Monthly Archives: September 2023

Photoresponsive Supramolecular Cages and Macrocycles

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Photoresponsive Supramolecular Cages and Macrocycles

Light manipulation of supramolecular assemblies is a promising method for developing complex, programmable, or multifunctional systems and nanoscopic machine-like entities. In this minireview, we discuss self-assembled and covalently bound cages and macrocycles containing photoswitches, allowing for a geometry change, breaking apart, or the disassembly and reassembly of the structures.


Abstract

The utilisation of light to achieve precise manipulation and control over the structure and function of supramolecular assemblies has emerged as a highly promising approach in the development of complex, configurable, or multifunctional systems and nanoscopic machine-like entities. In this minireview, we highlight recent examples of self-assembled and covalently bound cages and macrocycles with a focus on the external and internal functionalisation of a structure with a photoswitchable unit or the embedment of a photoswitch into the framework of a structure. Functionalising the interior or exterior of a supramolecular cage or macrocycle with a photoresponsive group enables control over different properties, such as guest binding or assembly in the solid-state, while the overall shape of the assembly often undergoes no significant change. By directly integrating a photoswitchable unit into the framework of a supramolecular structure, the isomerisation can either induce a geometry change, the disassembly, or the disassembly and reassembly of the structure. Historical and recent examples covered in this review are based on azobenzene, diarylethene, stilbene photoswitches, or alkene motors that were incorporated into macrocycles and cages constructed by metal-organic, dynamic covalent, or covalent bonds.

Siparuna guianensis Essential Oil Antitumoral Activity on Ehrlich Model and Its Effect on Oxidative Stress

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Siparuna guianensis Essential Oil Antitumoral Activity on Ehrlich Model and Its Effect on Oxidative Stress


Abstract

This work aims to evaluate the chemical composition, in vitro antioxidant capacity, and in vivo antitumoral activity of S. guianensis essential oil against Ehrlich's ascitic carcinoma and the effects on oxidative stress. The animals (Mus musculus) received a daily dose of S. guianensis oil orally (100 mg/kg) for 9 days. The main constituents of essential oil were curzerenone (16.4±1.5 %), drimenol (13.7±0.2 %), and spathulenol (12.4±0.8 %). S. guianensis oil showed antioxidant activity, inhibiting 11.1 % of DPPH radicals (95.7 mgTE/g); and 15.5 % of the β-carotene peroxidation. The group treated with S. guianensis showed a significant reduction in tumor cells (59.76±12.33) compared to the tumor group (96.88±19.15). Essential oil of S. guianensis decreased MDA levels and increased SOD levels in liver tissue. The essential oil of S. guianensis reduced oxidative stress, and showed antitumor and antioxidant activity, being characterized as a new chemical profile in the investigation of pathologies such as cancer.

Evaluations of Anticancer Effects of Combinations of Cisplatin and Tirucallane‐Type Triterpenes Isolated from Amphipterygium adstringens (Schltdl).

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Evaluations of Anticancer Effects of Combinations of Cisplatin and Tirucallane-Type Triterpenes Isolated from Amphipterygium adstringens (Schltdl).


Abstract

The cytotoxic activity of combinations of masticadienonic (AMD) or 3αOH-hydroxy-masticadienonic (3αOH-AMD) acids with cisplatin (CDDP) was evaluated against PC3 prostate and HCT116 colon cancer cell lines. Combinations A (half the IC50 value), B (IC50 value), and C (twice the IC50 value) were tested at a 1 : 1 ratio. All AMD plus CDDP combinations demonstrated increased cytotoxic effect, as determined by the sulforhodamine B test, in both cell types. The best combination was B, which showed 93 % and 91 % inhibition of the proliferation of PC3 and HCT116 cells, respectively. It also increased apoptosis in the PC3 cell lines, as evaluated by flow cytometry. However, in vivo tests showed no additional activity from the AMD plus CDDP combinations. These results showed that the increased cytotoxic activity of the combinations in vitro did not reflect in vivo tests. All combinations of 3αOH-AMD plus CDDP exerted antagonistic effects in both cell types.

Ambient Pressure X‐ray Photoelectron Spectroscopy Study of Oxidation Phase Transitions on Cu(111) and Cu(110)

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Ambient Pressure X-ray Photoelectron Spectroscopy Study of Oxidation Phase Transitions on Cu(111) and Cu(110)

Phase diagrams show the transitions of O/Cu→Cu2O→CuO on both Cu(111) and Cu(110) surfaces during the oxidation process. The oxygen adsorption induced c(6×2)-O reconstruction provides a relatively stable surface oxide layer on Cu(110), resulting a higher oxidation resistance than Cu(111).


Abstract

The surface structure effect on the oxidation of Cu has been investigated by performing ambient-pressure X-ray photoelectron spectroscopy (APXPS) on Cu(111) and Cu(110) surfaces under oxygen pressures ranging from 10−8 to 1 mbar and temperatures from 300 to 750 K. The APXPS results show a subsequential phase transition from chemisorbed O/Cu overlayer to Cu2O and then to CuO on both surfaces. For a given temperature, the oxygen pressure needed to induce initial formation of Cu2O on Cu(110) is about two orders of magnitude greater than that on Cu(111), which is in contrast with the facile formation of O/Cu overlayer on clean Cu(110). The depth profile measurements during the initial stage of Cu2O formation indicate the distinct growth modes of Cu2O on the two surface orientations. We attribute these prominent effects of surface structure to the disparities in the kinetic processes, such as the dissociation and surface/bulk diffusion over O/Cu overlayers. Our findings provide new insights into the kinetics-controlled process of Cu oxidation by oxygen.

Evaluation of Cytotoxicity and Antifungal Activity of Friedelanes from Salacia elliptica Roots

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Evaluation of Cytotoxicity and Antifungal Activity of Friedelanes from Salacia elliptica Roots


Abstract

Plants from Salacia genus are used in traditional medicine for a wide range of diseases. Previous studies reported bioactive pentacyclic triterpenoids from S. elliptica leaves and branches. In this study, the novel pentacyclic triterpenoid 7α,15α-dihydroxyfriedelan-3-one (1) was obtained from the roots of Salacia elliptica, along with seven known compounds: friedelan-3-one (2), friedelan-3β-ol (3), friedelan-1,3-dione (4), friedelan-3,15-dione (5), 15α-hydroxyfriedelan-3-one (6), 15α,26-dihydroxyfriedelan-3-one (7), and 26-hydroxyfriedelan-3,15-dione (8). Additionally, one steroid, spinasterol (9), was also identified. The chemical structures of all compounds were established through 1H and 13C-NMR. Compound 1 was analysed by additional 2D experiments (HMBC, HSQC, COSY, and NOESY) for complete elucidation. Furthermore, the cytotoxicity of compounds 2, 3, 6, 7 and 8 against the A549 lung cancer cells model was evaluated. The flow cytometry analysis revealed a significant cytotoxic activity similar to that exhibited by the triterpenoid lupeol. Additionally, compounds 2, 3, 6, and 7 were tested for in vitro antifungal activity against Candida, Cryptococcus and Sporothrix strains. However, all compounds showed no activity at the tested concentrations.

Inner‐Sphere Single Electron Transfer in Polynuclear Gold Photocatalysis

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Inner-Sphere Single Electron Transfer in Polynuclear Gold Photocatalysis

Upon photon absorption, polynuclear gold complexes undergo metal-centered excitation, resulting in long-lived triplets with an increasing coordination number. This feature facilitates direct binding with substrates in the inner coordination sphere. The formed exciplex can undergo inner-sphere electron transfer to reduce or oxidize molecules, even in cases where the redox potentials do not match.


Abstract

Photo-induced electron transfer is a fundamental step in photochemical reactions, where light energy is used to drive chemical transformations. However, conventional outer-sphere single electron transfer mechanisms encounter multiple limitations, notably requiring redox potential matching between photocatalysts and substrates, thereby impeding the activation of non-activated carbon-halogen bonds. In this concept review, we present an elucidation of the photophysical and photochemical properties exhibited by polynuclear gold photocatalysts, with a particular emphasis on their inner-sphere single electron transfer mechanism. By exploring these intricate aspects, we endeavor to furnish readers with a more profound insight into the remarkable potential of polynuclear gold photocatalysts and the indispensable role played by inner-sphere electron transfer in the realm of photocatalysis.

Antifungal Activity of Cadinane‐Type Sesquiterpenes from Eupatorium adenophorum against Wood‐Decaying Fungi

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Antifungal Activity of Cadinane-Type Sesquiterpenes from Eupatorium adenophorum against Wood-Decaying Fungi


Abstract

The present study aimed to evaluate the antifungal activities of Eupatorium adenophorum against four strains of wood-decaying fungi, including Inonotus hispida, Inonotus obliquus, and Inonotus cuticularis. Bioguided isolation of the methanol extract of E. adenophorum by silica gel column chromatography and high-performance liquid chromatography afforded six cadinane-type sesquiterpenes. Their structures were identified by nuclear magnetic resonance and MS analyses. According to the antifungal results, the inhibition rate of the compound was between 59.85 % and 77.98 % at a concentration of 200 μg/mL. The EC50 values ranged from 74.5 to 187.4 μg/mL.

A Graphene Oxide‐Supported PdCu Catalyst for Enhanced Electrochemical Synthesis of Ammonia

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A Graphene Oxide-Supported PdCu Catalyst for Enhanced Electrochemical Synthesis of Ammonia

A PdCu alloy catalyst loaded on a graphene oxide carrier was prepared through a simple liquid phase reduction method which greatly enhanced the catalytic performance with an ammonia yield of 1.62 mg h−1cm−2 and Faradaic efficiency of 38.2 % under the nitrate reduction ammonia synthesis (NO3RR) reaction at an overpotential of −0.4 V. For the nitrogen reduction ammonia, the ammonia yield was 20.83 μg h−1 cm−2 with a Faradaic efficiency of 3.8 %.


Abstract

The conventional Haber-Bosch method for the ammonia synthesis process requires high temperature and pressure. Electrochemical synthesis of ammonia, an emerging ammonia synthesis technology, is a promising approach for sustainable ammonia production that is energy-efficient and free of greenhouse gas emissions. The design and development of high-performance catalysts are the keys to promoting the sustainable ammonia production process. This work synthesized a PdCu alloy catalyst loaded on a graphene oxide carrier through a simple liquid phase reduction method. Which greatly enhanced the catalytic performance with an ammonia yield of 1.62 mg h−1cm−2 and Faradaic efficiency of 38.2 % under the nitrate reduction ammonia synthesis (NO3RR) reaction at an overpotential of −0.4 V. For the nitrogen reduction ammonia (NRR), the ammonia yield was 20.83 μg h−1 cm−2 with a Faradaic efficiency of 3.8 %. This study may provide a new idea for material design and promote ammonia synthesis development under ambient conditions.

Coupled Electrochemical Processes as Versatile Route for Converting Waste Substrates into Value Added Chemical Products

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Coupled Electrochemical Processes as Versatile Route for Converting Waste Substrates into Value Added Chemical Products

The conversion of waste substrates into value added chemical products is a promising pathway to implement principles of circular economy in chemical industry and replace fossil feedstocks. To overcome the chemical complexity and heterogenous nature of waste feedstocks coupled processes are ideally suited. Implementing electrochemical steps enhances sustainability and opens novel reaction pathways.


Abstract

There is a strong initiative in chemical industry to replace fossil resources by alternative feedstocks and implement more sustainable production routes for chemicals. Waste feedstocks are especially appealing, considering the principles of circular economy. They exhibit, however, great structural complexity, and it is challenging to convert them into defined chemical products. To still enable the conversion of waste feedstocks into value added chemicals, coupled catalytic processes are a viable solution. A first reaction step transforms the waste substrate into more defined and soluble intermediates which are subsequently converted into value added chemicals, in a second reaction step. Electrochemical reactions are of great interest for such processes, especially in the context of sustainability, as they can be powered by electricity from renewable sources and enable unique chemical transformations. In this review different strategies for converting waste substrates into value added chemicals are addressed by using process couplings including electrochemical reactions. Such coupled processes are of great interest to enable the transformation of chemical industry towards sustainable processes following the principles of circular economy.

Modulating the RAGE‐Induced Inflammatory Response: Peptoids as RAGE Antagonists

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Modulating the RAGE-Induced Inflammatory Response: Peptoids as RAGE Antagonists

Peptoids were designed to mimic receptors for advanced glycation end-products (RAGE) ligand amyloid-β (Aβ) and curtail RAGE inflammatory activation. Here, we reveal the nanomolar binding capability of the peptoid-based mimics to RAGE and demonstrate their ability to attenuate lipopolysaccharide (LPS)-induced pro-inflammatory cytokine production as well as reduce upregulation of cell surface RAGE at non-toxic concentrations.


Abstract

While the primary pathology of Alzheimer's disease (AD) is defined by brain deposition of amyloid-β (Aβ) plaques and tau neurofibrillary tangles, chronic inflammation has emerged as an important factor in AD etiology. Upregulated cell surface expression of the receptor for advanced glycation end-products (RAGE), a key receptor of innate immune response, is reported in AD. In parallel, RAGE ligands, including Aβ aggregates, HMGB1, and S100B, are elevated in AD brain. Activation of RAGE by these ligands triggers release of inflammatory cytokines and upregulates cell surface RAGE. Despite such observation, there are currently no therapeutics that target RAGE for treatment of AD-associated neuroinflammation. Peptoids, a novel class of potential AD therapeutics, display low toxicity, facile blood-brain barrier permeability, and resistance to proteolytic degradation. In the current study, peptoids were designed to mimic Aβ, a ligand that binds the V-domain of RAGE, and curtail RAGE inflammatory activation. We reveal the nanomolar binding capability of peptoids JPT1 and JPT1a to RAGE and demonstrate their ability to attenuate lipopolysaccharide-induced pro-inflammatory cytokine production as well as upregulation of RAGE cell surface expression. These results support RAGE antagonist peptoid-based mimics as a prospective therapeutic strategy to counter neuroinflammation in AD and other neurodegenerative diseases.