Synthesis of Tetrahydro-ß-carbolines by a Manganese-Catalysed Oxidative Pictet-Spengler Reaction.

Herein, an efficient and green procedure for the synthesis of tetrahydro-ß-carbolines via dehydrogenative coupling of alcohols with tryptamines is reported. The reaction was carried out under mild conditions in the presence of a catalytic amount of the iPr PNP-Mn catalyst and a weak base (Na2 CO3 ). This method tolerated a variety of benzylic and aliphatic alcohol substrates with different functional groups and afforded diverse products in good to excellent isolated yields using tryptamines. Using this strategy, we successfully synthesised pharmaceutical molecules harman, harmaline, and harmine in a concise manner.

A catalytic hairpin assembly-based Förster resonance energy transfer sensor for ratiometric detection of ochratoxin A in food samples.

Ochratoxin A (OTA) poses severe risks to the environment and human health, making the development of an accurate and sensitive analytical method for OTA detection essential. In this study, a catalytic hairpin assembly (CHA)-based Förster resonance energy transfer (FRET) aptasensor was developed to detect OTA using carbon quantum dots (CDs) and 6-carboxy-fluorescein (FAM) as dual signal readout. In the presence of OTA, the aptamer specifically interacted with OTA to release the helper DNA (HP), which could open the hairpin structure of FAM-labeled hairpin DNA 1 (H1-FAM) modified on the surface of gold nanoparticles (AuNPs). CHA between H1-FAM and hairpin H2 labeled with CDs (H2-CDs) can release HP for the next cycle, resulting in the occurrence of FRET with CDs as the energy donor and FAM as the energy acceptor. According to the ratio of FCDs/FFAM, the proposed aptasensor showed a wide linear range from 5.0 pg/mL to 3.0 ng/mL and a low detection limit of 1.5 pg/mL for OTA detection. Moreover, satisfactory results were obtained for OTA detection in rice, suggesting the potential application of this sensor in food safety analysis.

Synthesizing carbonyl furan derivatives by a dehydrogenative coupling reaction.

Herein, we report the development of an efficient green procedure for synthesizing carbonyl furan derivatives by dehydrogenative coupling of furfuryl alcohol with carbonyl compounds. The reaction is performed under mild reaction conditions in the presence of iPrPNP-Mn as the catalyst and a weak base (Cs2CO3). A range of ketones and aldehydes were efficiently diversified with furfuryl alcohol to afford furyl-substituted saturated ketones, and α,ß-unsaturated ketones and aldehydes in good isolated yields.

Synthesis, odor characteristics and biological evaluation of N-substituted pyrrolyl chalcones.

A novel approach for converting N-substituted acetylpyrroles and primary alcohols into N-substituted pyrrolyl chalcones in air with the assistance of t-BuOK is reported, and several prominent flavor and bioactive molecules were obtained. The process entails oxidizing the alcohols to the corresponding aldehydes, and t-BuOK is crucial to the effective production of CC bonds by aldol condensation. Gas chromatography-mass spectrometry-olfactometry (GC-MS-O) was used to examine the odor properties of pyrrolyl chalcones, which are usually different from those of the associated acetylpyrroles and alcohols. The biological evaluation assay showed that the products (E)-3-(3-fluorophenyl)-1-(1-methyl-1H-pyrrol-2-yl)prop-2-en-1-one (3j), (E)-1-(1-ethyl-1H-pyrrol-2-yl)-3-phenylprop-2-en-1-one (4a), (E)-3-(4-bromophenyl)-1-(1-ethyl-1H-pyrrol-2-yl)prop-2-en-1-one (4e), (E)-3-(4-chlorophenyl)-1-(1-ethyl-1H-pyrrol-2-yl)prop-2-en-1-one (4f) and (E)-1-(1-ethyl-1H-pyrrol-2-yl)-3-(4-fluorophenyl)prop-2-en-1-one (4g) exhibited excellent inhibitory activity against R. solani with EC50 values from 0.0107 to 0.0134 mg mL-1. Molecular docking of 3j with SDH (succinate dehydrogenase) was performed to reveal the binding modes in the active pocket and analyze the interactions between the molecules and the SDH protein. Meanwhile, they have good thermal stability according to the results of thermogravimetry (TG) analysis.

Label-free fluorescent sensor for one-step lysozyme detection via positively charged gold nanorods.

In the article, a simple and label-free strategy was proposed for the sensitive detection of lysozyme based on the fluorescence quenching of positively charged gold nanorods ((+)AuNRs) to DNA-templated silver nanoclusters (DNA/AgNCs). To construct the sensor, a DNA template was designed with a C-rich sequence at the 5'-terminal for the synthesis of AgNCs, while a lysozyme binding aptamer (LBA) at the 3'-terminal for the recognition of lysozyme, and such DNA/AgNCs was used as the fluorescence probe. Meantime, the fluorescence signal of such DNA/AgNCs can be quenched based on the electrostatic adsorption of them with (+)AuNRs, due to the surface energy transfer. In the presence of lysozyme, the specific binding happened between the LBA section of DNA/AgNCs and lysozyme, inducing the reduction of the total charge of DNA/AgNCs and weakening the adsorption of them with (+)AuNRs, which directly resulting in the recovery of the fluorescence signal. Besides, the fluorescence signal recovery of DNA/AgNCs has a linear positive proportional relationship with lysozyme concentration in the range of 10 pM-2.0 nM under the optimal conditions. Moreover, a satisfactory recovery (99.6-107.2%) was obtained while detecting lysozyme in human serum samples. Graphical abstract A simple and label-free strategy was proposed for the sensitive detection of lysozyme based on the fluorescence quenching of positively charged gold nanorods ((+)AuNRs) to DNA-templated silver nanoclusters (DNA/AgNCs).

Biosorption of sterols from tobacco waste extract using living and dead of newly isolated fungus Aspergillus fumigatus strain LSD-1.

Sterols are verified to be able to produce polycyclic aromatic hydrocarbons during its pyrolysis. In this study, a kind of Aspergillus fumigatus (LSD-1) was isolated from cigar leaves, and the biosorption effects on the stigmasterol, ß-sitosterol, campesterol, cholesterol, and ergosterol by using living and dead biomass of LSD-1 were investigated. The results showed that both living and dead biomass could efficiently remove these sterols in aqueous solution and tobacco waste extract (TWE). Interestingly, compared with the living biomass of LSD-1, the dead biomass of LSD-1 not only kept a high adsorption efficiency but also did not produce ergosterol. Overall, dead biomass of LSD-1 was a more suitable biosorbent to sterols in TWE. Furthermore, Brunner-Emmet-Teller (BET), Fourier transformed infrared spectrometer (FTIR) and scanning electron microscope (SEM) analysis were used to explore the biosorption process of living and dead biomass and their differences, suggesting that the biosorption of sterols was a physical process.

Regioselective Synthesis of Sulfonyl-Containing Benzyl Dithiocarbamates through Copper-Catalyzed Thiosulfonylation of Styrenes.

An efficient approach for the preparation of sulfonyl-containing benzyl dithiocarbamates has been developed using tetraalkylthiuram disulfides as the thiolating agents and sulfonyl chlorides as the sulfonyl sources in the presence of the copper catalyst. The dithiocarbamate group together with the sulfonyl group was simultaneously introduced into styrene in chemo- and regioselective manners. This protocol provides a convenient procedure, with good yields and functional group tolerance to various important sulfonyl-containing benzyl dithiocarbamates.

Transcriptome Analysis of Gene Expression Patterns Potentially Associated with Premature Senescence in Nicotiana tabacum L.

Senescence affects the remobilization of nutrients and adaption of the plant to the environment. Combined stresses can result in premature senescence in plants which exist in the field. In this study, transcriptomic analysis was performed on mature leaves and leaves in three stages of premature senescence to understand the molecular mechanism. With progressive premature senescence, a declining chlorophyll (chl) content and an increasing malonaldehyde (MDA) content were observed, while plasmolysis and cell nucleus pyknosis occurred, mitochondria melted, thylakoid lamellae were dilated, starch grains in chloroplast decreased, and osmiophilic granules increased gradually. Moreover, in total 69 common differentially expressed genes (DEGs) in three stages of premature senescing leaves were found, which were significantly enriched in summarized Gene Ontology (GO) terms of membrane-bounded organelle, regulation of cellular component synthesis and metabolic and biosynthetic processes. The Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis suggested that the plant hormone signal transduction pathway was significantly enriched. The common DEGs and four senescence-related pathways, including plant hormone signal transduction, porphyrin and chlorophyll metabolism, carotenoid biosynthesis, and regulation of autophagy were selected to be discussed further. This work aimed to provide potential genes signaling and modulating premature senescence as well as the possible dynamic network of gene expression patterns for further study.

Purification, Characterization, and Antioxidant Activity of Polysaccharides Isolated from Cortex Periplocae.

In this study, crude Cortex Periplocae polysaccharides (CCPPs) were extracted with water. CCPPs were decolored with AB-8 resin and deproteinated using papain-Sevage methods. Then, they were further purified and separated through DEAE-52 anion exchange chromatography and Sephadex G-100 gel filtration chromatography, respectively. Three main fractions-CPP1, CPP2, and CPP3, (CPPs)-were obtained. The average molecular weights, monosaccharide analysis, surface morphology, and chemical compositions of the CPPs were investigated by high-performance gel permeation chromatography (HPGPC), gas chromatography-mass spectrometry (GC/MS), UV-vis spectroscopy, Fourier transform infrared (FT-IR) spectrum, and nuclear magnetic resonance (NMR). In addition, the antioxidant activities of these three polysaccharides were investigated. The results indicated that all of the CPPs were composed of rhamnose, arabinose, mannose, glucose, and galactose. These three polysaccharides exhibited antioxidant activities in four assays including 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical, 2,2'-azino-bis(3-ethyl-benzthiazoline-6-sulfonic acid) (ABTS) radical, reducing power, and total antioxidant activity in vitro. The data indicated that these three polysaccharides could be utilized as potential natural sources of alternative additives in the functional food, cosmetics, and pharmaceutical industries.

Dynamic changes in fungal communities and functions in different air-curing stages of cigar tobacco leaves.

Introduction: Air curing (AC) plays a crucial role in cigar tobacco leaf production. The AC environment is relatively mild, contributing to a diverse microbiome. Fungi are important components of the tobacco and environmental microbiota. However, our understanding of the composition and function of fungal communities in AC remains limited. Methods: In this study, changes in the chemical constituents and fungal community composition of cigar tobacco leaves during AC were evaluated using flow analysis and high-throughput sequencing. Results: The moisture, water-soluble sugar, starch, total nitrogen, and protein contents of tobacco leaves exhibited decreasing trends, whereas nicotine showed an initial increase, followed by a decline. As determined by high-throughput sequencing, fungal taxa differed among all stages of AC. Functional prediction showed that saprophytic fungi were the most prevalent type during the AC process and that the chemical composition of tobacco leaves is significantly correlated with saprophytic fungi. Conclusion: This study provides a deeper understanding of the dynamic changes in fungal communities during the AC process in cigar tobacco leaves and offers theoretical guidance for the application of microorganisms during the AC process.

Enzymatic synthesis of pyridine heterocyclic compounds and their thermal stability.

An efficient method was discovered for catalyzing the esterification under air using Novozym 435 to obtain pyridine esters. The following conditions were found to be optimal: 60 mg of Novozyme 435, 5.0 mL of n-hexane, a molar ratio of 2:1 for nicotinic acids (0.4 mmol) to alcohols (0.2 mmol), 0.25 g of molecular sieve 3A, a revolution speed of 150 rpm, a reaction temperature of 50 °C, and reaction time of 48 h. Under nine cycles of Novozym 435, the 80 % yield was consistently obtained. Optimum conditions were used to synthesize 23 pyridine esters, including five novel compounds. Among them, gas chromatography-mass spectrometry-olfactometry (GC-MS-O) showed phenethyl nicotinate (3g), (E)-hex-4-en-1-yl nicotinate (3m), and octyl nicotinate (3n) possessed strong aromas. Thermogravimetric analysis (TG) revealed that the compounds 3g, 3m and 3n exhibited stability at the specified temperature. This finding provides theoretical support for adding pyridine esters fragrance to high-temperature processed food.

Microbial community and chemical composition of cigar tobacco (Nicotiana tabacum L.) leaves altered by tobacco wildfire disease.

Tobacco wildfire disease caused by Pseudomonas syringae pv. tabaci is one of the most destructive foliar bacterial diseases occurring worldwide. However, the effect of wildfire disease on cigar tobacco leaves has not been clarified in detail. In this study, the differences in microbiota and chemical factors between wildfire disease-infected leaves and healthy leaves were characterized using high-throughput Illumina sequencing and a continuous-flow analytical system, respectively. The results demonstrated significant alterations in the structure of the phyllosphere microbial community in response to wildfire disease, and the infection of P. syringae pv. tabaci led to a decrease in bacterial richness and diversity. Furthermore, the content of nicotine, protein, total nitrogen, and Cl- in diseased leaves significantly increased by 47.86%, 17.46%, 20.08%, and 72.77% in comparison to healthy leaves, while the levels of total sugar and reducing sugar decreased by 59.59% and 70.0%, respectively. Notably, the wildfire disease had little effect on the content of starch and K+. Redundancy analysis revealed that Pseudomonas, Staphylococcus, Cladosporium, and Wallemia displayed positive correlations with nicotine, protein, total nitrogen, Cl- and K+ contents, while Pantoea, Erwinia, Sphingomonas, Terrisporobacter, Aspergillus, Alternaria, Sampaiozyma, and Didymella displayed positive correlations with total sugar and reducing sugar contents. Brevibacterium, Brachybacterium, and Janibacter were found to be enriched in diseased leaves, suggesting their potential role in disease suppression. Co-occurrence network analysis indicated that positive correlations were prevalent in microbial networks, and the bacterial network of healthy tobacco leaves exhibited greater complexity compared to diseased tobacco leaves. This study revealed the impact of wildfire disease on the microbial community and chemical compositions of tobacco leaves and provides new insights for the biological control of tobacco wildfire disease.

The bacterial succession and its role in flavor compounds formation during the fermentation of cigar tobacco leaves.

Fermentation is the key process required for developing the characteristic properties of cigar tobacco leaves, complex microorganisms are involved in this process. However, the microbial fermentation mechanisms during the fermentation process have not been well-characterized. This study investigated the dynamic changes in conventional chemical composition, flavor compounds, and bacterial community during the fermentation of cigar tobacco leaves from Hainan and Sichuan provinces in China, as well as the potential roles of bacteria. Fermentation resulted in a reduction of conventional chemical components in tobacco leaves, with the exception of a noteworthy increase in insoluble protein content. Furthermore, the levels of 10 organic acids and 19 amino acids showed a significant decrease, whereas the concentration of 30 aromatic substances exhibited a unimodal trend. Before fermentation, the bacterial community structures and dominant bacteria in Hainan and Sichuan tobacco leaves differed significantly. As fermentation progressed, the community structures in the two regions became relatively similar, with Delftia, Ochrobactrum, Rhodococcus, and Stenotrophomonas being dominant. Furthermore, a total of 12 functional bacterial genera were identified in Hainan and Sichuan tobacco leaves using bidirectional orthogonal partial least squares (O2PLS) analysis. Delftia, Ochrobactrum, and Rhodococcus demonstrated a significant negative correlation with oleic acid and linoleic acid, while Stenotrophomonas and Delftia showed a significant negative correlation with undesirable amino acids, such as Ala and Glu. In addition, Bacillus showed a positive correlation with benzaldehyde, while Kocuria displayed a positive correlation with 2-acetylfuran, isophorone, 2, 6-nonadienal, and ß-damascenone. The co-occurrence network analysis of microorganisms revealed a prevalence of positive correlations within the bacterial network, with non-abundant bacteria potentially contributing to the stabilization of the bacterial community. These findings can improve the overall tobacco quality and provide a novel perspective on the utilization of microorganisms in the fermentation of cigar tobacco leaves.

Fluorescent probes for lighting up ferroptotic cell death: A review.

Ferroptosis is a newly discovered form of regulated cellular demise, characterized by the accumulation of intracellular oxidative stress that is dependent on iron. Ferroptosis plays a crucial role not only in the development and treatment of tumors but also in the pathogenesis of neurodegenerative diseases and illnesses related to ischemia-reperfusion injury. This mode of cell death possesses distinctive properties that differentiate it from other forms of cell death, including unique morphological changes at both the cellular and subcellular levels, as well as molecular features that can be detected using specific methods. The use of fluorescent probes has become an invaluable means of detecting ferroptosis, owing to their high sensitivity, real-time in situ monitoring capabilities, and minimal damage to biological samples. This review comprehensively elucidates the physiological mechanisms underlying ferroptosis, while also detailing the development of fluorescent probes capable of detecting ferroptosis-related active species across various cellular compartments, including organelles, the nucleus, and the cell membrane. Additionally, the review explores how the dynamic changes and location of active species from different cellular compartments can influence the ignition and execution of ferroptotic cell death. Finally, we discuss the future challenges and opportunities for imaging ferroptosis. We believe that this review will not only aid in the elucidation of ferroptosis's physiological mechanisms but also facilitate the identification of novel treatment targets and means of accurately diagnosing and treating ferroptosis-related diseases.

Enzymatic synthesis of novel pyrrole esters and their thermal stability.

In the present work a simple enzymatic approach (Novozym 435) for transesterification to synthesize pyrrole esters was reported. To generate the best reaction conditions, which resulted in the optimum yield of 92%, the effects of lipase type, solvent, lipase load, molecular sieves, substrate molar ratio of esters to alcohol, reaction temperature, reaction duration, and speed of agitation were evaluated. The range of alcohols was assessed under optimal circumstances. The spectrum observations conclusively demonstrated that the compounds could be generated with high yield under the circumstances utilized for synthesis. The odor characteristics of the pyrrolyl esters obtained were examined by gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Among them, compounds of benzhydryl 1H-pyrrole-2-carboxylate (3j), butyl 1H-pyrrole-2-carboxylate (3k) and pentyl 1H-pyrrole-2-carboxylate (3l) present sweet and acid aroma. In addition, the thermal degradation process was further studied using the Py-GC/MS (pyrolysis-gas chromatography/mass spectrometry), TG (thermogravimetry), and DSC (differential scanning calorimeter) techniques. The outcomes of the Py-GC/MS, TG, and DSC techniques show that they have excellent thermal stability.

Nickel-Catalyzed Amidation of Aryl Alkynyl Acids with Tetraalkylthiuram Disulfides: A Facile Synthesis of Aryl Alkynyl Amides.

Nickel-catalyzed amidation of aryl alkynyl acids using tetraalkylthiuram disulfides as the amine source is described, affording a series of aryl alkynyl amides in good to excellent yields under mild conditions. This general methodology provides an alternative pathway for the synthesis of useful aryl alkynyl amides in an operationally simple manner, which shows its practical synthetic value in organic synthesis. The mechanism of this transformation was explored through control experiments and DFT calculations.

Preparation of esterified biomass waste hydrogels and their removal of Pb2+, Cu2+ and Cd2+ from aqueous solution.

The treatment of polluted water is a serious environmental problem in the world. Biomass is easily modified and can be prepared into adsorbent materials, which is expected to solve the problem of heavy metal ion adsorption in sewage. In this paper, esterified tobacco straw based hydrogels (ETS-PAA) were synthesized from waste tobacco straw biomass. The structure and thermal stability of these hydrogels were characterized by FTIR, SEM, EDS, XPS and TG. The adsorption of metal ions by the hydrogel was measured by ICP-MS. The effects of initial ion concentration, adsorption time, pH, and temperature on the heavy metal adsorption were investigated. The results showed that ETS-PAA possessed more pores, which led to a better adsorption capacity. The maximum adsorption amounts of Pb2+, Cu2+ and Cd2+ were 2.41 mmol·g-1, 1.93 mmol·g-1 and 1.77 mmol·g-1, respectively. Finally, the adsorption mechanism and kinetics were analyzed. The adsorption was mainly accomplished by ion exchange of -COOK on the monomer chain with heavy metal ions, coordination of -OH and -CONH with heavy metal ions and interaction of ester bond, -COOH with heavy metal ions. The adsorption process was in accordance with the pseudo-second-order kinetic model and Freundlich model. The adsorption process belonged to multilayer chemisorption. This work shows that ETS-PAA was a promising material for the removal of heavy metal pollutants from aqueous solution.

Synthesis of Thiophene-Substituted Ketones via Manganese-Catalyzed Dehydrogenative Coupling Reaction.

This study reports an efficient and green one-step method for synthesizing thiophene-substituted ketones from 2-thiophenemethanol and ketones via dehydrogenative coupling using manganese complexes as catalysts. The manganese complex demonstrated a broad applicability under mild conditions and extended the range of usable substrates. Utilizing this strategy, we carried out an efficient and diverse reaction of ketones with 2-thiophenemethanol, and successfully synthesized a series of thiophene-substituted saturated ketones and α, ß-unsaturated ketones in good isolated yields.

Efficient Synthesis of C3-Alkylated and Alkenylated Indoles via Manganese-Catalyzed Dehydrogenation.

The catalytic dehydrogenation of alcohols is essential for the sustainable production of valuable products. This provides a new strategy for green organic synthesis in chemical industries. Herein, we describe a manganese-based catalytic system that enables the efficient synthesis of C3-alkylated indoles from benzyl alcohols and indoles via the borrowing hydrogen process. Furthermore, dehydrogenative coupling of 2-arylethanols and indoles yields C3-alkenylated indoles. Meanwhile, reacting 2-aminophenethanol instead of indoles can also obtain the corresponding indole products with high selectivity under the same conditions.

Influence of Genotypic and Environmental Factors on Tobacco Leaves Based on Metabolomics.

Environmental factors affect plant metabolites, different climates, cultivation conditions, and biotic stresses and genotypes strongly affect their chemical composition and contents. Our aim is to examine the environmental and genetic interaction effects on tobacco metabolite composition. UPLC-QTOF MS/MS coupled with multivariate data analyses were applied for the metabolomics analysis of three tobacco cultivars from different planting regions in China. Principal component analysis (PCA) revealed that environmental factors have a greater effect on tobacco metabolism compared to genotypes. Twelve biomarkers were screened by orthogonal partial least squares discrimination analysis (OPLS-DA). Univariate analysis indicated that Malate, conjugated chlorogenic acid, chlorogenic acid, quercetin 3-rutinoside-7-glucoside, and unknown compound 5 were only influenced by environmental factors (independent of genotype). Quinate, neochlorogenic acid, and ouabagenin, taxezopidine K1, taxezopidine K2, and taxezopidine K3 in tobacco were influenced by the interaction of environmental factors and the genotype. Our results suggest that metabolomics based on UPLC-QTOF MS/MS could be used to analyze the ecological functions of biomarker metabolites and understand the mechanisms of plant adaption to the environment.