Chemical Diversity, Pharmacology, Synthesis and Detection of Naturally Occurring Peroxides.

Natural occurring peroxides are interesting bioprospecting targets due to their molecular structural diversity and the wide range of pharmacological activities. In this systematic review, a total of 123 peroxide compounds were analysed from 99 published papers with the compounds distributed in 31 plants, 18 animals and 41 microorganisms living in land and water ecosystems. The peroxide moiety exists as both cyclic and acyclic entities and can include 1,2-dioxolanes, 1,2-dioxane rings and common secondary metabolites with a peroxo group. These peroxides possessed diverse bioactivities including anticancer, antimalarial, antimicrobial, anti-inflammatory, neuroprotective, adipogenic suppressor, antituberculosis, anti-melanogenic and anti-coagulant agents. Biosynthetic pathways and mechanisms of most endoperoxides have not been well established. Method development in peroxide detection has been a challenging task requiring multidisciplinary investigation and exploration on peroxy-containing secondary metabolites are necessary.

A Photoreactor-Interfaced Mass Spectrometer: An Online Platform to Monitor Photochemical Reactions.

An experimental platform is reported that allows for the online characterization of photochemical reactions by coupling a continuous flow photoreactor, equipped with LED light irradiation and a dual-tipped ESI source, directly to a mass spectrometer with electrospray ionization. The capabilities of this platform are demonstrated with two classes of photoreactions: (1) the photopolymerization of methyl methacrylate and (2) photocatalyzed alkyne insertion into a 1,2,3-benzotriazinone. The online technique provides rapid information to inform the underlying photochemical mechanism and evaluate the overall photochemistry.

A potent fluorescent transmembrane HCl transporter perturbs cellular pH and promotes cancer cell death.

A series of fluorescent coumarin bis-ureas 1-4 have been synthesised, and their anion transport properties studied. The compounds function as highly potent HCl co-transport agents in lipid bilayer membranes. Single crystal X-ray diffraction of compound 1 showed antiparallel stacking of the coumarin rings, stabilised by hydrogen bonds. Binding studies, using 1H-NMR titration, showed moderate chloride binding in DMSO-d6/0.5% with 1 : 1 binding mode (for transporter 1) and 1 : 2 binding mode (host: guest, for transporters 2-4). We examined the cytotoxicity of compounds 1-4 against three cancer cell lines, lung adenocarcinoma (A549), colon adenocarcinoma (SW620) and breast adenocarcinoma (MCF-7). The most lipophilic transporter, 4 showed a cytotoxic effect against all three cancer cell lines. Cellular fluorescence studies showed compound 4 crossed the plasma membrane and localised in the cytoplasm after a short time. Interestingly, compound 4, lacking any lysosome targeting groups, was co-localised with LysoTracker Red at 4 and 8 h in the lysosome. Cellular anion transport of compound 4 was assessed by measuring intracellular pH and showed a decrease in cellular pH, which may be due to the capacity of transporter 4 to co-transport HCl across biological membranes, as evidenced by the liposomal studies.

Synthesis of 7α-Methoxy-7-(4-phenyl-1H-1,2,3-triazol-1-yl)acetamino-3'-arylthio-cephalosporic Acid Derivatives from 7-Aminocephalosporic Acid.

The aim of this project was to develop a synthetic protocol for the preparation of a cephamycin scaffold that would readily allow the synthesis of its analogues with variations at the C-7 amino group and the C-3' position. We also aimed to develop a method that avoided the use of toxic and potentially explosive diphenyldiazomethane. These aims were achieved via the synthesis of the novel α-bromo acetamide 18 which allowed functionalization at the α-bromo acetamide position by azide and then the introduction of a 4-phenyl-1H-1,2,3-triazol-1-yl moiety via a Cu(I)-catalysed azide-alkyne cycloaddition reaction with phenylacetylene. Palladium-catalyzed arylthioallylation reactions then allowed the introduction of 3'-arylthiol substituents. We also report for the first time the synthesis of the 4-methoxybenzyl ester of (6R,7S)-3-[(acetyloxy)methyl]-7-amino-7-methoxy-8-oxo-5-thia-1-azabicyclo[4.2.0]oct-2-ene-2-carboxylic acid and the use of diphenyl trichloroacetimidate, instead of diphenyldiazomethane, and 4-methoxybenzyl trichloroacetimidate to prepare related 4-methoxybenzyl esters. The chemistry described, and several of the synthetic intermediates reported here, are potentially valuable methods and scaffolds, respectively, for further development of ß-lactam antibiotics.

Phytochemistry and Pharmacology of Medicinal Plants Used by the Tenggerese Society in Java Island of Indonesia.

The archipelagic country of Indonesia is inhabited by 300 ethnic groups, including the indigenous people of Tengger. Based on the reported list of medicinal plants used by the Tengger community, we have reviewed each of them for their phytochemical constituents and pharmacological activities. Out of a total of 41 medicinal plants used by the Tengerrese people, 33 species were studied for their phytochemical and pharmacological properties. More than 554 phytochemicals with diverse molecular structures belonging to different chemical classes including flavonoids, terpenoids, saponins and volatiles were identified from these studied 34 medicinal plants. Many of these medicinal plants and their compounds have been tested for various pharmacological activities including anti-inflammatory, antimicrobial, wound healing, headache, antimalarial and hypertension. Five popularly used medicinal plants by the healers were Garcinia mangostana, Apium graveolens, Cayratia clematidea, Drymocallis arguta and Elaeocarpus longifolius. Only A. graviolens were previously studied, with the outcomes supporting the pharmacological claims to treat hypertension. Few unexplored medicinal plants are Physalis lagascae, Piper amplum, Rosa tomentosa and Tagetes tenuifolia, and they present great potential for biodiscovery and drug lead identification.

The Cascade Reactions of Indigo with Propargyl Substrates for Heterocyclic and Photophysical Diversity.

The synthesis of structurally diverse heterocycles for chemical space exploration was achieved via the cascade reactions of indigo with propargylic electrophiles. New pyrazinodiindolodione, naphthyridinedione, azepinodiindolone, oxazinoindolone and pyrrolodione products were prepared in one pot reactions by varying the leaving group (-Cl, -Br, -OMs, -OTs) or propargyl terminal functionality (-H, -Me, -Ph, -Ar). Mechanistic and density functional theory studies revealed that the unsaturated propargyl moiety can behave as an electrophile when aromatic terminal substitutions are made, and therefore competes with leaving group substitution for new outcomes. Selected products from the cascade reactions were investigated for their absorption and fluorescence properties, including transient absorption spectroscopy. This revealed polarity dependent excited state relaxation pathways, fluorescence, and triplet formation, thus highlighting these reactions as a means to access diverse functional materials rapidly.

The Detosylation of Chiral 1,2-Bis(tosylamides).

The deprotection of chiral 1,2-bis(tosylamides) to their corresponding 1,2-diamines is mostly unsuccessful under standard conditions. In a new methodology, the use of Mg/MeOH with sufficient steric additions allows the facile synthesis of 1,2-diamines in 78-98% yields. These results are rationalized using density functional theory and the examination of inner and outer-sphere reduction mechanisms.

Mutations That Increase the Stability of the Postfusion gp41 Conformation of the HIV-1 Envelope Glycoprotein Are Selected by both an X4 and R5 HIV-1 Virus To Escape Fusion Inhibitors Corresponding to Heptad Repeat 1 of gp41, but the gp120 Adaptive Mutations Differ between the Two Viruses.

Binding of the gp120 surface subunit of the envelope glycoprotein (Env) of HIV-1 to CD4 and chemokine receptors on target cells triggers refolding of the gp41 transmembrane subunit into a six-helix bundle (6HB) that promotes fusion between virus and host cell membranes. To elucidate details of Env entry and potential differences between viruses that use CXCR4 (X4) or CCR5 (R5) coreceptors, we generated viruses that are resistant to peptide fusion inhibitors corresponding to the first heptad repeat region (HR1) of gp41 that target fusion-intermediate conformations of Env. Previously we reported that an R5 virus selected two resistance pathways, each defined by an early gp41 resistance mutation in either HR1 or the second heptad repeat (HR2), to escape inhibition by an HR1 peptide, but preferentially selected the HR1 pathway to escape inhibition by a trimer-stabilized HR1 peptide. Here, we report that an X4 virus selected the same HR1 and HR2 resistance pathways as the R5 virus to escape inhibition by the HR1 peptide. However, in contrast to the R5 virus, the X4 virus selected a unique mutation in HR2 to escape inhibition by the trimer-stabilized peptide. Significantly, both of these X4 and R5 viruses acquired gp41 resistance mutations that improved the thermostability of the six-helix bundle, but they selected different gp120 adaptive mutations. These findings show that these X4 and R5 viruses use a similar resistance mechanism to escape from HR1 peptide inhibition but different gp120-gp41 interactions to regulate Env conformational changes.IMPORTANCE HIV-1 fuses with cells when the gp41 subunit of Env refolds into a 6HB after binding to cellular receptors. Peptides corresponding to HR1 or HR2 interrupt gp41 refolding and inhibit HIV infection. Previously, we found that a CCR5 coreceptor-tropic HIV-1 acquired a key HR1 or HR2 resistance mutation to escape HR1 peptide inhibitors but only the key HR1 mutation to escape a trimer-stabilized HR1 peptide inhibitor. Here, we report that a CXCR4 coreceptor-tropic HIV-1 selected the same key HR1 or HR2 mutations to escape inhibition by the HR1 peptide but different combinations of HR1 and HR2 mutations to escape the trimer-stabilized HR1 peptide. All gp41 mutations enhance 6HB stability to outcompete inhibitors, but gp120 adaptive mutations differed between these R5 and X4 viruses, providing new insights into gp120-gp41 functional interactions affecting Env refolding during HIV entry.

The evolution of sexually dimorphic cuticular hydrocarbons in blowflies (Diptera: Calliphoridae).

Cuticular hydrocarbons (CHCs) are organic compounds found on the cuticles of all insects which can act as close-contact pheromones, while also providing a hydrophobic barrier to water loss. Given their widespread importance in sexual behaviour and survival, CHCs have likely contributed heavily to the adaptation and speciation of insects. Despite this, the patterns and mechanisms of their diversification have been studied in very few taxa. Here, we perform the first study of CHC diversification in blowflies, focussing on wild populations of the ecologically diverse genus Chrysomya. We convert CHC profiles into qualitative and quantitative traits and assess their inter- and intra-specific variation across 10 species. We also construct a global phylogeny of Chrysomya, onto which CHCs were mapped to explore the patterns of their diversification. For the first time, we demonstrate that blowflies express an exceptional diversity of CHCs, which have diversified in a nonphylogenetic and punctuated manner, are species-specific and sexually dimorphic. It is likely that both ecological and sexual selection have shaped these patterns of CHC diversification, and our study now provides a comprehensive framework for testing such hypotheses.

Perylene-Monoimides: Singlet Fission Down-Conversion Competes with Up-Conversion by Geminate Triplet-Triplet Recombination.

Triplet-excited-state energies of perylene-monoimides (PMIs) lie in the range 1.12 eV ± 2 meV when compared to singlet-excited-state energies of about 2.39 eV ± 2 meV; therefore, the corresponding naphthalene-linked PMI-Dimer was investigated as a novel singlet-fission (SF) material. Ultrafast transient absorption measurements demonstrated the (S1S0)-to-1(T1T1) transformation and the involvement of a mediating step in the overall 1(T1T1) formation. The intermediate is a charge-transfer state that links the initial (S1S0) with the final 1(T1T1), and imposes charge-transfer character on both, which are thus denoted (S1S0)CT and 1(T1T1)CT. At room temperature, the decorrelation and stability of 1(T1T1)CT is affected by the geminate triplet-triplet recombination (G-TTR) of the two triplets. Independent confirmation for G-TTR to afford up-converted (S1S0)UC in fsTA and nsTA measurements with PMI-Dimer, came from probing PMI-Monomer (T1)s in triplet-triplet annihilation up-conversion (TTA-UC). The G-TTR channel, active in the PMI-Dimer at room temperature, is suppressed by working at either low temperatures (∼140 K) or in polar solvents (benzonitrile): Both scenarios assist in stabilizing (T1T1)CT. As a consequence, the triplet quantum yields are 4.2% and 14.9% at room temperature and 140 K, respectively, in 2-methyltetrahydrofuran.

Major Transitions in Cuticular Hydrocarbon Expression Coincide with Sexual Maturity in a Blowfly (Diptera: Calliphoridae).

In many animals, there is a prolonged pre-reproductive period prior to sexual maturity. To avoid premature mating attempts, it is common for phenotypic changes to occur during this period that signal the onset of reproductive viability. Among the insects, pre-reproductive phases can last for up to 50% of the adult lifespan, but little is known about the accompanying phenotypic changes that signal sexual maturity. Contact pheromones such as cuticular hydrocarbons (CHCs) may fulfil this role, as they are known to change rapidly with age in many insects. Despite this, few studies have investigated CHC development in the context of sexual maturity or considered differences in CHC development between sexes. The blowflies (Diptera: Calliphoridae) provide an ideal system for such studies because CHCs are known to change rapidly with age and likely play an important role in sexual behaviour. As such, using the small hairy maggot blowfly Chrysomya varipes, we investigate whether there are age- and sex-specific changes in CHCs over the course of adult blowfly maturation. We show that: (1) major qualitative transitions in CHC expression coincide with the onset of sexual maturity and (2) these changes occur more slowly in females - in line with their extended pre-reproductive phase. We suggest that CHCs may play an important role in signalling sexual maturity in the small hairy maggot blowfly and that this species will likely serve as a useful model for understanding the complex ontogeny of cuticular hydrocarbons in insects.

Stimuli-Responsive Cycloaurated "OFF-ON" Switchable Anion Transporters.

Anion transporters have shown potential application as anti-cancer agents that function by disrupting homeostasis and triggering cell death. In this research article we report switchable anion transport by gold complexes of anion transporters that are "switched on" in situ in the presence of the reducing agent GSH by decomplexation of gold. GSH is found in higher concentrations in tumors than in healthy tissue and hence this approach offers a strategy to target these systems to tumors.

How To Make Nitroaromatic Compounds Glow: Next-Generation Large X-Shaped, Centrosymmetric Diketopyrrolopyrroles.

Red-emissive π-expanded diketopyrrolopyrroles (DPPs) with fluorescence reaching λ=750 nm can be easily synthesized by a three-step strategy involving the preparation of diketopyrrolopyrrole followed by N-arylation and subsequent intramolecular palladium-catalyzed direct arylation. Comprehensive spectroscopic assays combined with first-principles calculations corroborated that both N-arylated and fused DPPs reach a locally excited (S1 ) state after excitation, followed by internal conversion to states with solvent and structural relaxation, before eventually undergoing intersystem crossing. Only the structurally relaxed state is fluorescent, with lifetimes in the range of several nanoseconds and tens of picoseconds in nonpolar and polar solvents, respectively. The lifetimes correlate with the fluorescence quantum yields, which range from 6 % to 88 % in nonpolar solvents and from 0.4 % and 3.2 % in polar solvents. A very inefficient (T1 ) population is responsible for fluorescence quantum yields as high as 88 % for the fully fused DPP in polar solvents.

HIV-1 gp41 Residues Modulate CD4-Induced Conformational Changes in the Envelope Glycoprotein and Evolution of a Relaxed Conformation of gp120.

Entry of human immunodeficiency virus type 1 (HIV-1) into host cells is mediated by conformational changes in the envelope glycoprotein (Env) that are triggered by Env binding to cellular CD4 and chemokine receptors. These conformational changes involve the opening of the gp120 surface subunit, exposure of the fusion peptide in the gp41 transmembrane subunit, and refolding of the gp41 N- and C-terminal heptad repeat regions (HR1 and HR2) first into an extended prehairpin intermediate and then into a compact 6-helix bundle (6HB) that facilitates fusion between viral and host cell membranes. Previously, we reported that Envs resistant to HR1 peptide fusion inhibitors acquired key resistance mutations in either HR1 or HR2 that increased 6HB stability. Here, we identify residues in HR1 that contribute not only to fusion inhibitor resistance and 6HB stability but also to reduced reactivity to CD4-induced conformational changes that lead to 6HB formation. While all Envs show increased neutralization sensitivity to mimetic CD4 (mCD4), Envs with either the E560K or Q577R HR1 mutation reduced conformational reactivity to CD4 that resisted viral inactivation and triggering to the 6HB. Using a panel of monoclonal antibodies (mAbs), we further determined that Envs from both HR1 and HR2 resistance pathways exhibit a relaxed trimer conformation due to gp120 adaptive mutations in different regions of Env that segregate by resistance pathway. These findings highlight regions of cross talk between gp120 and gp41 and identify HR1 residues that play important roles in regulating CD4-induced conformational changes in Env.IMPORTANCE Binding of the HIV envelope glycoprotein (Env) to cellular CD4 and chemokine receptors triggers conformational changes in Env that mediate virus entry, but premature triggering of Env conformational changes leads to virus inactivation. Currently, we have a limited understanding of the network of residues that regulate Env conformational changes. Here, we identify residues in HR1 of gp41 that modulate conformational changes in response to gp120 binding to CD4 and show that the mutations in HR1 and HR2 that confer resistance to fusion inhibitors are associated with gp120 mutations in different regions of Env that confer a more open conformation. These findings contribute to our understanding of the regulation of Env conformational changes and efforts to design new entry inhibitors and stable Env vaccine immunogens.

Conformational Stability of the Hemagglutinin of H5N1 Influenza A Viruses Influences Susceptibility to Broadly Neutralizing Stem Antibodies.

Vaccines that elicit broadly neutralizing antibodies to the conserved stem of hemagglutinin (HA) are being developed as universal influenza vaccines that protect against influenza across multiple years. However, different influenza virus strains, even those in the same subtype with identical stem sequences, can vary in susceptibility to broadly neutralizing stem antibodies, and the reasons are not understood. Here we studied potential mechanisms underlying the differing sensitivities of a panel of H5N1 HA pseudoviruses to broadly neutralizing stem antibodies. We found that greater HA conformational stability, as measured by thermal inactivation and pH triggering of conformational changes, correlates with reduced neutralization sensitivity and antibody binding to HA under neutral- and low-pH conditions. Our data indicate that the conformational stability of HA is an important attribute of susceptibility to broadly neutralizing stem antibodies and is influenced by residues outside the stem antibody epitopes.IMPORTANCE The influenza virus surface glycoprotein hemagglutinin (HA) mediates virus attachment and membrane fusion between virus and host cells, allowing the viral core to enter the host cell cytoplasm for replication. Fusion occurs when HA undergoes low-pH-induced-conformational changes during endocytosis. Broadly neutralizing antibodies targeted to the conserved stem region of HA interfere with conformational changes required for fusion. Vaccines that elicit such antibodies are being developed as novel universal influenza vaccines for multiyear protection. We investigated why H5N1 HAs from different strains differ in their sensitivity to broadly neutralizing stem antibodies despite having conserved epitopes. We report that HA conformational stability due to residues outside the antibody binding site accounted for much of the variation in susceptibility to neutralization by stem antibodies. These findings highlight the importance of nonepitope residues in influencing neutralization sensitivity to stem antibodies and the complexities in developing universal vaccines targeting conserved epitopes in the HA stem.

Desymmetrization Reactions of Indigo with Grignard Reagents for the Synthesis of Selective Antiplasmodial [1H,3'H]-3-Aryl-2,2'-diindol-3'-ones.

The nucleophilic addition of organomagnesium and organolithium species to the cheap and robust natural dye indigo led to desymmetrization of the heterocyclic nucleus via a Grignard addition-dehydration procedure. Twenty-seven diversely functionalized [1H,3'H]-3-substituted 2,2'-diindol-3'-ones were synthesized by this methodology, with several showing submicromolar inhibition and exquisite selectivity against P. falciparum parasites (3D7 and Dd2 strains) in vitro. This work demonstrates the utility of indigo dye as a highly versatile scaffold for the synthesis of structurally diverse, bioactive heterocycles.

Synthesis and Density Functional Theory Studies of Azirinyl and Oxiranyl Functionalized Isoindigo and (3Z,3'Z)-3,3'-(ethane-1,2-diylidene)bis(indolin-2-one) Derivatives.

The design and synthesis of functionalized isoindigo compounds by reaction of isoindigo with (S)-glycidyl tosylate, epibromohydrin, 2-(bromomethyl)-1-(arylsulfonyl)aziridine, and 2-(bromomethyl)-1-(alkylsulfonyl)aziridine in the presence of MeONa proceed under mild conditions in moderate yields. (3Z,3'Z)-3,3'-(Ethane-1,2-diylidene)bis(1-(oxiran-2-ylmethyl)indolin-2-one), with an extended central olefin π-conjugated moiety was also reacted with methyl-oxiranes to give the corresponding N,N'-disubstituted derivative. Calculations with DFT and TD-DFT of hypothetical isoindigo-thiophene DA molecules with various electron withdrawing substituents, including aziridine, oxirane, nitrile, carbonyl, and sulfonate, indicated that the proximity and strength of the functional group have a significant effect on the HOMO, LUMO, vertical excitation energy, and oscillator strength of the π-π* transitions.

Anti-Infective and Anti-Cancer Properties of the Annona Species: Their Ethnomedicinal Uses, Alkaloid Diversity, and Pharmacological Activities.

Annona species have been a valuable source of anti-infective and anticancer agents. However, only limited evaluations of their alkaloids have been carried out. This review collates and evaluates the biological data from extracts and purified isolates for their anti-infective and anti-cancer activities. An isoquinoline backbone is a major structural alkaloid moiety of the Annona genus, and more than 83 alkaloids have been isolated from this genus alone. Crude extracts of Annona genus are reported with moderate activities against Plasmodium falciparum showing larvicidal activities. However, no pure compounds from the Annona genus were tested against the parasite. The methanol extract of Annona muricata showed apparent antimicrobial activities. The isolated alkaloids from this genus including liriodenine, anonaine, asimilobine showed sensitivity against Staphylococcus epidermidis. Other alkaloids such as (+)-Xylopine and isocoreximine indicated significant anti-cancer activity against A549 and K-562 cell lines, respectively. This review revealed that the alkaloids from Annona genus are rich in structural diversity and pharmacological activities. Further exploration of this genus and their alkaloids has potential for developing novel anti-infective and anticancer drugs.

Cascade reactions of indigo with oxiranes and aziridines: efficient access to dihydropyrazinodiindoles and spiro-oxazocinodiindoles.

The base-initiated alkylation of the abundant natural dye indigo 1 with ring-strained electrophiles results in the unprecedented, one-pot synthesis of functionalised dihydropyrazino[1,2-a:4,3-a']diindoles, dihydroepoxy[1,5]oxazocino[5,4-a:3,2-b']diindoles, and dihydrodiazepino[1,2-a:4,3-a']diindoles, resulting from intramolecular ring opening-expansion cyclisation processes of their parent oxiranes and aziridines. Regiochemical and stereochemical aspects of the reactions are reported together with integrated mechanistic proposals. This new indigo cascade chemistry should have broad applicability in the synthesis of chemical architectures, not readily-accessible by other means. The three-step synthesis of the useful synthetic precursor (R)-2-(chloromethyl)-1-tosylaziridine 14 is also described. Initial biological activity investigations into these new 2,2'-dindolyl-based heterocyclic derivatives revealed potent, selective antiplasmodial activity in vitro for several isolated structures, with IC50 values as low as 76.6 nM for (±)-8, while demonstrating low human cell toxicity.

An improved synthesis of pyrido[2,3-d]pyrimidin-4(1H)-ones and their antimicrobial activity.

The screening of a small library of diverse chemical structures resulted in the identification of 2-thioxodihydropyrido[2,3-d]pyrimidine 10a as having broad spectrum antibacterial activity (MIC 0.49-3.9 µg mL-1), and reasonable antifungal activity (MIC 31.25 µg mL-1). An expeditious synthesis of 10a was optimized by varying solvents, catalysts and the use of microwave irradiation with the best conditions using DMF as a solvent, I2 (10 mol%) and a 30 minutes reaction time compared to 15 h for classic conventional heating. The pharmacokinetic properties and calculation of drug likeness of 10a suggested good traditional drug-like properties and led to the synthesis of a small library with seven compounds 10a and 10d-i showing broad antimicrobial activity (MIC = 0.49-7.81 µg mL-1) and selectivity indices of more than 5.6 against the normal colon cell line (CCD-33Co). The antifungal activity of compounds 10d-i was moderate to strong with MIC values of 1.95-15.63 µg mL-1.