated ability of active compounds to induce apoptosis in leukemia cells by analysis of nuclear fragmentation and of cleavage of effector and executioner caspases. Apoptosis was preceded by accumulation of cells in G2/M phase with a pro-metaphase-like nuclear pattern as well as microtubular alterations. Prolonged and persistent arrest of cancer cells in early mitosis by the benzyl derivative identifies this compound as the most stable and effective one for further mechanistic and in vivo studies.