Advanced glycation end products(AGEs)are complex compounds formed through interaction of carbonyl groups from saccharides with amino groups in amino acids,proteins,lipids and nucleic acids,mainly via Maillard reaction...Advanced glycation end products(AGEs)are complex compounds formed through interaction of carbonyl groups from saccharides with amino groups in amino acids,proteins,lipids and nucleic acids,mainly via Maillard reaction.Studies have shown that AGEs can accumulate in the body and lead to neurodegenerative diseases,cardiovascular diseases,inflammatory responses,diabetes,and other diseases.This comment will provide a review of the inhibitory mechanism of flavonoids on dietary AGEs formation in food models and aims to provide a theoretical basis for the development of new therapeutic strategies and drugs.展开更多
[Objective] The research aimed to analyze the inhibitory mechanism of Sophora japonica n-hexane extract which significantly inhibited Microcystis aeruginosa in the prior research.[Method] S.japonica n-hexane extract w...[Objective] The research aimed to analyze the inhibitory mechanism of Sophora japonica n-hexane extract which significantly inhibited Microcystis aeruginosa in the prior research.[Method] S.japonica n-hexane extract was used to treat M.aeruginosa.By inspecting chlorophyll a content,protein content,cell membrane permeability and superoxide dismutase（SOD） activity,the inhibitory mechanism of S.japonica n-hexane extract on M.aeruginosa was analyzed initially.[Result] S.japonica n-hexane extract destroyed the cell membrane system of M.aeruginosa,and increased the cell membrane permeability.The contents of chlorophyll a and protein respectively declined to 10% and 50% of that in the control group after cultivated for 7 d,which indicated the photosynthetic reaction system of M.aeruginosa was destroyed.In addition,under the effect of S.japonica n-hexane extract,SOD activity of M.aeruginosa increased in the early period and decreased in the latter period.[Conclusion] The possible inhibitory mechanism of S.japonica n-hexane extract on M.aeruginosa was destroying the cell membrane to increase the membrane permeability;destroying the photosynthetic reaction system to decrease the contents of photosynthetic pigment and protein;making SOD activity showing the phased variation.展开更多
The inhibitory mechanism of copper（Ⅱ） on the aggegation of amyloid β-peptide （Aβ） was investigated by molecular dynamics simulations. The binding mode ofcopper（Ⅱ） with Aβ is characterized by the imidazole n...The inhibitory mechanism of copper（Ⅱ） on the aggegation of amyloid β-peptide （Aβ） was investigated by molecular dynamics simulations. The binding mode ofcopper（Ⅱ） with Aβ is characterized by the imidazole nitrogen atom, Nπ, of the histidine residue H 13, acting as the anchoring site, and the backbone＇s deprotoned amide nitogen atoms as the main binding sites. Drove by the coordination bonds and their induced hydrogen bond net, the conformations of Aβ converted from β-sheet non-β-sheet conformations, which destabilized the aggregation of Aβ into fibrils.展开更多
Aggregation of amyloid ?-peptide (A?) into insoluble fibrils is a key pathological event in Alzheimer’s disease (AD). Under certain conditions, Cu(II) exhibits strong inhibitory ef-fect on the Zn(II)-induced aggregat...Aggregation of amyloid ?-peptide (A?) into insoluble fibrils is a key pathological event in Alzheimer’s disease (AD). Under certain conditions, Cu(II) exhibits strong inhibitory ef-fect on the Zn(II)-induced aggregation, which occurs significantly even at nearly physiological concentrations of zinc ion in vitro. Cu(II) is considered as a potential factor in the normal brain preventing A? from aggregating. The possible mechanism of the inhibitory effect of Cu(II) is in-vestigated for the first time by molecular modeling method. In the mono-ring mode, the Y10 residue promotes typical quasi-helix conformations of A?. Specially, [Cu-H13(Np)-Y10(OH)] complex forms a local 3.010 helix conformation. In the multi-ring mode, the side chains of Q15 and E11 residues collaborate harmoniously with other chelating ligands producing markedly low energies and quasi-helix conformations. [Cu-3N-Q15(O)-E11(O1)] and [Cu-H13(Np)-Y10(OH)] complex with quasi-helix conformations may prefer soluble forms in solution. In addition, hydro-gen-bond interactions may be the main driving force for A? aggregation. All the results will pro-vide helpful clues for an improved understanding of the role of Cu(II) in the pathogenesis of AD and contribute to the development of an “anti-amyloid” therapeutic strategy.展开更多
Fusarium graminearum is a pathogen that can infect wheat,corn and other grain crops,resulting in a reduction in grain yield and nutritional value and even causing serious harm to public health.Ferulic acid(FA)is popul...Fusarium graminearum is a pathogen that can infect wheat,corn and other grain crops,resulting in a reduction in grain yield and nutritional value and even causing serious harm to public health.Ferulic acid(FA)is popularly extracted from a variety of traditional Chinese medicines,such as ferula,asafoetida and angelica,and is a promising fungicide for the preservation of foods due to its antibacterial,antioxidant and anti-inflammatory functions.Based on its efficacy,the inhibitory activity of FA against F.graminearum was evaluated and the involved mechanism was investigated as well.The EC_(50) and EC90 values were approximately 20μg/mL and 100μg/mL,respectively,according to the mycelial dry weight test.TEM and SEM analyses after FA treatment revealed that the cell membrane of hyphae was impaired and showed the following characteristics:coarse surface with wrinkles,blurry ultrastructure edges,and cytoplasmic leakage.In addition,cell integrity and permeability analyses were performed to identify its antifungal mechanism.After FA treatment,the fluorescence intensity of mycelia after PI staining increased significantly(p<0.001),and the high concentration group showed a continuous rise in extracellular relative conductivity and more significant leakage of nucleic acids and protein.Moreover,FA inhibited ergosterol synthesis in the F.graminearum cell membrane,which confirmed that the target site of FA antifungal action was the cell membrane.展开更多
Although herbal medicines(HMs)are widely used in the prevention and treatment of obesity and obesity-associated disorders,the key constituents exhibiting anti-obesity activity and their molecular mechanisms are poorly...Although herbal medicines(HMs)are widely used in the prevention and treatment of obesity and obesity-associated disorders,the key constituents exhibiting anti-obesity activity and their molecular mechanisms are poorly understood.Recently,we assessed the inhibitory potentials of several HMs against human pancreatic lipase(hPL,a key therapeutic target for human obesity),among which the root-extract of Rhodiola crenulata(ERC)showed the most potent anti-hPL activity.In this study,we adopted an integrated strategy,involving bioactivity-guided fractionation techniques,chemical profiling,and biochemical assays,to identify the key anti-hPL constituents in ERC.Nine ERC fractions(retention time=12.5e35 min),obtained using reverse-phase liquid chromatography,showed strong anti-hPL activity,while the major constituents in these bioactive fractions were subsequently identified using liquid chromatography-quadrupole time-of-flight mass spectrometry(LC-Q-TOF-MS/MS).Among the identified ERC constituents,1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose(PGG)and catechin gallate(CG)showed the most potent anti-hPL activity,with pIC50 values of 7.59±0.03 and 7.68±0.23,respectively.Further investigations revealed that PGG and CG potently inhibited hPL in a non-competitive manner,with inhibition constant(Ki)values of 0.012 and 0.082 mM,respectively.Collectively,our integrative analyses enabled us to efficiently identify and characterize the key anti-obesity constituents in ERC,as well as to elucidate their anti-hPL mechanisms.These findings provide convincing evidence in support of the anti-obesity and lipid-lowering properties of ERC.展开更多
Severe acute respiratory syndrome coronavirus 2(SARS-Co V-2) relies on the central molecular machine RNA-dependent RNA polymerase(Rd Rp) for the viral replication and transcription. Remdesivir at the template strand h...Severe acute respiratory syndrome coronavirus 2(SARS-Co V-2) relies on the central molecular machine RNA-dependent RNA polymerase(Rd Rp) for the viral replication and transcription. Remdesivir at the template strand has been shown to effectively inhibit the RNA synthesis in SARS-Co V-2 Rd Rp by deactivating not only the complementary UTP incorporation but also the next nucleotide addition. However, the underlying molecular mechanism of the second inhibitory point remains unclear. In this work, we have performed molecular dynamics simulations and demonstrated that such inhibition has not directly acted on the nucleotide addition at the active site. Instead, the translocation of Remdesivir from +1 to-1 site is hindered thermodynamically as the posttranslocation state is less stable than the pre-translocation state due to the motif B residue G683. Moreover, another conserved residue S682 on motif B further hinders the dynamic translocation of Remdesivir due to the steric clash with the 1′-cyano substitution. Overall,our study has unveiled an alternative role of motif B in mediating the translocation when Remdesivir is present in the template strand and complemented our understanding about the inhibitory mechanisms exerted by Remdesivir on the RNA synthesis in SARS-Co V-2 Rd Rp.展开更多
The harvested loquat fruits are prone to browning,leading to a decline in fruit quality.Inhibiting activity of polyphenol oxidase(PPO)is an important way to prevent browning.In this study,we evaluated the inhibitory i...The harvested loquat fruits are prone to browning,leading to a decline in fruit quality.Inhibiting activity of polyphenol oxidase(PPO)is an important way to prevent browning.In this study,we evaluated the inhibitory impact of oligomeric procyanidins(OPC)on hydroxylation of monophenol and oxidation of o-diphenol catalyzed by PPO and effect of OPC on loquat fruits storage.The obtained results revealed that OPC could attenuate the activity of monophenolase and diphenolase.For monophenolase activity,the inhibition rate was observed to be dose-dependent with an IC50 of 11.6±3.4μg/mL for the steady-state rate.For diphenolase activity,OPC inhibited PPO activity(IC50=15.75±2.1μg/mL)with a reversible and competitive mechanism and quenched fluorescence of PPO by forming OPC-PPO complex with one binding site in a static procedure.In addition,the data obtained from storage assays revealed that OPC could enhance the quality of harvested loquat fruits by attenuating the PPO activity,augmenting the content of total phenolics and flavonoids,and simultaneously delaying the browning of loquats.In this research,we identified a potent PPO inhibitor and expanded its potential as a food preservative.展开更多
Objectives:The contamination of Aspergillus flavus and aflatoxins(AFs)is one of the most serious safety problems in food and feed.The discovery and application of plant-sourced antifungal agents are hot topics in myco...Objectives:The contamination of Aspergillus flavus and aflatoxins(AFs)is one of the most serious safety problems in food and feed.The discovery and application of plant-sourced antifungal agents are hot topics in mycotoxin control.In this study,we aim to develop efficient strategies to control A.flavus and subsequent contamination by AFs.Materials and Methods:We focused on Zongye essential oil,which was extracted from Indocalamus latifolius leaves(Zongye,the traditional food-packaging materials).Its antifungal and antitoxin activities were observed by volatile test,and the significant morphological and ultrastructural variations were observed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM)analyses.The main components of Zongye essential oil were analyzed by gas chromatography-mass spectrometry(GC-MS).RNA sequencing(RNA-Seq)and real-time quantitative reverse transcription polymerase chain reaction(qRT-PCR)analyses were used to reveal the inhibitory mechanism.Results:Among them,No.2 Zongye essential oil completely inhibited the growth and toxin production of A.flavus after 10μL treatment.Under Zongye essential oil treatment,evidently morphological and ultrastructural variations were observed,such as hyphae shrinkage,partial distortion,and a decrease in conidia number.Longifolene and linalool were the major constituents of Zongye essential oil,accounting for 9.55% and 7.95%,respectively,and linalool had stronger inhibitory effects on fungal growth and mycotoxin biosynthesis than longifolene.Based on the experimental results,the antifungal mechanism was proposed:down-regulations of membrane proteins(AFLA_005560,AFLA_019420,and AFLA_084310,etc.)and conidial genes(fblC,steA,and abaA,etc.)inhibited fungal development,and anti-aflatoxigenic activity might be due to significant down-regulation of AF clustergenes andglobal regulators(AtfA and AtfB).Conclusion:A novel antifungal agent,Zongye essential oil,was identified,and its inhibitory mechanism was comprehensively clarified,which is helpful to control AF contamination in an environmentally friendly way.展开更多
The kinetic parameters of partially purified phenoloxidase （PO, EC. 1.14.18.1） from the 5th instar larvae of Pieris rapae （Lepidoptera） were determined, using L-3, 4- dihydroxyphenylalanine （L-DOPA） as substrate...The kinetic parameters of partially purified phenoloxidase （PO, EC. 1.14.18.1） from the 5th instar larvae of Pieris rapae （Lepidoptera） were determined, using L-3, 4- dihydroxyphenylalanine （L-DOPA） as substrate. The optimal pH and temperature of the enzyme for the oxidation of L-DOPA were determined to be at pH 7.0 and at 42℃, respectively. The enzyme was stable between pH 6.5 and 7.4 and at temperatures lower than 37℃. At pH 6.8 and 37℃, the Michaelis constant （Kin） and maximal velocity （V） of the enzyme for the oxidation of L-DOPA were determined to be 0.80 mmol/L and 1.84 μmol/ L/min, respectively. Tetra-hexylresorcinol and 4-dodecylresorcinol effectively inhibited activity of phenoloxidase and this inhibition was reversible and competitive, with the IC50 of 1.50 and 1.12 μmol/L, respectively. The inhibition constants were estimated to be 0.50 and 0.47μmol/L, respectively.展开更多
Objectives:This study was conducted to investigate the xanthine oxidase(XO)inhibitory activities of 18 monomeric anthocyanins from berry fruits and roselle,and to illustrate the underlying mechanism of the most active...Objectives:This study was conducted to investigate the xanthine oxidase(XO)inhibitory activities of 18 monomeric anthocyanins from berry fruits and roselle,and to illustrate the underlying mechanism of the most active anthocyanin delphinidin-3-O-sambubioside.Materials and Methods:Eighteen monomeric anthocyanins were prepared and purified in our laboratory.The inhibitory properties of anthocyanins were investigated by in vitro inhibitory activity studies and fluorescence quenching studies;the inhibitory mechanism was explored through kinetic studies,fluorescence quenching studies,circular dichroism analysis and computational docking simulations.Results:XO inhibitory activities of anthocyanins were related to the structures of B rings and glycosides.Among all the tested anthocyanins,delphinidin-3-O-sambubioside showed the most potent inhibitory activity with an IC_(50) of 17.1μmol/L,which was comparable to the positive control allopurinol.Spectroscopic results revealed that delphinidin-3-O-sambubioside could spontaneously interact with XO and induce conformational changes.Computational docking study indicated that delphinidin-3-O-sambubioside could bind to XO with a proper orientation,stably formed π-π interactions and hydrogen bonds with key residues,thus preventing the substrate from entering the active pocket.Conclusions:In brief,our study identified delphinidin-3-O-sambubioside as a potent XO inhibitor from natural anthocyanins,which is potentially applicable for prevention and treatment of hyperuricemia.展开更多
基金financially supported by the National Natural Science Foundation of China(Grant No.32472468 and No.32001817)the Fundamental Research Program of Shanxi Province(202303021221123).
文摘Advanced glycation end products(AGEs)are complex compounds formed through interaction of carbonyl groups from saccharides with amino groups in amino acids,proteins,lipids and nucleic acids,mainly via Maillard reaction.Studies have shown that AGEs can accumulate in the body and lead to neurodegenerative diseases,cardiovascular diseases,inflammatory responses,diabetes,and other diseases.This comment will provide a review of the inhibitory mechanism of flavonoids on dietary AGEs formation in food models and aims to provide a theoretical basis for the development of new therapeutic strategies and drugs.
基金Supported by National Natural Science Foundation of China(41076097,41006097,41106113)Science and Technology Research Key Projectof Chinese Ministry of Education(211065)+2 种基金Natural Science Foundation of Jiangsu Province,China(BK2010322)Open Research of Jiangsu Key Laboratory of Environmental Material and Environmental Engineering(K090027,K090025,K090026,K090028)"New Century"Talent Project of Yangzhou University,China~~
文摘[Objective] The research aimed to analyze the inhibitory mechanism of Sophora japonica n-hexane extract which significantly inhibited Microcystis aeruginosa in the prior research.[Method] S.japonica n-hexane extract was used to treat M.aeruginosa.By inspecting chlorophyll a content,protein content,cell membrane permeability and superoxide dismutase（SOD） activity,the inhibitory mechanism of S.japonica n-hexane extract on M.aeruginosa was analyzed initially.[Result] S.japonica n-hexane extract destroyed the cell membrane system of M.aeruginosa,and increased the cell membrane permeability.The contents of chlorophyll a and protein respectively declined to 10% and 50% of that in the control group after cultivated for 7 d,which indicated the photosynthetic reaction system of M.aeruginosa was destroyed.In addition,under the effect of S.japonica n-hexane extract,SOD activity of M.aeruginosa increased in the early period and decreased in the latter period.[Conclusion] The possible inhibitory mechanism of S.japonica n-hexane extract on M.aeruginosa was destroying the cell membrane to increase the membrane permeability;destroying the photosynthetic reaction system to decrease the contents of photosynthetic pigment and protein;making SOD activity showing the phased variation.
基金This work was supported by the National Natural Science Foundation of China(Nos.30470408 and 20637010).
文摘The inhibitory mechanism of copper（Ⅱ） on the aggegation of amyloid β-peptide （Aβ） was investigated by molecular dynamics simulations. The binding mode ofcopper（Ⅱ） with Aβ is characterized by the imidazole nitrogen atom, Nπ, of the histidine residue H 13, acting as the anchoring site, and the backbone＇s deprotoned amide nitogen atoms as the main binding sites. Drove by the coordination bonds and their induced hydrogen bond net, the conformations of Aβ converted from β-sheet non-β-sheet conformations, which destabilized the aggregation of Aβ into fibrils.
基金supported by the National Natural Science Foundation of China(Grant No.30470408).
文摘Aggregation of amyloid ?-peptide (A?) into insoluble fibrils is a key pathological event in Alzheimer’s disease (AD). Under certain conditions, Cu(II) exhibits strong inhibitory ef-fect on the Zn(II)-induced aggregation, which occurs significantly even at nearly physiological concentrations of zinc ion in vitro. Cu(II) is considered as a potential factor in the normal brain preventing A? from aggregating. The possible mechanism of the inhibitory effect of Cu(II) is in-vestigated for the first time by molecular modeling method. In the mono-ring mode, the Y10 residue promotes typical quasi-helix conformations of A?. Specially, [Cu-H13(Np)-Y10(OH)] complex forms a local 3.010 helix conformation. In the multi-ring mode, the side chains of Q15 and E11 residues collaborate harmoniously with other chelating ligands producing markedly low energies and quasi-helix conformations. [Cu-3N-Q15(O)-E11(O1)] and [Cu-H13(Np)-Y10(OH)] complex with quasi-helix conformations may prefer soluble forms in solution. In addition, hydro-gen-bond interactions may be the main driving force for A? aggregation. All the results will pro-vide helpful clues for an improved understanding of the role of Cu(II) in the pathogenesis of AD and contribute to the development of an “anti-amyloid” therapeutic strategy.
基金This work was partially supported by the National Natural Science Foundation of China(32072310)Fundamental Research Funds for the Central Universities(JUSRP221004)+1 种基金Guangzhou Science and Technology Project(202206010096)Collaborative innovation center of food safety and quality control in Jiangsu Province.
文摘Fusarium graminearum is a pathogen that can infect wheat,corn and other grain crops,resulting in a reduction in grain yield and nutritional value and even causing serious harm to public health.Ferulic acid(FA)is popularly extracted from a variety of traditional Chinese medicines,such as ferula,asafoetida and angelica,and is a promising fungicide for the preservation of foods due to its antibacterial,antioxidant and anti-inflammatory functions.Based on its efficacy,the inhibitory activity of FA against F.graminearum was evaluated and the involved mechanism was investigated as well.The EC_(50) and EC90 values were approximately 20μg/mL and 100μg/mL,respectively,according to the mycelial dry weight test.TEM and SEM analyses after FA treatment revealed that the cell membrane of hyphae was impaired and showed the following characteristics:coarse surface with wrinkles,blurry ultrastructure edges,and cytoplasmic leakage.In addition,cell integrity and permeability analyses were performed to identify its antifungal mechanism.After FA treatment,the fluorescence intensity of mycelia after PI staining increased significantly(p<0.001),and the high concentration group showed a continuous rise in extracellular relative conductivity and more significant leakage of nucleic acids and protein.Moreover,FA inhibited ergosterol synthesis in the F.graminearum cell membrane,which confirmed that the target site of FA antifungal action was the cell membrane.
基金supported by the National Natural Science Foundation of China(Grant Nos.:82160739,81922070,81973286,and 81973393)Sailing Special Project of Shanghai Rising-Star Program(Grant No.:22YF1441500)+6 种基金Program for Innovative Leading Talents of Qinghai Province(2018&2019)Innovation Team and Talents Cultivation Program of National Administration of Traditional Chinese Medicine(Grant No.:ZYYCXTD-D-202004)Shanghai Science and Technology Innovation Action Plans(Grant Nos.:20S21901500 and 20S21900900)supported by the Shanghai Science and Technology CommitteeProject of the National Multidisciplinary Innovation Team of Traditional Chinese Medicine supported by the National Administration of Traditional Chinese MedicineKey R&D and Transformation Science and Technology Cooperation Project of Qinghai Province(Grant No.:2019-HZ-819)Basic Public Welfare Research Program of Zhejiang Province(Grant No.:LGF22H280012).
文摘Although herbal medicines(HMs)are widely used in the prevention and treatment of obesity and obesity-associated disorders,the key constituents exhibiting anti-obesity activity and their molecular mechanisms are poorly understood.Recently,we assessed the inhibitory potentials of several HMs against human pancreatic lipase(hPL,a key therapeutic target for human obesity),among which the root-extract of Rhodiola crenulata(ERC)showed the most potent anti-hPL activity.In this study,we adopted an integrated strategy,involving bioactivity-guided fractionation techniques,chemical profiling,and biochemical assays,to identify the key anti-hPL constituents in ERC.Nine ERC fractions(retention time=12.5e35 min),obtained using reverse-phase liquid chromatography,showed strong anti-hPL activity,while the major constituents in these bioactive fractions were subsequently identified using liquid chromatography-quadrupole time-of-flight mass spectrometry(LC-Q-TOF-MS/MS).Among the identified ERC constituents,1,2,3,4,6-penta-O-galloyl-β-D-glucopyranose(PGG)and catechin gallate(CG)showed the most potent anti-hPL activity,with pIC50 values of 7.59±0.03 and 7.68±0.23,respectively.Further investigations revealed that PGG and CG potently inhibited hPL in a non-competitive manner,with inhibition constant(Ki)values of 0.012 and 0.082 mM,respectively.Collectively,our integrative analyses enabled us to efficiently identify and characterize the key anti-obesity constituents in ERC,as well as to elucidate their anti-hPL mechanisms.These findings provide convincing evidence in support of the anti-obesity and lipid-lowering properties of ERC.
基金supported by the National Key RD program of China(No.2021YFA1502300)the National Natural Science Foundation of China(No.21733007)。
文摘Severe acute respiratory syndrome coronavirus 2(SARS-Co V-2) relies on the central molecular machine RNA-dependent RNA polymerase(Rd Rp) for the viral replication and transcription. Remdesivir at the template strand has been shown to effectively inhibit the RNA synthesis in SARS-Co V-2 Rd Rp by deactivating not only the complementary UTP incorporation but also the next nucleotide addition. However, the underlying molecular mechanism of the second inhibitory point remains unclear. In this work, we have performed molecular dynamics simulations and demonstrated that such inhibition has not directly acted on the nucleotide addition at the active site. Instead, the translocation of Remdesivir from +1 to-1 site is hindered thermodynamically as the posttranslocation state is less stable than the pre-translocation state due to the motif B residue G683. Moreover, another conserved residue S682 on motif B further hinders the dynamic translocation of Remdesivir due to the steric clash with the 1′-cyano substitution. Overall,our study has unveiled an alternative role of motif B in mediating the translocation when Remdesivir is present in the template strand and complemented our understanding about the inhibitory mechanisms exerted by Remdesivir on the RNA synthesis in SARS-Co V-2 Rd Rp.
基金supported by the Open Research Fund of Jiangsu Key Laboratory for Biomass Energy and Material(JSBEM202009)the National Nature Science Foundation of China(32100439)+1 种基金the Science and Technology Foundation of Suzhou(SNG201909)the Foundation of Suzhou Academy of Agricultural Sciences(21010).
文摘The harvested loquat fruits are prone to browning,leading to a decline in fruit quality.Inhibiting activity of polyphenol oxidase(PPO)is an important way to prevent browning.In this study,we evaluated the inhibitory impact of oligomeric procyanidins(OPC)on hydroxylation of monophenol and oxidation of o-diphenol catalyzed by PPO and effect of OPC on loquat fruits storage.The obtained results revealed that OPC could attenuate the activity of monophenolase and diphenolase.For monophenolase activity,the inhibition rate was observed to be dose-dependent with an IC50 of 11.6±3.4μg/mL for the steady-state rate.For diphenolase activity,OPC inhibited PPO activity(IC50=15.75±2.1μg/mL)with a reversible and competitive mechanism and quenched fluorescence of PPO by forming OPC-PPO complex with one binding site in a static procedure.In addition,the data obtained from storage assays revealed that OPC could enhance the quality of harvested loquat fruits by attenuating the PPO activity,augmenting the content of total phenolics and flavonoids,and simultaneously delaying the browning of loquats.In this research,we identified a potent PPO inhibitor and expanded its potential as a food preservative.
基金supported by the Beijing Natural Science Foundation(Nos.6212028 and 6222053)the National Natural Science Foundation of China(No.32372457)the Agricultural Science and Technology Innovation Program of Institute of Food Science and Technology,CAAS(No.CAAS-ASTIP-G2022-IFST-01).
文摘Objectives:The contamination of Aspergillus flavus and aflatoxins(AFs)is one of the most serious safety problems in food and feed.The discovery and application of plant-sourced antifungal agents are hot topics in mycotoxin control.In this study,we aim to develop efficient strategies to control A.flavus and subsequent contamination by AFs.Materials and Methods:We focused on Zongye essential oil,which was extracted from Indocalamus latifolius leaves(Zongye,the traditional food-packaging materials).Its antifungal and antitoxin activities were observed by volatile test,and the significant morphological and ultrastructural variations were observed by scanning electron microscopy(SEM)and transmission electron microscopy(TEM)analyses.The main components of Zongye essential oil were analyzed by gas chromatography-mass spectrometry(GC-MS).RNA sequencing(RNA-Seq)and real-time quantitative reverse transcription polymerase chain reaction(qRT-PCR)analyses were used to reveal the inhibitory mechanism.Results:Among them,No.2 Zongye essential oil completely inhibited the growth and toxin production of A.flavus after 10μL treatment.Under Zongye essential oil treatment,evidently morphological and ultrastructural variations were observed,such as hyphae shrinkage,partial distortion,and a decrease in conidia number.Longifolene and linalool were the major constituents of Zongye essential oil,accounting for 9.55% and 7.95%,respectively,and linalool had stronger inhibitory effects on fungal growth and mycotoxin biosynthesis than longifolene.Based on the experimental results,the antifungal mechanism was proposed:down-regulations of membrane proteins(AFLA_005560,AFLA_019420,and AFLA_084310,etc.)and conidial genes(fblC,steA,and abaA,etc.)inhibited fungal development,and anti-aflatoxigenic activity might be due to significant down-regulation of AF clustergenes andglobal regulators(AtfA and AtfB).Conclusion:A novel antifungal agent,Zongye essential oil,was identified,and its inhibitory mechanism was comprehensively clarified,which is helpful to control AF contamination in an environmentally friendly way.
基金Acknowledgments The present investigation was supported in part by grant N0. 30270887, 30571237 of the National Natural Science Foundation of China for W. C. Luo.
文摘The kinetic parameters of partially purified phenoloxidase （PO, EC. 1.14.18.1） from the 5th instar larvae of Pieris rapae （Lepidoptera） were determined, using L-3, 4- dihydroxyphenylalanine （L-DOPA） as substrate. The optimal pH and temperature of the enzyme for the oxidation of L-DOPA were determined to be at pH 7.0 and at 42℃, respectively. The enzyme was stable between pH 6.5 and 7.4 and at temperatures lower than 37℃. At pH 6.8 and 37℃, the Michaelis constant （Kin） and maximal velocity （V） of the enzyme for the oxidation of L-DOPA were determined to be 0.80 mmol/L and 1.84 μmol/ L/min, respectively. Tetra-hexylresorcinol and 4-dodecylresorcinol effectively inhibited activity of phenoloxidase and this inhibition was reversible and competitive, with the IC50 of 1.50 and 1.12 μmol/L, respectively. The inhibition constants were estimated to be 0.50 and 0.47μmol/L, respectively.
文摘Objectives:This study was conducted to investigate the xanthine oxidase(XO)inhibitory activities of 18 monomeric anthocyanins from berry fruits and roselle,and to illustrate the underlying mechanism of the most active anthocyanin delphinidin-3-O-sambubioside.Materials and Methods:Eighteen monomeric anthocyanins were prepared and purified in our laboratory.The inhibitory properties of anthocyanins were investigated by in vitro inhibitory activity studies and fluorescence quenching studies;the inhibitory mechanism was explored through kinetic studies,fluorescence quenching studies,circular dichroism analysis and computational docking simulations.Results:XO inhibitory activities of anthocyanins were related to the structures of B rings and glycosides.Among all the tested anthocyanins,delphinidin-3-O-sambubioside showed the most potent inhibitory activity with an IC_(50) of 17.1μmol/L,which was comparable to the positive control allopurinol.Spectroscopic results revealed that delphinidin-3-O-sambubioside could spontaneously interact with XO and induce conformational changes.Computational docking study indicated that delphinidin-3-O-sambubioside could bind to XO with a proper orientation,stably formed π-π interactions and hydrogen bonds with key residues,thus preventing the substrate from entering the active pocket.Conclusions:In brief,our study identified delphinidin-3-O-sambubioside as a potent XO inhibitor from natural anthocyanins,which is potentially applicable for prevention and treatment of hyperuricemia.
