Reaction Of Tryptophan Research Articles

Mechanism of bioactive 3,3′-diindolylmethane formation in flaxseed meal-xylose-tryptophan maillard reaction

3,3′-Diindolylmethane (DIM) has attracted extensive attention due to its bioactivity, and is applied to the fields of food, medicine and so on. In the study, DIM was isolated from the flaxseed meal-xylose-tryptophan Maillard reaction products. Its formation mechanism was investigated using the isotope labeling method. The reactive sites in DIM were analyzed by quantum chemistry calculation. The results showed that the Maillard reaction of tryptophan and xylose produced indole-3-formaldehyde, which further reacted to generate indole-3-methanol. Indole-3-methanol was unstable and eventually formed DIM. The molecular structure of DIM was determined and then the best configuration was obtained by frequency calculation. The molecular potential energy and frontier molecular orbital analysis showed that the main action site in DIM was near the indole ring. This study may provide a theoretical basis for in-depth studies on the relationship between the molecular structure and properties of DIM, broaden its applications in food, and offer a reference for the rational development of functional foods.

Formation, Identification, and Occurrence of the Furan-Containing β-Carboline Flazin Derived from l-Tryptophan and Carbohydrates.

β-Carbolines (βCs) are bioactive indole alkaloids found in foods and in vivo. This work describes the identification, formation, and occurrence in foods of the βC with a furan moiety flazin (1-[5-(hydroxymethyl)furan-2-yl]-9H-pyrido[3,4-b]indole-3-carboxylic acid). Flazin was formed by the reaction of l-tryptophan with 3-deoxyglucosone but not with 5-hydroxymethylfurfural. Its formation was favored in acidic conditions and heating (70-110 °C). The proposed mechanism of formation occurs through the formation of intermediates 3,4-dihydro-β-carboline-3-carboxylic acid (imines), followed by the oxidation to C═O in the carbohydrate chain and aromatization to βC ring with subsequent dehydration steps and cyclization to afford the furan moiety. Flazin is generated in the reactions of tryptophan with carbohydrates. Its formation from fructose was higher than from glucose, whereas sucrose gave flazin under acidic conditions and heating owing to hydrolysis. Flazin was identified in foods by HPLC-MS, and its content was determined by HPLC-fluorescence. It occurred in numerous processed foods, such as tomato products, including crushed tomato puree, fried tomato, ketchup, tomato juices, and jams, but also in soy sauce, beer, balsamic vinegar, fruit juices, dried fruits, fried onions, and honey. Their concentrations ranged from not detected to 22.3 μg/mL, with the highest mean levels found in tomato concentrate (13.9 μg/g) and soy sauce (9.4 μg/mL). Flazin was formed during the heating process, as shown in fresh tomato juice and crushed tomatoes. These results indicate that flazin is widely present in foods and is daily uptaken in the diet.

S2O82−/CeO2 Solid Superacid Catalyst Prepared by Radio-Frequency Plasma-Assisted Hydrothermal Method

CeO2 was prepared using a hydrothermal method, modified by radio-frequency plasma in the form of glow discharge, and then the solid superacid S2O82−/CeO2 was prepared by the impregnation method. A series of properties such as pore structure was characterized by N2 adsorption–desorption experiments, surface morphology was characterized by TEM, crystal phase was characterized by XRD, and surface acidity of the catalyst was characterized by Py-IR and Hammett titration. The methyl esterification reaction of tryptophan was used to evaluate the activity of the solid superacid. The results showed that the catalyst modified by radio-frequency plasma had a larger specific surface area, more surface oxygen vacancies, smaller particle size, and higher total acid content. The yield of tryptophan methyl ester reached a higher level of 94.5% (150 °C, 1 MPa, 2 h), catalyzed by the modified S2O82−/CeO2. This work verified the feasibility of plasma technology in the field of catalytic activity enhancement of solid superacid.

Identification, Formation, and Occurrence of Perlolyrine: A β-Carboline Alkaloid with a Furan Moiety in Foods.

β-Carbolines are naturally occurring bioactive alkaloids found in foods and in vivo. This research reports the identification, characterization, mechanism of formation, and occurrence of perlolyrine (1-(5-(hydroxymethyl)furan-2-yl)-9H-pyrido[3,4-b]indole), a β-carboline with a furan moiety. Perlolyrine did not arise from l-tryptophan and hydroxymethylfurfural but from the reaction of l-tryptophan with 3-deoxyglucosone, an intermediate of carbohydrate degradation. The mechanism of formation occurs through 3,4-dihydro-β-carboline-3-carboxylic acid intermediates (imines), followed by the oxidation of C1'-OH to ketoimine and oxidative decarboxylation at C-3, along with dehydration and cyclization to afford the β-carboline with a furan moiety. The formation of perlolyrine was favored in acidic conditions and temperatures in the range of 70-110 °C. Perlolyrine occurred in the reactions of tryptophan with carbohydrates. The formation rate from fructose was much higher than from glucose. Sucrose also gave perlolyrine under acidic conditions and heating. Perlolyrine was identified in many foods by HPLC-MS and analyzed by HPLC-fluorescence. It occurred in many processed foods such as tomato products including tomato puree, fried tomato, ketchups, tomato juices, and jams but also in soy sauce, beer, balsamic vinegar, fruit juices, dried fruits, fried onion, and honey. The concentrations ranged from an undetected amount to 3.5 μg/g with the highest average levels found in tomato concentrate (1.9 μg/g) and soy sauce (1.5 μg/mL). The results show that perlolyrine formed during the heating process of foods. It is concluded that perlolyrine is widely present in foods and it is daily ingested in the diet.

Effect of amphiphilic polymers and sodium alginate on the activity of methylene blue in photogeneration of singlet oxygen 1О2

The influence of amphiphilic polymers (APs): poly-N-vinylpyrrolidone, polyethylene glycol and pluronics F127, F108, as well as sodium alginate (SA) on the activity of methylene blue (MB) in the photogeneration of singlet oxygen 1О2, specifically, in a model photooxidation reaction of tryptophan in water was studied. It was shown that in the presence of all the above-mentioned AP, an increase in the effective rate constant (k eff) of tryptophan photooxidation is observed. It was suggested that the observed effect is associated with the interaction of MB with APs, which leads to disaggregation of dye associates. Such disaggregation leads to an increase in the optical density and intensity of MB luminescence. It was also shown that the photocatalytic activity of MB decreases by a factor of 1.5–3.5 in the presence of SA, which is due to the ionic interaction of the cationic MB with polyanionic SA. The interaction of MB with polysaccharide is confirmed by changes in the absorption and fluorescence spectra of the dye. The introduction of APs into a solution containing MB and SA prevents the interaction between MB and polysaccharide, which leads to an increase in the k eff values of tryptophan photooxidation in the presence of MB-AP-SA system, as well as to an increase in the optical density and fluorescence intensity of MB when AP and SA are added. The existence of weak interactions between the hydrophobic groups of MB molecules and the AP (polyvinylpyrrolidone) is also evidenced by the data obtained through 1H-NMR spectroscopy and the degree of MB fluorescence anisotropy. The AFM method shows the change in the surface structure of a thin film obtained by evaporating an aqueous solution of MB-F108-SA compared to the corresponding structure of a film obtained by evaporating an aqueous solution of MB-SA. MB-AP and MB-AP-SA systems may be promising for practical application in the aPDT treatment of chronic microbial superficial infections.

On Water Pictet‐Spengler Reaction of Tryptophan followed by Buchwald Coupling for the Synthesis of Natural Products Stellarines A, B and β‐Carboline Derivatives: Their Molecular Docking against SARS‐CoV‐2 MPro

AbstractNatural products are versatile moiety in the drug discovery and development, however, their synthesis being one of the major challenges in this field. In this regard, an environment friendly synthesis of 1‐benzoyl‐9H‐pyrido[3,4‐b] indole‐3‐carboxamide β‐carboline derivatives has been reported via Pictet‐Spengler reaction of tryptophan methyl ester with 2‐oxoaldehydes in water as solvent. Natural products Stellarines A and Stellarines B having anti‐inflammatory activity against iNOS inhibition (IC50 value of 19.3 and 18.6 μM) isolated from the root of Stellaria dichotoma L. var. lanceolata Bunge were also synthesized from β‐carboline derivatives using amidation followed by Buchwald coupling. The synthetic strategy has advantage of using non toxic and inexpensive materials for producing excellent yields. These functionalized β‐carboline carboxamide derivatives have been evaluated against SARS‐CoV‐2 Mpro(7BQY) using molecular docking studies.

Polymer photosensitizing systems containing porphyrins, dinitrosyl iron complexes, and sodium alginate in the generation of singlet oxygen

The activity of photosensitizing systems based on water-soluble photoditazine (PDZ) and hydrophobic fluorinated tetraphenylporphyrin (TPPF20) solubilized polyvinylpyrrolidone (PVP) (in the case PDZ) and pluronic F127 (in the case TPPF20) was studied in a model reaction of tryptophan (Trp) photooxidation. We also studied the effect of dinitrosyl iron complex (DNIC) and sodium alginate (SA) polysaccharide on the photosensitizing activity of both PDZ in the presence of PVP and TPPF20 solubilized with pluronic F127 in a model reaction of Trp photooxidation. It was shown that TPPF20 solubilized with pluronic F127 exhibits high photocatalytic activity in the presence of both DNIC and SA. It was also shown that PVP is able to prevent the damaging effect exerted by active NO radicals produced during the photodecomposition of DNIC on PDZ molecules. Moreover, it was demonstrated that SA does not influence the photocatalytic activity of PDZ in the presence and absence of PVP. Using the dynamic light scattering method, it was found that SA macromolecules in the presence of PVP are capable of self-association, which, due to the ‘excluded volume’ effect, can cause a slight increase in the rate of photocatalytic reaction. The effectiveness of using PDZ in combination with PVP in the presence of SA and DNIC as a photosensitizer in antimicrobial photodynamic therapy was studied via in vivo experiments on a model of a full-layer planar wound in laboratory rats. Morphological studies have shown that under photodynamic action on wounds, the use of these systems (compared to photoexcitation of an aqueous solution of the initial PDZ) stimulates the transition of the inflammatory phase to the reparative (proliferative) phase. In addition, the process of cleansing wounds from microflora and devitalized tissues is accelerated, the disturbed microcirculation is restored, the proliferation of fibroblasts and blood vessels, and collagen synthesis are accelerated. It is suggested that the PDZ-PVP-SA-DNIC systems can be used in PDT procedures for the treatment of inflammatory diseases of the skin and soft tissues.

Synthesis and properties of L(AS)3-type low-molecular-mass organic gelators based on citryl aromatic amino acid cholesteryl ester

Three types of L(AS)3 gelators have been synthesized by the reaction of phenylalanine, tyrosine and tryptophan，whose amino were protected and reacted with cholesterol under the condition of citric acid as a linker, respectively. The synthetic gelators performed strong gelation ability in cyclohexane and isopropanol. The structure, thermal stability and mechanical properties of the gels were observed; the gel formation mechanism was analyzed with XRD and SEM and the results showed that the hydrogen bonding and the π-π interaction force remarkably increased due to the existence of a great deal of amide bonds, ester bonds and aromatic rings in gelators. The gels are packed in a layered structure and are stable against temperature change. Among three gelators, citric acid tyrosine cholesterol ester displays a good gel-solution conversion under trifluoroacetic acid-triethylamine simulation in isopropanol. The study is expected to have application in the detection of organic amines in the field of sensing.

Influence of viscosity on mechanism and products of radical reactions of kynurenic acid and tryptophan

Influence of viscosity on mechanism and products of radical reactions of kynurenic acid and tryptophan

Occurrence, Formation from d-Fructose and 3-Deoxyglucosone, and Activity of the Carbohydrate-Derived β-Carbolines in Foods

β-Carbolines are naturally occurring bioactive alkaloids. In this work, carbohydrate-derived β-carbolines (βCs), 1-(1,3,4,5-tetrahydroxypent-1-yl)-β-carboline isomers (1a/b), 1-(1,4,5-trihydroxypent-1-yl)-β-carboline (2), 1-(1,5-dihydroxypent-3-en-1-yl)-β-carboline (3), and 1-(1,2,3,4,5-pentahydroxypent-1-yl)-β-carboline (4) were identified and analyzed in commercial foods. The concentrations of βCs 1–4 in foods ranged from undetectable to 11.4 μg/g levels, suggesting their intake in the diet. Processed foods contained higher amounts than fresh or unprocessed foods, and the highest content was found in processed tomato and fruit products, sauces, and baked foods. βCs 1–3 were formed in foods during heating, and 1a/b were the main compounds. The formation of carbohydrate-derived βCs was studied in model reactions of tryptophan and carbohydrates. They formed in reactions of tryptophan with glucose under acidic conditions at temperatures higher than 80 °C. The formation of 1a/b was favored, but 2–3 increased at high temperatures. Noticeably, the βCs 1–3 formed in the reactions of tryptophan with fructose or sucrose, and the formation from fructose was much higher than from glucose. Thus, fructose was the main carbohydrate involved in the formation of 1–3, whereas sucrose gave these βCs after acid hydrolysis. It is shown for the first time that the mechanism of formation of βCs 1–3 occurs from the sugar intermediate 3-deoxyglucosone that reacts with tryptophan affording these carbohydrate-derived βCs. A mechanism of reaction to give βCs 1–3 is proposed that relies on the tautomerism (keto–enediol or enamine–imine) of intermediates involved in the reaction. Carbohydrate βCs 1–4 were assessed as inhibitors of monoamine oxidase (MAO), as antioxidants, and for their interaction with DNA. They were not good inhibitors of MAO-A or -B, were poor antioxidants, and did not appreciably interact with DNA.

Structure Revision of Protoaculeine B, a Post-translationally Modified N-Terminal Residue in the Peptide Toxin Aculeine B

The structure of protoaculeine B, the N-terminal residue of the marine peptide toxin aculeine B, is revised to the cis-1,3-disubstituted tetrahydro-β-carboline framework. We prepared two truncated model compounds that lack a long-chain polyamine using the one-step Pictet-Spengler reaction of tryptophan and compared their NMR, mass spectra, and chemical reactivity with those of the natural protoaculeine B. The synthetic models reproduced the profiles of the natural product well, which confirmed the appropriateness of the structure revision.

Influence of acetic acid on the photocatalytic activity of photosensitiser–amphiphilic polymer complexes in the oxidation reaction of tryptophan

The effect of acetic acid on the photosensitizing activity of dimegin (DMG), chlorin e6 (Ce6), and their complexes with amphiphilic polymers-Pluronic F-127 and poly-N-vinylpyrrolidone (PVP)-in the model reaction of tryptophan photo-oxidation has been established. It was shown that the photocatalytic activity of photosensitizers (PS), which is characterized by the effective constant of the tryptophan photo-oxidation rate (keff), increases by 1.4 times for DMG, while for Ce6, it decreases by 1.2 times in a weak acidic medium (pH ∼ 4). The influence of acetic acid on the effective constant keff of the tryptophan photo-oxidation rate in the presence of PS-amphiphilic polymer complexes is determined by the nature of the polymer. Thus, the photocatalytic activity of the PS-F127 system decreases at pH ∼ 4.0, and the photocatalytic activity of PS-PVP complexes is insensitive to the presence of acetic acid in the medium. It has been suggested that the observed effects in the PS-F127 system in a weak acidic medium (pH ∼ 4) are associated with the influence of acetic acid on the supramolecular structure of Pluronic F127.

Conformational Changes and Charge Transfer in Biomolecules Resolved Using Dynamic Enhanced Raman Correlation Spectroscopy.

In this contribution, we report that conformational changes of molecules that are often buried in a wide-distributed Gaussian distribution can be discerned by analyzing the dynamics of specific Raman lines. We investigate the pertinence of the auto- and cross-correlation functions applied to the dynamics of three Raman lines of an amino acid, the tryptophan. The cross-correlation between intensity and the Raman band is an indicator of the charge transfer during the diffusion limited reaction of tryptophan and the gold surface. The Péclet number Pe can provide a valuable indicator of the convective and/or diffusive features of each Raman band. Adsorption induced conformation changes can be identified using the autocorrelation of the multiples states within the Raman band centered at 1550 cm-1.

Hydrothermal reaction of tryptophan over Ni-based bimetallic catalysts

The major products from hydrothermal reactions of tryptophan at 350 and 400 °C in the absence of catalyst were indole and methyl indoles, indicating simultaneous deoxygenation and deamination. In the presence of carbon-supported Ni and NiM catalysts (M = Ru, Cu, Pd, Pt) primary aromatic amines also appeared, via cleavage of the heterocyclic ring of the indoles. Ni and NiCu catalysts have the lowest selectivity for the formation of this family of compounds, while NiRu had the highest selectivity. Catalysts containing noble metals also produced monosubstituted alkylaromatics, due to the deamination of the aromatic amines, with the NiPt catalyst providing the highest molar yield (∼7%). We propose catalytic and non-catalytic hydrothermal reaction pathways for tryptophan based on the observed product distributions. The bimetallic particles were smaller than the pure Ni particles and the surfaces of NiRu and NiPd particles were enriched in Ni, relative to the nominal bulk composition.

Isolation and structure determination of a new diketopiperazine dimer from marine-derived fungus Aspergillus sp. SF-5280

A new diketopiperazine dimer designated as SF5280-415 (1) was isolated from an EtOAc extract of the marine-derived fungus Aspergillus sp. SF-5280 by various chromatographic methods. The structure of 1 was mainly determined by analysis of the NMR spectroscopic data and MS data, along with Marfey’s method. This compound is a new diastereoisomer of known bispyrrolidinoindoline diketopiperazine alkaloid WIN 64745, which possesses unique architecture biosynthetically derived from an indole oxidation reaction of tryptophan.

3-Nitro-2-pyridinesulfenates as Efficient Solution- and Solid-Phase Disulfide Bond Forming Agents.

In this paper, a new disulfide-forming agent based on the finding that alkoxy 3-nitro-2-pyridinesulfenates (Npys-OR) can oxidize thiol groups is reported. Methyl 3-nitro-2-pyridinesulfenate (Npys-OMe), which is easily prepared from 3-nitro-2-pyridinesulfenyl chloride in a one-step reaction and has a reduction peak potential (Epc ) of -0.541 V versus Ag/AgCl, produces the cyclic nonapeptide oxytocin from its linear form in good yield (92 %) with minimal oligomer formation. Npys-OMe in the solid phase also demonstrated excellent results in oxytocin synthesis. Other disulfide-containing peptides, such as α-human atrial natriuretic peptide and α-conotoxin ImI, were also successfully synthesized. During these syntheses, no side reactions of methionine (Met) and tryptophan (Trp) residues or the S-acetamidomethyl (Acm) protecting group were detected. These results suggested that Npys-OMe or its solid-phase analog provides a new strategy for regioselective disulfide bond formation to assist the synthesis of complex disulfide-rich peptides.

Comparative studies on histology and histochemistry of pancreas between Labeo calbasu (Hamilton, 1822) and Mystus gulio (Hamilton, 1822)

The cellular architecture and histochemical nature of the enzyme secretory acinar cells of pancreas have been investigated in two species of fish, Labeo calbasu and Mystus gulio having different feeding habits. Histological analysis illustrates that the exocrine pancreatic tissues are scattered within the hepatic parenchyma as hepatopancreas and spleen as spleenpancreas in L. calbasu . The structural analysis also shows that exocrine as well as endocrine pancreatic tissues are also diffused in the adipose tissues in between the intestinal coiling of L. calbasu . In M. gulio the discrete pancreatic tissue is attached to the outer wall of the stomach and formed cluster of acini interspersed with small areas of islet of Langerhans and blood vessels. The exocrine pancreatic acinar cells are provided with conspicuous nuclei and densely packed acidophilic zymogen granules. The endocrine component of pancreas, islet of Langerhans is encircled by a thin connective tissue and comprised of α, β and δ cells. Different cell types in the islets are differentiated based mainly upon their shape, position, staining intensity and density of the cytoplasmic secretory granules. α cells contain sparse cytoplasm and densely stained nuclei, are generally located to the periphery of the islet Aldehyde fuchsin positive β cells bear spherical nucleus and granular cytoplasm, are in the center of islet of Langerhans contacted with blood vessels. δ cells are few in number with light stained nuclei disperse in the pancreatic islet. Histochemical detection displays that the zymogen granules of exocrine acinar cells showing variegated intensities of tryptophan reaction, the precursor of numerous pancreatic enzymes which probably related to the food and feeding habits of the fishes concerned. The zymogen granules are larger in size and heavily deposited in the acinar cells of hepatopancreas of L. calbasu in comparison to M. gulio may be correlated with the herbivorous feeding habit in respect to secretion of digestive enzymes.

Nanomolar simultaneous determination of tryptophan and melatonin by a new ionic liquid carbon paste electrode modified with SnO2-Co3O4@rGO nanocomposite

This work describes the development of a new sensor for simultaneous determination of tryptophan and melatonin. The proposed sensor was an ionic liquid carbon paste electrode modified with reduced graphene oxides decorated with SnO2-Co3O4 nanoparticles. The voltammetric oxidation of the analytes by the proposed sensor confirmed that the electrooxidation process undergoes a two-electron/one-proton reaction for melatonin and a two-electron/two-proton reaction for tryptophan in diffusion-controlled processes. Moreover, based on the excellent electrochemical properties of the modified electrode, a sensitive voltammetric method was used for individual and simultaneous determination of melatonin and tryptophan in the aqueous solutions. Under the optimized experimental conditions, a linear response obtained in the range of 0.02 to 6.00μmolL−1 with detection limits of 4.1 and 3.2nmolL−1 for melatonin and tryptophan, respectively. The prepared sensor possessed accurate and rapid response toward melatonin and tryptophan with a good sensitivity, selectivity, stability, and repeatability. Finally, the applicability of the proposed sensor was verified by evaluation of melatonin and tryptophan in various real samples including human serum and tablet samples.

Graphitic carbon nitride nanosheets modified multi-walled carbon nanotubes as 3D high efficient sensor for simultaneous determination of dopamine, uric acid and tryptophan

Graphitic carbon nitride (g-C3N4) nanosheets, as graphene-like ultrathin semiconductor material, have strong covalent bonds between carbon and nitride atoms. The nitrogen atoms doping in the carbon architecture that greatly enhancing electrical properties and accelerating the electrontransfer rate, which can improve the electrical properties of g-C3N4 nanosheets. Herein, a novel electrochemical sensor was developed by immobilizing a three-dimensional (3D) hybrid nanocomposite which consisted of one-dimensional (1D) multi-walled carbon nanotubes (MWNTs) and two-dimensional (2D) g-C3N4 nanosheets on a glassy carbon electrode (g-C3N4/MWNTs/GCE). The g-C3N4/MWNTs/GCE exhibited excellent response toward the oxidation reactions of dopamine (DA), uric acid (UA) and tryptophan (Trp). Under the optimum conditions, the electrochemical sensor was used in the detection of DA, UA and Trp, and achieved wide ranges of 2.0–43.5μM, 5.0–189.0μM and 65.0–1815.0μM with low detection limits (S/N=3) of 5.0×10−8M, 5.0×10−7M and 1.0×10−6M, respectively. In addition, the coexistence of ascorbic acid (AA) has no obvious interference toward the detection of DA, UA and Trp. Thus, the modified electrodes were successfully applied for the determination of DA, UA and Trp in urine and serum samples using the standard adding method with satisfactory results.

Effect of Pluronic F127 on the photosensitizing properties of dimegine in the presence of nanoparticles

It is shown that the activity of the water-soluble porphyrin photosensitizer dimegine (DMG) in the oxidation reaction of tryptophan, a test reaction for photodynamic therapy (PDT), can be enhanced by introducing silver, gold, and hydroxyapatite nanoparticles (NP) into the reaction medium if an amphiphilic polymer (AP) with the properties of a SAS is introduced into this mixture. It is concluded that the effect of enhancing the photosensitizing activity of dimegine is due to the formation of nanoparticle-Pluronic-porphyrin triple systems in which Pluronic (PL) plays the role of a bridge, forming complex and adsorption bonds with porphyrin and nanoparticles.