Activity of mushroom polyphenol oxidase in organic medium

A kinetic study of the activity of mushroom polyphenol oxidase in an organic system was carried out to obtain detailed enzyme kinetic data in relation to optimization of reaction conditions and substrate specificity. A simple method for consistent measurement of reaction rates in the heterogeneous enzyme/organic solvent system (consisting of immobilized polyphenol oxidase and a hydrated solution of the substrate in chloroform) was designed. The aqueous content of the system was optimized using p-cresol as the substrate. With this system, a crude extract of Agaricus bisporus was used to hydroxylate and oxidize a range of selected p-substituted phenolic substrates, yielding o-quinone products. Michaelis-Menten kinetics were used to obtain apparent K(M) and V(max) values with respect to each of these substrates. Results from this analysis indicated a correlation between the enzymic kinetic parameters obtained and the steric requirements of the substrates, which could be rationalized in terms of the restricted flexibility of the enzyme when it is in chloroform and also in terms of substrate and solvent hydrophobicity. In the course of the investigation UV molar absorption coefficients of several o-quinones were measured by a novel method: (1)H nuclear magnetic resonance (NMR) spectroscopy was employed to determine component concentrations in reaction mixtures resulting from the transformation of phenols by polyphenol oxidase in chloroform. Thus the UV molar absorption coefficients could be obtained directly, avoiding the necessity to isolate the water-sensitive, unstable o-quinones. (c) 1993 John Wiley & Sons, Inc.     

Biochemical characteristics of urban maple trees

The study, which covers the period between 2014 and 2018, was carried out in the city of Naberezhnye Chelny, Republic of Tatarstan, Russia. The aim of the study was to examine the biochemical response of maple trees growing in the anthropogenic environments. Leaf samples from 600 trees (Acer platanoides L. and Acer negundo L.) were collected at monthly intervals from June through August. Sampling was performed early in the morning (11 a.m.) in the middle of the month. The study offers statistical data on the tannin content, determined via permanganometry; the ascorbic acid concentration, found via titration with 2.6-dichlorophenolindophenol; the ascorbate oxidase activity determined by absorbance at 265 nm; and the polyphenol oxidase activity, found by the spectrophotometric method. Relatively higher ascorbate oxidase activity was detected in August among ash-leaved Acer platanoides L. and Acer negundo L. in areas with strong anthropogenic impact. Due to increased air pollution, maple trees were found to exhibit an increase of polyphenol oxidase activities. The condensed tannin content in Norway maple trees dropped over time: by 1.24 in July (avenue); by 0.94 (buffer area) and 0.76 (avenue) in August. The condensed tannin content in the ash-leaved maple trees also decreased: by 0.69 (buffer area) and 0.22 (avenue) in July; by 0.37 (buffer area) and 0.61(avenue) in August.     

New zeolite adsorbents for downstream processing of polyphenols from renewable resources

Commercial materials with polyvinylpolypyrrolidone and polymeric amberlites (XAD7HP, XAD16) are commonly used for the adsorptive downstream processing of polyphenols from renewable resources. In this study, beta‐zeolite‐based adsorbent systems were examined, and their properties were compared to organic resins. Batch adsorption experiments were conducted with synthetic solutions of major polyphenols. Adsorption isotherms and desorption characteristics of individual adsorbent were determined based on these results. Maximum adsorption capacities were calculated using the Langmuir model. For example, the zeolites had capacities up to 203.2 mg/g for ferulic acid. To extend these results to a complex system, additional experiments were performed on rapeseed meal and wheat seed extracts as representative renewable resources. HPLC analysis showed that with 7.5% w/v, which is regarded as the optimum amount of zeolites, zeolites A and B could bind 100% of the major polyphenols as well as release polyphenols at high yields. Additionally, regeneration experiments were performed with isopropyl alcohol at 99°C to evaluate how zeolites regenerate under mild conditions. The results showed only a negligible loss of adsorption capacity and no loss of desorption capacity. In summary, it was concluded that beta‐zeolites were promising adsorbents for developing new processes to isolate polyphenols from renewable resources.     

New ellagitannin and galloyl esters of phenolic glycosides from sapwood of Quercus mongolica var. crispula (Japanese oak)

Two novel glycosides, 4,5-dimethoxy-3-hydroxyphenol 1-O-β-(6′-O-galloyl)-glucopyranoside (1) and (+)-2α-O-galloyl lyoniresinol 3α-O-β-d-xylopyranoside (2), as well as a novel ellagitannin named epiquisqualin B (3), were isolated from sapwood of Quercus mongolica var. crispula along with 19 known phenolic compounds. The structures of the novel compounds were elucidated on the basis of chemical and spectroscopic investigation. Compound 2 is the first example of a lignan galloyl ester, and 3 is the oxidation product of vescalagin, which is the major ellagitannin of this plant.     

3D NMR structure of a complex between the amyloid beta peptide (1–40) and the polyphenol ε-viniferin glucoside: Implications in Alzheimer's disease

Background

Alzheimer's disease (AD) is a progressive neurodegenerative disorder. There is a consensus that Aβ is a pathologic agent and that its toxic effects, which are at present incompletely understood, may occur through several potential mechanisms. Polyphenols are known to have wide-ranging properties with regard to health and for helping to prevent various diseases like neurodegenerative disorders. Thus inhibiting the formation of toxic Aβ assemblies is a reasonable hypothesis to prevent and perhaps treat AD

Methods

Solution NMR and molecular modeling were used to obtain more information about the interaction between the Aβ_1–40 and the polyphenol ε-viniferin glucoside (EVG) and particularly the Aβ residues involved in the complex.

Results

The study demonstrates the formation of a complex between two EVG molecules and Aβ_1–40 in peptide characteristic regions that could be in agreement with the inhibition of aggregation. Indeed, in previous studies, we reported that EVG strongly inhibited in vitro the fibril formation of the full length peptides Aβ_1–40 and Aβ_1–42, and had a strong protective effect against PC12 cell death induced by these peptides.

Conclusion

For the full length peptide Aβ_1–40, the binding sites observed could explain the EVG inhibitory effect on fibrillization and thus prevent amyloidogenic neurotoxicity.

General significance

Even though this interaction might be important at the biological level to explain the protective effect of polyphenols in neurodegenerative diseases, caution is required when extrapolating this in vitro model to human physiology.     

PGPR mediated management of stem blight of Phyllanthus amarus (Schum and Thonn) caused by Corynespora cassiicola (Berk and Curt) Wei

Bacillus subtilis (BSCBE4), Pseudomonas chlororaphis (PA23), endophytic P. fluorescens (ENPF1) inhibited the mycelial growth of stem blight pathogen Corynespora casiicola (Berk and Curt)Wei under in vitro. All these bacterial isolates produced both hydroxamate and carboxylate type of siderophores. But the siderophore production was maximum with the isolate ENPF1. Delivering of talc based formulation of BSCBE4 through seedling dip and foliar application effectively reduced stem blight disease incidence and increased the dry matter production under pot culture and field conditions. Application of BSCBE4, PA23 and ENPF1 increased the defense related enzymes such as peroxidase, polyphenol oxidase, chitinase and β-1,3 glucanase in P. amarus up to ten days after challenge inoculation with C. cassicola. Native gel electrophoretic analysis revealed that challenge inoculation of pathogen with BSCBE4 and PA23 induced both peroxidase and polyphnol oxidase isoforms.     

Overexpression of the laccase gene,lcc1, in Lentinula edodes using the pChG vector

Lentinula edodes secretes laccase (Lcc: EC 1.10.3.2), an industrially useful enzyme. In this study, we introduced and expressed the L. edodes Lcc gene, lcc1, driven by L. edodes glyceraldehyde-3-phosphate dehydrogenase gene promoter into L. edodes. The resulting transformants showed 2-fold Lcc activity than that of the host strain, and expression of the recombinant lcc1 was confirmed by RT-PCR.     

Inhibitory effects of brown algal phlorotannins on secretory phospholipase A2s, lipoxygenases and cyclooxygenases

The inhibitory effects of brown algal phlorotannins on secretory phospholipase A₂s (sPLA₂s), lipoxygenases (LOXs) and cyclooxygenases (COXs) were determined with an in vitro assay. Oligomers of phloroglucinol; eckol (a trimer), phlorofucofuroeckol A (a pentamer), dieckol (a hexamer) and 8,8-bieckol (a hexamer) isolated from the brown alga Eisenia bicyclis had pronounced inhibitory effects on sPLA₂ from porcine pancreas and bee venom (IC₅₀ 100–200 M). The phlorotannins inhibited LOX activity more effectively than the well-known LOX inhibitors; resveratrol and epigallocatechin gallate. 8,8-Bieckol, the strongest LOX inhibitor in this study, inhibited soybean LOX and 5-LOX with IC₅₀ values of 38 and 24 M, respectively. Negligible or very weak effects of the phlorotannins on COX-1 and COX-2 were found, except for an inhibitory effect of dieckol on COX-1 (74.7%) and of eckol on COX-2 (43.2%) at 100 M.     

Transport mechanism and metabolism of olive oil hydroxytyrosol in Caco-2 cells

3,4-dihydroxyphenylethanol (hydroxytyrosol; DPE) is the major phenolic antioxidant present in extra virgin olive oil, either in a free or esterified form. Despite its relevant biological effects, no data are available on its bioavailability and metabolism. The aim of the present study is to examine the molecular mechanism of DPE intestinal transport, using differentiated Caco-2 cell monolayers as the model system. The kinetic data demonstrate that [(14)C]DPE transport occurs via a passive diffusion mechanism and is bidirectional; the calculated apparent permeability coefficient indicates that the molecule is quantitatively absorbed at the intestinal level. The only labelled DPE metabolite detectable in the culture medium by HPLC (10% conversion) is 3-hydroxy-4-methoxyphenylethanol, the product of catechol-O-methyltransferase; when DPE is assayed in vitro with the purified enzyme a K(m) value of 40 microM has been calculated.     

不同条件下荔枝多酚氧化酶活性的分析(英)

经硫酸铵盐析和ＳｅｐｈａｄｅｓＧ－１００,Ｑ－Ｓｅｐｈａｒｏｓｅ和ＰｈｅｎｙｌＳｅｐｈａｒｏｓｅ柱层析分别纯化后,得到了电泳均一的荔枝多酚氧化酶,荔枝多酚氧化酶在ＳＤＳ和ＣＡＴＢ存在下测得的酶活性略有降低,但在ＴｒｉｔｏｎＸ－１００下活性有所增加,丁酸等短链的脂肪酸对酶活性起抑制作用,而亚油酸等长链的不饱和脂肪酸则起促进作用,另外,荔枝多酚氧化酶活性还明显受ＦｅＳＯ４和ＳｎＣｌ２所抑制,但能补Ｃａ