Phenolic Degradation Products Research Articles

Polyphenols Cause Structure Dependent Effects on the Metabolic Profile of Human Hepatocarcinogenic Cells.

Although many beneficial health effects are attributed to polyphenols their influence on the human metabolome has not been elucidated yet. The ubiquitous occurrence of polyphenols in the human diet demands comprehensive knowledge about physiological and toxicological effects of these compounds on human cells. The human hepatocarcinogenic cell line HepG2 is used to elucidate the effects of 13 polyphenols and three respective phenolic degradation products on the human metabolome using HPLC-MS/MS. To investigate structure-activity-relationships, structurally related examples of polyphenols from different compound classes are selected. The analysis of catechins points toward a relation between the degree of hydroxylation and the extent of metabolic effects particularly on the urea cycle and the pentose phosphate pathway (PPP). A correlation between the modulation of the PPP and the stability of the compounds is demonstrated, which may be caused by reactive oxygen species (ROS). The incubation of flavones and alkenylbenzenes demonstrates reduced activity of methoxylated compounds and no impact of the B-ring position. In general, polyphenols induce a multitude of metabolic effects, for example, on energy metabolism, PPP, and urea cycle. These metabolic alterations may be related to the widely reported bioactivity of these compounds such as the anticarcinogenic effects.

Degradation of phenolic inhibitors by laccase immobilized on tannic acid/polyethylenimine modified magnetic nanoparticles

Magnetic Fe3O4 nanoparticles were successfully functionalized with the low-cost mussel-inspired tannic acid (TA)/polyethylenimine (PEI) under mild conditions and then activated with glutaraldehyde (GA) to covalently immobilize laccase for degradation of four model phenolic inhibitors commonly found in lignocellulosic hydrolysate. The immobilized laccase showed the highest relative enzyme activity with the laccase loading of 39.9 mg/g and the enzyme activity recovery of 53.1%. Compared with free laccase, immobilized laccase possessed better relative enzyme activity at acidic pH and wide temperature range, as well as exhibited excellent storage stability and satisfactory reusability. Moreover, it was found that the phenolic degradation products by immobilized laccase did not exhibit obvious inhibition on subsequent enzymatic cellulose hydrolysis. Thus, the low-cost TA/PEI coating for modification of magnetic nanoparticles will provide a promising support for laccase immobilization and the immobilized laccase has great potential in removal of phenolic inhibitors present in lignocellulosic hydrolysate.

Release of Small Phenolic Metabolites from Isotopically Labeled 13C Lignin in the Pig Cecum Model.

A diet with a high dietary fiber content is often recommended in today's nutrition due to several beneficial health effects related to its intake. Lignin as a part of dietary fiber is the second most abundant natural polymer and considered to be stable during digestion. However, some studies indicate a partial degradation during the intestinal metabolism. To further elucidate this hypothesis, the aim of this study was to investigate whether lignin is metabolized by the gut microbiota using the ex vivo pig cecum model. As potential lignin-derived metabolites might already naturally occur in the pig cecal matrix, an approach using isotopically labeled 13C lignin was chosen for this study. Ten small phenolic lignin degradation products and their time-dependent metabolism were identified via an untargeted HPLC-HRMS approach, and the quantity of the metabolites was estimated. From the results, we conclude that lignin is partially degraded releasing small phenolic metabolites.

Study of membrane fouling mechanism during the phenol degradation in microbial fuel cell and membrane bioreactor coupling system

This study evaluated the feasibility of phenol degradation in microbial fuel cell (MFC) and membrane bioreactor (MBR) coupling system, and explored the mechanism of MBR membrane fouling. Four aspects were researched in open and closed circuit conditions: the degradation capacity of the coupling system, the increase of trans-membrane pressure (TMP), and the adhesion of phenol degradation products and microorganisms on the membrane. The results showed that the degradation of phenol and COD in the closed circuit coupling system was higher than that in the open circuit. The micro-electric field can inhibit the growth of TMP and keep dodecamethylcyclohexasiloxane away from the membrane, meanwhile can also reduce the abundance and species diversity of microorganisms. Nevertheless, the micro-electric field could not completely eliminate the membrane fouling due to the fact that the phenol degradation product of ethanethiol, microorganisms of Proteobacteria and Actinobacteria were more favorable on the membrane.

Decrypting bacterial polyphenol metabolism in an anoxic wetland soil

Microorganisms play vital roles in modulating organic matter decomposition and nutrient cycling in soil ecosystems. The enzyme latch paradigm posits microbial degradation of polyphenols is hindered in anoxic peat leading to polyphenol accumulation, and consequently diminished microbial activity. This model assumes that polyphenols are microbially unavailable under anoxia, a supposition that has not been thoroughly investigated in any soil type. Here, we use anoxic soil reactors amended with and without a chemically defined polyphenol to test this hypothesis, employing metabolomics and genome-resolved metaproteomics to interrogate soil microbial polyphenol metabolism. Challenging the idea that polyphenols are not bioavailable under anoxia, we provide metabolite evidence that polyphenols are depolymerized, resulting in monomer accumulation, followed by the generation of small phenolic degradation products. Further, we show that soil microbiome function is maintained, and possibly enhanced, with polyphenol addition. In summary, this study provides chemical and enzymatic evidence that some soil microbiota can degrade polyphenols under anoxia and subvert the assumed polyphenol lock on soil microbial metabolism.

Flow effects on phenol degradation and sonoluminescence at different ultrasonic frequencies.

Current literature shows a direct correlation between the sonochemical (SC) process of iodide oxidation and the degradation of phenol solution. This implies phenol degradation occurs primarily via oxidisation at the bubble surface. There is no work at present which considers the effect of fluid flow on the degradation process. In this work, parametric analysis of the degradation of 0.1mM phenol solution and iodide dosimetry under flow conditions was undertaken to determine the effect of flow. Frequencies of 44, 300 and 1000kHz and flow rates of 0, 24, 228 and 626mL/min were applied with variation of power input, air concentration, and surface stabilisation. Phenol degradation was analysed using the 4-aminoantipyrine (4-AAP) method, and sonoluminescence (SL) images were evaluated for 0.1, 20 and 60mM phenol solutions. Flow, at all frequencies under certain conditions, could augment phenol degradation. At 300kHz there was excellent correlation between phenol degradation and dosimetry indicating a SC process, here flow acted to increase bubble transience, fragmentation and radical transfer to solution. At 300kHz, although oxidation is the primary phenol degradation mechanism, it is limited, attributed to degradation intermediates which reduce OH radical availability and bubble collapse intensity. For 44 and 1000kHz there was poor correlation between the two SC processes. At 44kHz (0.01mM), there was little to suggest high levels of intermediate production, therefore it was theorised that under more transient bubble conditions additional pyrolytic degradation occurs inside the bubbles via diffusion/nanodroplet injection mechanisms. At 1000kHz, phenol degradation was maximised above all other systems attributed to increased numbers of active bubbles combined with the nature of the ultrasonic field. SL quenching, by phenol, was reduced in flow systems for the 20 and 60mM phenol solutions. Here, where the standing wave field was reinforced, and bubble localisation increased, flow and the intrinsic properties of phenol acted to reduce coalescence/clustering. Further, at these higher concentrations, and in flow conditions, the accumulation of volatile phenol degradation products inside the bubbles are likely reduced leading to an increase SL.

Passive membrane transport of lignin-related compounds

Lignin is an abundant aromatic polymer found in plant secondary cell walls. In recent years, lignin has attracted renewed interest as a feedstock for bio-based chemicals via catalytic and biological approaches and has emerged as a target for genetic engineering to improve lignocellulose digestibility by altering its composition. In lignin biosynthesis and microbial conversion, small phenolic lignin precursors or degradation products cross membrane bilayers through an unidentified translocation mechanism prior to incorporation into lignin polymers (synthesis) or catabolism (bioconversion), with both passive and transporter-assisted mechanisms postulated. To test the passive permeation potential of these phenolics, we performed molecular dynamics simulations for 69 monomeric and dimeric lignin-related phenolics with 3 model membranes to determine the membrane partitioning and permeability coefficients for each compound. The results support an accessible passive permeation mechanism for most compounds, including monolignols, dimeric phenolics, and the flavonoid, tricin. Computed lignin partition coefficients are consistent with concentration enrichment near lipid carbonyl groups, and permeability coefficients are sufficient to keep pace with cellular metabolism. Interactions between methoxy and hydroxy groups are found to reduce membrane partitioning and improve permeability. Only carboxylate-modified or glycosylated lignin phenolics are predicted to require transporters for membrane translocation. Overall, the results suggest that most lignin-related compounds can passively traverse plant and microbial membranes on timescales commensurate with required biological activities, with any potential transport regulation mechanism in lignin synthesis, catabolism, or bioconversion requiring compound functionalization.

Evolution of extractive composition in thermally modified Scots pine during artificial weathering

Abstract In order to clarify the evolution and role of extractives in thermally modified wood during the process of weathering, the compositions of acetone extractives from thermally modified Scots pine after exposure in an accelerated weathering tester for different durations were determined using gas chromatography-mass spectrometry (GC-MS). Fatty acids and phenolics were proved to be the main types of extractives in weathered thermally modified Scots pine, and some sugars, terpenes and alcohols were also collected. With the progress of weathering, the content of fatty acids decreases significantly while that of phenolics increases. The reduction or even elimination of the fatty acids is presumed to be a physical process, namely, a discharge from wood during exposure to radiation and elevated temperature. The increase of phenolic extractives is mainly due to the photodegradation of other wood components. Phenolic degradation products play the role as a “barrier” against further photodegradation of thermally modified wood, among which vanillin or its derivatives appeared to be the most predominant and important ones.

N-methylcarbamate pesticides and their phenolic degradation products: hydrolytic decay, sequestration and metal complexation studies

We report on the rates of decomposition of a group of N-methylcarbamate (NMC) pesticides (carbaryl, carbofuran and propoxur) under pre-determined tropical field conditions. Rates of decomposition for three NMCs were determined at pH 7.08 and T = 20 °C and pH 7.70 and T = 33 °C respectively, as follows: carbaryl (78 days and 69 days); carbofuran (143 days and 83 days) and propoxur (116 days and 79 days). Investigation on methods for removal of NMCs and their phenolic decomposition products shows that activated charcoal outperforms zeolite, alumina, diatomaceous earth, cellulose and montmorillonite clay in the removal of both NMCs and phenols from aqueous solution. Furthermore, metal complexation studies on the NMCs and phenols showed that Fe (III) forms a complex with isopropoxyphenol (IPP) within which the Fe:IPP ratio is 1:3, indicative of the formation of a metal chelate complex with the formula Fe(IPP)3.

Oxidative Degradation of Phenol using in situ Generated Hydrogen Peroxide Combined with Fenton’s Process

Oxidative destruction of organic compounds in water streams could significantly reduce environmental effects associated with discharging waste. We report the development of a process to oxidise phenol in aqueous solutions, a model for waste stream contaminants, using Fenton’s reactions combined with in situ synthesised hydrogen peroxide (H2O2). Bifunctional palladium-iron supported catalysts, where Pd is responsible for H2O2 synthesis while Fe ensures the production of reactive oxygen species required for the degradation of phenol to less toxic species is reported. A comparison is made between in situ generated and commercial H2O2 and the effect of phenol degradation products on catalyst stability is explored.

Flavan-3-ol/Procyanidin Metabolomics in Rat Urine Using HPLC-Quadrupole TOF/MS.

Several studies have demonstrated that flavan-3-ol/procyanidins are associated with biological functions in the prevention of various chronic diseases, including obesity and diabetes. Knowledge of their mechanisms, including bioavailability, has significantly progressed in the last decade. However, the differences of the metabolic signatures among flavan-3-ol/procyanidins remain ambiguous. The metabolites in urine over time after acute administration of three typical flavan-3-ol/procyanidins ((epi)catechin [EPC], epigallocatechin gallate [EGCG], and procyanidin dimer [PC]) in view of the chemical structure were analyzed by HPLC-quadrupole TOF/MS. Several bile acid and amino acid derivatives including tryptophan and tyrosine, as well as flavan-3-ol/procyanidin conjugates and phenolic acid degradation products generated by the gut microbiota were observed in rat urine. Multivariate statistical analyses suggest that the exogenous and endogenous metabolites of flavan-3-ol/procyanidins greatly differ, although the chemical structures of three typical flavan-3-ol/procyanidins-EPC, EGCG, and PC-are similar. Thus, metabolomic differences likely affect their biological functions and health benefits.

Biodegradation-mediated alterations in acute toxicity of water-accommodated fraction and single crude oil components in cold seawater

Hydrocarbon biodegradation may be slower in cold Arctic than in temperate seawater, and this will affect the toxicity time window of the hydrocarbons. In this study, the acute toxicities of water-soluble phases of 1,3-dimethylnaphthalene, phenanthrene, fluoranthene, and low energy water-accommodated fractions (LE-WAFs) of an evaporated (200 °C+) crude oil, were screened by a Microtox bioassay during biodegradation in cold seawater (4–5 °C). The water-solubility of fluoranthene was too low to provoke a toxic response at any time, whereas the toxicity of 1,3-dimethylnaphthalene and phenanthrene decreased over time in relation to biotransformation of these compounds. In LE-WAFs, the Microtox EC50 was associated with biodegradation of the predominant hydrocarbons (naphthalenes, 2- to 3-ring PAH), as well as with phenol degradation products. The acute toxicities of single hydrocarbons and LE-WAFs persisted for a longer period in the cold seawater than previously shown at higher seawater temperatures. These results suggest implications for fate and effects assessment of hydrocarbons after oil spills in cold environments, like the Arctic. However, further biodegradation studies using Arctic seawater and relevant species for toxicity testing are needed for confirmation.

Study of the Process and Mechanism of the Remediation of Phenol Contaminated Soil by Plasma Vibrated Bed

Soil pollution is an important problem. The organic components of soil pollution are complex, and pose a significant threat to human health. In this work, a low-temperature plasma vibrated bed is applied to remediation of soil polluted by organics, with attention focused on phenol as a model pollutant. In the experiment, many factors of phenol degradation are studied and determined, such as discharge voltage, carrier gas, and soil moisture content. Increasing vibration frequency, decreasing electrode spacing, increasing voltage and a weakly alkaline soil are conducive to the degradation of pollutants. Air and oxygen give better degradation than nitrogen. The active particles generated in the discharge, such as ·OH, H2O2 and O3, are shown to play an important role in degradation of phenol. In addition, maleic acid and oxalic acid are found as intermediate product during the process of phenol degradation. Furthermore, according to the qualitative and quantitative analysis of phenol degradation products, the degradation mechanism diagram of phenol in soil is drawn up, which is instructive to improve the performance of the plasma vibrated bed in the future research.

Biodegradation of phenol with chromium (VI) reduction by the Pseudomonas sp. strain JF122

A bacterium capable of degrading phenol coupled with reducing chromium (VI) was isolated and was identified as being Pseudomonas sp. JF122 using 16S rRNA sequence analysis. The bacterium was able to simultaneously remove 600 mg/L phenol and 2.0 mg/L Cr(VI) within 72 h. Results from a study of the phenol biodegradation coupled with chromium (VI) reduction suggested that the electron donors involved in the reduction of Cr(VI) were intermediate phenol degradation products. Phenol concentrations higher than 800 mg/L inhibited both phenol degradation and Cr(VI) reduction. However, at a phenol concentration of 200 mg/L, not enough electron donors were produced to fully reduce the initial Cr(VI) concentration (1.2 mg/L). Cr(VI) concentrations below 2.0 mg/L enhanced both phenol degradation and Cr(VI) reduction. Cr(VI) was reduced to soluble Cr(III), which remained in the supernatant solution. This bacterium seems to have potential for the efficient and simultaneous treatment of organic pollutants and heavy metals in complex wastewaters.

The metabolic fate of anthocyanins in humans

High intakes of anthocyanins (ACN) have been linked to decreased cardiovascular disease risk. However, due to their apparent low bioavailability, it has been postulated that phenolic degradation products of ACNs may be responsible for their bioactivity. We examined the metabolic fate of ACNs following a single dose and short‐term (12 wk) exposure to an elderberry extract, to establish the differential effects of acute v short‐term exposure on metabolism. Biological samples from a 12 wk intervention study (n=15 postmenopausal women, 500 mg/day elderberry ACNs) were analysed for ACN metabolites using HPLC‐MS/MS. 29 metabolites were identified in urine (12 ACN and 17 phenolic metabolites) and 21 in plasma (4 ACN and 17 phenolic metabolites). ACNs reached concentrations of 0.55±0.05 μM/mM creatinine in urine after 3h and 0.034 μM in plasma after 2h. The phenolic degradation products and their metabolites reached concentrations of 31.15±2.37 μM/mM creatinine in urine after 3h and 1.24 μM in plasma after 2h. The profile of metabolites was not significantly different after 12 wks of intake. These results indicate that ACNs are extensively metabolised in vivo, with little suggestion of plasma accumulation following repeated exposure. The reported bioactivity of ACN most likely relates to the high concentrations of circulating phenolic metabolites. Research support: Norwich Medical School, University of East Anglia.Grant Funding Source: Department of Nutrition, Norwich Medical School, University of East Anglia.

Absorption, distribution, metabolism and elimination of a stable isotope‐labelled anthocyanin in Humans

Evidence suggests anthocyanins beneficially affect cardiovascular health; yet their absorption, distribution, metabolism and elimination (ADME) is poorly understood. We characterised the ADME of a13C‐labeled anthocyanin in humans. 8 male participants consumed 500 mg of labeled cyanidin‐3‐glucoside. Serum, urine, feces and breath collected over 48 h were analysed using isotoperatio mass spectrometry and liquid chromatography‐tandem mass spectrometry. 43.9 ± 25.9% of 13C was recovered in the urine, breath and feces, with a calculated relative bioavailability of 12.3 ± 1.3%. Metabolites were identified as degradation products (protocatechuic acid and phloroglucinaldehyde), phenolic, hippuric, phenylacetic and phenylpropenoic acids. Maximum rates of 13C absorption were achieved 30 min post ingestion (32.5 ± 14.2 μg/mL/h), while 13C‐labeled metabolites collectively peaked (6.0 ± 2.1 μmol/L) in the serum at 10.2 ± 4.1 h; with the total phase II conjugates of protocatechuic acid reaching 2.3 ± 0.1 μmol/L at 13.4 ± 2.5 h. The half‐lives for metabolites ranged between 12.4 ± 4.2 h for the phenolic degradation products to 51.6 ± 22.5 h for ferulic acid. Our data suggest that anthocyanins are more bioavailable than previously perceived and their metabolites are still present in the circulation after 48 h. Research support: UK Biotechnology and Biological Sciences Research Council (BBSRC‐DRINC; BB/H004963/1).

A state-wide survey in Oregon (USA) of trace metals and organic chemicals in municipal effluent

Oregon's Senate Bill 737, enacted in 2007, required the state's 52 largest municipal wastewater treatment plants (WWTP) and water pollution control facilities (WPCF) to collect effluent samples in 2010 and analyze them for persistent organic pollutants. These facilities are located state-wide and represent a variety of treatment types, service population sizes, geographic areas, and flow conditions. Of the 406 chemicals ultimately analyzed, 114 were detected above the level of quantification (LOQ) in at least one sample. Few persistent pollutants were found possibly because of their diversion from effluent via sorption to sludge (solids phase) or high LOQs for certain chemicals. Several pesticides, as well as benzene and phenol degradation products, all previously unreported in effluent, were detected. Ten polychlorinated biphenyls (PCB) congeners were present at low concentrations in ≤10 samples, while polychlorinated naphthalenes and dioxins/furans were not detected at all. Twenty-one polybrominated diphenyl ether (PBDE) congeners were found, nine of which have been reported in Osprey eggs in Oregon and Washington. Methylmercury was present in 65% of samples, with average and maximum concentrations of 0.18 and 1.36ng/L, respectively. Although they are generally assumed to be innocuous by-products of sewage treatment, additional research is needed on potential impacts to aquatic ecosystems of high loadings of coprostanol and cholesterol. These results suggest that effluent, rather than just receiving waters, should itself be analyzed for a wide range of contaminants in order to understand how upstream sources, conveyed through WWTPs and WPCFs, could be impacting aquatic ecosystems.

Anthocyanins Remain Stable during Commercial Blackcurrant Juice Processing

It remains important to establish the stability of anthocyanins throughout commercial processing in order to maintain the bioactivity of the processed food/s. The present study aimed to assess the recovery and formation of anthocyanins and their free phenolic acid degradation products during the commercial processing of blackcurrant juice concentrate. A bench-scale processing model was also established to allow for alteration of predefined parameters to identify where commercial processes could be modified to influence anthocyanin yield. No significant loss in anthocyanins was observed throughout the commercial processing of blackcurrants, from whole berry through milling, to pectin hydrolysis and sodium bisulphite addition (P ≥ 0.7). No significant loss in anthocyanins was observed following the subsequent processing of pressed juice, through pasteurization, decantation, filtration, and concentration (P ≥ 0.9). Similarly, the bench-scale model showed no significant losses in anthocyanin content except during pasteurization (22%± 0.7%, P < 0.001). In the full-factorial Design of Experiment model analysis, only sodium bisulphite concentration had an impact on anthocyanin recovery, which resulted in an increase (23% to 27%; P < 0.001) in final anthocyanin concentration. No phenolic degradation products (free protocatechuic acid or gallic acid derived from cyanidin and delphinin species, respectively) were identified in any processed sample when compared to authentic analytical standards, analyzed by ultra-performance liquid chromatography DAD. This article provides crucial data directly applicable to commercial juice processing, such as improving anthocyanin yield and practical considerations for anthocyanin stability and degradation. This aspect is particularly pertinent considering the current commercial interest in anthocyanin-derived phenolic acids and their health-related benefits. Further research and development targets in the area of commercial juice product development are identified.

Fourier transform infrared spectroscopy as a metabolite fingerprinting tool for monitoring the phenotypic changes in complex bacterial communities capable of degrading phenol

The coking process produces great volumes of wastewater contaminated with pollutants such as cyanides, sulfides and phenolics. Chemical and physical remediation of this wastewater removes the majority of these pollutants; however, these processes do not remove phenol and thiocyanate. The removal of these compounds has been effected during bioremediation with activated sludge containing a complex microbial community. In this investigation we acquired activated sludge from an industrial bioreactor capable of degrading phenol. The sludge was incubated in our laboratory and monitored for its ability to degrade phenol over a 48 h period. Multiple samples were taken across the time-course and analysed by Fourier transform infrared (FT-IR) spectroscopy. FT-IR was used as a whole-organism fingerprinting approach to monitor biochemical changes in the bacterial cells during the degradation of phenol. We also investigated the ability of the activated sludge to degrade phenol following extended periods (2-131 days) of storage in the absence of phenol. A reduction was observed in the ability of the microbial community to degrade phenol and this was accompanied by a detectable biochemical change in the FT-IR fingerprint related to cellular phenotype of the microbial community. In the absence of phenol a decrease in thiocyanate vibrations was observed, reflecting the ability of these communities to degrade this substrate. Actively degrading communities showed an additional new band in their FT-IR spectra that could be attributed to phenol degradation products from the ortho- and meta-cleavage of the aromatic ring. This study demonstrates that FT-IR spectroscopy when combined with chemometric analysis is a very powerful high throughput screening approach for assessing the metabolic capability of complex microbial communities.

Anthocyanins form potentially-bioactive phenolic degradation products under simulated physiological conditions

Anthocyanins form potentially-bioactive phenolic degradation products under simulated physiological conditions