Phenylacetic Acid Research Articles

Investigating the biosynthesis and roles of the auxin phenylacetic acid during Pseudomonas syringae-Arabidopsis thaliana pathogenesis.

Several plant-associated microbes synthesize the auxinic plant growth regulator phenylacetic acid (PAA) in culture; however, the role of PAA in plant-pathogen interactions is not well understood. In this study, we investigated the role of PAA during interactions between the phytopathogenic bacterium Pseudomonas syringae strain PtoDC3000 (PtoDC3000) and the model plant host, Arabidopsis thaliana. Previous work demonstrated that indole-3-acetaldehyde dehydrogenase A (AldA) of PtoDC3000 converts indole-3-acetaldehyde (IAAld) to the auxin indole-3-acetic acid (IAA). Here, we further demonstrated the biochemical versatility of AldA by conducting substrate screening and steady-state kinetic analyses, and showed that AldA can use both IAAld and phenylacetaldehyde as substrates to produce IAA and PAA, respectively. Quantification of auxin in infected plant tissue showed that AldA-dependent synthesis of either IAA or PAA by PtoDC3000 does not contribute significantly to the increase in auxin levels in infected A. thaliana leaves. Using available arogenate dehydratase (adt) mutant lines of A. thaliana compromised for PAA synthesis, we observed that a reduction in PAA-Asp and PAA-Glu is correlated with elevated levels of IAA and increased susceptibility. These results provide evidence that PAA/IAA homeostasis in A. thaliana influences the outcome of plant-microbial interactions.

Impact of a poly(ethylene glycol) corona block on drug encapsulation during polymerization induced self-assembly.

Polymerization induced self-assembly (PISA) provides a facile platform for encapsulating therapeutics within block copolymer nanoparticles. Performing PISA in the presence of a hydrophobic drug alters both the nanoparticle shape and encapsulation efficiency. While previous studies primarily examined the interactions between the drug and hydrophobic core block, this work explores the impact of the hydrophilic corona block on encapsulation. Poly(ethylene glycol) (PEG) and poly(2-hydroxypropyl methacrylate) (PHPMA) are used as the model corona and core blocks, respectively, and phenylacetic acid (PA) is employed as the model drug. Attachment of a dithiobenzoate end group to the PEG homopolymer - transforming it into a macroscopic reversible addition-fragmentation chain transfer agent - causes the polymer to form a small number of nanoscopic aggregates in solution. Adding PA to the PEG solution encourages further aggregation and macroscopic phase separation. During the PISA of PEG-PHPMA block copolymers, inclusion of PA in the reaction mixture promotes faster nucleation of spherical micelles. Although increasing the targeted PA loading from 0 to 20 mg mL-1 does not affect the micelle size or shape, it alters the drug spatial distribution within the PISA microenvironment. PA partitions into either PEG-PHPMA micelles, deuterium oxide, or other polymeric species - including PEG aggregates and unimer chains. Increasing the targeted PA loading changes the fraction of drug within each encapsulation site. This work indicates that the corona block plays a critical role in dictating drug encapsulation during PISA.

Synthetic macromolecular peptide-mimetics with amino acid substructure residues as protein stabilising excipients.

The clinical use of protein and peptide biotherapeutics requires fabrication of stable products. This particularly concerns stability towards aggregation of proteins or peptides. Here, we tested a hypothesis that interactions between a synthetic peptide, which is an aggregation-prone region analogue, and its homologous sequence on a protein of interest, could be exploited to design excipients which stabilise the protein against aggregation. A peptide containing the analogue of lysozyme aggregation-prone region (GILQINSRW) was conjugated to a RAFT agent and used to initiate the polymerisation of N-hydroxyethyl acrylamide, generating a GILQINSRW-HEA90 polymer, which profoundly reduced lysozyme aggregation. Substitution of tryptophan in GILQINSRW with glycine, to form GILQINSRG, revealed that tryptophan is a critical amino acid in the protein stabilisation by GILQINSRW-HEA90. Accordingly, polymeric peptide-mimetics of tryptophan, phenylalanine and isoleucine, which are often present in aggregation-prone regions, were synthesized. These were based on synthetic oligomers of acrylamide derivatives of indole-3 acetic acid (IND), phenylacetic acid (PHEN), or 2-methyl butyric acid (MBA), respectively, conjugated with hydrophilic poly(N-hydroxyethyl acrylamide) blocks to form amphiphilic copolymers denoted as INDm-, PHENm- and MTBm-b-HEAn. These materials were tested as protein stabilisers and it was shown that solution properties and the abilities of these materials to stabilise insulin and the peptide IDR 1018 towards aggregation are dependent on the chemical nature of their side groups. These data suggest a structure-activity relationship, whereby the indole-based INDm-b-HEAn peptide-mimetic displays properties of a potential stabilising excipient for protein formulations.

Isolation, characterization, and LC MS/MS determination of anti-obesity components from pine needles of Cedrus deodara (Roxb.) G. Don.

This study aimed to isolate and analyze the components in cedar pine needles (needle leaves of Cedrus deodara (Roxb.) G. Don) that exhibit anti-obesity effects, as determined through animal experiments. The extract of cedar pine needles was separated into four fractions of different polarities using a macroporous resin column. The fraction that retained anti-obesity activity was evaluated based on the results of animal experiments. Monomeric compounds were structurally characterized and isolated from the active fraction using a preparative liquid chromatography system. Combined with subsequent glucose gel chromatographic separation. The content of the separated components was determined using ultrahigh performance liquid chromatography coupled with triple quadrupole mass spectrometry (UPLC-QQQ-MS/MS). The water-washed fraction retained anti-obesity activity of the cedar pine needles more effectively. A total of 16 compounds were separated from this fraction, and the contents of 14 of these compounds were determined to be present in cedar pine needles. Nine components, namely p-hydroxy benzyl alcohol, chlorogenic acid, vanillic acid, syringic acid, P-coumaric acid, sinapic acid, benzoic acid, phenylacetic acid, salicylic acid, were characterized and determined for the first time in cedar pine needles. The components with anti-obesity activity in the pine needles of Cedrus are mainly derived from phenolic acids.

Metabolic profiling of (poly)phenolic compounds in mouse urine following consumption of hull-less and purple-grain barley.

The present study attempted for the first time to investigate the metabolic fate of (poly)phenolic compounds provided by a hull-less and purple grain barley genotype biofortified in anthocyanins. Balb/c mice were supplemented either with standard purified diet (SD) or whole-grain barley supplemented diet (WGB) for six weeks. Subsequently, (poly)phenolic metabolites were determined in urine samples by UPLC-MS/MS, and the principal metabolic pathways were elucidated. Thirty-nine (poly)phenolics compounds were identified in WGB which were distributed between the free (58%) and bound (42%) fractions, encompassing anthocyanins, phenolic acids, flavan-3-ols and flavones. Upon WGB intake, forty-two (poly)phenolic metabolites were identified, predominantly comprising phase-II sulphate, glucuronide, and/or methylated conjugates, along with colonic catabolites. Noteworthy metabolites included peonidin-3-O-glucuronide, peonidin-3-O-6''-O-malonylglucoside, and peonidin-3-O-glucoside among anthocyanins; hydroxyphenylpropanoic acid-O-sulphate among phenolic acids; and 5-(3',4'-dihydroxyphenyl)-γ-valerolactone-O-sulphate among flavan-3-ols. Metabolites like phenylpropionic, phenylacetic, hydroxybenzoic, and hippuric acids were found in both WGB and SD groups, with higher levels after barley consumption, indicating both endogenous and polyphenolic metabolism origins. Overall, this study offers valuable insights into the metabolism of (poly)phenols in purple barley, setting the stage for future investigations into the health benefits linked to the consumption of purple grain barley.

Biosynthesis of the bacterial antibiotic 3,7-dihydroxytropolone through enzymatic salvaging of catabolic shunt products.

The non-benzenoid aromatic tropone ring is a structural motif of numerous microbial and plant natural products with potent bioactivities. In bacteria, tropone biosynthesis involves early steps of the widespread CoA-dependent phenylacetic acid (paa) catabolon, from which a shunt product is sequestered and surprisingly further utilized as a universal precursor for structurally and functionally diverse tropone derivatives such as tropodithietic acid or (hydroxy)tropolones. Here, we elucidate the biosynthesis of the antibiotic 3,7-dihydroxytropolone in Actinobacteria by in vitro pathway reconstitution using paa catabolic enzymes as well as dedicated downstream tailoring enzymes, including a thioesterase (TrlF) and two flavoprotein monooxygenases (TrlCD and TrlE). We furthermore mechanistically and structurally characterize the multifunctional key enzyme TrlE, which mediates an unanticipated ipso-substitution involving a hydroxylation and subsequent decarboxylation of the CoA-freed side chain, followed by ring oxidation to afford tropolone. This study showcases a remarkably efficient strategy for 3,7-dihydroxytropolone biosynthesis and illuminates the functions of the involved biosynthetic enzymes.

Palladium-Catalyzed Regioselective C4-H Acyloxylation of Indoles with Carboxylic Acids via a Transient Directing Groups Strategy.

The development of an efficient method for the synthesis of C4 oxy-substituted indoles is an appealing yet challenging task. Herein, we report a general palladium-catalyzed TDG approach for the direct C4-H acyloxylation of indoles. The protocol features atom and step economy, excellent regioselectivity, and good tolerance of functional groups. Moreover, the reaction can accommodate a range of carboxylic acids including benzoic acids, phenylacetic acids, and aliphatic acids.

Gut microbiota functional profiling in autism spectrum disorders: bacterial VOCs and related metabolic pathways acting as disease biomarkers and predictors.

Autism spectrum disorder (ASD) is a multifactorial neurodevelopmental disorder. Major interplays between the gastrointestinal (GI) tract and the central nervous system (CNS) seem to be driven by gut microbiota (GM). Herein, we provide a GM functional characterization, based on GM metabolomics, mapping of bacterial biochemical pathways, and anamnestic, clinical, and nutritional patient metadata. Fecal samples collected from children with ASD and neurotypical children were analyzed by gas-chromatography mass spectrometry coupled with solid phase microextraction (GC-MS/SPME) to determine volatile organic compounds (VOCs) associated with the metataxonomic approach by 16S rRNA gene sequencing. Multivariate and univariate statistical analyses assessed differential VOC profiles and relationships with ASD anamnestic and clinical features for biomarker discovery. Multiple web-based and machine learning (ML) models identified metabolic predictors of disease and network analyses correlated GM ecological and metabolic patterns. The GM core volatilome for all ASD patients was characterized by a high concentration of 1-pentanol, 1-butanol, phenyl ethyl alcohol; benzeneacetaldehyde, octadecanal, tetradecanal; methyl isobutyl ketone, 2-hexanone, acetone; acetic, propanoic, 3-methyl-butanoic and 2-methyl-propanoic acids; indole and skatole; and o-cymene. Patients were stratified based on age, GI symptoms, and ASD severity symptoms. Disease risk prediction allowed us to associate butanoic acid with subjects older than 5 years, indole with the absence of GI symptoms and low disease severity, propanoic acid with the ASD risk group, and p-cymene with ASD symptoms, all based on the predictive CBCL-EXT scale. The HistGradientBoostingClassifier model classified ASD patients vs. CTRLs by an accuracy of 89%, based on methyl isobutyl ketone, benzeneacetaldehyde, phenyl ethyl alcohol, ethanol, butanoic acid, octadecane, acetic acid, skatole, and tetradecanal features. LogisticRegression models corroborated methyl isobutyl ketone, benzeneacetaldehyde, phenyl ethyl alcohol, skatole, and acetic acid as ASD predictors. Our results will aid the development of advanced clinical decision support systems (CDSSs), assisted by ML models, for advanced ASD-personalized medicine, based on omics data integrated into electronic health/medical records. Furthermore, new ASD screening strategies based on GM-related predictors could be used to improve ASD risk assessment by uncovering novel ASD onset and risk predictors.

Quantitative investigations of Zebrafish olfactory receptor ORA1 responsiveness to three pheromones: Microscopic and macroscopic characterizations via an advanced statistical physics treatment

In this work, an adsorption phenomenon putatively involved in the olfactory sense of phenylacetic acid, 4-chlorophenylacetic acid, and 4-methoxyphenylacetic acid pheromones in the Zebrafish olfactory receptor ORA1 was a helpful mechanism in interpreting and characterizing the olfaction process at a molecular level. Hence, the experimental dose-olfactory response curves were fitted by applying the one-layer adsorption model with a single energy (1LM1E). On one hand, the different parameters introduced in the selected model were used to microscopically study the three olfactory systems. Indeed, the fitting results showed that phenylacetic acid displayed the greatest maximum olfactory response at saturation, due to the effect of functional groups at the R4 position. The three pheromones were docked via a non-parallel orientation and the adsorption process was a multi-molecular mechanism. The sizes of different binding pockets of ORA1 were determined through the estimation of the olfactory receptor site size distributions (stereographic characterization). The estimated adsorption energies, ranging from 17.340 to 21.332 kJ/mol, can be used to describe the energetic interactions between the studied pheromones and the Zebrafish ORA1 binding pockets. The spectrums of the adsorption energy distributions of phenylacetic acid, 4-chlorophenylacetic acid, and 4-methoxyphenylacetic acid, which were spread out from 10 to 32.5 kJ/mol, 5 to 30 kJ/mol, and 10 to 32.5 kJ/mol, respectively, was determined to estimate the corresponding olfactory bands (energetic characterization). On the other hand, three thermodynamic functions were estimated in order to macroscopically study the three olfactory systems.

Scalable Preparation of 1‐Aminoethyl Oxindoles From Simple Benzaldehydes

AbstractOxindoles are prevalent structures in natural products and pharmaceutically active molecules. To support structure–activity‐relationship (SAR) studies in a medicinal chemistry program, we developed a straightforward and scalable synthesis route to 1‐aminoethyl oxindole building blocks harboring various types of substituents. Our strategy relies on an intramolecular Buchwald–Hartwig amidation of a 2‐bromophenylacetic amide precursor. The cyclization substrates can be prepared from readily available benzaldehydes by ortho‐selective C(sp2)−H bromination followed by homologation to the corresponding phenylacetic acid derivatives. The process was optimized to allow for preparation of 246 g of one representative example.

Novel synthesis and docking studies of selected drug derivatives

A superior medication alternative can be found through the structural modification of a bioactive compound of either synthetic or natural origin. Synthetically altering a drug's molecule is meant to give it the desired features, such as improving its pharmacological effects and reducing its negative effects. The design, technique development, characterization, and molecular docking of new drug molecules are the main areas of the current study. With the precedence of molecular docking, the binding site of novel derivatives was demonstrated. The computer-generated three-dimensional structure of ligands ispositioned into receptor structures through molecular docking in a variety of orientations, conformations, and sites. The active pharmaceutical intermediates (API’s) used for structural modification and docking studies are Diclofenac sodium and Metformin. The NSAID diclofenac belongs to the phenylacetic acid class and has anti-inflammatory, analgesic, and antipyretic effects. An anti-diabetic medicine called metformin is used to treat type 2 diabetes mellitus. API’s have an established commercial market value, but each one of them is having an undesirable side effect. The synthesized derivatives are characterized by UV–Visible and FTIR spectral methods, and the derivatization strategy is anticipated to lessen the adverse effect and further boost its efficacy.

Antibacterial activity of two actinomycetes species isolated from black sand in North Egypt

Increasingly high levels of multidrug-resistant (MDR) pathogens have necessitated the discovery of novel bioactive compounds. For this reason, two actinomycetes strains, Streptomyces griseorubens and Streptomyces rochei, were isolated for the first time from the black sand shores of Kafr El Sheikh in Egypt, which is home to several large fish farms. Isolates were identified via phenotypic, biochemical and 16S rRNA sequence protocols. Both strains exhibited powerful antimicrobial activity against three serious MDR pathogens: Bacillus subtilis, Salmonella enteritidis and Pseudomonas aeruginosa. The bioactive compounds of isolates’ filtrates were identified using gas chromatography–mass spectroscopy (GC-MS). For S. griseorubens, the detectable antibacterial compounds were hexanoic acid, 2-ethyl-, 2-ethylhexyl ester, n-Decane, hexadecanoic acid methyl ester, benzene acetic acid, ricinolic acid, and ethylparaben, while S. rochei secretes heptadecane, 2,6-dimethyl-, benzene acetic acid, dibutyl phthalate, octacosane, hexacosane, and vitamin A aldehyde. These results strongly encourage the use of these eco-friendly isolates as a biocontrol against MDR pathogens that attack fish farms. Significance: Streptomyces spp. act as strong weapons for fighting multidrug resistance in pathogenic bacteria – one of the most important current threats to public health. They are additionally regarded as eco-friendly organisms that can be used as a biocontrol agent against infections that endanger fish farms.

Dietary fibre fractions rich in (poly)phenols from orange by-products and their metabolisation by in vitro digestion and colonic fermentation

Orange peel is an interesting by-product because of its composition, particularly its dietary fibre and flavanones. The aim of this work was to extract different fibre fractions from orange peel to obtain potential added-value ingredients and evaluate how the presence of fibre may interfere with (poly)phenol metabolism. Using an aqueous extraction, as a green extraction method, an insoluble fibre fraction (IFF) and a water-soluble extract (WSE) were obtained. Those fractions were analysed to determine the proximate and dietary fibre composition, hydration properties, (poly)phenol composition and antioxidant capacity, comparing the results with the orange peel (OP). The IFF presented the highest content of insoluble dietary fibre and the WSE showed the highest content of (poly)phenols, these being mainly flavanones. An in vitro faecal fermentation was carried out to evaluate the production of short-chain fatty acids (SCFAs) and lactate as prebiotic indicators; the IFF gave the highest production, derived from the greater presence of dietary fibre. Moreover, catabolites from (poly)phenol metabolism were also analysed, phenylpropanoic acids being the major ones, followed by phenylacetic acids and benzoic acids. These catabolites were found in higher quantities in WSE, because of the greater presence of (poly)phenols in its composition. IFF also showed a significant production of these catabolites, which was delayed by the greater presence of fibre. These results reveal that the new ingredients, obtained by an environmentally friendly water extraction procedure, could be used for the development of new foods with enhanced nutritional and healthy properties.

Structural characterization of PaaX, the main repressor of the phenylacetate degradation pathway in Escherichia coli W: A novel fold of transcription regulator proteins

PaaX is a transcriptional repressor of the phenylacetic acid (PAA) catabolic pathway, a central route for bacterial aerobic degradation of aromatic compounds. Induction of the route is achieved through the release of PaaX from its promoter sequences by the first compound of the pathway, phenylacetyl-coenzyme A (PA-CoA). We report the crystal structure of PaaX from Escherichia coli W. PaaX displays a novel type of fold for transcription regulators, showing a dimeric conformation where the monomers present a three-domain structure: an N-terminal winged helix-turn-helix domain, a dimerization domain similar to the Cas2 protein and a C-terminal domain without structural homologs. The domains are separated by a crevice amenable to harbour a PA-CoA molecule. The biophysical characterization of the protein in solution confirmed several hints predicted from the structure, i.e. its dimeric conformation, a modest importance of cysteines and a high dependence of solubility and thermostability on ionic strength. At a moderately acidic pH, the protein formed a stable folding intermediate with remaining α-helical structure, a disrupted tertiary structure and exposed hydrophobic patches. Our results provide valuable information to understand the stability and mechanism of PaaX and pave the way for further analysis of other regulators with similar structural configurations.

Barley Vinegar Relieves Loperamide-Induced Constipation in Mice via the Modulation of the Gut Microbiota and Serum Metabolism

This study investigated the effect of barley vinegar on constipation by regulating the structure of intestinal microbiota and the level of short-chain fatty acids (SCFAs). BALB/c mice with loperamide-induced constipation were treated with barley vinegar in the intervention. After treatment, constipation-related factors were identified. The effect of barley vinegar on the composition of the intestinal microbiota was evaluated by means of 16S rDNA gene sequencing, and the content of SCFAs in enteral feces was determined via the GC-MS method. Treating constipated mice with barley vinegar accelerated gastrointestinal peristalsis, inhibited the inflammatory response, protected the intestinal barrier, upregulated the production of beneficial intestinal bacteria, and downregulated the production of harmful intestinal bacteria. These therapeutic effects are attributed to reversed gut microbiota dysfunction, which favors the production of intestinal metabolites such as SCFAs. The purgative function of highland barley vinegar may improve the intestinal environment by regulating the balance of intestinal flora and the concentration of SCFAs. In addition, LC-MS metabolomics was used to analyze the effect of barley vinegar on intestinal metabolites in mice with constipation. The results show that the treatment of barley vinegar inhibited the decrease in aspartate, L-threonine, L-serine, L-proline, 3,4-dihydroxymandelic acid, epinephrine, glyceric acid, and 3,4-dihydroxymandelic acid content in intestinal metabolites caused by constipation. 4-2 hydroxy benzene acetic acid and fumaric acid content increased. KEGG pathway analysis showed that digestive system, amino acid and lipid metabolism pathways were important pathways for highland barley vinegar relieving constipation. This study proves that highland barley vinegar mainly regulates lipid metabolism, the digestive system and amino acid metabolism to maintain a steady state, prevent intestinal injury, and improve constipation. In short, this study demonstrates that highland barley vinegar can alleviate constipation in mice and repair colitis damage.

Microbial products linked to steatohepatitis are reduced by deletion of nuclear hormone receptor SHP in mice

Deletion of the nuclear hormone receptor small heterodimer partner (Shp) ameliorates the development of obesity and nonalcoholic steatohepatitis (NASH) in mice. Liver-specific SHP plays a significant role in this amelioration. The gut microbiota has been associated with these metabolic disorders, and the interplay between bile acids (BAs) and gut microbiota contributes to various metabolic disorders. Since hepatic SHP is recognized as a critical regulator in BA synthesis, we assessed the involvement of gut microbiota in the antiobesity and anti-NASH phenotype of Shp−/− mice. Shp deletion significantly altered the levels of a few conjugated BAs. Sequencing the 16S rRNA gene in fecal samples collected from separately housed mice revealed apparent dysbiosis in Shp−/− mice. Cohousing Shp−/− mice with WT mice during a Western diet regimen impaired their metabolic improvement and effectively disrupted their distinctive microbiome structure, which became indistinguishable from that of WT mice. While the Western diet challenge significantly increased lipopolysaccharide and phenylacetic acid (PAA) levels in the blood of WT mice, their levels were not increased in Shp−/− mice. PAA was strongly associated with hepatic peroxisome proliferator-activated receptor gamma isoform 2 (Pparg2) activation in mice, which may represent the basis of the molecular mechanism underlying the association of gut bacteria and hepatic steatosis. Shp deletion reshapes the gut microbiota possibly by altering BAs. While lipopolysaccharide and PAA are the major driving forces derived from gut microbiota for NASH development, Shp deletion decreases these signaling molecules via dysbiosis, thereby partially protecting mice from diet-induced metabolic disorders.

Standardisation of the C:N ratio in ileal digesta changes relationships among fermentation end-products during in vitro hindgut fermentation in pigs

Undigested proteins that become available for the microbiota in the hindgut can be used as building blocks for bacterial cells, or can enter various catabolic pathways. Degradation via protein fermentation pathways is least preferred, as several fermentation end-products released can be toxic for the host. Directing microbial protein metabolism towards protein synthesis or degradative pathways that result in less toxic end-products, for example through nutritional interventions, is an interesting strategy for improving health. We studied variation in protein fermentation patterns, resulting from variation in substrate composition. Ileal digesta, obtained from cannulated pigs fed different protein sources, were subjected to fermentation in vitro under different conditions; (1) ileal digesta were fermented as-is, (2) ileal digesta were fermented after standardisation to a constant high C:N ratio, by addition of high fermentable carbohydrates and (3) ileal digesta samples were incubated under limiting N concentrations. Gas production was monitored as an indirect measure of microbial activity, and fermentation end-products at different points in time were analysed by gas chromatography and high resolution mass spectrometry. Using principal component analysis, we identified patterns in protein fermentation end-products and related them to the composition of ileal digesta. Protein-associated fermentation end-product concentrations of e.g. isovaleric-, isobutyric-, phenylacetic acid and p-cresol were negatively affected by the available amount of high fermentable carbohydrates combined with a high C:N ratio. The aforementioned fermentation end-products positively correlated with NH3 concentrations and negatively with short-chain fatty acid (SCFA) concentrations. Standardisation to a constant high C:N ratio changed their relationship; isovaleric-, isobutyric-, phenylacetic acid and p-cresol lost their correlation with NH3 concentrations, became positively correlated with SCFA concentrations, and now showed a positive correlation with available amounts of high fermentable carbohydrates. Our observations demonstrate an important role of the C:N ratio in the relationship between fermentation end-products. At constant C:N, protein fermentation end-products correlate with end-products of carbohydrate fermentation and NH3, often considered as a proxy for protein fermentation, loses its predictive power.

Heterologous expression of PtAAS1 reveals the metabolic potential of the common plant metabolite phenylacetaldehyde for auxin synthesis in planta.

Aromatic aldehydes and amines are common plant metabolites involved in several specialized metabolite biosynthesis pathways. Recently, we showed that the aromatic aldehyde synthase PtAAS1 and the aromatic amino acid decarboxylase PtAADC1 contribute to the herbivory-induced formation of volatile 2-phenylethanol and its glucoside 2-phenylethyl-β-D-glucopyranoside in Populus trichocarpa. To unravel alternative metabolic fates of phenylacetaldehyde and 2-phenylethylamine beyond alcohol and alcohol glucoside formation, we heterologously expressed PtAAS1 and PtAADC1 in Nicotiana benthamiana and analyzed plant extracts using untargeted LC-qTOF-MS and targeted LC-MS/MS analysis. While the metabolomes of PtAADC1-expressing plants did not significantly differ from those of control plants, expression of PtAAS1 resulted in the accumulation of phenylacetic acid (PAA) and PAA-amino acid conjugates, identified as PAA-aspartate and PAA-glutamate. Herbivory-damaged poplar leaves revealed significantly induced accumulation of PAA-Asp, while levels of PAA remained unaltered upon herbivory. Transcriptome analysis showed that members of auxin-amido synthetase GH3 genes involved in the conjugation of auxins with amino acids were significantly upregulated upon herbivory in P. trichocarpa leaves. Overall, our data indicates that phenylacetaldehyde generated by poplar PtAAS1 serves as a hub metabolite linking the biosynthesis of volatile, non-volatile herbivory-induced specialized metabolites, and phytohormones, suggesting that plant growth and defense can be balanced on a metabolic level.

CHEMICAL, TECHNO-FUNCTIONAL, AND ANTIOXIDANT PROPERTIES OF TIGERNUT (CYPERUS ESCULENTUS L.) RESIDUE FLOURS

Tigernut processing generates nutritionally-rich residue, mostly discarded as waste. This research reports for the first time the amino acid profile, phenolic profile, and pasting properties of tigernut residues. Yellow and brown tigernut residues were analysed for amino acid and phenolic profile, antioxidant, techno-functional and pasting properties. The total essential amino acids were 49 and 56% for yellow and brown tigernut residue flours, respectively. The flavonoid content and ferric reducing antioxidant property were 0.91 and 0.32 mg GAE/ g, and 3.43 and 1.41 AAE/ g for yellow and brown residue, respectively. Caffeic acid (29 – 56 mg/ 100 g), ferulic acid (39 mg/ 100 g), vanillic acid (38 mg/ 100 g), Quercetin (48 mg/ 100 g), and phenyl acetic acid (3 – 68 mg/ 100 g) occur in abundance in the residue flours. The oil absorption capacity (3.40 ml/ g), L* value (63.78), and b* value (15.61) were higher in yellow than in brown residue. Brown tigernut residue flour cooked faster (5.77 min) than yellow tigernut residue flour (6.97 min). Some essential amino acids detected were lysine, leucine, and methionine. The reports obtained in this work showed that tigernut residues have the potential to be incorporated in food due to their richness in essential amino acids, phenolic compounds, and antioxidant activity

Electrochemical response of MoS2 nanosheets/SiO2–NH2 nanoparticles modified glassy carbon electrode to phenylacetic acid

Electrochemical response of MoS2 nanosheets/SiO2–NH2 nanoparticles modified glassy carbon electrode to phenylacetic acid