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1.
J Med Chem ; 2024 Jul 05.
Artigo em Inglês | MEDLINE | ID: mdl-38967641

RESUMO

We implemented isosteric replacement of sulfur to selenium in a novel thiosemicarbazone (PPTP4c4mT) to create a selenosemicarbazone (PPTP4c4mSe) that demonstrates potentiated anticancer efficacy and selectivity. Their design specifically incorporated cyclohexyl and styryl moieties to sterically inhibit the approach of their Fe(III) complexes to the oxy-myoglobin heme plane. Importantly, in contrast to the Fe(III) complexes of the clinically trialed thiosemicarbazones Triapine, COTI-2, and DpC, the Fe(III) complexes of PPTP4c4mT and PPTP4c4mSe did not induce detrimental oxy-myoglobin oxidation. Furthermore, PPTP4c4mSe demonstrated more potent antiproliferative activity than the homologous thiosemicarbazone, PPTP4c4mT, with their selectivity being superior or similar, respectively, to the clinically trialed thiosemicarbazone, COTI-2. An advantageous property of the selenosemicarbazone Zn(II) complexes relative to their thiosemicarbazone analogues was their greater transmetalation to Cu(II) complexes in lysosomes. This latter effect probably promoted their antiproliferative activity. Both ligands down-regulated multiple key receptors that display inter-receptor cooperation that leads to aggressive and resistant breast cancer.

2.
Chem Sci ; 15(3): 974-990, 2024 Jan 17.
Artigo em Inglês | MEDLINE | ID: mdl-38239703

RESUMO

The di-2-pyridylthiosemicarbazone (DpT) analogs demonstrate potent and selective anti-proliferative activity against human tumors. The current investigation reports the synthesis and chemical and biological characterization of the Fe(iii), Co(iii), Ni(ii), Cu(ii), Zn(ii), Ga(iii), and Pd(ii) complexes of the promising second generation DpT analog, di-2-pyridylketone-4-ethyl-4-methyl-3-thiosemicarbazone (Dp4e4mT). These studies demonstrate that the Dp4e4mT Co(iii), Ni(ii), and Pd(ii) complexes display distinct biological activity versus those with Cu(ii), Zn(ii), and Ga(iii) regarding anti-proliferative efficacy against cancer cells and a detrimental off-target effect involving oxidation of oxy-myoglobin (oxy-Mb) and oxy-hemoglobin (oxy-Hb). With regards to anti-proliferative activity, the Zn(ii) and Ga(iii) Dp4e4mT complexes demonstrate facile transmetallation with Cu(ii), resulting in efficacy against tumor cells that is strikingly similar to the Dp4e4mT Cu(ii) complex (IC50: 0.003-0.006 µM and 72 h). Relative to the Zn(ii) and Ga(iii) Dp4e4mT complexes, the Dp4e4mT Ni(ii) complex demonstrates kinetically slow transmetallation with Cu(ii) and intermediate anti-proliferative effects (IC50: 0.018-0.076 µM after 72 h). In contrast, the Co(iii) and Pd(ii) complexes demonstrate poor anti-proliferative activity (IC50: 0.262-1.570 µM after 72 h), probably due to a lack of transmetallation with Cu(ii). The poor efficacy of the Dp4e4mT Co(iii), Ni(ii), and Pd(ii) complexes to transmetallate with Fe(iii) markedly suppresses the oxidation of oxy-Mb and oxy-Hb. In contrast, the 2 : 1 Dp4e4mT: Cu(ii), Zn(ii), and Ga(iii) complexes demonstrate facile reactions with Fe(iii), leading to the redox active Dp4e4mT Fe(iii) complex and oxy-Mb and oxy-Hb oxidation. This study demonstrates the key role of differential transmetallation of Dp4e4mT complexes that has therapeutic ramifications for their use as anti-cancer agents.

3.
J Med Chem ; 66(22): 15453-15476, 2023 11 23.
Artigo em Inglês | MEDLINE | ID: mdl-37922410

RESUMO

The di-2-pyridylketone thiosemicarbazones demonstrated marked anticancer efficacy, prompting progression of DpC to clinical trials. However, DpC induced deleterious oxy-myoglobin oxidation, stifling development. To address this, novel substituted phenyl thiosemicarbazone (PPP4pT) analogues and their Fe(III), Cu(II), and Zn(II) complexes were prepared. The PPP4pT analogues demonstrated potent antiproliferative activity (IC50: 0.009-0.066 µM), with the 1:1 Cu:L complexes showing the greatest efficacy. Substitutions leading to decreased redox potential of the PPP4pT:Cu(II) complexes were associated with higher antiproliferative activity, while increasing potential correlated with increased redox activity. Surprisingly, there was no correlation between redox activity and antiproliferative efficacy. The PPP4pT:Fe(III) complexes attenuated oxy-myoglobin oxidation significantly more than the clinically trialed thiosemicarbazones, Triapine, COTI-2, and DpC, or earlier thiosemicarbazone series. Incorporation of phenyl- and styryl-substituents led to steric blockade, preventing approach of the PPP4pT:Fe(III) complexes to the heme plane and its oxidation. The 1:1 Cu(II):PPP4pT complexes were inert to transmetalation and did not induce oxy-myoglobin oxidation.


Assuntos
Antineoplásicos , Tiossemicarbazonas , Mioglobina , Compostos Férricos , Ensaios de Seleção de Medicamentos Antitumorais , Relação Estrutura-Atividade , Tiossemicarbazonas/farmacologia , Oxirredução , Antineoplásicos/farmacologia , Cobre
4.
J Med Chem ; 66(2): 1426-1453, 2023 01 26.
Artigo em Inglês | MEDLINE | ID: mdl-36649565

RESUMO

A novel, potent, and selective antitumor agent, namely (E)-3-phenyl-1-(2-pyridinyl)-2-propen-1-one 4,4-dimethyl-3-thiosemicarbazone (PPP44mT), and its analogues were synthesized and characterized and displayed strikingly distinctive properties. This activity was mediated by the inclusion of a styrene moiety, which through steric and electrochemical mechanisms prevented deleterious oxy-myoglobin or oxy-hemoglobin oxidation relative to other potent thiosemicarbazones, i.e., di-2-pyridylketone-4-cyclohexyl-4-methyl-3-thiosemicarbazone (DpC) or di-2-pyridylketone-4,4-dimethyl-3-thiosemicarbazone (Dp44mT). Structure-activity relationship analysis demonstrated specific tuning of PPP44mT electrochemistry further inhibited oxy-myoglobin or oxy-hemoglobin oxidation. Both PPP44mT and its Cu(II) complexes showed conspicuous almost immediate cytotoxicity against SK-N-MC tumor cells (within 3 h). In contrast, [Zn(PPP44mT)2] demonstrated a pronounced delay in activity, taking 48 h before marked antiproliferative efficacy was apparent. As such, [Zn(PPP44mT)2] was designated as a "stealth Zn(II) complex" that overcomes the near immediate cytotoxicity of PPP44mT or its copper complexes. Upon examination of the suppression of oncogenic signaling, [Zn(PPP44mT)2] was superior at inhibiting cyclin D1 expression compared to DpC or Dp44mT.


Assuntos
Antineoplásicos , Tiossemicarbazonas , Linhagem Celular Tumoral , Zinco/química , Mioglobina , Antineoplásicos/química , Tiossemicarbazonas/química , Hemoglobinas , Estirenos , Heme , Cobre/metabolismo
5.
Molecules ; 27(11)2022 May 26.
Artigo em Inglês | MEDLINE | ID: mdl-35684388

RESUMO

Tetrachlorinated phthalimide analogues bearing a boron-pinacolate ester group were synthesised via two synthetic routes and evaluated in their glycosidase modulating and anticancer properties, with a view to use them in boron neutron capture therapy (BNCT), a promising radiation type for cancer, as this therapy does little damage to biological tissue. An unexpected decarbonylation/decarboxylation to five 2,3,4,5-tetrachlorobenzamides was observed and confirmed by X-ray crystallography studies, thus, giving access to a family of borylated 2,3,4,5-tetrachlorobenzamides. Biological evaluation showed the benzamide drugs to possess good to weak potencies (74.7-870 µM) in the inhibition of glycosidases, and to have good to moderate selectivity in the inhibition of a panel of 18 glycosidases. Furthermore, in the inhibition of selected glycosidases, there is a core subset of three animal glycosidases, which is always inhibited (rat intestinal maltase α-glucosidase, bovine liver ß-glucosidase and ß-galactosidase). This could indicate the involvement of the boron atom in the binding. These glycosidases are targeted for the management of diabetes, viral infections (via a broad-spectrum approach) and lysosomal storage disorders. Assays against cancer cell lines revealed potency in growth inhibition for three molecules, and selectivity for one of these molecules, with the growth of the normal cell line MCF10A not being affected by this compound. One of these molecules showed both potency and selectivity; thus, it is a candidate for further study in this area. This paper provides numerous novel aspects, including expedited access to borylated 2,3,4,5-tetrachlorophthalimides and to 2,3,4,5-tetrachlorobenzamides. The latter constitutes a novel family of glycosidase modulating drugs. Furthermore, a greener synthetic access to such structures is described.


Assuntos
Terapia por Captura de Nêutron de Boro , Neoplasias , Animais , Boro/química , Boro/farmacologia , Compostos de Boro/farmacologia , Bovinos , Glicosídeo Hidrolases , Ratos
6.
J Nat Prod ; 85(6): 1641-1657, 2022 06 24.
Artigo em Inglês | MEDLINE | ID: mdl-35640100

RESUMO

Chemical investigation of Australian pasture plant-derived Streptomyces sp. CMB-PB041, supported by miniaturized cultivation profiling and molecular network analysis, led to the isolation and characterization of 13 new macrocyclic spirotetronates, glenthmycins A-M (1-13), with structures assigned by detailed spectroscopic analysis, chemical degradation and derivatization, and mechanistic and biosynthetic considerations. Hydrolysis of glenthmycin B (2) yielded the aglycone 14, whose structure and absolute configuration were secured by X-ray analysis, along with the unexpected amino sugar residues glenthose lactams A (15) and B (16), with Mosher analysis of 15 facilitating assignment of absolute configurations of the amino sugar. While the glenthmycins proved to be acid stable, treatment of isomeric glenthmycins (i.e., 3, 6, and 8) with base catalyzed rapid intramolecular trans-esterification to regio-isomeric mixtures (i.e., 3 + 6 + 8). Exposure of 5 to base achieved the same intramolecular trans-esterification and was instrumental in detecting and tentatively identifying two additional minor co-metabolites, glenthmycins N (19) and O (20). A structure-activity relationship analysis carried out on 1-13 and the semisynthetic analogues 14 and 21-26 revealed a promising Gram +ve antibacterial pharmacophore, effective against methicillin-resistant Staphylococcus aureus (MRSA) and vancomycin-resistant Enterococci (VRE), but with no detectable cytotoxicity to eukaryotic cells (i.e., fungal and human carcinoma). Of particular note, the semisynthetic analogue glenthmycin K 9-valerate (26) was unique among glenthmycins in potently inhibiting growth of the full panel of Gram +ve pathogens (IC50 0.2-1.6 µM). We conclude with an observation that any future evaluation of the antibacterial potential of glenthmycins and related macrocyclic spirotetronates may do well to include important soil-derived Gram +ve pathogens, such as Bacillus anthrax, Clostridium botulinum, and Rhodococcus equi, the causative agents of anthrax, botulism, and livestock pneumonia.


Assuntos
Antraz , Staphylococcus aureus Resistente à Meticilina , Policetídeos , Streptomyces , Amino Açúcares , Antibacterianos/química , Austrália , Humanos , Testes de Sensibilidade Microbiana , Estrutura Molecular , Policetídeos/metabolismo , Policetídeos/farmacologia , Streptomyces/química
7.
Biochim Biophys Acta Gen Subj ; 1866(4): 130078, 2022 04.
Artigo em Inglês | MEDLINE | ID: mdl-34974127

RESUMO

BACKGROUND: Iron (Fe)-induced oxidative stress leads to reactive oxygen species that damage biomembranes, with this mechanism being involved in the activity of some anti-cancer chemotherapeutics. METHODS: Herein, we compared the effect of the ligand, di-2-pyridylketone 4,4-dimethyl-3-thiosemicarbazone (Dp44mT), or the potential ligand, Emodin, on Fe-catalyzed lipid peroxidation in cell membrane models (micelles and bicelles). These studies were performed in the presence of hydrogen peroxide (H2O2) and the absence or presence of ascorbate. RESULTS: In the absence of ascorbate, Fe(II)/Emodin mixtures incubated with H2O2 demonstrated slight pro-oxidant properties on micelles versus Fe(II) alone, while the Fe(III)-Dp44mT complex exhibited marked antioxidant properties. Examining more physiologically relevant phospholipid-containing bicelles, the Fe(II)- and Fe(III)-Dp44mT complexes demonstrated antioxidant activity without ascorbate. Upon adding ascorbate, there was a significant increase in the peroxidation of micelles and bicelles in the presence of unchelated Fe(II) and H2O2. The addition of ascorbate to Fe(III)-Dp44mT substantially increased the peroxidation of micelles and bicelles, with the Fe(III)-Dp44mT complex being reduced by ascorbate to the Fe(II) state, explaining the increased reactivity. Electron paramagnetic resonance spectroscopy demonstrated ascorbyl radical anion generation after mixing ascorbate and Emodin, with signal intensity being enhanced by H2O2. This finding suggested Emodin semiquinone radical formation that could play a role in its reactivity via ascorbate-driven redox cycling. Examining cultured melanoma cells in vitro, ascorbate at pharmacological levels enhanced the anti-proliferative activity of Dp44mT and Emodin. CONCLUSIONS AND GENERAL SIGNIFICANCE: Ascorbate-driven redox cycling of Dp44mT and Emodin promotes their anti-proliferative activity.


Assuntos
Emodina , Tiossemicarbazonas , Ácido Ascórbico/química , Emodina/farmacologia , Compostos Ferrosos , Peróxido de Hidrogênio , Ferro/metabolismo , Ligantes , Micelas , Oxirredução , Espécies Reativas de Oxigênio , Tiossemicarbazonas/farmacologia
8.
J Nat Prod ; 85(2): 337-344, 2022 02 25.
Artigo em Inglês | MEDLINE | ID: mdl-35073486

RESUMO

Chemical investigations into solid phase cultivations of an Australian sheep station pasture plant derived Streptomyces sp. CMB-PB042 yielded the rare enamine naphthopyranoquinones BE-54238A (1) and BE-54238B (2), together with four new analogues, glenthenamines B-D (4-6) and F (8), and two handling artifacts, glenthenamines A (3) and E (7). Single-crystal X-ray analyses of 1 and 2 resolved configurational ambiguities in the scientific literature, while detailed spectroscopic analysis and biosynthetic considerations assigned structures inclusive of absolute configuration to 3-8. We propose a plausible sequence of biosynthetic transformations linking structural and configurational features of 1-8 and apply a novel Schiff base "fishing" approach to detect a key deoxyaminosugar precursor. These enamine naphthopyranoquinones disclose a new P-gp inhibitory pharmacophore capable of reversing doxorubicin resistance in P-gp overexpressing colon carcinoma cells.


Assuntos
Neoplasias do Colo , Streptomyces , Animais , Austrália , Estrutura Molecular , Bases de Schiff , Ovinos , Streptomyces/química
9.
Sci Rep ; 11(1): 207, 2021 01 08.
Artigo em Inglês | MEDLINE | ID: mdl-33420238

RESUMO

The long-standing perception of Protein Kinase C (PKC) as a family of oncoproteins has increasingly been challenged by evidence that some PKC isoforms may act as tumor suppressors. To explore the hypothesis that activation, rather than inhibition, of these isoforms is critical for anticancer activity, we isolated and characterized a family of 16 novel phorboids closely-related to tigilanol tiglate (EBC-46), a PKC-activating epoxytigliane showing promising clinical safety and efficacy for intratumoral treatment of cancers. While alkyl branching features of the C12-ester influenced potency, the 6,7-epoxide structural motif and position was critical to PKC activation in vitro. A subset of the 6,7-epoxytiglianes were efficacious against established tumors in mice; which generally correlated with in vitro activation of PKC. Importantly, epoxytiglianes without evidence of PKC activation showed limited antitumor efficacy. Taken together, these findings provide a strong rationale to reassess the role of PKC isoforms in cancer, and suggest in some situations their activation can be a promising strategy for anticancer drug discovery.


Assuntos
Antineoplásicos/química , Antineoplásicos/farmacologia , Diterpenos/química , Diterpenos/farmacologia , Proteína Quinase C/metabolismo , Animais , Linhagem Celular Tumoral , Ativação Enzimática/efeitos dos fármacos , Camundongos , Transdução de Sinais/efeitos dos fármacos
10.
Dalton Trans ; 50(2): 612-623, 2021 Jan 19.
Artigo em Inglês | MEDLINE | ID: mdl-33320137

RESUMO

The tetradentate N2S2 Schiff base ligands derived from condensing S-methyl or S-benzyl dithiocarbazate with acetylacetone have been found to be versatile chelators for copper and able to stabilise unusually high oxidation states. Herein we report their Ni coordination chemistry and a variety of products ensue depending on the reaction conditions. Unusual examples of linkage isomerism have been observed upon complexation with nickel acetate and these asymmetrically and symmetrically coordinated NiIIN2S2 complexes have been characterised both crystallographically and in solution by NMR. These compounds react rapidly with dioxygen and the ligands are particularly susceptible to oxidation which lead to various products including dinuclear NiII complexes derived from radical homocoupling reactions. These dinuclear NiII complexes are also redox active and spectroelectrochemistry has revealed new electronic transitions from their formally NiIII/NiII mixed valent state.

11.
Chemistry ; 26(59): 13372-13377, 2020 Oct 21.
Artigo em Inglês | MEDLINE | ID: mdl-32991008

RESUMO

The tigliane ring system, which encompasses iconic members such as phorbol and TPA, is widely renowned due to numerous observations of displaying potent biological activity, and subsequent use as mainstream biochemical tools. Traditionally, naturally occurring phorboids are regarded as tumor promotors through PKC activation, although in recent times more highly oxidized natural derivatives have been identified as anti-tumor agents. In the view that only limited synthetic investigations toward skeletal stereochemical modification have been undertaken, non-natural systems could be useful for a better understanding of the tigliane pharmacophore via interrogation of cellular sensitivity. In this context the concise construction of a number of highly functionalized non-natural D-ring inverted phorbol esters were synthesized, via a rhodium-catalyzed [4+3] cycloaddition, and biologically evaluated using a range of cancer cell lines. The biological results highlight the notion that subtle changes in structure have dramatic effects on potency. Furthermore, although the non-natural derivatives did not outcompete the natural systems in the PKC-activation sensitive MCF7 cancer cell line, they outperformed in other cancer cell lines (MM96L and CAL27). This observation strongly suggested an alternate mode of action not involving activation of PKC, but instead involves thiol addition as indicated by glutathione addition and NF-κB reporter activity.


Assuntos
Neoplasias , Forbóis , Proteína Quinase C/química , Compostos de Sulfidrila/química , Linhagem Celular , Humanos
12.
J Nat Prod ; 83(5): 1473-1479, 2020 05 22.
Artigo em Inglês | MEDLINE | ID: mdl-32302147

RESUMO

Dysphania is a genus of plants endemic to the Australian continent, occurring primarily in arid and temperate zones. Despite their prevalence, very little in the way of phytochemical and/or bioactivity investigation of native Dysphania has been performed. Herein reported is the isolation and elucidation of (6E,9E)-zerumbone epoxide and a hitherto unreported isomer, (6Z,9E)-zerumbone epoxide, from D. kalpari. In addition, a novel isodaucane sesquiterepene, kalparinol, was isolated from both D. kalpari and D. rhadinostachya. The coisolation of the humulene and isodaucane skeletons, combined with the lack of any cadalane systems, could suggest an alternate novel biogenetic pathway originating from zerumbone, which is unlike any other proposals for the isodaucene system.


Assuntos
Amaranthaceae/química , Sesquiterpenos/farmacologia , Antifúngicos/química , Antifúngicos/farmacologia , Antineoplásicos Fitogênicos/farmacologia , Austrália , Linhagem Celular Tumoral , Ensaios de Seleção de Medicamentos Antitumorais , Fungos/efeitos dos fármacos , Humanos , Testes de Sensibilidade Microbiana , Estrutura Molecular , Extratos Vegetais/química , Sesquiterpenos/química , Sesquiterpenos/metabolismo , Difração de Raios X
13.
J Nat Prod ; 83(2): 497-504, 2020 02 28.
Artigo em Inglês | MEDLINE | ID: mdl-31975579

RESUMO

Chemical analysis of the fungus Chrysosporium sp. CMB-F294 isolated from the gastrointestinal tract of a market-purchased specimen of Mugil mullet yielded eight new alkaloids, belonging to a rare class of phenylpropanoid piperazines. Chrysosporazines F-M (1-8) occur as an equilibrium mixture of acetamide rotamers and feature unprecedented carbocyclic and heterocyclic scaffolds. Structures inclusive of absolute configuration were assigned by detailed spectroscopic analysis, supported by biosynthetic considerations. Structure-activity relationship studies determined that selected chrysosporazines were promising noncytotoxic inhibitors of the multidrug resistance efflux pump P-glycoprotein (P-gp), capable of reversing doxorubicin resistance in P-gp-overexpressing human colon carcinoma cells (SW620 Ad300). Chrysosporazine F (1) was particularly noteworthy, with a 2.5 µM cotreatment inducing a doxorubicin gain in sensitivity (GS 14) > 2-fold that of the positive control verapamil (GS 6.1).


Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/química , Alcaloides/química , Chrysosporium/efeitos dos fármacos , Neoplasias do Colo/tratamento farmacológico , Resistência a Múltiplos Medicamentos/efeitos dos fármacos , Fungos/química , Piperazinas/química , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/metabolismo , Alcaloides/isolamento & purificação , Alcaloides/farmacologia , Animais , Austrália , Chrysosporium/química , Doxorrubicina/farmacologia , Inibidores Enzimáticos/farmacologia , Fungos/efeitos dos fármacos , Humanos , Estrutura Molecular , Relação Estrutura-Atividade
14.
Chemistry ; 26(7): 1653-1660, 2020 Feb 03.
Artigo em Inglês | MEDLINE | ID: mdl-31961021

RESUMO

Dysphania is an abundant genus of plants, many of which are endemic to the Australian continent, occurring primarily in arid and temperate zones. Despite their prevalence, very few investigations into the phytochemistry of native Dysphania have been undertaken. Described herein, is the isolation and elucidation of two enantiomeric diastereomers of humulene diepoxide C from D. kalpari and D. rhadinostachya, of which unassigned diastereomers of humulene diepoxide C have been previously reported as components in beer brewed from aged hops. In addition, two (+)-humulene diepoxiols (humulene diepoxiol C-I and C-II) were isolated from D. rhadinostachya. Analysis of Chinook hops oil confirmed the presence of both humulene diepoxide C-I and C-II as trace components, and in turn enabled GC-MS peak assignment to the relative stereochemistry. Anticancer assays did not reveal any significant activity for the (+)-humulene diepoxides. Antifungal assays showed good activity against a drug-resistant strain of C. auris, with MIC50 values of 8.53 and 4.91 µm obtained for (+)-humulene diepoxide C-I and C-II, respectively.

15.
Org Lett ; 21(21): 8761-8764, 2019 11 01.
Artigo em Inglês | MEDLINE | ID: mdl-31626552

RESUMO

Phorbol esters are long regarded as tumor promotors, due to protein kinase C (PKC) activation, but more recently higher oxidized natural derivatives have been shown to display antitumor activity. Given the synthetic difficulty, systematic non-natural systems are not readily available to further interrogate PKC binding. Herein reported is the concise construction of a considerably advanced intermediate toward D-ring inverted phorbol esters, enabled by a rhodium-catalyzed [4 + 3] cycloaddition involving a highly functionalized tetrahydrobenzofuran.

16.
Dalton Trans ; 48(44): 16578-16587, 2019 Nov 28.
Artigo em Inglês | MEDLINE | ID: mdl-31657430

RESUMO

The kinetics of oxidation of different biologically-active FeII bis-thiosemicarbazone complexes in water has been monitored at varying dioxygen concentration, temperature, pressure, and pH. The oxidation reactions observed can be resolved as a single-step process, producing the expected ferric complex, with rates increasing with decreasing pH. From the pH-dependence of the observed rate constants, a rate law with two terms can be derived, one of them being independent of the acid concentration and the other term showing a saturation behaviour with respect to [H+]. These results indicate the existence of two parallel pathways for oxidation: the acid-independent pathway is only operative for the complexes with ligands bearing terminal, non-coordinated, unsubstituted amines, whereas the term with a [H+]-limiting kinetic behaviour is observed for all the complexes and indicates that the reacting species has to be protonated prior to the oxidation step. From the data collected, the rate law and the thermal and pressure activation parameters have been used to interpret the operating reaction mechanisms. Given the fact that the empirical trends rule out an outer-sphere oxidation process, DFT calculations have been carried out to explain the results and suggest the likely formation, under steady-state very low concentration conditions, of FeIII superoxo and hydroperoxo intermediates.

17.
Chemistry ; 25(68): 15594-15608, 2019 Dec 05.
Artigo em Inglês | MEDLINE | ID: mdl-31529537

RESUMO

5-(2-Oxopropylideneamino)-6-d-ribitylaminouracil (5-OP-RU) is a natural product formed during bacterial synthesis of vitamin B2. It potently activates mucosal associated invariant T (MAIT) cells and has immunomodulatory, inflammatory, and anticancer properties. This highly polar and unstable compound forms a remarkably stable Schiff base with a lysine residue in major histocompatibility complex class I-related protein (MR1) expressed in antigen-presenting cells. Inspired by the importance of the ribityl moiety of 5-OP-RU for binding to both MR1 and the T cell receptor (TCR) on MAIT cells, each OH was removed in silico. DFT calculations and MD simulations revealed a very stable hydrogen bond between the C3'-OH and uracil N1H, which profoundly restricts flexibility and positioning of each ribityl-OH, potentially impacting their interactions with MR1 and TCR. By using deoxygenation strategies and kinetically controlled imine formation, four monodeoxyribityl and four monohydroxyalkyl analogues of 5-OP-RU were synthesised as new tools for probing T cell activation mechanisms.


Assuntos
Células T Invariantes Associadas à Mucosa/química , Receptores de Antígenos de Linfócitos T/química , Riboflavina/metabolismo , Bases de Schiff/química , Uracila/química , Simulação por Computador , Humanos , Ativação Linfocitária/imunologia , Receptores de Antígenos de Linfócitos T/genética , Uracila/metabolismo
18.
Org Lett ; 21(19): 8097-8100, 2019 10 04.
Artigo em Inglês | MEDLINE | ID: mdl-31544463

RESUMO

Chemical analysis of Chrysosporium sp. CMB-F214, yielded five new piperazines, chrysosporazines A-E (1-5), with structures assigned by spectroscopic and X-ray analyses and biosynthetic considerations. The chrysosporazines 2-5 exist as an equilibrium of major and minor N-acyl rotamers, while 1-3 incorporate an unprecedented hexahydro-6H-pyrazino[1,2-b]isoquinolin-6-one scaffold. The noncytotoxic chrysosporazines reverse doxorubicin drug resistance in P-glycoprotein overexpressing colon carcinoma cells (SW620 Ad300), with 2 delivering a comparable gain in sensitivity to the positive control, verapamil.


Assuntos
Membro 1 da Subfamília B de Cassetes de Ligação de ATP/antagonistas & inibidores , Chrysosporium/química , Neoplasias Colorretais/tratamento farmacológico , Piperazinas/farmacologia , Membro 1 da Subfamília B de Cassetes de Ligação de ATP/genética , Antibióticos Antineoplásicos/química , Antibióticos Antineoplásicos/farmacologia , Proliferação de Células/efeitos dos fármacos , Neoplasias Colorretais/genética , Neoplasias Colorretais/patologia , Cristalografia por Raios X , Doxorrubicina/química , Doxorrubicina/farmacologia , Modelos Moleculares , Estrutura Molecular , Piperazinas/química , Piperazinas/isolamento & purificação , Estereoisomerismo
19.
J Nat Prod ; 82(10): 2828-2834, 2019 10 25.
Artigo em Inglês | MEDLINE | ID: mdl-31553187

RESUMO

The highly oxygenated pimarane diterpenoids basimarols A, B, and C (3-5) were isolated from the plant species Basilicum polystachyon, which was collected within the Australian arid zone. Structure elucidation was performed using a suite of spectroscopic techniques, including X-ray crystallography. Anticancer and anti-DENV activity of 3-5 was explored, but only limited activity was observed. More extensive antiviral evaluation of stachyonic acid A (1), which was also isolated from B. polystachyon, revealed broad spectrum antiviral activity against West Nile virus (Kunjin strain, WNVKun) and human influenza viruses H1N1 and H3N2.


Assuntos
Abietanos/isolamento & purificação , Antineoplásicos Fitogênicos/isolamento & purificação , Antivirais/isolamento & purificação , Lamiaceae/química , Abietanos/química , Abietanos/farmacologia , Antineoplásicos Fitogênicos/química , Antineoplásicos Fitogênicos/farmacologia , Antivirais/química , Antivirais/farmacologia , Linhagem Celular Tumoral , Humanos
20.
Mar Drugs ; 17(8)2019 Aug 16.
Artigo em Inglês | MEDLINE | ID: mdl-31426405

RESUMO

Chemical analysis of a cultivation of an Australian Mugil mullet gastrointestinal tract (GIT) derived fungus, Scopulariopsis sp. CMB-F458, yielded the known lipodepsipeptides scopularides A (1) and B (2). A comparative global natural product social (GNPS) molecular networking analysis of ×63 co-isolated fungi, detected two additional fungi producing new scopularides, with Beauveria sp. CMB-F585 yielding scopularides C-G (3-7) and Scopulariopsis sp. CMB-F115 yielding scopularide H (8). Structures inclusive of absolute configurations were assigned by detailed spectroscopic and C3 Marfey's analysis, together with X-ray analyses of 3 and 8, and biosynthetic considerations. Scopularides A-H (1-8) did not exhibit significant growth inhibitory activity against a selection of Gram positive (+ve) and negative (-ve) bacteria, a fungus, or a panel of three human carcinoma cell lines.


Assuntos
Depsipeptídeos/química , Peixes/microbiologia , Trato Gastrointestinal/microbiologia , Scopulariopsis/química , Animais , Antibacterianos/química , Antibacterianos/farmacologia , Austrália , Bactérias/efeitos dos fármacos , Produtos Biológicos/química , Carcinoma/tratamento farmacológico , Linhagem Celular Tumoral , Células Hep G2 , Humanos
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