P-dimethylaminocinnamaldehyde Research Articles

Deep Learning Used with a Colorimetric Sensor Array to Detect Indole for Nondestructive Monitoring of Shrimp Freshness.

Intelligent colorimetric freshness indicator is a low-cost way to intuitively monitor the freshness of fresh food. A colorimetric strip sensor array was prepared by p-dimethylaminocinnamaldehyde (PDL)-doped poly(vinyl alcohol) (PVA) and chitosan (Chit) for the quantitative analysis of indole, which is an indicator of shrimp freshness. As a result of indole simulation, the array strip turned from faint yellow to pink or mulberry color with the increasing indole concentration, like a progress bar. The indicator film exhibited excellent permeability, mechanical and thermal stability, and color responsiveness to indole, which was attributed to the interactions between PDL and Chit/PVA. Furthermore, the colorimetric strip sensor array provided a good relationship between the indole concentration and the color intensity within a range of 50-350 ppb. The pathogens and spoilage bacteria of shrimp possessed the ability to produce indole, which caused the color changes of the strip sensor array. In the shrimp freshness monitoring experiment, the color-changing progress of the strip sensor array was in agreement with the simulation and could distinguish the shrimp freshness levels. The image classification system based on deep learning were developed, the accuracies of four DCNN algorithms are above 90%, with VGG16 achieving the highest accuracy at 97.89%. Consequently, a "progress bar" strip sensor array has the potential to realize nondestructive, more precise, and commercially available food freshness monitoring using simple visual inspection and intelligent equipment identification.

Synthesis of 3-[4-(dimethylamino)phenyl]alkyl-2-oxindole derivatives and their effects on neuronal cell death

Novel 3-[4-(dimethylamino)phenyl]alkyl-2-oxindole analogs were synthesized by either of the following two pathways: (1) a sequence of Knoevenagel condensation of oxindole with (4-dimethylamino)cinnamaldehyde–hydrogenation, or (2) alkylation of oxindole dianion with [(4-dimethylamino)phenyl]alkyl halides. Subsequent alkylation at C-3 and/or N-1 of the oxindole skeleton by anion-based methods provided additional substituted derivatives for structure-activity relationship studies. Their effects on neuronal cell death induced by oxidative stress were evaluated by lactate dehydrogenase assay. Compounds with the alkyl chain length of 2–4 significantly suppressed the neuronal cell death. No significant change occurred in the activity by substitution with less-polar groups. The stereochemistry at C-3 of the oxindole core was also irrelevant for the neuroprotective effects of these compounds.

Assesment of the antioxidant activity and content of polyphenolic compounds in grapevine seeds

Our work was focused on the study of the antioxidant properties of grapevine seeds. We monitored the grapevine seeds of 6 cultivars of Vitis vinifera, L. (Nativa, Kofranka, Blaufränkish, Marlen, Cabernet Moravia and Italian Riesling). Antioxidant activity was determined by three principally different methods (DPPH, ABTS and FRAP), the content of the total polyphenolic compounds was determined by the Folin ciocalteu method, and the content of the total flavanols was determined by DMACA reagent (p-dimethylaminocinnamaldehyde). Results are presented as an equivalent of gallic acid in g.L-1, respectively were expressed as g.L-1 of catechin equivalents (DMACA method). The highest values of antioxidant activity were measured in the cultivar Nativa (DPPH - 7.75 g.L-1, ABTS - 4.888 g.L-1, FRAP - 4.25 g.L-1). Conversely, the lowest values of antioxidant activity were detected in the cultivar Kofranka (DPPH - 7.08 g.L-1, ABTS - 4.17 g.L-1, FRAP - 4.55 g.L-1). Cultivar Nativa also reached the highest content of flavonols (3.77 g.L-1). The highest measured values of the content of total polyphenolic compounds were identified in the cultivar Cabernet Moravia (15.2 g.L-1 of GAE). Conversely, the lowest values of the content of total polyphenolic compounds were detected in the cultivar Nativa (8.04 g.L-1). Pearson correlation coefficients were calculated for the existing values between antioxidant activity (DPPH, ABTS, FRAP), contents of flavonols, and contents of total polyphenols. The highest correlation coefficient was found between the DPPH and ABTS methods; specifically, it was 0.857.

DNA and Flavonoids Leach out from Active Nuclei of Taxus and Tsuga after Extreme Climate Stresses.

Severe over-stresses of climate caused dramatic changes in the intracellular distribution of the flavonoids. This was studied in needles from the current year’s growth of the following species and varieties: Tsuga canadensis, Taxus baccata, T. aurea, T. repens, T. nana, and T. compacta. The mode of steady changes in flavonoids was evaluated by microscopic techniques. Most of the flavonoids stain visibly yellow by themselves. The colorless flavanol subgroup can be stained blue by the DMACA reagent. In mid-summer 2013, outstanding high temperatures and intense photo-oxidative irradiation caused in a free-standing tree of Taxus baccata dramatic heat damage in a limited number of cells of the palisade layers. In these cells, the cytoplasm was burned brown. However, the nucleus maintained its healthy “blue” colored appearance which apparently was a result of antioxidant barrier effects by these flavanols. In late May 2014, excessive rainfall greatly affected all study trees. Collectively, in all study trees, a limited number of the mesophyll nuclei from the needless grown in 2013 and 2014 became overly turgid, enlarged in size and the flavanols leached outward through the damaged nuclear membranes. This diffusive stress event was followed one to three days later by a similar efflux of DNA. Such a complete dissolution of the nuclei in young tissues was the most spectacular phenomenon of the present study. As a common feature, leaching of both flavanols and DNA was markedly enhanced with increasing size and age of the cells. There is evidence that signalling flavonoids are sensitized to provide in nuclei and cytoplasm multiple mutual protective mechanisms. However, this well-orchestrated flavonoid system is broken down by extreme climate events.

Simple spectrophotometric methods for estimation of aceclofenac from bulk and formulations

Two simple, precise and accurate visible spectrophotometric methods were developed for the estimation of Aceclofenac in bulk drug and in pharmaceutical formulations. The proposed methods were indirect and based on determination of aceclofenac after its reaction with either (p-dimethylaminocinnamaldehyde (PDAC) or 3-Methyl-2- benzothiazolinone hydrazine hydrochloride (MBTH) and measuring the chromogen at the λmax by 658 and 592, respectively. Beers law obeyed in the concentration range of 1–200μg/ml for method A and 1–100μg/ml for method B. The accuracy of the methods was determined by recovery studies. The methods showed good reproducibility and recovery with relative standard deviation (RSD) (in %) less than 2. The methods were found to be simple, economical, accurate and reproducible and can be used for routine analysis of Aceclofenac in bulk drug and in pharmaceutical formulations.

Nuclei ofTaxus baccata: Flavanols Linked to Chromatin Remodeling Factors

Microscopic studies of young needles and shoot tips fromTaxus baccatashowed that flavanols are localized in the nuclei. This observation is based on the histochemical staining of flavanols with the DMACA reagent. The colour that is obtained with this reagent varies from pale to deep blue, depending on the amount of flavanols. This study is focused on nondifferentiated cell lineages and on differentiating cells. The key point to note is that all nuclei of a cell lineage showed a uniform DMACA staining pattern based on the amount and structural appearence of nuclear flavanols. This points to transcriptional and epigenetic programming. However, comparing various cell lineages from different shoot tips and needles revealed a lineage-specific expression of nuclear flavanols. This result implied that both positional and developmental signals from neighbouring cells were involved in the nuclear flavanol binding of lineages. The cells of a developmentally advanced lineage loose their intimate contact and, then, they separate from each other to undergo an autonomous, individual sequence of differentiation. This in turn was accompanied by differences in the nuclear flavanol patterns of the single cells. Investigating different mitotic stages revealed a wide spectrum in flavanol staining intensities of the chromosomes. These observations should be linked to UV-VIS spectroscopical kinetic results indicating that nuclear flavanols bound to histones are involved in epigenetically regulated modification of chromatin. The kinetic studies show that catechin is relatively rapidly degraded by oxygen in the presence of -ions. However, this degradation reaction is strongly inhibited when histone proteins were added. This behaviour is a clear indication that coregulatory interactions exist between catechin and histones.

Characterization of superoxide production from aldehyde oxidase: An important source of oxidants in biological tissues

Aldehyde oxidase, a molybdoflavoenzyme that plays an important role in aldehyde biotransformation, requires oxygen as substrate and produces reduced oxygen species. However, little information is available regarding its importance in cellular redox stress. Therefore, studies were undertaken to characterize its superoxide and hydrogen peroxide production. Aldehyde oxidase was purified to >98% purity and exhibited a single band at ∼290 kDa on native polyacrylamide gradient gel electrophoresis. Superoxide generation was measured and quantitated by cytochrome c reduction and EPR spin trapping with p-dimethyl aminocinnamaldehyde as reducing substrate. Prominent superoxide generation was observed with an initial rate of 295 nmol min −1 mg −1. Electrochemical measurements of oxygen consumption and hydrogen peroxide formation yielded values of 650 and 355 nmol min −1 mg −1. In view of the ubiquitous distribution of aldehydes in tissues, aldehyde oxidase can be an important basal source of superoxide that would be enhanced in disease settings where cellular aldehyde levels are increased.

Determination of hydrochlorothiazide in pharmaceutical formulations by diffuse reflectance spectroscopy

This paper describes a method for quantitative spot test analysis of hydrochlorothiazide usingdiffuse reflectance spectroscopy. The reflectance measurements were performed analyzing the coloredcompound (l = 585 nm) produced from the reaction between hydrochlorothiazide and p-dimethylaminocinnamaldehyde (PDAC) in acid medium. This reaction occurred on filter paper after heatingto 80oC for 8 minutes. Factorial designs allowed varying multiple reaction factors simultaneously in orderto obtain the best reaction conditions. These factors included heating temperature, heating time, acidvolume and PDAC volume. The linearity was studied in the range of 3.36x10 -2 to 1.01x10 -1 mol L -1 with acorrelation coefficient of 0.998. The limit of detection was estimated to be 1.32x10 –2 mol L -1 . Commercialsamples were analyzed using the proposed method and the results were favorably compared with those ofthe United States Pharmacopeia method, showing that quantitative spot test analysis by diffuse reflectancecould be successfully used to determine hydrochlorothiazide in medicines.

Determination of hydrochlorothiazide in pharmaceutical formulations by diffuse reflectance spectroscopy

This paper describes a method for quantitative spot test analysis of hydrochlorothiazide using diffuse reflectance spectroscopy. The reflectance measurements were performed analyzing the colored compound (l = 585 nm) produced from the reaction between hydrochlorothiazide and p-dimethylaminocinnamaldehyde (PDAC) in acid medium. This reaction occurred on filter paper after heating to 80ºC for 8 minutes. Factorial designs allowed varying multiple reaction factors simultaneously in order to obtain the best reaction conditions. These factors included heating temperature, heating time, acid volume and PDAC volume. The linearity was studied in the range of 3.36x10-2 to 1.01x10-1 mol L-1 with a correlation coefficient of 0.998. The limit of detection was estimated to be 1.32x10² mol L-1. Commercial samples were analyzed using the proposed method and the results were favorably compared with those of the United States Pharmacopeia method, showing that quantitative spot test analysis by diffuse reflectance could be successfully used to determine hydrochlorothiazide in medicines.

Are histones the targets for flavan-3-ols (catechins) in nuclei?

Binding of flavan-3-ols to nuclei is characteristic of Tsuga canadensis (coniferous tree). This is achieved with the DMACA reagent (p-dimethylamino-cinnamaldehyde), which stains almost exclusively monomeric and oligomeric flavan-3-ols with an intense blue colour. Deep flavanol staining also occurred when calf cells of small intestine were enriched with added catechins. In order to detect the components of nuclei that may associate with catechins, the principal components of chromatin (DNA, histones) were subjected to UV-VIS spectroscopic titration. DNA or histone sulphate containing the histones H1, H2A, H2B, H3 and H4 were dissolved in cationic and anionic buffers (Tris, phosphate) at different pH values (pH 8.0, 7.4 and 7.0) and titrated with EGCG (epigallocatechin gallate) or catechin. The results show that DNA of calf thymus and the catechins investigated form no spectroscopically detectable association equilibria. However, strong association complexes are found between histone sulphate and EGCG or catechin by means of the Mauser diagrams (A and AD diagrams). The association equilibria can be accompanied by aggregation (precipitation) of histone proteins, especially initiated by EGCG. The titration equilibria are spectroscopically more pronounced in Tris buffers at higher pH values than at lower values, whereas in phosphate buffers the opposite trend is found. Surprisingly, catechin shows nearly no interactions with histone sulphate in phosphate buffers in the pH range 7.0-8.0, which is in contrast to EGCG. Fundamentally, the targets of chromosomes for catechins seem to be the histone proteins of chromatin.

Nuclei of plants as a sink for flavanols.

Onion cepa (L.) and Tsuga canadensis (L.) Carr. were investigated histochemically on the association of flavanols to nuclei. The young roots of Onion cepa are totally devoid of flavanol structures. Therefore, the excised roots tips were directly incubated into different solutions of flavanols. After 3 h of incubation a flavanol binding on the nuclei was recognizable, as seen by a yellowish-brown tanning reaction. Still to ensure the presence of flavanols on the nuclei, subsequent staining with the p-dimethylaminocinnamaldehyde reagent (DMACA) resulted in an intense blue colouration. Tsuga canadensis has significant amounts of vacuolar flavanol deposits in all parts of the tree as indicated by the DMACA reagent. It is obvious that also the nuclei were associated strongly with flavanols which can be demonstrated particularly elegant in the cells of the seed wings by histochemical methods. However, the mode of flavanol release from the original deposits is not yet clear.

Analysis of catechins from green and black tea in humans: a specific and sensitive colorimetric assay of total catechins in biological fluids

Catechins are a group of flavonoids widely occurring in fruits, wine and tea, which are strong antioxidants with demonstrated anticarcinogenic effects in animal models. There is currently little knowledge on the bioavailability of catechins due to a lack of suitable analytical methods. Therefore a simple colorimetric assay was developed for the determination of the concentration of catechins in plasma. Following precipitation of proteins with methanol, tea flavonoids were accumulated by solid phase adsorption to alumina. Reactions of adsorbed catechins with 4-dimethyl amino cinnamaldehyde under strong acidic conditions results in desorption and development of a highly selective coloured complex (λ = 637 nm). The method is highly specific for catechins with equimolar responses for catechin, epicatechin, epigallocatechin, epicatechin gallate and epigallocatechin gallate. The detection limit in plasma is 0.05 μmol/L and the within and between day variation was 1.1% and 2.6%, respectively. Following consumption of a single dose of green tea, equivalent to six cups of tea, plasma levels of total catechins of 2.36 ± 0.55 μmol/L (n = 5) were reached after 60 min. This novel method is a rapid and sensitive way to gain more insight in the bioavailability of catechins from tea, wine and foods.

Localization of proanthocyanidins using in situ-hydrolysis with sulfuric acid.

A valuable method for specific localization of proanthocyanidins in plant tissues is given. The specificity is based on the acid hydrolysis of condensed tannins in situ via hot sulfuric acid, yielding bright red anthocyanidins. This treatment did not cause noticeable damage of tissue embedded in glycol methacrylate prior to sectioning. Further proof of specificity was achieved by control staining with the flavan-3-ol-selective p-dimethylaminocinnamaldehyde (DMACA) reagent. In addition, comparison of adjacent sections stained with the DMACA reagent may give coarse information about the degree of polymerization of the proanthocyanidins.

A Spot Test for Estimating Ureides in Soyabean Petioles

SUMMARYThe ureides allantoic acid and allantoin form a bright pink compound with acidic p-dimethylamino cinnamaldehyde. It is possible to estimate the ureide content of a soyabean petiole segment by crushing it on filter paper and developing the colour with this reagent. There is a strong correlation between the spot test and estimates from colorimetric determination of ureides. In field grown soyabeans, there was a positive correlation between the petiole ureide content during pod fill and the integrated seasonal acetylene reduction activity. The spot test can be used to identify plants with low nitrogen fixation activity.

Colorimetric Determination of Sympathomimetic Amines Methyldopa and Noradrenaline

The chromogenic reagent p-dimethylaminocinnamaldehyde (PDAC) is introduced for the determination of the sympathomimetic amines methyldopa and noradrenaline. The method is based on measurement of the orange color developed when the alkaline solution of methyldopa and noradrenaline is allowed to react with PDAC at pH 5.0. The color developed obeys Beer's law in the concentration range 0.1-1.5 mL of 2 X 10(-3)M solution of noradrenaline and methyldopa. The results are compared with those obtained with another chromogenic reagent, p-dimethylaminobenzaldehyde (PDAB). Determinations on dosage forms of the drugs, using PDAC and PDAB reagents, agreed well with results of determinations by official pharmacopoeial methods.

A simple assay for measurement of urinary p-aminobenzoic acid in the oral pancreatic function test

A simple method for the measurement of p-aminobenzoic acid (PABA) in urine following oral administration of N-benzoyl- l-tyrosyl- p-aminobenzoic acid (Bz-ty-PABA), a synthetic peptide used for the assessment of exocrine pancreatic function, was investigated using p-dimethylamino cinnamaldehyde (DACA) as a chromogenic reagent. DACA reacted with PABA in acidic solution and the red dye which developed had an absorption spectrum with maximum at 550 nm. Urine containing PABA and its conjugated metabolites was hydrolyzed with HCl, DACA solution was added to a portion of the hydrolysate, and the color intensity was determined. When Bz-ty-PABA was administered orally to healthy humans and patients with pancreatic insufficiency, urinary PABA content determined by the DACA method was in good agreement with that by the diazo-coupling method. This DACA method is preferable to the diazo-coupling method with respect to the simplicity and rapidity of the procedure and to the stability of the reagent solution. It is especially useful for the above application in the clinical laboratory.

Studies on Analysis of Pharmaceutical Preparations. XXIX. Colorimetric Determination of Acetaminophen in Anti-cold Pharmaceutical Preparations

Spectrophotometric Determination of acetaminophen in pharmaceutical preparations is described. Acetaminophen was hydrolysed by refluxing with perchloric acid to produce p-aminophenol which was reacted with p-dimethyl aminocinnamaldehyde in dilute trichloracetic acid solution to give a red color, which showed absorption maximum at 520 nm. Interference by the presence of phenacetin and sulpyrine can be eliminated by their extraction with chloroform in basic medium or extraction with ethyl acetate in acidic medium.

Evaluation of Two Spot-Indole Reagents

Two spot-indole reagents, p-dimethylaminobenzaldehyde (DMABA) and p-dimethylaminocinnamaldehyde, were evaluated quantitatively. Although fourfold less sensitive, DMABA proved to be more stable and economical.

Studies on the Oxidation of Indole-3-Acetic Acid by Peroxidase Enzymes. I. Colorimetric Determination of Indole-3-Acetic Acid Oxidation Products

The method described here is based on a brief report by Harley-Mason and Archer. It involves the use of p-dimethylaminocinnamaldehyde (DMACA), a vinylogue of Ehrlich's reagent, as a color reagent for indoles. Colorimetric analyses of indoleacetic acid (IAA) oxidation reaction mixtures were made with the DMACA reagent as a solution rather than a spray. DMACA reagent will yield a wine-red color with IAA oxidation products in solution. Under similar conditions DMACA reacts with authentic IAA to yield only slight coloration at best. In comparison with other indoles, DMACA is more relative with IAA oxidation reaction products than either Salkowski or Ehrlich's reagents. Data discussed support a concept that the color produced with DMACA is due to the presence of tautomeric oxidation product(s) of IAA.