Two Pairs of New Bisabolane‐Type Sesquiterpenoids from Aspergillus sydowii

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Two Pairs of New Bisabolane-Type Sesquiterpenoids from Aspergillus sydowii


Abstract

Two pairs of new bisabolane-type sesquiterpenoids, (+)-aspersydowin A (7S) [(+)-1], (−)-aspersydowin A (7R) [(−)-1], (+)-aspersydowin B (7S,11S) [(+)-2], (−)-aspersydowin B (7R,11R) [(−)-2], along with six known compounds (1–8) were isolated from the fungus Aspergillus sydowii. Compounds 1 and 2 are enantiomers resolved by the Chiralpak IC, using a hexane- propan-2-ol mobile phase. The structure of 1 and 2 with absolute configuration were assigned tentatively by 1D (1H, 13C, and DEPT) & 2D (HSQC, 1H–1H COSY, HMBC, and NOESY) NMR data analyses and ECD calculations. Compounds 1–8 were screened for the biological activities in vitro. The results showed that compounds 3, 4 and 8 exhibited immunosuppressive activities with IC50 values of 10.9, 17.6 and 13.4 μM, respectively.

Defect‐induced Synthesis of Highly Dispersed Hydroxyapatite‐Supported Vanadium Oxide for the Oxidative Dehydrogenation of Cyclohexane

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Defect-induced Synthesis of Highly Dispersed Hydroxyapatite-Supported Vanadium Oxide for the Oxidative Dehydrogenation of Cyclohexane

Hydroxyapatite (HAP) contains abundant defect sites and easily releases hydroxyl groups to produce new vacancies under calcination at high temperature. The highly dispersed VOx/HAP catalyst was prepared by an impregnation method using these defects as inducement. VOx species with different structures were analysed by XRD, XPS, H2-TPR, Raman and UV–vis spectroscopy. At low calcination temperatures (500 °C and 600 °C), the V species are mainly V2O5 crystals. At high calcination temperatures (above 700 °C), VOx on the HAP surface fills these defect sites and strongly interacts with HAP to form Ca−O−V or P−O−V bands. These scattered defects improved the dispersion of V species. An emphasis is given to the study of the catalytic performances in ODH of cyclohexane over the VHAP catalysts. The highly dispersed VOx/HAP catalyst showed a high selectivity of cyclohexene, and the selectivity reached 48.2 % when the conversion of was 13.1 % at 410 °C. These improved selectivity is directly related to the chemical environment of highly dispersed VOx species. In addition, the acidity reduction caused by high temperature calcination leads to the decrease of the adsorption capacity of VHAP to cyclohexene, which promotes the desorption of cyclohexene on the catalyst surface, inhibits the deep oxidation of cyclohexene and improves the selectivity.


Abstract

Hydroxyapatite (HAP) contains abundant defect sites and easily releases hydroxyl groups to produce new vacancies under calcination at high temperature. The highly dispersed VOx/HAP catalyst was prepared by an impregnation method using these defects as inducement. VOx species with different structures were analysed by XRD, XPS, H2-TPR, Raman and UV–vis spectroscopy. At low calcination temperatures (500 °C and 600 °C), the V species are mainly V2O5 crystals. At high calcination temperatures (above 700 °C), VOx on the HAP surface fills these defect sites and strongly interacts with HAP to form Ca−O−V or P−O−V bands. These scattered defects improved the dispersion of V species. These highly dispersed VOx/HAP catalysts were used for oxidative dehydrogenation (ODH) of cyclohexane to cyclohexene. The highly dispersed VOx/HAP catalyst showed a high selectivity for cyclohexene, and the selectivity reached 48.2 % when the conversion of cyclohexane was 13.1 % at 410 °C.

Anchoring (fullerol‐)Ru‐based‐complex onto TiO2 for Efficient Water Oxidation Catalysis

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Anchoring (fullerol-)Ru-based-complex onto TiO2 for Efficient Water Oxidation Catalysis

A fullerol-based ruthenium complex was prepared, and the heterogeneous (fullerol)-Ru-based water oxidation catalysts (WOC) anchored on the surface of the nano-TiO2 were developed. Mechanistic studies revealed the anchoring of Ru-based WOC to TiO2 result in a decrease in the redox potentials of RuIV/III couples,a nd decrease the barrier of the crucial O−O bond-forming step, and thus the catalytic activity of the nano-catalysts was improved.


Abstract

Ruthenium polypyridine complexes are the most effective catalysts for the water oxidation reaction (WOR), but the catalytic activity still has a large room for improvement. Herein, a fullerol-based ruthenium complex was prepared by the covalent grafting of the polypyridyl ruthenium complex of water oxidation catalyst (WOC) with fullerol, and the (fullerol)-Ru-based WOCs anchored on the surface of nano-TiO2 were prepared through a sensitization strategy. The synthesized heterogeneous nano-catalysts are fully characterized by X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), transmission electron microscopy (TEM), infrared spectroscopy (IR), Brunauer–Emmett–Teller (BET) specific surface area and pore size distribution, and diffusion reflection ultraviolet-visible spectrum (DRS). The chemical oxygen evolution experiments reveal that the WOR catalyzed by the catalyst is a first-order reaction with respect to Ce (NH4)2(NO3)6 (denoted as CAN) concentration when using CAN as the sacrificial oxidant under acidic conditions. The anchoring of Ru-based WOC to TiO2 result in a decrease in the redox potentials of RuIV/III couples, which decrease the barrier of the crucial O−O bond-forming step, and the heterogeneous nano-catalyst exhibit a high catalytic activity with a turnover frequency of 13.4 s−1 and more excellent stability with a 15-min-turn over number of 1054 for TiO2-fullerol-based ruthenium complex WOC.

Synthesis and Antioxidant Properties of Psoralen Derivatives

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Synthesis and Antioxidant Properties of Psoralen Derivatives


Abstract

Five psoralen derivatives were synthesized and the structures of them were characterized by 1H-NMR, 13C-NMR, and IR. The antioxidant properties of the compounds were tested by inhibiting the free radical-initiated DNA oxidation and scavenging the radical reaction. The results showed that the effective stoichiometric factors (n) of the compounds V and IV could reach 2.00 and 2.11 in the system of inhibiting the DNA oxidation reaction initiated by 2,2′-Azobis(2-methylpropionamidine) dihydrochloride (AAPH). In the inhibition of ⋅OH-oxidation of the DNA system, compounds I~V showed antioxidant properties. The thiobarbituric acid absorbance (TBARS) percentages of compounds IV and V were 76.19 % and 78.84 %. Compounds I~V could also inhibit Cu2+/GSH-oxidation of DNA, and all compounds exhibited good antioxidant properties except compound II (94.00 %). All the five compounds were able to trap diammonium 2,2′-azinobis(3-ethylbenzothiazoline-6-sulfonate) salt radical (ABTS+⋅), 2,2-diphenyl-1-picrylhydrazyl radical (DPPH⋅) and 2,6-di-tert-butyl-alpha-(3,5-di-tert-butyl-4-oxo-2,5-cyclohexadien-p-tolylox radical (galvinoxyl⋅). The ability of compounds I~V to scavenge those free radicals can be measured by the k values. The k values ranged from 0.07 to 0.82 in scavenging ABTS+⋅, galvinoxyl, and DPPH radicals, respectively.

Biochemical and Structural Characterization of a Uronic Acid Oxidase from Citrus sinensis

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Biochemical and Structural Characterization of a Uronic Acid Oxidase from Citrus sinensis

Aldaric acids are attractive diacids that can be prepared by selective oxidation of carbohydrates. The discovery, biochemical and structural characterization of a VAO-type flavin-containing carbohydrate oxidase from Citrus sinensis: URAOCs3 is reported. The selective oxidation of D-galacturonic acid in a complex mixture is demonstrated.


Abstract

Aldaric acids are attractive diacids that can be prepared by selective oxidation of carbohydrates. For this, effective biocatalysts are in demand. This work reports on the discovery, biochemical and structural characterization of a VAO-type flavin-containing carbohydrate oxidase from Citrus sinensis: URAOCs3. URAOCs3 could be overexpressed using prokaryotic and eukaryotic expression systems. Extensive biochemical characterization revealed that the enzyme displays a high thermostability and an exquisite selectivity for uronic acids, galacturonic acid and glucuronic acid. The enzyme was further investigated by determining the crystal structure. The selective oxidation of D-galacturonic acid in a complex mixture was demonstrated, showing how URAOCs3 was found to be highly effective in selectively producing galactaric acid while leaving other carbohydrates untouched. In addition to the specific discovery of URAOCs3, these findings suggest that plant proteomes can be an interesting source for new biocatalysts.

Virus‐Bionic Mesoporous Silica Nanoplatform for Malignant Tumor Inhibition via Effective Cellular Uptake and Precise Drug Delivery

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Virus-Bionic Mesoporous Silica Nanoplatform for Malignant Tumor Inhibition via Effective Cellular Uptake and Precise Drug Delivery

Virus-bionic mesoporous-silica-based nanocarriers can be successfully prepared for precise programmed drug delivery. These unique viral mimic nanovesicles not only present virus bionic counterparts and nanostructures, but also have infectious virus-like properties toward tumor cells and tumor tissues, showing rapid cell uptake.


Abstract

Over the past few decades, sophisticated nanomaterials have been used as carries for the targeted delivery of therapeutics to solid tumors. However, the low efficiency of intracellular internalization of nanocarriers in current use restricts their biomedical application. In this work, we demonstrate that novel virus-bionic mesoporous-silica-based nanocarriers can be successfully prepared for programmed precise drug delivery. These unique viral mimic nanovesicles not only present virus bionic counterparts and nanostructures, but also have infectious virus-like properties toward tumor cells and tumor tissues. Encouragingly, their large surface area (322.1 m2/g) endows them with high loading capacity for therapeutic agents, especially, they have more effective gene transfection properties than the commercially available LipoGeneTM transfection reagent. Thanks to their virus-inspired morphology, they exhibit outstanding cellular uptake efficiency with living tumor cells and the ability to invade cells in large quantities with incubation times as short as 5 min, which is much faster than traditional mesoporous silica nanoparticles (mSN) with smooth appearance. Importantly, after doxorubicin (DOX) loading and surface modification of tumor recognition motifs, RGD (Arg-Gly-Asp, vMN@DOX-RGD), the bionic drug-loaded viral mimics elicit potent tumor cell elimination both in vitro and in vivo, greatly exceeding the mSN-based group. Our work paves the way toward virus bionic nanocarrier design for malignant tumor suppression in the clinic.

Repurposing Salicylamides to Combat Phytopathogenic Bacteria and Induce Plant Defense Responses

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Based on the research strategy of "drug repurposing", a series of derivatives and marketed drugs that containing salicylic acid skeleton were tested for their antibacterial activities against phytopathogens. Salicylic acid can not only regulate some important growth metabolism of plants, but also induce plant disease resistance. The bioassay results showed that the salicylamides exhibited excellent antibacterial activity. Especially, oxyclozanide showed the best antibacterial effect against Xanthomonas oryzae, Xanthomonas axonopodis pv. citri and Pectobacterium atroseptica with MICs of 0.78, 3.12 and 12.5 μg.mL-1, respectively. In vivo experiments with rice bacterial leaf blight had further demonstrated that oxyclozanide exhibited stronger antibacterial activity than the commercial bactericide, thiodiazole copper. Oxyclozanide could induce plant defense responses through the determination of salicylic acid content and the activities of defense-related enzymes including CAT, POD, and SOD in rice. The preliminarily antibacterial mechanism study indicated that oxyclozanide exhibited the antibacterial activity by disrupting cell integrity and reducing bacterial pathogenicity. Additionally, oxyclozanide could induce plant defense responses through the determination of salicylic acid content.

Piano‐stool dinuclear ruthenium (II) complexes of pyrazine‐carboxylate/carboxamide ligands: Structural studies and catalytic transfer hydrogenation of ketones

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Piano-stool dinuclear ruthenium (II) complexes of pyrazine-carboxylate/carboxamide ligands: Structural studies and catalytic transfer hydrogenation of ketones

Dinuclear piano-stool ruthenium (II) complexes anchored on pyrazine-based carboxylic carboxamide ligands catalyse transfer hydrogenation of a wide of ketones at low catalyst loadings.


Reactions of ligand pyrazine-2-carboxylic acid (HL1) with [Ru(η6-p-cymene)Cl2]2 precursor gave the dinuclear piano-stool ruthenium (II) complex [{Ru(η6-p-cymene)Cl2}-μ-(L1)-{Ru(p-cymene)Cl}] (Ru1). Separately, reactions of N-(quinolin-8-yl) pyrazine-2-carboxamide (HL2), 5-methyl-N-(−(quinolin-8-yl) pyridine-2-carboxamide (HL3) and 5-chloro-N-(quinolin-8-yl) pyridine-2-carboxamide (HL4) with [Ru(η6-p-cymene)Cl2]2 dimer in the presence of KPF6 afforded the cationic dinuclear complexes [{Ru(η6-p-cymene)Cl}2-μ-(L2)][PF6] (Ru2), [{Ru(η6-p-cymene)Cl}2-μ-(L3)][Ru(L3)Cl3] (Ru3) and [{Ru(η6-p-cymene)Cl}2-μ-(L4)][PF6] (Ru4). The Ru (II) complexes were analysed using FT-IR, 1H, 13C{1H}, 31P{1H} (Ru2 and Ru4) and 19F (Ru2 and Ru4) NMR spectroscopic techniques, micro-analyses and mass spectrometry. Molecular structures of complexes Ru1 and Ru3 were confirmed to display piano-stool coordination nature using single-crystal X-ray crystallography analyses. All the complexes (Ru1–Ru4) mediated the transfer hydrogenation (TH) of a broad spectrum of ketones in isopropanol in the presence of a base and demonstrated high catalytic activities (TON of 24,000) at catalyst concentrations of 0.002 mol%. In general, the catalytic performance of these Ru (II) complexes depended on the identity of the ligands, coordination chemistry and ketone substrates.

Chiroptical Generation, Switching, and Long‐Term Memory in Supramolecular Azobenzene‐Pendant Polymer: Regulation by Cellulose Peralkyl Esters, D‐/L‐Glucose Permethyl Esters, Solvents, UV Light Irradiation, and Thermal Annealing Process

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Chiroptical Generation, Switching, and Long-Term Memory in Supramolecular Azobenzene-Pendant Polymer: Regulation by Cellulose Peralkyl Esters, D-/L-Glucose Permethyl Esters, Solvents, UV Light Irradiation, and Thermal Annealing Process†

The chirality transfer from a natural chiral biosource to achiral azobenzene polymers is developed based on the simple and efficient spin-coated film. The annealing treatment, the content of chiral inducer and the molecular weight of the Azo polymer are key to the induction of supramolecular chirality by cellulose derivatives. The corresponding chirality-inducing mechanism was demonstrated to arise from the aggregation chirality induced by the C-H/O=C and C-H/π interactions between the glucose repeating units and the PMMAzo polymer side-chains.


Comprehensive Summary

Various optically active polymers are known to afford sophisticated chirality-related functionalities, i.e., asymmetric catalysis, chiroptical switching and memory in UV-vis-NIR region, chromatographic separation of enantiomers, and sensors for molecular chirality. Recently, material researchers have paid much attention to the design of chiral supramolecular architectures from achiral polymers upon intermolecular interactions with help of greener biosources. The present article reports an instantaneous generation of ambidextrous supramolecules revealing light-driven chiroptical switching/memory in UV-vis region when achiral azobenzene-containing vinylpolymers are non-covalently interacted with alkyl ester derivatives of natural cellulose and D-/L-glucose. It was recognized that the semi-synthetic biomaterials efficiently work as chirality-inducing scaffoldings to several achiral and optically inactive molecules, oligomers, and polymers. Our successful results shed light on a new approach of how inexpensive poly-/mono-saccharide derivatives can afford supramolecular chiroptical systems with the azobenzene pendant polymer as aggregates in suspension and liquid-crystalline films with minimal energy, time, and cost.

Manganese Exacerbates Seasonal Health Declines in a Suicidally‐Breeding Mammal

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Abstract

Reproductive costs must be balanced with survival to maximise lifetime reproductive rates; however, some organisms invest in a single, suicidal bout of breeding known as semelparity. The northern quoll (Dasyurus hallucatus) is an endangered marsupial in which males, but not females, are semelparous. Northern quolls living near mining sites on Groote Eylandt, Northern Territory, Australia, accumulate manganese (Mn) in their brains, testes, and hair, and elevated Mn impacts motor performance. Whether Mn is associated with other health declines is yet unknown. Here, we show that male and female northern quolls with higher Mn accumulation had a 20% reduction in immune function and a trend toward reduced cortisol concentrations in hair. The telomere lengths of male quolls did not change pre- to post-breeding, but those with higher Mn levels had longer telomeres; in contrast, the telomeres of females shortened during the breeding season but recovered between the first year and second year of breeding. In addition, the telomeres of quolls that were re-captured declined at significantly higher rates in quolls with higher Mn between pre-breeding, breeding, and/or post-breeding seasons. Future work should determine whether changes in cortisol, immune function, or telomere length affect reproductive output or survival—particularly for semelparous males.