scholarly journals Kinetic studies on the hydroxylation of p-coumaric acid to caffeic acid by spinach-beet phenolase

1975 ◽  
Vol 149 (2) ◽  
pp. 447-461 ◽  
Author(s):  
R J McIntyre ◽  
P F T. Vaughan
Keyword(s):  
Caffeic Acid ◽  
Electron Donor ◽  
Active Site ◽  
Initial Velocity ◽  
Kinetic Studies ◽  
Reaction Scheme ◽  
Spectrophotometric Assay ◽  
Electron Donors ◽  
Coumaric Acid ◽  
Substrate Addition

1. A spectrophotometric assay is described that enables the hydroxylation of p-coumaric acid to caffeic acid, catalysed by spinach-beet phenolase, to be followed continuously. 2. Initial-velocity and inhibitor studies indicate that the order of substrate addition is oxygen, p-coumaric acid and electron donor, with an irreversible step separating the binding of each substrate. 3. Caffeic acid is most likely to act as electron donor at the active site; other electron donors, such as ascorbic acid, NADH and dimethyltetrahydropteridine, function mainly to recycle cofactor amounts of caffeic acid. 4. A reaction scheme, consistent with these data, is proposed.

scholarly journals A Simple Method for Evaluating the Bioactive Phenolic Compounds’ Presence in Brazilian Craft Beers

Molecules ◽  
2021 ◽  
Vol 26 (16) ◽  
pp. 4716
Author(s):  
Marcelo Coelho Silva ◽  
Jeancarlo Pereira dos Anjos ◽  
Lilian Lefol Nani Guarieiro ◽  
Bruna A. Souza Machado
Keyword(s):  
Phenolic Compounds ◽  
Caffeic Acid ◽  
Good Accuracy ◽  
Limit Of Detection ◽  
Coumaric Acid ◽  
Simple Method ◽  
Craft Beer ◽  
Extraction Step ◽  
Satisfactory Precision ◽  
Craft Beers

There are a significant number of analytical methodologies employing different techniques to determine phenolic compounds in beverages. However, these methods employ long sample preparation processes and great time consumption. The aim of this paper was the development of a simple method for evaluating the phenolic compounds’ presence in Brazilian craft beers without a previous extraction step. Catechin, caffeic acid, epicatechin, p-coumaric acid, hydrated rutin, trans-ferulic acid, quercetin, kaempferol, and formononetin were analyzed in fifteen different craft beers. The method showed good linearity (R2 ≥ 0.9966). The limit of detection ranged from 0.08 to 0.83 mg L−1, and limits of quantification were between 0.27 and 2.78 mg L−1. The method showed a satisfactory precision (RSD ≤ 16.2%). A good accuracy was obtained by the proposed method for all phenolic compounds in craft beer (68.6% ˂ accuracy ˂ 112%). Catechin showed higher concentrations (up to 124.8 mg L−1) in the samples, followed by epicatechin (up to 51.1 mg L−1) and caffeic acid (up to 8.13 mg L−1). Rutin and formononetin were observed in all analyzed samples (0.52 mg L−1 to 2.40 mg L−1), and kaempferol was less present in the samples. The presence of plant origin products was determinant for the occurrence of the highest concentrations of phenolic compounds in Brazilian craft beers.

scholarly journals Relationships Between the Content of Phenolic Compounds and the Antioxidant Activity of Polish Honey Varieties as a Tool for Botanical Discrimination

Molecules ◽  
2021 ◽  
Vol 26 (6) ◽  
pp. 1810
Author(s):  
Monika Kędzierska-Matysek ◽  
Małgorzata Stryjecka ◽  
Anna Teter ◽  
Piotr Skałecki ◽  
Piotr Domaradzki ◽  
...  
Keyword(s):  
Principal Component Analysis ◽  
Antioxidant Activity ◽  
Phenolic Compounds ◽  
Caffeic Acid ◽  
Principal Component ◽  
Total Content ◽  
Component Analysis ◽  
Total Phenolic ◽  
Hydroxybenzoic Acid ◽  
Coumaric Acid

The study compared the content of eight phenolic acids and four flavonoids and the antioxidant activity of six Polish varietal honeys. An attempt was also made to determine the correlations between the antioxidant parameters of the honeys and their polyphenol profile using principal component analysis. Total phenolic content (TPC), total flavonoid content (TFC), antioxidant activity (ABTS) and reduction capacity (FRAP) were determined spectrophotometrically, and the phenolic compounds were determined using high-performance liquid chromatography (HPLC). The buckwheat honeys showed the strongest antioxidant activity, most likely because they had the highest concentrations of total phenols, total flavonoids, p-hydroxybenzoic acid, caffeic acid, p-coumaric acid, vanillic acid and chrysin. The principal component analysis (PCA) of the data showed significant relationships between the botanic origin of the honey, the total content of phenolic compounds and flavonoids and the antioxidant activity of the six Polish varietal honeys. The strongest, significant correlations were shown for parameters of antioxidant activity and TPC, TFC, p-hydroxybenzoic acid, caffeic acid and p-coumaric acid. Analysis of four principal components (explaining 86.9% of the total variance), as a classification tool, confirmed the distinctiveness of the Polish honeys in terms of their antioxidant activity and content of phenolic compounds.

scholarly journals A Microcosm Treatability Study for Evaluating Wood Mulch-Based Amendments as Electron Donors for Trichloroethene (TCE) Reductive Dechlorination

Water ◽  
2021 ◽  
Vol 13 (14) ◽  
pp. 1949
Author(s):  
Edoardo Masut ◽  
Alessandro Battaglia ◽  
Luca Ferioli ◽  
Anna Legnani ◽  
Carolina Cruz Viggi ◽  
...  
Keyword(s):  
Electron Donor ◽  
Environmental Sustainability ◽  
Reductive Dechlorination ◽  
Environmental Remediation ◽  
Low Cost ◽  
Chlorinated Solvents ◽  
Electron Donors ◽  
Chlorinated Ethenes ◽  
Dehalococcoides Mccartyi ◽  
Wood Mulch

In this study, wood mulch-based amendments were tested in a bench-scale microcosm experiment in order to assess the treatability of saturated soils and groundwater from an industrial site contaminated by chlorinated ethenes. Wood mulch was tested alone as the only electron donor in order to assess its potential for stimulating the biological reductive dechlorination. It was also tested in combination with millimetric iron filings in order to assess the ability of the additive to accelerate/improve the bioremediation process. The efficacy of the selected amendments was compared with that of unamended control microcosms. The results demonstrated that wood mulch is an effective natural and low-cost electron donor to stimulate the complete reductive dechlorination of chlorinated solvents to ethene. Being a side-product of the wood industry, mulch can be used in environmental remediation, an approach which perfectly fits the principles of circular economy and addresses the compelling needs of a sustainable and low environmental impact remediation. The efficacy of mulch was further improved by the co-presence of iron filings, which accelerated the conversion of vinyl chloride into the ethene by increasing the H2 availability rather than by catalyzing the direct abiotic dechlorination of contaminants. Chemical analyses were corroborated by biomolecular assays, which confirmed the stimulatory effect of the selected amendments on the abundance of Dehalococcoides mccartyi and related reductive dehalogenase genes. Overall, this paper further highlights the application potential and environmental sustainability of wood mulch-based amendments as low-cost electron donors for the biological treatment of chlorinated ethenes.

scholarly journals Kinetic studies and homology modeling of a dual-substrate linalool/nerolidol synthase from Plectranthus amboinicus

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Nur Suhanawati Ashaari ◽  
Mohd Hairul Ab. Rahim ◽  
Suriana Sabri ◽  
Kok Song Lai ◽  
Adelene Ai-Lian Song ◽  
...  
Keyword(s):  
Active Site ◽  
Catalytic Efficiency ◽  
Kinetic Studies ◽  
Homology Model ◽  
Biochemical Properties ◽  
Terpene Synthase ◽  
Monoterpene Synthase ◽  
Terminal Domain ◽  
Catalytic Active Site ◽  
Plectranthus Amboinicus

AbstractLinalool and nerolidol are terpene alcohols that occur naturally in many aromatic plants and are commonly used in food and cosmetic industries as flavors and fragrances. In plants, linalool and nerolidol are biosynthesized as a result of respective linalool synthase and nerolidol synthase, or a single linalool/nerolidol synthase. In our previous work, we have isolated a linalool/nerolidol synthase (designated as PamTps1) from a local herbal plant, Plectranthus amboinicus, and successfully demonstrated the production of linalool and nerolidol in an Escherichia coli system. In this work, the biochemical properties of PamTps1 were analyzed, and its 3D homology model with the docking positions of its substrates, geranyl pyrophosphate (C10) and farnesyl pyrophosphate (C15) in the active site were constructed. PamTps1 exhibited the highest enzymatic activity at an optimal pH and temperature of 6.5 and 30 °C, respectively, and in the presence of 20 mM magnesium as a cofactor. The Michaelis–Menten constant (Km) and catalytic efficiency (kcat/Km) values of 16.72 ± 1.32 µM and 9.57 × 10–3 µM−1 s−1, respectively, showed that PamTps1 had a higher binding affinity and specificity for GPP instead of FPP as expected for a monoterpene synthase. The PamTps1 exhibits feature of a class I terpene synthase fold that made up of α-helices architecture with N-terminal domain and catalytic C-terminal domain. Nine aromatic residues (W268, Y272, Y299, F371, Y378, Y379, F447, Y517 and Y523) outlined the hydrophobic walls of the active site cavity, whilst residues from the RRx8W motif, RxR motif, H-α1 and J-K loops formed the active site lid that shielded the highly reactive carbocationic intermediates from the solvents. The dual substrates use by PamTps1 was hypothesized to be possible due to the architecture and residues lining the catalytic site that can accommodate larger substrate (FPP) as demonstrated by the protein modelling and docking analysis. This model serves as a first glimpse into the structural insights of the PamTps1 catalytic active site as a multi-substrate linalool/nerolidol synthase.

METABOLISM OF PHENYLPROPANOID COMPOUNDS IN SALVIA: II. BIOSYNTHESIS OF PHENOLIC CINNAMIC ACIDS

1959 ◽  
Vol 37 (1) ◽  
pp. 537-547 ◽  
Author(s):  
D. R. McCalla ◽  
A. C. Neish
Keyword(s):  
Caffeic Acid ◽  
Phenolic Acids ◽  
Cinnamic Acid ◽  
Shikimic Acid ◽  
Sinapic Acid ◽  
Coumaric Acid ◽  
Cinnamic Acids ◽  
Phenyllactic Acid ◽  
Salvia Splendens ◽  
Specific Activities

p-Coumaric, caffeic, ferulic, and sinapic acids were found to occur in Salvia splendens Sello in alkali-labile compounds of unknown constitution. A number of C14-labelled compounds were administered to leafy cuttings of salvia and these phenolic acids were isolated after a metabolic period of several hours and their specific activities measured. Cinnamic acid, dihydrocinnamic acid, L-phenylalanine, and (−)-phenyllactic acid were found to be good precursors of the phenolic acids. D-Phenylalanine, L-tyrosine, and (+)-phenyllactic acid were poor precursors. A kinetic study of the formation of the phenolic acids from L-phenylalanine-C14 gave data consistent with the view that p-coumaric acid → caffeic acid → ferulic acid → sinapic acid, and that these compounds can act as intermediates in lignification. Feeding of C14-labelled members of this series showed that salvia could convert any one to a more complex member of the series but not so readily to a simpler member. Caffeic acid-β-C14 was obtained from salvia after the feeding of L-phenylalanine-β-C14 or cinnamic acid-β-C14, and caffeic acid labelled only in the ring was obtained after feeding generally labelled shikimic acid.

Microbial Perchlorate Reduction in Groundwater with Different Electron Donors

2013 ◽  
Vol 295-298 ◽  
pp. 1402-1407
Author(s):  
Rui Wang ◽  
Ming Chen ◽  
Jia Wen Zhang ◽  
Fei Liu ◽  
Hong Han Chen
Keyword(s):  
Removal Efficiency ◽  
Electron Donor ◽  
Electron Acceptor ◽  
Reduction Rate ◽  
Electron Donors ◽  
Monod Equation ◽  
Hydrogen Addition ◽  
Perchlorate Reduction ◽  
Perchlorate Removal

Effects of different electron donors (acetate and hydrogen), acetate and perchlorate concentrations on microbial perchlorate reduction in groundwater were studied. The results showed that acetate and hydrogen addition as an electron donor can significantly improve perchlorate removal efficiency while a longer period was observed for hydrogen (15 d) than for acetate (8 d). The optical ratio of electron donor (acetate)-to-electron acceptor (perchlorate) was approximately 1.65 mg COD mg perchlorate-1. The highest specific reduction rate of perchlorate was achieved at the acetate-to-perchlorate ratio of 3.80 mg COD mg perchlorate-1. The perchlorate reduction rates corresponded well to the theoretical values calculated by the Monod equation and the parameters of Ks and Vm were determined to be 15.6 mg L-1 and 0.26 d-1, respectively.

Photocatalytic CO2 reduction using water as an electron donor by a powdered Z-scheme system consisting of metal sulfide and an RGO–TiO2 composite

2017 ◽  
Vol 198 ◽  
pp. 397-407 ◽  
Author(s):  
Tomoaki Takayama ◽  
Ko Sato ◽  
Takehiro Fujimura ◽  
Yuki Kojima ◽  
Akihide Iwase ◽  
...  
Keyword(s):  
Aqueous Solution ◽  
Graphene Oxide ◽  
Visible Light ◽  
Water Splitting ◽  
Electron Donor ◽  
Visible Light Irradiation ◽  
Co2 Reduction ◽  
Metal Sulfide ◽  
Electron Donors ◽  
Reduced Graphene

CuGaS2, (AgInS2)x–(ZnS)2−2x, Ag2ZnGeS4, Ni- or Pb-doped ZnS, (ZnS)0.9–(CuCl)0.1, and ZnGa0.5In1.5S4 showed activities for CO2 reduction to form CO and/or HCOOH in an aqueous solution containing K2SO3 and Na2S as electron donors under visible light irradiation. Among them, CuGaS2 and Ni-doped ZnS photocatalysts showed relatively high activities for CO and HCOOH formation, respectively. CuGaS2 was applied in a powdered Z-scheme system combining with reduced graphene oxide (RGO)-incorporated TiO2 as an O2-evolving photocatalyst. The powdered Z-scheme system produced CO from CO2 in addition to H2 and O2 due to water splitting. Oxygen evolution with an almost stoichiometric amount indicates that water was consumed as an electron donor in the Z-schematic CO2 reduction. Thus, we successfully demonstrated CO2 reduction of artificial photosynthesis using a simple Z-scheme system in which two kinds of photocatalyst powders (CuGaS2 and an RGO–TiO2 composite) were only dispersed in water under 1 atm of CO2.

ELECTRON DONORS AND COFAGTORS FOR DENITRIFIGATION BY PSEUDOMONAS PERFECTOMARINUS

1963 ◽  
Vol 9 (6) ◽  
pp. 799-807 ◽  
Author(s):  
Martha Rhodes ◽  
Audrey Best ◽  
W. J. Payne
Keyword(s):  
Amino Acids ◽  
Electron Donor ◽  
Electron Donors ◽  
Resting Cells ◽  
Test Compound ◽  
Whole Cell ◽  
Minimal Media

Pseudomonas perfectomarinus released nitrogen fiom nitrate in media containing a variety of amino acids, pyruvate, or urea, but only if these minimal media were supplemented with glucose or, preferably, citrate. L-Arabinose (and to a lesser degree, D-arabinose) served as electron donor in combination with glucose or citrate, whereas other sugars did not. Asparagine, however, was the most effective oxidizable substrate tested and was the only test compound supporting denitrification without supplementary glucose or citrate. Mano-metric experiments revealed that adapted resting cells liberated nitrogen very rapidly with asparagine but less rapidly with citrate. Furthermore, cell-free extracts of adapted bacteria denitrified nitrate when provided with these substrates. Flavine mononucleotide was more effective as a stimulatory cofactor for denitrification than flavine adenine dinucleotide in whole-cell experiments, but not with cell-free extracts. Experiments with dialyzed cell-free extracts revealed that the enzymes which oxidized asparagine and citrate (or actually isocitrate) were linked with triphosphopyridine nucleotide. Additional experiments with cell-free extracts revealed that oxidation of reduced triphosphopyridine nucleotide was enzymatically linked with flavine mononucleotide.

scholarly journals Roles of citrus secondary metabolites in tree and fruit defence against pests and pathogens

2021 ◽  
Vol 1 (2) ◽  
pp. 51-62
Author(s):  
Ibrahim Kahramanoglu ◽  
Serhat Usanmaz
Keyword(s):  
Secondary Metabolites ◽  
Human Health ◽  
Caffeic Acid ◽  
Positive Impact ◽  
Plant Defence ◽  
Background Information ◽  
Diverse Group ◽  
Coumaric Acid ◽  
Horticultural Crops ◽  
Potential Benefits

Plants have evolved several mechanisms to protect themselves from different biotic and abiotic challenges, including pest and pathogen attacks. One of the most important mechanisms is the secondary metabolites (SM) (terpenes, phenolics and nitrogen/sulphur-containing compounds). The plants have synthesised a diverse group of compounds in different concentrations (mostly in very small quantities) and have important roles in plant defence, survival, adaptation, and reproduction. Citrus crops are among the most essential cultivated fruit groups and are rich in terpenoids and phenolics. Besides the well-known benefits of these compounds on human health, they have a significant role in plant/fruit defence against biotic and abiotic challenges. This review aims to highlight the importance of these compounds (such as limonene, citral, saponin, hesperidin, quercetin, tangeritine, caffeic acid, p-coumaric acid, scoparone, etc.) and discuss their roles in tree and fruit defence against pests and pathogens. In today’s world, where there is an essential human impact on nature, a need is raised to reduce pesticides against pests and pathogens. Therefore, understanding the roles of these SM and their induction is believed to have a significant positive impact on the production and/or storage of horticultural crops and may help reduce the use of synthetic agrochemicals. In line with this information, present review was aimed to provide a background information for researchers, farmers, horticulturalists and technology developers about the potential benefits of SM on plant/fruit defence and a guideline about their induction.

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