A novel inhibition based biosensor of glucose oxidase(GOx) for environmental mercury detection was developed. An electropolymerized aniline membrane was prepared on a platinum electrode containing ferrocene as electro...A novel inhibition based biosensor of glucose oxidase(GOx) for environmental mercury detection was developed. An electropolymerized aniline membrane was prepared on a platinum electrode containing ferrocene as electron transfer mediator, on which GOx was cross-linked by glutaraldehyde. The response of the sensor was based on the current reduction in the electrochemical system by inhibition of mercury against GOx electrode. The detection limit of the inhibition-based sensor for mercury is 0.49 μg/L, and the linear response ranges are 0.49-783.21 μg/L and 783.21 μg/L-25.55 mg/L. The GOx membrane can be completely reactivated after inhibition, and remains 70% of the activity in more than one month. The sensor was used for mercury determination in compost extract with good results.展开更多
Semicarbazide-sensitive the metabolism of glucose and fat, amine oxidase （SSAO） has been considered to be associated with and elevated SSAO activity was observed in obese patients. In the present study, an in vitro ...Semicarbazide-sensitive the metabolism of glucose and fat, amine oxidase （SSAO） has been considered to be associated with and elevated SSAO activity was observed in obese patients. In the present study, an in vitro SSAO activity-based method was developed to screen inhibitors from 15 an- ti-obesity drugs. Among the fifteen anti-obesity drugs, four drugs including caffeine, fenfluramine, bumetanide and amfebutamone inhibited SSAO activity, and caffeine was the most effective one. When the concentration of caffeine was 1.4 mmol/L, the inhibition ratio was 31.9% and 18.8% in rabbit serum and rat adipose tissue, respectively. Inhibition of SSAO activity by caffeine was also confirmed in the in vivo study, showing the inhibition ratio of 15.6% on serum SSAO. Caffeine pro- vides a natural source of inhibition of SSAO activity and may be a promising inhibitor for the study of SSAO.展开更多
The use of food additives with xanthine oxidase (XO) inhibitory activity offers an alternative approach to hyperuricemic and gout disease treatment, and provides an example of antioxidant nutraceutics. The in vitro an...The use of food additives with xanthine oxidase (XO) inhibitory activity offers an alternative approach to hyperuricemic and gout disease treatment, and provides an example of antioxidant nutraceutics. The in vitro and in silico XO inhibitory activity of polyphenols from Uruguayan Tannat grape pomaces and propolis extracts was evaluated as well as the scavenging capacity of said compounds. When comparing propolis and grape pomace samples, the in vitro studies demonstrated that polyphenols extracted from propolis are more active as free radical scavengers than those from Tannat grape pomace. Both natural products effectively inhibited XO but the capacity of phenols present in GP is higher than the one present in P. The high content of anthocyanins in GP, absent in P, could account for this observation. In silico assays allowed us to determine relevant ligand-receptor interactions between polyphenols, from a database built with previously reported polyphenols from both natural products, and the active site of XO. The in silico results showed that compound (E)-isoprenylcaffeate from propolis was the best potential XO inhibitor displaying hydrophobic aromatic interaction between the conjugated ring of the caffeate moiety and polar interactions between hydroxyl groups from caffeate with the active site polar residues. Among grape pomaces, the Cyanidin-3-O-(6-(E)-p-coumaroyl)-glucoside was the best XO inhibitor;its moiety oxychromenyl being relevant to the docking stabilization. All these results lead us to propose Uruguayan propolis and Tannat grape pomace extracts as food additives as well as phytopharmaceuticals to decrease the uric acid levels in gout disease and to act against oxidative stress.展开更多
Gnaphalium affine D. Don, a medicinal and edible plant, has been used to treat gout in traditional Chinese medicine and popularly consumed in China for a long time. A detailed phytochemical investigation on the aerial...Gnaphalium affine D. Don, a medicinal and edible plant, has been used to treat gout in traditional Chinese medicine and popularly consumed in China for a long time. A detailed phytochemical investigation on the aerial part of G. affine led to the isolation of two new esters of caffeoylquinic acid named(-) ethyl 1, 4-di-O-caffeoylquinate(1) and(-) methyl 1, 4-di-O-caffeoylquinate(2), together with 35 known compounds(3-37). Their structures were elucidated by spectroscopic data and first-order multiplet analysis. All the isolated compounds were tested for their xanthine oxidase inhibitory activity with an in vitro enzyme inhibitory screening assay. Among the tested compounds, 1(IC_(50) 11.94 μmol·L^(-1)) and 2(IC_(50) 15.04 μmol·L^(-1)) showed a good inhibitory activity. The current results supported the medical use of the plant.展开更多
In this study, the kinetics of inhibition of polyphenol oxidase by L-cysteine has been investigated. The inhibition of tobacco polyphenol oxidase was studied using the progress-of-substrate-reaction method proposed by...In this study, the kinetics of inhibition of polyphenol oxidase by L-cysteine has been investigated. The inhibition of tobacco polyphenol oxidase was studied using the progress-of-substrate-reaction method proposed by Tsou, following the substrate reaction during irreversible inhibition of the enzyme activity. Analysis of the inhibition kinetics shows that inhibition occurs by an irreversible and non-complexation reaction. The microscopic rate constants were determined for reaction of the inhibitor both with the free enzyme and with the enzyme-substrate complex. The results show that the presence of the substrate has a significant protective effect of the enzyme against inactivation by L-cysteine.展开更多
Flos Sophorae Immaturus (FSI) possessed potential xanthine oxidase (XO) inhibitory activity as a uric acid-lowing natural product.The present work identified and quantified the free and bound polyphenols of FSI by UPL...Flos Sophorae Immaturus (FSI) possessed potential xanthine oxidase (XO) inhibitory activity as a uric acid-lowing natural product.The present work identified and quantified the free and bound polyphenols of FSI by UPLC-QTOF-MS.Then determined the primary polyphenols with XO inhibitory effect and clarified their potential mechanisms by omission experiment,interaction assay,inhibition type,and fluorescence measurements.The results revealed that nine polyphenols were detected in the free polyphenol extract and ten polyphenols were detected in the bound polyphenol extract.Meanwhile,seven polyphenols were identified as XO inhibitors,including quercetin,kaempferol,isorhamnetin,rutin,hyperoside,protocatechuic acid,and quercitrin with the IC50 values of 0.03,0.11,0.07,5.62,11.48,22.13,and 367.82 mg/mL,but their inhibition stability was lower than 24 h.Although the content of quercetin (18.87 mg/g) was not the highest,it played a crucial role to the XO inhibitory effect of FSI.Furthermore,kaempferol and isorhamnetin alone revealed the sub-additive effect with quercetin,while the combination of other polyphenols with quercetin generated the interference or antagonism effects.Quercetin,isorhamnetin,and kaempferol were mixed-type and competitive inhibitors,which significantly quenched the fluorescence intensity of XO.Moreover,the binding processes of quercetin-XO,kaempferol-XO,and isorhamnetin-XO were spontaneous and endothermic,and the hydrophobic interaction was the key driving force.In general,quercetin,kaempferol,and isorhamnetin in FSI can be used as potential XO inhibitors.展开更多
Polyphenol oxidase （PPO） is the enzyme responsible for enzymatic browning during the growth of insects. It is also involved in defense reactions and is related with immunities in insects. PPO a metalloenzyme oxidase...Polyphenol oxidase （PPO） is the enzyme responsible for enzymatic browning during the growth of insects. It is also involved in defense reactions and is related with immunities in insects. PPO a metalloenzyme oxidase, catalyzes the oxidation of o-diphenol to o-quinone. The present paper describes the effects of benzaldehyde and its p-substituted derivatives on the activity of PPO from the fifth instar of Pieris rapae L. PPO from the fifth instar of Pieris rapae L. was purified using ammonium sulfate fractionation and chromatography on Sephadex G-100. The enzyme kinetics was characterized using L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The results show that benzaldehyde, phydroxybenzaldehyde, p-chlorobenzaldehyde, and p-cyanobenzaldehyde can inhibit the PPO activity for the oxidation of L-DOPA. The inhibitor concentration leading to 50% activity lost, IC50, was estimated to be 5.90, 5.62, 2.83, and 2.91 mmol/L for the four tested inhibitors, respectively. Kinetic analyses show that the inhibitory effects of these compounds are reversible. Benzaldehyde, phydroxybenzaldehyde, and p-chlorobenzaldehyde are noncompetitive inhibitors while p-cyanobenzaldehyde is a mixed-type inhibitor. The inhibition constants were determined for all four inhibitors. p-chlorobenzaldehyde and p-cyanobenzaldehyde were more potent inhibitors than the other compounds. These results provide a basis for developing PPO inhibition-based pesticides.展开更多
Protoporphyrinogen oxidase （PPO, EC 1.3.3.4） is one of the most significant targets for a large family of in- hibitors that may be used as herbicide, bactericide, fungicide, or photosensitizing activator to treat ca...Protoporphyrinogen oxidase （PPO, EC 1.3.3.4） is one of the most significant targets for a large family of in- hibitors that may be used as herbicide, bactericide, fungicide, or photosensitizing activator to treat cancer through photodynamic therapy （PDT）. Molecular docking and CoMFA were combined in a multistep framework with the ultimate goal of identifying important factor contributing to the activity of PPO inhibitors. As a continuation of the previous research work on the development of new PPO inhibitors, the bioassay results indicated that good PPO in- hibitors were discovered in all of the three chemical series with ICs0 values ranging from 0.010 to 0.061 pmol·L ^-1. Using the crystal structure of tobacco mitochondrial PPO （mtPPO） as template, all the compounds were docked into the enzyme active site. The docking pose of each compound was subsequently used in a receptor-based alignment, leading to the development of a significant CoMFA model with r^2 value of 0.98 and q^2 （cross validation r^2） value of 0.63. This novel multistep framework gives insight into the and it can be extended to other classes of PPO inhibitors. In be particularly applicable in virtual screening procedures. structural characteristics for the binding of inhibitors, addition, the simplicity of the proposed approach may展开更多
基金Project(50608029) supported by the National Natural Science Foundation of ChinaProject(2004AA649370) supported by the Hi-tech Research and Development Program of China+1 种基金Project(2005CB724203) supported by the National Basic Research Program of ChinaProject(IRT0719) supported by the Program for Changjiang Scholars and Innovative Research Team in University of China
文摘A novel inhibition based biosensor of glucose oxidase(GOx) for environmental mercury detection was developed. An electropolymerized aniline membrane was prepared on a platinum electrode containing ferrocene as electron transfer mediator, on which GOx was cross-linked by glutaraldehyde. The response of the sensor was based on the current reduction in the electrochemical system by inhibition of mercury against GOx electrode. The detection limit of the inhibition-based sensor for mercury is 0.49 μg/L, and the linear response ranges are 0.49-783.21 μg/L and 783.21 μg/L-25.55 mg/L. The GOx membrane can be completely reactivated after inhibition, and remains 70% of the activity in more than one month. The sensor was used for mercury determination in compost extract with good results.
基金Supported by the Ministry of Science and Technology of China(2008AA12A218 2009BAK59B01)
文摘Semicarbazide-sensitive the metabolism of glucose and fat, amine oxidase （SSAO） has been considered to be associated with and elevated SSAO activity was observed in obese patients. In the present study, an in vitro SSAO activity-based method was developed to screen inhibitors from 15 an- ti-obesity drugs. Among the fifteen anti-obesity drugs, four drugs including caffeine, fenfluramine, bumetanide and amfebutamone inhibited SSAO activity, and caffeine was the most effective one. When the concentration of caffeine was 1.4 mmol/L, the inhibition ratio was 31.9% and 18.8% in rabbit serum and rat adipose tissue, respectively. Inhibition of SSAO activity by caffeine was also confirmed in the in vivo study, showing the inhibition ratio of 15.6% on serum SSAO. Caffeine pro- vides a natural source of inhibition of SSAO activity and may be a promising inhibitor for the study of SSAO.
文摘The use of food additives with xanthine oxidase (XO) inhibitory activity offers an alternative approach to hyperuricemic and gout disease treatment, and provides an example of antioxidant nutraceutics. The in vitro and in silico XO inhibitory activity of polyphenols from Uruguayan Tannat grape pomaces and propolis extracts was evaluated as well as the scavenging capacity of said compounds. When comparing propolis and grape pomace samples, the in vitro studies demonstrated that polyphenols extracted from propolis are more active as free radical scavengers than those from Tannat grape pomace. Both natural products effectively inhibited XO but the capacity of phenols present in GP is higher than the one present in P. The high content of anthocyanins in GP, absent in P, could account for this observation. In silico assays allowed us to determine relevant ligand-receptor interactions between polyphenols, from a database built with previously reported polyphenols from both natural products, and the active site of XO. The in silico results showed that compound (E)-isoprenylcaffeate from propolis was the best potential XO inhibitor displaying hydrophobic aromatic interaction between the conjugated ring of the caffeate moiety and polar interactions between hydroxyl groups from caffeate with the active site polar residues. Among grape pomaces, the Cyanidin-3-O-(6-(E)-p-coumaroyl)-glucoside was the best XO inhibitor;its moiety oxychromenyl being relevant to the docking stabilization. All these results lead us to propose Uruguayan propolis and Tannat grape pomace extracts as food additives as well as phytopharmaceuticals to decrease the uric acid levels in gout disease and to act against oxidative stress.
基金supported by the Natural Science Foundation of Shanghai(No.15ZR1440100)the National Natural Science Foundation of China(No.81603279)
文摘Gnaphalium affine D. Don, a medicinal and edible plant, has been used to treat gout in traditional Chinese medicine and popularly consumed in China for a long time. A detailed phytochemical investigation on the aerial part of G. affine led to the isolation of two new esters of caffeoylquinic acid named(-) ethyl 1, 4-di-O-caffeoylquinate(1) and(-) methyl 1, 4-di-O-caffeoylquinate(2), together with 35 known compounds(3-37). Their structures were elucidated by spectroscopic data and first-order multiplet analysis. All the isolated compounds were tested for their xanthine oxidase inhibitory activity with an in vitro enzyme inhibitory screening assay. Among the tested compounds, 1(IC_(50) 11.94 μmol·L^(-1)) and 2(IC_(50) 15.04 μmol·L^(-1)) showed a good inhibitory activity. The current results supported the medical use of the plant.
基金the National Key Basic Research and Develop-ment (973) Program of China (No. G1999075607) and the Henan Natural Science Foundation (No. G0111010700)
文摘In this study, the kinetics of inhibition of polyphenol oxidase by L-cysteine has been investigated. The inhibition of tobacco polyphenol oxidase was studied using the progress-of-substrate-reaction method proposed by Tsou, following the substrate reaction during irreversible inhibition of the enzyme activity. Analysis of the inhibition kinetics shows that inhibition occurs by an irreversible and non-complexation reaction. The microscopic rate constants were determined for reaction of the inhibitor both with the free enzyme and with the enzyme-substrate complex. The results show that the presence of the substrate has a significant protective effect of the enzyme against inactivation by L-cysteine.
基金subsidized by the Jiangsu Key R&D plan,China(BE2019309)Construction Project of Innovative Talents Base of Guizhou Province([2016]22)which has enabled us to accomplish this study.
文摘Flos Sophorae Immaturus (FSI) possessed potential xanthine oxidase (XO) inhibitory activity as a uric acid-lowing natural product.The present work identified and quantified the free and bound polyphenols of FSI by UPLC-QTOF-MS.Then determined the primary polyphenols with XO inhibitory effect and clarified their potential mechanisms by omission experiment,interaction assay,inhibition type,and fluorescence measurements.The results revealed that nine polyphenols were detected in the free polyphenol extract and ten polyphenols were detected in the bound polyphenol extract.Meanwhile,seven polyphenols were identified as XO inhibitors,including quercetin,kaempferol,isorhamnetin,rutin,hyperoside,protocatechuic acid,and quercitrin with the IC50 values of 0.03,0.11,0.07,5.62,11.48,22.13,and 367.82 mg/mL,but their inhibition stability was lower than 24 h.Although the content of quercetin (18.87 mg/g) was not the highest,it played a crucial role to the XO inhibitory effect of FSI.Furthermore,kaempferol and isorhamnetin alone revealed the sub-additive effect with quercetin,while the combination of other polyphenols with quercetin generated the interference or antagonism effects.Quercetin,isorhamnetin,and kaempferol were mixed-type and competitive inhibitors,which significantly quenched the fluorescence intensity of XO.Moreover,the binding processes of quercetin-XO,kaempferol-XO,and isorhamnetin-XO were spontaneous and endothermic,and the hydrophobic interaction was the key driving force.In general,quercetin,kaempferol,and isorhamnetin in FSI can be used as potential XO inhibitors.
基金Supported by the Science and Technology Foundation of Fujian Province (No. 2004N002)the National Natural Science Foundation of China (No. 30570408)
文摘Polyphenol oxidase （PPO） is the enzyme responsible for enzymatic browning during the growth of insects. It is also involved in defense reactions and is related with immunities in insects. PPO a metalloenzyme oxidase, catalyzes the oxidation of o-diphenol to o-quinone. The present paper describes the effects of benzaldehyde and its p-substituted derivatives on the activity of PPO from the fifth instar of Pieris rapae L. PPO from the fifth instar of Pieris rapae L. was purified using ammonium sulfate fractionation and chromatography on Sephadex G-100. The enzyme kinetics was characterized using L-3,4-dihydroxyphenylalanine （L-DOPA） as substrate. The results show that benzaldehyde, phydroxybenzaldehyde, p-chlorobenzaldehyde, and p-cyanobenzaldehyde can inhibit the PPO activity for the oxidation of L-DOPA. The inhibitor concentration leading to 50% activity lost, IC50, was estimated to be 5.90, 5.62, 2.83, and 2.91 mmol/L for the four tested inhibitors, respectively. Kinetic analyses show that the inhibitory effects of these compounds are reversible. Benzaldehyde, phydroxybenzaldehyde, and p-chlorobenzaldehyde are noncompetitive inhibitors while p-cyanobenzaldehyde is a mixed-type inhibitor. The inhibition constants were determined for all four inhibitors. p-chlorobenzaldehyde and p-cyanobenzaldehyde were more potent inhibitors than the other compounds. These results provide a basis for developing PPO inhibition-based pesticides.
文摘Protoporphyrinogen oxidase （PPO, EC 1.3.3.4） is one of the most significant targets for a large family of in- hibitors that may be used as herbicide, bactericide, fungicide, or photosensitizing activator to treat cancer through photodynamic therapy （PDT）. Molecular docking and CoMFA were combined in a multistep framework with the ultimate goal of identifying important factor contributing to the activity of PPO inhibitors. As a continuation of the previous research work on the development of new PPO inhibitors, the bioassay results indicated that good PPO in- hibitors were discovered in all of the three chemical series with ICs0 values ranging from 0.010 to 0.061 pmol·L ^-1. Using the crystal structure of tobacco mitochondrial PPO （mtPPO） as template, all the compounds were docked into the enzyme active site. The docking pose of each compound was subsequently used in a receptor-based alignment, leading to the development of a significant CoMFA model with r^2 value of 0.98 and q^2 （cross validation r^2） value of 0.63. This novel multistep framework gives insight into the and it can be extended to other classes of PPO inhibitors. In be particularly applicable in virtual screening procedures. structural characteristics for the binding of inhibitors, addition, the simplicity of the proposed approach may
