The chemistry and biology of organic guanidine derivatives

Development of Novel Membrane Disrupting Lipoguanidine Compounds Sensitizing Gram-Negative Bacteria to Antibiotics

A new class of amphiphilic molecules, the lipoguanidines, designed as hybrids of guanidine and fatty acid compounds, has been synthesized and developed. The new molecules present both a guanidine polar head and a lipophilic tail that allow them to disrupt bacterial membranes and to sensitize Gram-negative bacteria to the action of the narrow-spectrum antibiotics rifampicin and novobiocin. The lipoguanidine 5g sensitizes Klebsiella pneumonia, Acinetobacter baumannii, Pseudomonas aeruginosa, and Escherichia coli to rifampicin, thereby reducing the antibiotic minimum inhibitory concentrations (MIC) up to 256-fold. Similarly, 5g is able to potentiate novobiocin up to 64-fold, thereby showing a broad spectrum of antibiotic potentiating activity. Toxicity and mechanism studies revealed the potential of 5g to work synergistically with rifampicin through the disruption of bacterial membranes without affecting eukaryotic cells.

A synthesis of functionalized 3-amino-1,2,4-triazoles from nitrile imines and guanidine derivatives

A regioselective synthesis of trisubstituted 1,2,4-triazoles through reaction of nitrile imines with guanidine derivatives is described. These 1,3-dipolar cycloaddition reactions proceeded smoothly in moderate to good yields and excellent regioselectivity under ambient conditions. This method provides fast access to a range of functionalized 3-amino-1,2,4-triazoles.

Silver acetate-catalyzed synthesis of cyclic sulfonyl guanidine with exocyclic double bond

An efficient protocol for the synthesis of cyclic guanidine with exocyclic double bond has been developed. The synthesis has been achieved via intramolecular hydroamination of an intermediate propargyl guanidine by using silver acetate as catalyst in the presence of acetic acid. The reaction proceeds via the formation of acyclic propargyl guanidine in a one-pot reaction of N,N-dibromoarylsulfonamides, isonitriles, and propargylamine in the presence of K2CO3. In the second stage of the synthesis, the acyclic guanidine selectively undergoes 5-exo-dig cyclization in the presence of silver acetate and acetic acid to produce the five-membered cyclic guanidine framework having an exocyclic double bond as the constituent part. Short reaction time, wide substrate scope with good to high yields, and good functional group tolerance are the remarkable achievement of the present protocol.

Exploring the antileishmanial activity of N1,N2-disubstituted-benzoylguanidines: synthesis and molecular modeling studies

In this report, we describe the synthesis and evaluation of nine N¹,N²-disubstituted-benzoylguanidines against promastigotes and amastigotes forms of Leishmania amazonensis. The derivatives 2g and 2i showed low IC₅₀ values against promastigote form (90.8 ± 0.05 µM and 68.4 ± 0.03 µM, respectively), low cytotoxicity profile (CC₅₀ 396 ± 0.02 µM and 857.9 ± 0.06 µM) for peritoneal macrophages cells and SI of 5.5 and 12.5, respectively. Investigations about the mechanism of action of 2g and 2i showed that both compounds cause mitochondrial depolarization, increase in ROS levels, and generation of autophagic vacuoles on free promastigotes forms. These compounds were also capable of reducing the number of infected macrophages with amastigotes forms (59.5% ± 0.08% and 98.1% ± 0.46%) and the number of amastigotes/macrophages (79.80% ± 0.05% and 96.0% ± 0.16%), through increasing induction of microbicide molecule NO. Additionally, ADMET-Tox in silico predictions showed drug-like features and free of toxicological risks. The molecular docking studies with arginase and gp63 showed that relevant intermolecular interactions could explain the experimental results. Therefore, these results reinforce that benzoylguanidines could be a starting scaffold for the search for new antileishmanial drugs.Communicated by Ramaswamy H. Sarma.

Guanidinates as Alternative Ligands for Organometallic Complexes

For decades, ligands such as phosphanes or cyclopentadienyl ring derivatives have dominated Coordination and Organometallic Chemistry. At the same time, alternative compounds have emerged that could compete either for a more practical and accessible synthesis or for greater control of steric and electronic properties. Guanidines, nitrogen-rich compounds, appear as one such potential alternatives as ligands or proligands. In addition to occurring in a plethora of natural compounds, and thus in compounds of pharmacological use, guanidines allow a wide variety of coordination modes to different metal centers along the periodic table, with their monoanionic chelate derivatives being the most common. In this review, we focused on the organometallic chemistry of guanidinato compounds, discussing selected examples of coordination modes, reactivity and uses in catalysis or materials science. We believe that these amazing ligands offer a new promise in Organometallic Chemistry.

Metal-catalyzed reactions of organic nitriles and boronic acids to access diverse functionality

The nitrile or cyano (-CN) group is one of the most appreciated and effective functional groups in organic synthesis, having a polar unsaturated C-N triple bond. Despite sufficient stability and being intrinsically inert, the nitrile group can be easily transformed into many other functional groups, such as amines, carboxylic acids, ketones, etc. which makes it a vital group in organic synthesis. On the other hand, despite several boronic acids having a low level of genotoxicity, they have found wide applicability in the field of organic synthesis, especially in transition metal-catalyzed cross-coupling reactions. Recently, transition-metal-catalyzed cascade additions or addition/cyclization processes of boronic acids to the nitrile group open up exciting and useful strategies to prepare a variety of functional molecules through the formation of C-C, C-N and CO bonds. Boronic acids can be added to the cyano functionality through catalytic carbometallation or through a radical cascade process to provide newer pathways for the rapid construction of various important acyclic ketones or amides, carbamidines, carbocycles and N,O-heterocycles. The present review focuses on various transition-metal-catalyzed additions of boronic acids via carbometallation or radical cascade processes using the cyano group as an acceptor.

Discovery, Biosynthetic Origin, and Heterologous Production of Massinidine, an Antiplasmodial Alkaloid

Bacteria of the genus Massilia represent an underexplored source of bioactive natural products. Here, we report the discovery of massinidine (1), a guanidine alkaloid with antiplasmodial activity, from these microbes. The unusual scaffold of massinidine is shown to originate from l-phenylalanine, acetate, and l-arginine. Massinidine biosynthesis genes were identified in the native producer and validated through heterologous expression in Myxococcus xanthus. Bioinformatic analyses indicate that the potential for massinidine biosynthesis is distributed in various proteobacteria.

Copper-Catalyzed C-N Bond Cleavage: Synthesis of N-Sulfonylformamidines from N-( 2-pyridinylmethyl)benzenesulfonamides

AIMS

Find an innovative approach to synthesizing N-sulfonylformamidines from new N source.

BACKGROUND

N-sulfonylamidines have gained considerable attention from school and industry because of unique bioactivity. Since Pinner's strategy, expanding the synthesis methods of N-sulfonylamidines has been the goal of many organic chemists over the past decades. Beside of the crash reaction conditions and the participation of undesirable reagents, the production of N-sulfonylamidines commonly required unstable ammonia and azides as the source of nitrogen which hindered the further development and application of N-sulfonylamidine derivatives.

OBJECTIVE

Find a stable N source to replace NaN3 or NH3 to synthesis N-sulfonylamidines.

METHOD

Firstly, N-( 2-pyridinylmethyl)benzenesulfonamides were smoothly synthesized via 2-pyridinemethanamine and sulfonyl chlorides. Then the reaction conditions of N-(2-pyridinylmethyl)benzenesulfonamides and N,N-dimethylformamide dimethyl acetal(DMF-DMA) were screened and optimized: the reaction was processed in glycol at 80 ℃ for 8 hours with the addition of 5 mol% Cu(OAc)2·H2O as catalyst.

RESULT

Taking the advantage of pyridin-2-ylmethyl, a scope of N-Sulfonylformamidines were synthesized from those N-(2-pyridinylmethyl)benzenesulfonamides under copper-catalyzed C-N bond cleavage.

CONCLUSION

This ready synthetic method will be more a promising inspiration of bioactive compound synthesis and drug development than of an innovative approach to synthesizing N-sulfonylformamidines.

Expeditious assembly of biuret-guanidine derivatives via the catalyst-free transformation

We disclose a mild and practical catalyst-free transformation for the expeditious construction of biuret-guanidine derivatives using aromatic isocyanates. This synthetic transformation is featured with mild reaction conditions and high efficiency.

Aluminium alkyl complexes supported by imino-phosphanamide ligand as precursors for catalytic guanylation reactions of carbodiimides

Herein, we report the synthesis, characterisation, and application of three aluminium alkyl complexes, [κ2-{NHIRP(Ph)NDipp}AlMe2] (R = Dipp (2a), Mes (2b); tBu (2c), Dipp = 2,6-diisopropylphenyl, Mes = mesityl, and tBu = tert-butyl), supported by unsymmetrical imino-phosphanamide [NHIRP(Ph)NDipp]- [R = Dipp (1a), Mes (1b), tBu (1c)] ligands as molecular precursors for the catalytic synthesis of guanidines using carbodiimides and primary amines. All the imino-phosphanamide ligands 1a, 1b and 1c were prepared in good yield from the corresponding N-heterocyclic imine (NHI) with phenylchloro-2,6-diisopropylphenylphosphanamine, PhP(Cl)NHDipp. The aluminium alkyl complexes 2a, 2b and 2c were obtained in good yield upon completion of the reaction between trimethyl aluminium and the protic ligands 1a, 1b and 1c in a 1 : 1 molar ratio in toluene via the elimination of methane, respectively. The molecular structures of the protic ligands 1b and 1c and the aluminium complexes 2a, 2b and 2c were established via single-crystal X-ray diffraction analysis. Complexes 2a, 2b and 2c were tested as pre-catalysts for the hydroamination/guanylation reaction of carbodiimides with aryl amines to afford guanidines at ambient temperature. All the aluminium complexes exhibited a high conversion with 1.5 mol% catalyst loading and broad substrate scope with a wide functional group tolerance during the guanylation reaction. We also proposed the most plausible mechanism, involving the formation of catalytically active three-coordinate Al species as the active pre-catalyst.

(−)-Agelasidine A Induces Endoplasmic Reticulum Stress-Dependent Apoptosis in Human Hepatocellular Carcinoma

Liver cancers, such as hepatocellular carcinoma (HCC), are a highly prevalent cause of cancer-related deaths. Current treatments to combat liver cancer are limited. (−)-Agelasidine A, a compound isolated from the methanol extract of Agelasnakamurai, a sesquiterpene guanidine derived from sea sponge, has antibacterial activity. We demonstrated its anticancer capabilities by researching the associated mechanism of (−)-agelasidine A in human liver cancer cells. We found that (−)-agelasidine A significantly reduced viability in Hep3B and HepG2 cells, and we determined that apoptosis was involved in the (−)-agelasidine A-induced Hep3B cell deaths. (−)-Agelasidine A activated caspases 9, 8, and 3, as well as PARP. This effect was reversed by caspase inhibitors, suggesting caspase-mediated apoptosis in the (−)-agelasidine A-treated Hep3B cells. Moreover, the reduced mitochondrial membrane potential (MMP) and the release of cytochrome c indicated that the (−)-agelasidine A-mediated mitochondrial apoptosis was mechanistic. (−)-Agelasidine A also increased apoptosis-associated proteins (DR4, DR5, FAS), which are related to extrinsic pathways. These events were accompanied by an increase in Bim and Bax, proteins that promote apoptosis, and a decrease in the antiapoptotic protein, Bcl-2. Furthermore, our results presented that (−)-agelasidine A treatment bridged the intrinsic and extrinsic apoptotic pathways. Western blot analysis of Hep3B cells treated with (−)-agelasidine A showed that endoplasmic reticulum (ER) stress-related proteins (GRP78, phosphorylated PERK, phosphorylated eIF2α, ATF4, truncated ATF6, and CHOP) were upregulated. Moreover, 4-PBA, an ER stress inhibitor, could also abrogate (−)-agelasidine A-induced cell viability reduction, annexin V+ apoptosis, death receptor (DR4, DR5, FAS) expression, mitochondrial dysfunction, and cytochrome c release. In conclusion, by activating ER stress, (−)-agelasidine A induced the extrinsic and intrinsic apoptotic pathways of human HCC.

Rugonidines A-F, Diastereomeric 1,6-Dioxa-7,9-diazaspiro[4.5]dec-7-en-8-amines from the Leaves of Alchornea rugosa

Rugonidines A-F (1-6), three pairs of novel configurationally semistable diastereomers featuring an unprecedented 1,6-dioxa-7,9-diazaspiro[4.5]dec-7-en-8-amine scaffold, were isolated from Alchornea rugosa based on MS/MS-based molecular networking analysis. Their structures were elucidated by NMR spectroscopy in combination with quantum-chemical calculations. Compounds 1-3 showed a significant increase in glucose uptake level in differentiated 3T3-L1 adipocytes using 2-deoxy-2-[(7-nitro-2,1,3-benzoxadiazol-4-yl)amino]-d-glucose (2-NBDG) as a fluorescent-tagged glucose probe.

A review on synthetic chalcone derivatives as tubulin polymerisation inhibitors

Microtubules play an important role in the process of cell mitosis and can form a spindle in the mitotic prophase of the cell, which can pull chromosomes to the ends of the cell and then divide into two daughter cells to complete the process of mitosis. Tubulin inhibitors suppress cell proliferation by inhibiting microtubule dynamics and disrupting microtubule homeostasis. Thereby inducing a cell cycle arrest at the G2/M phase and interfering with the mitotic process. It has been found that a variety of chalcone derivatives can bind to microtubule proteins and disrupt the dynamic balance of microtubules, inhibit the proliferation of tumour cells, and exert anti-tumour effects. Consequently, a great number of studies have been conducted on chalcone derivatives targeting microtubule proteins. In this review, synthetic or natural chalcone microtubule inhibitors in recent years are described, along with their structure-activity relationship (SAR) for anticancer activity.

Recent Advances in the Synthesis of Heterocycles by the Aza-Wittig Reaction

The formation of the C=N bond in recent studies on heterocyclic compounds via the aza-Wittig reaction is reviewed. Furthermore, two different strategies for the formation of heterocyclic compounds, including intermolecular and intramolecular aza-Wittig reactions are described. The primary aim of this review is to provide up-to-date information on the application of the aza-Wittig reaction in the synthesis of a wide range of N-containing heterocyclic compounds in the chemical literature since 2010.

1 Introduction

2 Mechanism of the Staudinger and Aza-Wittig Reactions

3 Intramolecular Aza-Wittig Reaction

4 Intermolecular Aza-Wittig Reaction

5 Conclusion

Synthesis and antiproliferative screening of novel doubly modified colchicines containing urea, thiourea and guanidine moieties

A new series of 10-demethoxy-10-methylaminocolchicines bearing urea, thiourea or aguanidine moieties at position C7 has been designed, synthesized and evaluated for in vitro anticancer activity against different cancer cell lines (A549, MCF-7, LoVo, LoVo/DX). The majority of the new derivatives were active in the nanomolar range and were characterized by lower IC₅₀ values than cisplatin or doxorubicin. Two ureas (4 and 8) and thioureas (19 and 25) were found to be good antiproliferative agents (low IC₅₀ values and high SI) and could prove to be promising candidates for further research in the field of anticancer drugs based on the colchicine skeleton.

A unique high-diversity natural product collection as a reservoir of new therapeutic leads

We review the successful application of computer-aided methods to screen a unique and high-diversity in house collection library composed of around 1000 individual natural products.

The chemistry and biology of guanidine secondary metabolites

Covering: 2017-2019Guanidine natural products isolated from microorganisms, marine invertebrates and terrestrial plants, amphibians and spiders, represented by non-ribosomal peptides, guanidine-bearing polyketides, alkaloids, terpenoids and shikimic acid derived, are the subject of this review. The topics include the discovery of new metabolites, total synthesis of natural guanidine compounds, biological activity and mechanism-of-action, biosynthesis and ecological functions.

Marine alkaloid monanchoxymycalin C: a new specific activator of JNK1/2 kinase with anticancer properties

Monanchoxymycalin C (MomC) is a new marine pentacyclic guanidine alkaloid, recently isolated from marine sponge Monanchora pulchra by us. Here, anticancer activity and mechanism of action was investigated for the first time using a human prostate cancer (PCa) model. MomC was active in all PCa cell lines at low micromolar concentrations and induced an unusual caspase-independent, non-apoptotic cell death. Kinase activity screening identified activation of mitogen-activated protein kinase (MAPK) c-Jun N-terminal protein kinase (JNK1/2) to be one of the primary molecular mechanism of MomC anticancer activity. Functional assays demonstrated a specific and selective JNK1/2 activation prior to the induction of other cell death related processes. Inhibition of JNK1/2 by pretreatment with the JNK-inhibitor SP600125 antagonized cytotoxic activity of the marine compound. MomC caused an upregulation of cytotoxic ROS. However, in contrast to other ROS-inducing agents, co-treatment with PARP-inhibitor olaparib revealed antagonistic effects indicating an active PARP to be necessary for MomC activity. Interestingly, although no direct regulation of p38 and ERK1/2 were detected, active p38 kinase was required for MomC efficacy, while the inhibition of ERK1/2 increased its cytotoxicity. In conclusion, MomC shows promising activity against PCa, which is exerted via JNK1/2 activation and non-apoptotic cell death.

Divergent 2-Chloroquinazolin-4(3H)-one Rearrangement: Twisted-Cyclic Guanidine Formation or Ring-Fused N-Acylguanidines via a Domino Process

A highly efficient 2-chloroquinazolin-4(3H)-one rearrangement was developed that predictably generates either twisted-cyclic or ring-fused guanidines in a single operation, depending on the presence of a primary versus secondary amine in the accompanying diamine reagent. Exclusive formation of twisted-cyclic guanidines results from pairing 2-chloroquinazolinones with secondary diamines. Use of primary amine-containing diamines permits a domino quinazolinone rearrangement/intramolecular cyclization, gated through (E)-twisted-cyclic guanidines, to afford ring-fused N-acylguanidines. This scalable, structurally tolerant transformation generated 55 guanidines and delivered twisted-cyclic guanidines with robust plasma stability and an abbreviated total synthesis of an antitumor ring-fused guanidine (4 steps, 55 % yield).

Generation and Reactivity of 2-Amido-1,3-diaminoallyl Cations: Cyclic Guanidine Annulations via Net (3 + 2) and (4 + 3) Cycloadditions

Toward a method for direct conversion of alkenes to cyclic guanidines, we report that 1,3-dipolar cycloadditions of 2-amido-1,3-diamino allylic cations with alkenes provide a new method for direct cyclic guanidine annulation. Generated under oxidative conditions, the 2-amido-1,3-diaminoallyl cations react as 1,3-dipoles providing rapid access to 2-amino imidazolines through net (3 + 2) cycloadditions. The utility is demonstrated through a concise synthesis of the oroidin alkaloid, phakellin. The described 1,3-dipole also participates in net (4 + 3) cycloadditions with dienes.

Small molecule inhibitors and stimulators of inducible nitric oxide synthase in cancer cells from natural origin (phytochemicals, marine compounds, antibiotics)

Nitric oxide synthases (NOS) are a family of isoforms, which generate nitric oxide (NO). NO is one of the smallest molecules in nature and acts mainly as a potent vasodilator. It participates in various biological processes ranging from physiological to pathological conditions. Inducible NOS (iNOS, NOS2) is a calcium-independent and inducible isoform. Despite high iNOS expression in many tumors, the role of iNOS is still unclear and complex with both enhancing and prohibiting actions in tumorigenesis. Nature presents a broad variety of natural stimulators and inhibitors, which may either promote or inhibit iNOS response. In the present review, we give an overview of iNOS-modulating agents with a special focus on both natural and synthetic molecules and their effects in related biological processes. The role of iNOS in physiological and pathological conditions is also discussed.

Micelle-Enabled One-Pot Guanidine Synthesis in Water Directly from Isothiocyanate using Hypervalent Iodine(III) Reagents under Mild Conditions

In this work, we developed a one-pot synthesis of guanidine directly from isothiocyanate using DIB (diacetoxyiodobenzene) as a desulfurizing agent under micellar conditions in water. Our optimization study revealed that the use of 1 % TPGS-750-M as a surfactant with NaOH as an additive base at room temperature can convert a variety of isothiocyanates and amines into corresponding guanidines in excellent yields (69-95 %). This synthetic process in water can be applied to prepare guanidine at gram-scale quantity. Our aqueous micellar medium also demonstrated high reusability as the reaction can be performed for several cycles without losing its efficiency. The reaction is metal-free, utilizes water as solvent and practical (room temperature and open flask).

Stereocontrolled synthesis of bicyclic ureas and sulfamides via Pd-catalyzed alkene carboamination reactions

The synthesis of bicyclic ureas and sulfamides via palladium-catalyzed alkene carboamination reactions between aryl/alkenyl halides/triflates and alkenes bearing pendant cyclic sulfamides and ureas is described. The substrates for these reactions are generated in 3-5 steps from commercially available materials, and products are obtained in good yield with up to >20:1 diastereoselectivity. The stereochemical outcome of the sulfamide alkene addition is consistent with a mechanism involving anti-aminopalladation of the alkene, whereas the stereochemical outcome of the urea alkene addition is consistent with a syn-aminopalladation mechanism.

Approaches for the isolation and identification of hydrophilic, light-sensitive, volatile and minor natural products

Water-soluble, volatile, minor and photosensitive natural products are yet poorly known, and this review discusses the literature reporting the isolation strategies for some of these metabolites.

Metal-catalysed reactions enabled by guanidine-type ligands

A review of metal–guanidine complexes, which are selective and powerful catalysts for organic transformations, asymmetric synthesis, and polymerisation.

New Crambescidin-Type Alkaloids from the Indonesian Marine Sponge Clathria bulbotoxa

A crude methanolic extract of the Indonesian sponge Clathria bulbotoxa showed a potent cytotoxic activity against the human epidermoid carcinoma A431 cells. An investigation of the active components led to the isolation of three new compounds named crambescidins 345 (1), 361 (2), and 373 (3), together with the known related metabolites crambescidins 359 (4), 657 (5), and 800 (6). The structures of the compounds were determined by spectroscopic analysis. These compounds 1–4 that possess a simple pentacyclic guanidine core exhibited moderate cytotoxicity against the A431 cells with the IC₅₀ values of 7.0, 2.5, 0.94, and 3.1 μM, respectively, while the known compounds 5 and 6 that possess a long aliphatic side chain were found to be significantly cytotoxic. On the other hand, in an anti-oomycete activity test against the fungus-like plant pathogen Phytophthora capsici, 1–4 showed a higher activity than that of 5 and 6, suggesting that the long aliphatic side chain plays a significant role for cytotoxicity, but is not effective or suppressive for anti-oomycete activity.

Crambescidin 800, Isolated from the Marine Sponge Monanchora viridis, Induces Cell Cycle Arrest and Apoptosis in Triple-Negative Breast Cancer Cells

Triple negative breast cancer (TNBC) is currently the only group of breast cancers without an effective targeted therapy. Marine sponges have historically been a source of compounds with anticancer activity. In this study, we screened extracts from twenty marine sponges collected off the coast of Western Australia for cytotoxic activity against TNBC cells. One very active extract derived from the sponge Monanchora viridis was selected for bioactivity-guided fractionation. Through multiple steps of purification, we isolated a potent cytotoxic compound, which was identified as crambescidin 800 (C800). We found that C800 exhibited cytotoxic potency in a panel of breast cancer cells, of which TNBC and luminal cancer cell models were the most sensitive. In addition, C800 induced cell cycle arrest at the G2/M phase, resulting in a decline in the expression of cyclin D1, CDK4, and CDK6 in TNBC cells. This effect was associated with the inhibition of phosphorylation of Akt, NF-κB, and MAPK pathways, resulting in apoptosis in TNBC cells.

Morphological and molecular systematics of the ‘Monanchora arbuscula complex’ (Poecilosclerida : Crambeidae), with the description of five new species and a biogeographic discussion of the genus in the Tropical Western Atlantic

Monanchora Carter, 1883 is a genus of shallow-water marine sponges comprising 16 species distributed worldwide, two of them in the Tropical Western Atlantic (TWA): M. arbuscula (Duchassaing & Michelotti, 1864) and M. brasiliensis Esteves, Lerner, Lôbo-Hajdu & Hajdu, 2012. The former species stands out as one of the most variable demosponges, and is very similar in spicule complement and in secondary metabolite chemistry to the Mediterranean/eastern Atlantic Crambe crambe (Schmidt, 1862), type species of Crambe Vosmaer, 1880. The aim of the present study was to revise the genus Monanchora in the TWA. In addition, we critically analyse the monophyly of Crambe and Monanchora. Maximum Likelihood and Bayesian Inference analyses of 28S and 16S rRNA sequences of the latter genera, and a redescription of the ‘M. arbuscula complex’, revealed three species: M. arbuscula s.s., M. coccinea, sp. nov. and a new species of Acarnidae – Iophon parvachela, sp. nov. Three other new species from the TWA previously assigned to Monanchora were revealed by morphological analyses, and are also described: M. bahamensis, sp. nov., M. megasigmifera, sp. nov. and a new species of Chondropsidae – Batzella catarinensis, sp. nov. A key for species identification is provided. Our results suggest that the Eastern Brazil and Southeastern Brazil Ecoregions may represent centres of diversity for Monanchora in the TWA.

Interactions of Protonated Guanidine and Guanidine Derivatives with Multiply Deprotonated RNA Probed by Electrospray Ionization and Collisionally Activated Dissociation

Interactions of ribonucleic acid (RNA) with guanidine and guanidine derivatives are important features in RNA-protein and RNA-drug binding. Here we have investigated noncovalently bound complexes of an 8-nucleotide RNA and six different ligands, all of which have a guanidinium moiety, by using electrospray ionization (ESI) and collisionally activated dissociation (CAD) mass spectrometry (MS). The order of complex stability correlated almost linearly with the number of ligand atoms that can potentially be involved in hydrogen-bond or salt-bridge interactions with the RNA, but not with the proton affinity of the ligands. However, ligand dissociation of the complex ions in CAD was generally accompanied by proton transfer from ligand to RNA, which indicated conversion of salt-bridge into hydrogen-bond interactions. The relative stabilities and dissociation pathways of [RNA+m L-n H] n- complexes with different stoichiometries (m=1-5) and net charge (n= 2-5) revealed both specific and unspecific ligand binding to the RNA.

Targeting activator protein 1 signaling pathway by bioactive natural agents: Possible therapeutic strategy for cancer prevention and intervention

Activator protein 1 (AP-1) is a key transcription factor in the control of several cellular processes responsible for cell survival proliferation and differentiation. Dysfunctional AP-1 expression and activity are involved in several severe diseases, especially inflammatory disorders and cancer. Therefore, targeting AP-1 has recently emerged as an attractive therapeutic strategy for cancer prevention and therapy. This review summarizes our current understanding of AP-1 biology and function as well as explores and discusses several natural bioactive compounds modulating AP-1-associated signaling pathways for cancer prevention and intervention. Current limitations, challenges, and future directions of research are also critically discussed.