Synthesis strategies of covalent organic frameworks: An overview from nonconventional heating methods and reaction media

Covalent organic frameworks(COFs), as an emerging class of porous crystalline materials constructed by covalent links between the building monomers, have gained tremendous attention. Over the past 15 years, COFs have made rapid progress and substantial development in the chemistry and materials fields. However, the synthesis of COFs has been dominated by solvothermal methods for a long time and it usually involves high temperature, high pressure and toxic organic solvents, which created many challenges for environmental considerations. Recently,the exploration of new approaches for facile fabrication of COFs has aroused extensive interest. Hence, in this review, we comprehensively describe the synthetic strategies of COFs from the aspects of nonconventional heating methods and reaction media. In addition, the advantages,limitations and properties of the preparation methods are compared. Finally, we outline the main challenges and development prospects of the synthesis of COFs in the future and propose some possible solutions.

Diterpenoid Alkaloids and One Lignan from the Roots of Aconitum pendulum Busch

Diterpenoid alkaloids have neroprotective activity.Herein,three napelline-type diterpenoid alkaloids 1-3,two aconitine-type diterpenoid alkaloids 4-5,and one isoquinline-type alkaloid 6,as well as one lignan glycoside 7,have been isolated from the roots of Aconitum pendulum Busch.Compounds 1 and 7 were new compounds,and their chemical structures were determined on the basis of nuclear magnetic resonance(NMR)spectra and mass spectrometry analysis.A ThT assay revealed that compound 2 showed significant disaggregation potency on the Aβ_(1−42)aggregates.

Wolfberry extracts inhibit Aβ1-42 aggregation and rescue memory loss of AD drosophila

This study is to investigate the potential of wolfberry water extracts for the treatment of Alzheimer’s disease(AD)and the relationship between their anti-AD property and the geographic locations in China.Total extracts of all wolfberry samples showed the potent to decrease self-induced Aβ1-42 aggregation and Cu2+-induced Aβ1-42 aggregation and the antioxidant capacity as well as the bioactivity for binding biometal.A transgenic drosophila model assay revealed that TE of S1 and S6(S1-TE and S6-TE)at 100μg/mL demonstrated the potent rescue effect on memory loss compared to the positive control memantine at 20μg/mL.Further study also revealed the polysaccharide extracts could contribute to their anti-AD property,and the anti-AD activity conspicuously depends on growing environment.Wolfberry samples S1 and S6 showed much more potent anti-AD property.Meanwhile this study demonstrated that the Chinese commonly consumed wolfberry in boiling water might have the beneficial function to prevent AD pathology.

Phytochemicals and biological activities of Ligularia species

Ligularia,an important genus of the Compositae family,has captured the interest of natural product chemists for years.Phytochemical investigations on the title genus have led to isolation of hundreds of secondary metabolites with various skeletons.Herein,we summarized the chemical constituents of this genus and their biological activities over the past few decades.

Sesquiterpenoids from the Rhizomes of Homalomena occulta

Naturally occurring oplopanane sesquiterpenoids are rarely reported.A phytochemical investigation on the rhizomes of Homalomena occulta(Lours)has resulted in the discovery of six oplopanane sesquiterpenoids(1–6),including four new(1–4)and one 3,5-seco-oplopanane(6),together with three previously reported sesquiterpenoids(7-9).In addition three new oplopananes(2a–4a)were also obtained by chemical transformation.All structures of these sesquiterpenoids were established based on the comprehensive spectroscopic analyses,including NMR,MS,and IR,and comparing with the literatures.

Two New Eudesmane Sesquiterpenoids from the Flowers of Chrysanthemum indicum

The fowers of Chrysanthemum indicum,i.e.Ye-ju-hua recorded in the Chinese Pharmacopoeia,has been widely used in China as an important heat-clearing and detoxifying herb for the treatment of infammation,headache,and vertigo.A phytochemical investigation of this herb has led to the isolation of two new eudesmane sesquiterpenoids,7-epi-eudesm4(15),11(13)-diene-1β,3β-diol(1)and 7-epi-1β-hydroxy-β-eudesmol(2).The molecular structures of these new sesquiterpenoids were established based on the comprehensive spectroscopic analyses,including NMR,MS,and IR,and comparing with the literatures.

Effect of Occupational Manganese Exposure on Uric Acid Levels in Human Urine

Objective To investigate the effect of long-term and low-level occupational Mn exposure on the level of uric acid （UA） in human urine. Methods In this study, 65 volunteers were recruited, who were working on welding and foundry work in an plant in Gansu province, China. Additionally, 29 control samples were collected from individuals who did not have any history of excessive Mn exposure. An improved high performance liquid chromatography system equipped with a diode-array detector （HPLC-DAD） method was developed to determine the UA level in human urine. A Spectra AA 220 Atomic Absorption Spectrophotometer （AAS） was used to measure the Mn level in the urine. Results The analytical method was validated acceptable accuracy, precision, and recovery significantly lower than that of control samples for concentrations ranging from 3.82-45.84 pg/mL with Overall, the UA levels of Mn exposure samples were （P〈O.O5）. Conclusion The practical method developed here is suitable for both routine monitoring of UA level in human urine and metabolism research. Long-term and low-level occupational Mn exposure may lead to a lower UA level in urine, and UA might be an indicator of the early stage of manganism.

Effects of Different Wall-breaking Methods on Extraction of Solanesol from Stems and Leaves of Potato

In order to extract solanesol from potato stems and leaves more effectively and improve the extraction rate of solanesol, the same batch of potato stems and leaves harvested from Guyuan, Ningxia was selected as a research object, cell wall of potato stems and leaves was broken by enzymolysis with cellulase and high- speed shearing, and then reflux-extracted with 95% ethanol. Solanesol content was determined by HPLC, and extract yield was calculated. Extract yield and solanesol extraction rate was used as an index for comparison of difference between the 2 wall-breaking methods, so as to select the optimal wall-breaking method. The results showed that enzymolysis with cellulase exhibited extraction rate and extract yield of solanesol of 91.38% and 8.02%, respectively, which were better than those under high-speed shear emulsification technique. The enzymolysis wall-breaking method has the advantages of simple operation and strong feasibility.

Colorimetric detection of α-glucosidase activity using Ni-CeO_(2)nanorods and its application to potential natural inhibitor screening

In this work,we established an exceptionally facile method for the preparation of Ni-CeO_(2)nanorods in a kind of deep eutectic solvents(DESs)composed of l-proline and Ce(NO_(3))_(3)·6H_(2)O.First,Ni-CeO_(2)nanorods were successfully prepared by adding Ni(NO_(3))_(3)·6H_(2)O to DESs.Then,we found that Ni-CeO_(2)nanorods prepared in DESs have more prominent oxidase-like activity than pure CeO_(2).The outstanding catalytic activity of Ni-CeO_(2)could be ascribed to its high Ce^(3+)/Ce^(4+)ratio.As a proof-of-concept application,the Ni-CeO_(2)nanorods were successfully acted as a colorimetric platform for the sensitive determination of ascorbic acid andα-glucosidase activity,which displays excellent analytical performance.Moreover,this sensing platform was applied for screening naturalα-glucosidase inhibitors,such as terpenoids from natural products.The results indicated that ursolic acid and oleanolic acid had good inhibitory rates.This strategy not only provides a new way to construct more kinds of nanomaterials from DESs,but also offers a facile and effective tool to screen theα-glucosidase natural inhibitors as potential anti-diabetic drugs.

Dual-physical network PVA hydrogel commensurate with articular cartilage bearing lubrication enabled by harnessing nanoscale crystalline domains

Hydrogel, as one of potential soft materials for articular cartilage, has encountered pressing obstacles, such as insufficient mechanical properties, poor lubrication, and easy to wear. To tackle these, we propose a strong yet slippery polyvinyl alcohol/chitosan (PVA/CS) hydrogel with dual-physically crosslinked networks by harnessing freeze-thawing, salting-out, annealing, and rehydration. High mechanical properties of PVA/CS hydrogel can be readily regulated by adjusting proportion of PVA/CS and annealing temperature. The optimized hydrogel exhibits high mechanical properties with tensile strength of ∼ 19 MPa at strain of 550%, compression strength of ∼ 11 MPa at small strain of 39%, and outstanding toughness and antifatigue owing to the robust physical interactions, including hydrogen bonds, crystallization, and ionic coordination. Moreover, the equilibrium hydrogel shows low friction coefficient of ∼ 0.05 against Al_(2)O_(3) ball under the condition of 30 N, 1 Hz, with water as the tribological medium, which is close to the lubrication performance of native cartilage. And meanwhile, the proposed cartilage-like slippery hydrogel displays stable long-term lubrication performance for 1 × 10^(5) reciprocating cycles without destructive wear and structure damage. It is therefore believed that the biocompatible cartilage-like slippery hydrogel opens innovative scenarios for developing cartilage-mimicking water-lubricated coating and biomedical implants with satisfactory load-bearing and lubrication performance.

Deep eutectic solvent-driven self-assembly of metal mercaptide complexes with enzyme-mimicking activities for detection of uric acid through one-step cascade catalytic reaction

This work presents a generic strategy to create a series of metal mercaptides complexes via coordination selfassembly between transition metals(Mn,Cu,Co,Fe,and Ni)and cysteine(Cys)by forming the sulfur-metal bridges.This strategy involves dissolving metal chlorides and Cys into deep eutectic solvents(DES),followed by the precipitation of metal mercaptides complexes(such as Cys-Mn)by adding water as an antisolvent,where DES serves as the solvent,shape directing,and capping agent,thereby preventing the formation of other metal impurities.Interestingly,the prepared complexes possess both laccase and peroxidase-like properties,allowing the design of a technique for the detection of L-3,4-dihydroxyphenylalanine(L-DOPA)and uric acid,respectively.The prepared Cys-Mn can linearly oxidize L-DOPA with its concentrations from 0.1 to 130μM and the detection limit was calculated to be 75.5 n M.Additionally,the Cys-Mn can mimic the activity of peroxidase towards oxidization of o-phenylenediamine at neutral p H,allowing single-step and one-pot cascade reactions for visual and fluorometric measurements of uric acid(UA)that could work in the range of 0.2-500μM UA with a detection limit of 0.06μM and 0.054μМ,respectively.The assay was successful in detecting UA in serum and urine samples with relative standard deviation(RSD)ranging from 7.3%to 10.2%and 3.0%-8.5%respectively,suggesting that it may prove useful in medical diagnostic testing.

Colorimetric Detection of Acid Phosphatase and Malathion Using NiCo_(2)O_(4)Nanosheets as Peroxidase-Mimicking Activity

The establishment of a low-cost and facile approach for the assay of acid phosphatase(ACP)and its inhibitor is a research focus.In this paper,we successfully synthesized NiCo_(2)O_(4)nanosheets with peroxidase-mimicking activity in alkaline deep eutectic solvents(DESs)composed of NaOH and PEG-200,which can catalyze 3,3',5,5'-tetramethylbenzidine(TMB)to the oxidation state TMB(ox-TMB)in the presence of H2O2.Due to L-ascorbic acid-2-phosphate can be hydrolyzed into ascorbic acid by ACP,the peroxidase-like activity of NiCo_(2)O_(4)nanosheets is inhibited.However,the addition of malathion,an inhibitor of ACP,can inhibit the activity of ACP and thus limit the production of ascorbic acid(AA).Therefore,a colorimetric approach can be established for highly sensitive and selective detection of ACP and malathion with detection limits of 0.032 U/L and 0.65 nmol/L,respectively.More importantly,this method can be successfully applied to malathion detection in environmental samples tap water and food cucumber juice,indicating that it has potential application prospects in environmental and agricultural fields.

Slippery hydrogel with desiccation-tolerant‘skin’for high-precision additive manufacturing

Hydrogels inevitably undergo dehydration,structural collapse,and shrinkage deformation due to the uninterrupted evaporation in the atmosphere,thereby losing their flexibility,slipperiness,and manufacturing precision.Here,we propose a novel bioinspired strategy to construct a spontaneously formed‘skin’on the slippery hydrogels by incorporating biological stress metabolites trehalose into the hydrogel network,which can generate robust hydrogen bonding interactions to restrain water evaporation.The contents of trehalose in hydrogel matrix can also regulate the desiccation-tolerance,mechanical properties,and lubricating performance of slippery hydrogels in a wide range.Combining vat photopolymerization three-dimensional printing and trehalose-modified slippery hydrogels enables to achieve the structural hydrogels with high resolution,shape fidelity,and sophisticated architectures,instead of structural collapse and shrinkage deformation caused by dehydration.And thus,this proposed functional hydrogel adapts to manufacture large-scale hydrogels with sophisticated architectures in a long-term process.As a proof-of-concept demonstration,a high-precision and sophisticated slippery hydrogel vascular phantom was easily fabricated to imitate guidewire intervention.Additionally,the proposed protocol is universally applicable to diverse types of hydrogel systems.This strategy opens up a versatile methodology to fabricate dry-resistant slippery hydrogel for functional structures and devices,expanding their high-precision processing and broad applications in the atmosphere.

Synthesis and modification of spherical/hollow metal-organic frameworks for efficient extraction of sulfonamides in aqueous environments

In this study,two novel spherical/hollow metal-organic frameworks were successfully synthesized,and further modified by a mild non-covalent modification strategy with dopamine and 1,4-benzenedithiol(BDT)as polymeric monomers to obtain pB DT@PDA-Ni-MOF and p BDT@PDA-Ni/Co-MOF,respectively.The results showed that the above MOFs possessed extremely fast adsorption rates and ideal adsorption capacities for sulfonamides(SAs)and the modified MOFs exhibited enhanced adsorption capacities for SAs owing to a large number of additional functional groups.Then,benefit of their regular morphology and size,a facile syringe-assisted dispersive solid phase extraction(S-DSPE)method was developed for efficient detection of SAs,which will provide a powerful tool for monitoring trace level of SAs in aqueous environment.

Preparation and Evaluation of Silicon Quantum Dots-Bonded Silica Stationary Phase for Reversed-Phase Chromatography

In this paper,silicon quantum dots(SiQDs)with green fluorescence are synthesized by solvothermal reaction of 3-(2,3-epoxypropoxy)propyltrimethoxysilane(GPTMS)and ethylenediaminetetraacetic acid(EDTA),and then SiQDs are bonded to the surface of silica to obtain a new nano-on-micro stationary phase(SiO_(2)-SiQDs)for reversed-phase chromatography.The successful preparation of SiO_(2)-SiQDs stationary phase is demonstrated by a variety of characterizations,such as transmission electron microscopy,laser confocal microscopy,elemental analysis and Fourier infrared spectroscopy.In addition,the chromatographic performance of the prepared stationary phase is evaluated and it shows good separation performance for non-polar substances such as alkylbenzene,aniline and polycyclic aromatic hydrocarbons in reversed-phase liquid chromatography.It is also verified that the stationary phase has good methyl selectivity and shape selectivity.More interestingly,the separation of prednisolone and hydrocortisone isomers can also be achieved at a low ratio of organic solvents,indicating that this new stationary phase has a good application prospect in isomer separation.

Phytochemicals and Their Biological Activities of Plants in Tagetes L.

Tagetes L.,the genus in the family Asteraceae,consists of about 30 species spread in South and Middle America as well as Mexico.More than one hundred secondary metabolites have been obtained in phytochemical investigation on the species,some of which have potent biological activities.The advances in phytochemical studies and biological activities of the plants in Tagetes L.from 1925 to 2011 are summarized in this paper.

New deep eutectic solvents composed of crown ether, hydroxide and polyethylene glycol for extraction of non-basic N-compounds

Here we firstly report a series of new deep eutectic solvents(DESs) induced by small amounts of crown ether complex and mainly formed by polyethylene glycol. These DESs not only presented the ultra-deep extraction of non-basic N-compounds from fuel oils, but also opened up the possibility of other new applications in chemistry and materials science.

Basic deep eutectic solvents as reactant, template and solvents for ultra-fast preparation of transition metal oxide nanomaterials

Developing a new type of deep eutectic solvents(DESs)is indispensable for expanding their application in various fields.Here,we report a series of new highly basic DESs.FT-IR,quantitative 1 H NMR,MD simulation and physical properties show that these basic liquids are made up of hydroxide acceptor of alkali metal hydroxides in which the hydrogen bonding interactions coordinate the donor.These DESs can be played three roles as new solvents,template and reactant for facile and ultra-fast preparation of transition metal oxide nanomaterials such as NiCo2 O4,MnCo2 O4,NiMn2 O4,CoCu2 O4 and Co3 O4 under mild condition.This work shows one of the low energy-intensive methods for nanomaterial preparation.These initial findings of basic deep eutectic solvents provide a potential applicability around the systematic development of transition metal oxide nanosheets.

A novel off-on fluorescent probe for specific detection and imaging of cysteine in live cells and in vivo

Cysteine(Cys)plays a pivotal role in many physiological and pathological processes,including detoxification and protein synthesis.The abnormal levels of Cys are linked to many diseases.In this study,a novel red-emitting off-on fluorescent probe Cys-TCF was masterly constructed for discriminative detection of Cys.After a series of experimental assessment,Cys-TCF displayed higher selectivity and sensitivity for Cys over other biothilols with a low detection limit(0.04μmol/L).More notably,the probe was also successfully applied to image Cys in live cells and live zebrafishes with low cytotoxicity.

Porous graphene decorated silica as a new stationary phase for separation of sulfanilamide compounds in hydrophilic interaction chromatography

Porous graphene(PG) has potential applications in numerous fields because of the existence of nanopores in the plane. In this study, porous graphene decorated silica microspheres(Sil-PG) were successfully fabricated by assembling PG onto the silica particles surface in deep eutectic solvents(DESs).Experimental results demonstrate that this new stationary phase can facilitate the separation of six sulfonamides compounds in hydrophilic chromatographic conditions. The successful synthesis of the SilPG stationary phase provides a basis for the application of porous graphene-modified materials as the stationary phase for liquid chromatography, and offers the possibility to broaden the application of PG in the field of chromatography.