A novel tetrazole analogue of resveratrol is a potent anticancer agent

A series of novel tetrazole analogues of resveratrol were synthesized and evaluated for their anti-leukemic activity against an extensive panel of human cancer cell lines and against the MV4-11 AML cell line. These molecules were designed as drug-like derivatives of the resveratrol analogue DMU-212 and its cyano derivatives. Four compounds 8g, 8h, 10a and 10b exhibited LD₅₀ values of 4.60?µM, 0.02?µM, 1.46?µM, and 1.08?µM, respectively, against MV4-11 leukemia cells. The most potent compounds, 8h and 10b, were also found to be active against an extensive panel of human hematological and solid tumor cell lines; compound 8h was the most potent compound with GI₅₀ values <10?nM against more than 90% of the human cancer cell lines in the 60-cell panel. Analogues 8g, 8h, 10a and 10b were also tested for their ability to inhibit the polymerization of tubulin, and compound 8h was found to be the most potent analogue. Molecular modeling studies demonstrated that 8h binds to the colchicine binding site on tubulin. Thus, compound 8h is considered to be a lead druglike molecule from this tetrazole series of compounds.     

Tridemethylisovelleral, a potent cytotoxic agent

The synthesis and in vitro cytotoxicity toward various tumor cell lines of (+/-)-tridemethylisovelleral, an analogue of the bioactive fungal sesquiterpene (+)-isovelleral retaining the bicyclo[4,1,0]hept-2-en-1,2-dicarbaldehyde system but lacking the three methyl groups, is reported. The cytotoxicity of tridemethylisovelleral toward several tumor cell lines was found to be comparable with those of established antitumor drugs, and significantly higher than that of isovelleral.     

New analogue of arenastatin A, a potent cytotoxic spongean depsipeptide, with anti-tumor activity

Two analogues possessing steric hindered substituents on C-15 of arenastatin A (1), a potent cytotoxic spongean depsipeptide, were synthesized and shown to enhance stability in mouse serum. Notably, 15-tert-butylanalogue (6) with higher cytotoxicity exhibited in vivo anti-tumor activity through iv administration different from 1. Additionally, conformation analysis among the two analogues and arenastatin A (1) indicated that the torsion angle from C-14 to C-20 is a conclusive factor for the potent cytotoxicity of 1.     

Sangivamycin, a nucleoside analogue, is a potent inhibitor of protein kinase C

Protein kinase C functions prominently in cell regulation via its pleiotropic role in signal transduction processes. Certain oncogene products resemble elements involved in transmembrane signaling, elevate cellular sn-1,2-diacylglycerol second messenger levels, and activate protein kinase C. Sangivamycin was unique among the nucleoside compounds tested in its ability to potently inhibit protein kinase C activity. Inhibition was competitive with respect to ATP for both protein kinase C and the catalytic fragment of protein kinase C prepared by trypsin digestion. Sangivamycin was a noncompetitive inhibitor with respect to histone and lipid cofactors (phosphatidylserine and diacylglycerol). Sangivamycin inhibited native protein kinase C and the catalytic fragment identically, with apparent Ki values of 11 and 15 microM, respectively. Sangivamycin was an effective an inhibitor of protein kinase C as H-7, an isoquinolinsulfonamide. Sangivamycin did not inhibit [3H]phorbol-12,13-dibutyrate binding to protein kinase C. Sangivamycin did not exert its action through the lipid binding/regulatory domain; inhibition was not affected by the presence of lipid or detergent. Unlike H-7, sangivamycin selectively inhibited protein kinase C compared to cAMP-dependent protein kinase. The discovery that protein kinase C is inhibited by sangivamycin and other antitumor agents suggests that protein kinase C may be a target for rational design of antitumor compounds.     

Shrimp thioredoxin is a potent antioxidant protein

Thioredoxin (TRX) is a main component of the redox homeostasis machinery in the cell and it is required for ribonucleotide reductase function among others. In invertebrates, the redox balance is compromised during disease and changes in the physiological state and it is one of the components of the innate immune response. In this work, the shrimp (Litopenaeus vannamei) LvTRX cDNA was sequenced, cloned and over-expressed in bacteria to further characterize the function of the recombinant protein. LvTRX was able to reduce insulin disulfides and it was a better antioxidant compared to reduced glutathione and ascorbic acid, by means of the Trolox Equivalent Antioxidant Capacity (TEAC) assay. Interestingly, LvTRX contains aside of the canonical active site CXXC disulfide motif, one Cys (C73) residue in the interface of a putative dimer previously reported for human TRX. Using qRT-PCR, we found that shrimp LvTRX is mainly expressed in gills and pleopods; the variation of LvTRX mRNA upon hypoxia and re-oxygenation is not statistically significant. LvTRX stands as an important antioxidant that must be considered in future physiological and immune challenges studies.     

Curcumin is a potent DNA hypomethylation agent

Molecular docking of the interaction of curcumin and DNMT1 suggested that curcumin covalently blocks the catalytic thiolate of C1226 of DNMT1 to exert its inhibitory effect. This was validated by showing that curcumin inhibits the activity of M. SssI with an IC₅₀ of 30 nM, but no inhibitory activity of hexahydrocurcumin up to 100 μM. In addition, curcumin can induce global DNA hypomethylation in a leukemia cell line.     

Actinonin, a naturally occurring antibacterial agent, is a potent deformylase inhibitor

Peptide deformylase (PDF) is essential in prokaryotes and absent in mammalian cells, thus making it an attractive target for the discovery of novel antibiotics. We have identified actinonin, a naturally occurring antibacterial agent, as a potent PDF inhibitor. The dissociation constant for this compound was 0.3 x 10(-)(9) M against Ni-PDF from Escherichia coli; the PDF from Staphylococcus aureus gave a similar value. Microbiological evaluation revealed that actinonin is a bacteriostatic agent with activity against Gram-positive and fastidious Gram-negative microorganisms. The PDF gene, def, was placed under control of P(BAD) in E. coli tolC, permitting regulation of PDF expression levels in the cell by varying the external arabinose concentration. The susceptibility of this strain to actinonin increases with decreased levels of PDF expression, indicating that actinonin inhibits bacterial growth by targeting this enzyme. Actinonin provides an excellent starting point from which to derive a more potent PDF inhibitor that has a broader spectrum of antibacterial activity.     

Discovery,synthesis and in combo studies of a tetrazole analogue of clofibric acid as a potent hypoglycemic agent

A tetrazole isosteric analogue of clofibric acid (1) was prepared using a short synthetic route and was characterized by elemental analysis, NMR (¹H, ¹³C) spectroscopy, and single-crystal X-ray diffraction. The in vitro inhibitory activity of 1 against 11β-hydroxysteroid dehydrogenase type 1 (11β-HSD1) was evaluated, showing a moderate inhibitory enzyme activity (51.17% of inhibition at 10 μM), being more active than clofibrate and clofibric acid. The antidiabetic activity of compound 1 was determined at 50 mg/Kg single dose using a non insulin dependent diabetes mellitus rat model. The results indicated a significant decrease of plasma glucose levels, during the 7 h post-administration. Additionally, we performed a molecular docking of 1 into the ligand binding pocket of one subunit of human 11β-HSD1. In this model, compound 1 binds into the catalytic site of 11β-HSD1 in two different orientations. Both of them, show important short contacts with the catalytic residues Ser 170, Tyr 183, Asp 259 and also with the nicotinamide ring of NADP⁺.     

In planta production of the highly potent resveratrol analogue pterostilbene via stilbene synthase and O-methyltransferase co-expression

Resveratrol and related stilbenes are thought to play important roles in defence responses in several plant species and have also generated considerable interest as nutraceuticals owing to their diverse health-promoting properties. Pterostilbene, a 3,5-dimethylether derivative of resveratrol, possesses properties similar to its parent compound and, additionally, exhibits significantly higher fungicidal activity in vitro and superior pharmacokinetic properties in vivo. Recombinant enzyme studies carried out using a previously characterized O-methyltransferase sequence from Sorghum bicolor (SbOMT3) demonstrated its ability to catalyse the A ring-specific 3,5-bis-O-methylation of resveratrol, yielding pterostilbene. A binary vector was constructed for the constitutive co-expression of SbOMT3 with a stilbene synthase sequence from peanut (AhSTS3) and used for the generation of stably transformed tobacco and Arabidopsis plants, resulting in the accumulation of pterostilbene in both species. A reduced floral pigmentation phenotype observed in multiple tobacco transformants was further investigated by reversed-phase HPLC analysis, revealing substantial decreases in both dihydroquercetin-derived flavonoids and phenylpropanoid-conjugated polyamines in pterostilbene-producing SbOMT3/AhSTS3 events. These results demonstrate the potential utility of this strategy for the generation of pterostilbene-producing crops and also underscore the need for the development of additional approaches for minimizing concomitant reductions in key phenylpropanoid-derived metabolites.     

N-acetyl-sphingenine-1-phosphate is a potent calcium mobilizing agent.

Calcium mobilization induced by phosphorylated sphingoid bases was analyzed in calf pulmonary artery endothelial cells by confocal microscopy. A sphingenine-1-phosphate (SeP) analogue, N-acetyl-sphingenine-1-phosphate (N-C2-SeP), exogenously added to these cells, caused a fast and transient intracellular rise in calcium and was as potent as SeP. A minimal concentration of 0.6 nM for N-C2-SeP versus 1 nM for SeP was determined. The N-C2-SeP-induced Ca2+-signaling, like the response to SeP, was due to a release from thapsigargin-sensitive, ryanodine-insensitive, intracellular Ca2+-stores and not to a Ca2+-influx. N-C2-SeP can be considered as a truncated ceramide-phosphate, a lipid already reported to be mitogenic (Gomez-Munoz, A., Duffy, P.A., Martin, A., O'Brien, L., Byun, H.S., Bittman, R. and Brindley, D.N. (1995) Mol. Pharmacol. 47, 833-839), an effect that might be secondary to Ca2+-mobilization.     

Synthesis of 15,20-triamide analogue with polar substituent on the phenyl ring of arenastatin A, an extremely potent cytotoxic spongean depsipeptide

In order to increase metabolic stability and water solubility of arenastatin A, an extremely potent cytotoxic depsipeptide from the Okinawan marine sponge of Dysidea arenaria, several 15,20-triamide analogues with a polar substituent on the phenyl ring were synthesized. The 15,20-triamide analogues with a polar substituent (24, 30, and 31) showed increased solubility to MeOH and stronger cytotoxicity against KB cells in comparison with the parental 15,20-triamide analogue (2). Furthermore, the diethylamine analogue (30) exhibited in vivo anti-tumor activity against subcutaneously implanted murine sarcoma.     

Ricin B chain converts a non-cytotoxic antibody-ricin A chain conjugate into a potent and specific cytotoxic agent

A method is described for the preparation of partially and fully phosphorylated chicken gizzard myosin. When fully phosphorylated it possessed an actin-activated Mg2+-ATPase of similar specific activity to that of mammalian skeletal muscle myosin. The Mg2+-ATPase activity of these preparations was related in a non-linear fashion to increasing phosphorylation of the P light chain. When P light chain phosphorylation occurred during enzymic assay the Mg2+-ATPase activity remained constant. Fully phosphorylated preparations of gizzard myosin possessed an actin-activated Mg2+-ATPase that was not Ca2+-sensitive, whereas the Mg2+-ATPase of partially phosphorylated myosin preparations was Ca2+-sensitive.     

白藜芦醇及其水溶性衍生物的合成

目的:合成白藜芦醇及其水溶性衍生物。方法:以3,5-二甲氧基苯甲醛和4-甲氧基碘苯为原料,经Wittig反应,Heck偶联,脱甲基反应,连接侧链等合成白藜芦醇及其衍生物,并使用紫外法测定其在水中的溶解度大小。结果:目标化合物经核磁共振氢谱,质谱等确证为白藜芦醇及其水溶性衍生物,且水溶性提高3倍。结论:该方法的反应路线步骤短,操作简便,对反式产物选择性高。     

The ND2 subunit is labeled by a photoaffinity analogue of asimicin, a potent complex I inhibitor

NADH:ubiquinone oxidoreductase (complex I) is the entry enzyme of mitochondrial oxidative phosphorylation. To obtain the structural information on inhibitor/quinone binding sites, we synthesized [³H]benzophenone-asimicin ([³H]BPA), a photoaffinity analogue of asimicin, which belongs to the acetogenin family known as the most potent complex I inhibitor. We found that [³H]BPA was photo-crosslinked to ND2, ND1 and ND5 subunits, by the three dimensional separation (blue-native/doubled SDS-PAGE) of [³H]BPA-treated bovine heart submitochondrial particles. The cross-linking was blocked by rotenone. This is the first finding that ND2 was photo-crosslinked with a potent complex I inhibitor, suggesting its involvement in the inhibitor/quinone-binding.     

Pyrrolidine dithiocarbamate is a potent antioxidant against hypochlorous acid-induced protein damage

The antioxidant potential of the dithiol compound pyrrolidine dithiocarbamate (PDTC) against protein damage induced by hypochlorous acid (HOCl) was investigated. The effects of PDTC were compared to those of reduced glutathione (GSH) and N-acetylcysteine (NAC). PDTC markedly and in a concentration-dependent manner inhibited HOCl-induced inactivation of alpha(1)-antiproteinase, protein carbonyl formation on serum albumin and oxidation of human low-density lipoprotein. The direct scavenging of HOCl by PDTC was demonstrated by two quantitative methods, oxidation of ferrocyanide and chlorination of monochlorodimedon. In all assay systems, PDTC was two to three times more potent than GSH and NAC, while diethyldithiocarbamate was about as effective as PDTC. These data demonstrate that PDTC is a potent antioxidant against HOCl-induced protein oxidative damage, suggesting that PDTC might be useful in the prevention and treatment of inflammatory conditions.     

Synthesis and cytotoxic evaluation of a series of resveratrol derivatives

A total of 17 resveratrol (=(E)-5-[2-(4-hydroxyphenyl)ethenyl]benzene-1,3-diol) derivatives were synthesized from resveratrol (RES) through a facile approach. Among them, 13 compounds, 2 and 6-17, were reported for the first time, while 1 and 3-5 had already been reported several years ago. The cytotoxic activities of these compounds were evaluated against human nasopharyngeal epidermoid tumor cell line KB, and compounds 1 and 8-11 showed strong anticancer activities in vitro, comparable with that of 5-fluorouracil, an anticancer drug. On the basis of the experimental data obtained, structure-activity relationships are discussed.     

Mutasynthesis of a potent anticancer sibiromycin analogue

Pursuit of the actinomycete pyrrolobenzodiazepine natural product sibiromycin as a chemotherapeutic agent has been limited by its cardiotoxicity. Among pyrrolobenzodiazepines, cardiotoxicity is associated with hydroxylation at position 9. Deletion of the methyltransferase gene sibL abolishes the production of sibiromycin. Supplementation of growth media with 4-methylanthranilic acid can substitute for its native 3-hydroxy congener. Cultures grown in this fashion yielded 9-deoxysibiromycin. In this study, we characterize the structure and biological activity of sibiromycin and 9-deoxysibiromycin methyl carbinolamines. Preliminary in vitro evidence suggests that 9-deoxysibiromycin exhibits reduced cardiotoxicity while gaining antitumor activity. These results strongly support further exploration of the production and evaluation of monomeric and dimeric glycosylated pyrrolobenzodiazepine analogues of sibiromycin.     

Quinobene, a new potent anti-HIV agent.

A simple synthesis of the sulfonated azo dye Quinobene (3) and its derivatives, as well as the results of their evaluation in anti-HIV screening have been described. Thus, reacting the diazonium salt of 4,4'-diaminostilbene-2,2'-disulfonic acid with 8-hydroxyquinoline-5-sulfonic acid yielded the readily isolable title compound. The lithium and tetramethylammonium salts of Quinobene and its complexes with Cu(II), Zn(II), Mg(II) were also prepared. In vitro tests showed considerable activity of these compounds against HIV-1.     

The anti-cancer agent nemorosone is a new potent protonophoric mitochondrial uncoupler

Nemorosone, a natural-occurring polycyclic polyprenylated acylphloroglucinol, has received increasing attention due to its strong in vitro anti-cancer action. Here, we have demonstrated the toxic effect of nemorosone (1-25 μM) on HepG2 cells by means of the MTT assay, as well as early mitochondrial membrane potential dissipation and ATP depletion in this cancer cell line. In mitochondria isolated from rat liver, nemorosone (50-500 nM) displayed a protonophoric uncoupling activity, showing potency comparable to the classic protonophore, carbonyl cyanide m-chlorophenyl hydrazone (CCCP). Nemorosone enhanced the succinate-supported state 4 respiration rate, dissipated mitochondrial membrane potential, released Ca(2+) from Ca(2+)-loaded mitochondria, decreased Ca(2+) uptake and depleted ATP. The protonophoric property of nemorosone was attested by the induction of mitochondrial swelling in hyposmotic K(+)-acetate medium in the presence of valinomycin. In addition, uncoupling concentrations of nemorosone in the presence of Ca(2+) plus ruthenium red induced the mitochondrial permeability transition process. Therefore, nemorosone is a new potent protonophoric mitochondrial uncoupler and this property is potentially involved in its toxicity on cancer cells.