Color Reaction Research Articles

Morphological structure of enamel caries in the dynamic process of demineralization and remineralization

According to modern ideas, the carious process at the white spot stage is reversible, so all the attention of scientists is directed to the development of means to restore the crystal lattice of tooth enamel. The purpose of the study is to evaluate morphological changes in caries at the white spot stage and the process of structural remineralization of the carious lesion area. Clinically active initial lesions were detected visually, using optical magnification and positive staining. Structural changes in enamel were studied by scanning electron microscopy of surface impressions obtained from the surface of demineralized enamel. Remineralizing therapy was carried out by applying ApaCare restorative gel (Germany) with nanodispersed highly active hydroxyapatite. Determination of the intensity of dental caries by the DMFT and dmft index showed 9.04 ± 0.40 points on average in the group of subjects, children with code 1 according to the ICDAS index made up 50.8%. Colour reactions showed 7.80 ± 0.21 points on average in the group. SEM visualized characteristic structural changes in the area of the carious spot – an increase in the porosity of the enamel surface with exposure of the fine crystalline structure and destruction of interprismatic fibrillar structures. When using a remineralizing agent, a roller-like deposition of an amorphous remineralizing substance is characteristic, and at the final stage, a smooth enamel surface with a fine crystal lattice is restored. The restoration of the prismatic structure of the enamel occurs due to the mineralization of the preserved fibrillar walls in the interprismatic space. Clinically, at this stage, the enamel visually restores its original shine, smoothness, and colour. In 81.8% of cases, the dye did not penetrate the previously demineralized enamel. The high level of non-cavitated active caries lesions can be largely controlled by the use of remineralizing agents. Further research involves studying the quantitative characteristics of the processes of de- and remineralization of tooth enamel.

Storage performance of non-waxy Japonica rice varieties preferred by Japanese consumers: Evaluation of physicochemical properties and in vitro starch digestibility

This study aimed to evaluate the changes during storage in the composition, texture, and starch digestibility of non-waxy Japonica rice varieties (cv. Yudai 21, Koshihikari, and Milky Queen) preferred by Japanese consumers. Stored grains were prepared by storing fresh grains at 30 °C for 6 months. Changes in pH of the rinse water and the color reaction of catalase activity showed a decrease in freshness and significant differences between varieties, between storage periods and by interaction. The total and resistant starch content decreased during storage and had significant correlations with pH and color reaction. Yudai 21 had higher surface adhesiveness, surface adhesion, and overall adhesiveness than Koshihikari with a similar apparent amylose (AA) content and Milky Queen with a lower AA content, regardless of storage. The equilibrium concentration of starch hydrolysis ranged from 84.1% to 94.9% with no significant difference and showed a significant correlation with pH (r = 0.78). The estimated glycemic index (eGI) was significantly affected by variety, with Koshihikari having the highest eGI and Yudai 21 having the lowest eGI, but was not affected by storage. Among the varieties, Yudai 21 was a suitable variety not only for fresh grains but also for stored grains, with high eating quality and low starch digestibility.

Irreversible thermochromic ink in the identification of over- and under-processed product segments in microwave-assisted freeze drying

The formation of over- and under-processed product regions is an inherent drawback of microwave-assisted freeze drying (MWFD) of food attributed to the inhomogeneity of microwave energy distribution. To overcome limitations in the investigation of inhomogeneity effects, the scope of this study was the development and validation of a new method using an irreversible thermochromic colour-component (ITC) with a particular colour intensity profile as a function of temperature (40–70 °C). For validation, thermal images and spatially-resolved biomarker inactivation was compared to the colour intensity pattern resulting from the temperature-induced colour reaction of ITC in MWFD. The ITC method provides advantages over existing methods, as it visualises the spatial distribution of maximum processing temperature independently of post-treatment effects and existing dryer design. This easy-to-use method has the potential to eliminate or reduce preconceptions due to poorly known inhomogeneity of microwave applications and pave the way for energy-efficient and fast MWFD of food.

DETECTION AND IDENTIFICATION OF CITALOPRAM AND ITS BIOTRANSFORMATION PRODUCT IN THE URINE BY THIN LAYER CHROMATOGRAPHY AND MASS SPECTROM- ETRY

The conditions for detection of сitalopram and its metabolite in the urine after admin- istration of a single therapeutic dose of the antidepressant using Thin Layer Chromatography have been proposed. The Rf values of the native compound and its metabolite were determined in TLC screening systems. The сitalopram biotransformation product was identified as N- desmethylcitalopram by Mass Spectrometric study of the eluates from chromatograms. Colour reactions for сitalopram and N-desmethylcitalopram with the range of chromogenic reagents have been studied.

QUALITATIVE AND QUANTITATIVE ANALYSIS OF HYDROQUINONE CONTENT IN MARKETPLACE FACIAL WHITENING CREAMS

Hydroquinone is one of the dangerous ingredients in facial whitening cream cosmetics which can cause skin irritation, skin redness and a burning feeling. The purpose of this study was to determine the hydroquinone content in facial whitening cream cosmetics sold in the marketplace. The method used in this study was a qualitative test using a colour reagent test and the Thin Layer Chromatography (TLC) method with toluene:glacial acetic acid as the mobile phase (5:5) and Silica Gel254 Plate as the stationary phase. Quantitative analysis used the UV Vis spectrophotometry method at a wavelength of 541 nm. The results of the qualitative test in the TLC test showed that 4 samples tested positive for hydroquinone in samples A, B, D, and E, with a range of Rf values of 0.44, 0.5, 0.52, and 0.5, respectively. The results of the quantitative test showed that 9 samples contained hydroquinone with a sample content range of 0.22 to 3.62 ppm with an LoD value of 0.637 ppm and an LoQ of 2.124 ppm. The results of this study indicate that there are still cosmetics containing hydroquinone, these results are not following the Regulation of Badan Pengawas Obat dan Makanan (BPOM) No. KH. 00.01.43.2503 of 2009 where the use of this hydroquinone ingredient is prohibited for use in facial whitening creams because it can endanger health.Keywords: Analysis, Hydroquinone, TLC, Whitening Cream

Development of a Simple Identification Method for Omphalotus guepiniformis by Color Reaction

A simple method of identification using a color reaction was developed for Omphalotus guepiniformis. Only Omphalotus guepiniformis turned turquoise green. Other edible mushrooms resembling the mushroom did not change color when the beam reagent (5 w/v% potassium hydroxide ethanolic solution) was dripped onto the mushroom pileus. Furthermore, ethanol extract and mock cooking products of this mushroom exhibited the same color reaction. These results demonstrate this method as useful for identifying Omphalotus guepiniformis during mushroom hunting or during investigations of food poisoning.

Enzymatic colorimetric method for turn-on determination of l-lactic acid through indicator displacement assay

l-Lactic acid is a natural α-hydroxy carboxylic acid and is commonly used as an addictive. Quantitation of l-lactic acid is indispensable in food and cosmetic industries. An enzymatic colorimetric method was developed for the determination of l-lactic acid by competitive indicator displacement assay. Boric acid inhibited the colorimetric reaction of l-3,4-dihydroxyphenylalanine (l-DOPA) catalyzed by tyrosinase. l-Lactic acid competitively displaced and released l-DOPA bound with boric acid to serve as substrate, and thus restored the tyrosinase activity. Recovery of color reaction could be spectrophotometrically determined at 475nm and was proportional to the amount of l-lactic acid. A calibration curve between l-lactic acid concentration and recovery of absorbance were built. The concentration range of the l-lactic acid was 0.25-2.25mM. The limit of detection (LOD) and the limit of quantification (LOQ) for l-lactic acid was estimated to be 0.05mM and 0.16mM, respectively. The method achieved turn-on and visual sensing with good precision, accuracy, specificity, and robustness. The assay method exhibited a promising prospect to determine the content of l-lactic acid in foods and cosmetics.

A novel cysteine catalytic oxidation-based colorimetric approach for sensitive analysis of acute pancreatitis-related microRNA

It is essential to establish simple, sensitive and accurate quantitative approaches for microRNAs (miRNAs) identification due to its crucial roles in a variety of physiological and pathological processes. Herein, we propose a novel RCA-based colorimetric method for sensitive and reliable miRNA analysis. In this approach, cyclization of the padlock sequence by miRNA-21 initiates the RCA to produce numerous G-rich sequences. The generated G-rich sequences fold to G-quadruplex DNAzyme that is capable of catalyzing cysteine to cystine which could mediate the gold nanoparticle-based color reaction, outputting results that can be observed directly by naked eyes. Based on this, the approach exhibits a wide detection range with a low limit of detection of 4 fM. In addition, the dual target recognition endows the method a greatly improved selectivity.

Investigating the active chemical constituents and pharmacology of Nanocnide lobata in the treatment of burn and scald injuries.

To identify the most effective fraction of Nanocnide lobata in the treatment of burn and scald injuries and determine its bioactive constituents. Chemical identification methods were used to analyze solutions extracted from Nanocnide lobata using petroleum ether, ethyl acetate, n-butanol using a variety of color reactions. The chemical constituents of the extracts were identified by ultra-performance liquid chromatography (UPLC)-mass spectrometry (MS). A total of 60 female mice were randomly divided into the following 6 groups: the petroleum ether extract-treated group; the ethyl acetate extract-treated group; the n-butanol extract-treated group; the model group; the control group; and the positive drug group. The burn/scald model was established using Stevenson's method. At 24 hours after modeling, 0.1 g of the corresponding ointment was evenly applied to the wound in each group. Mice in the model group did not undergo treatment, while those in the control group received 0.1 g of Vaseline. Wound characteristics, including color, secretions, hardness, and swelling, were observed and recorded. Photos were taken and the wound area calculated on the 1st, 5th, 8th, 12th, 15th, 18th and 21st days. Hematoxylin-eosin (HE) staining was utilized to observe the wound tissue of mice on the 7th, 14th, and 21st days. An enzyme-linked immunosorbent assay (ELISA) kit was used to measure the expression of tumor necrosis factor (TNF)-α, interleukin (IL)-10, vascular endothelial growth factor (VEGF) and transforming growth factor (TGF)-β1. The chemical constituents of Nanocnide lobata mainly include volatile oils, coumarins, and lactones. UPLC-MS analysis revealed 39 main compounds in the Nanocnide lobata extract. Among them, ferulic acid, kaempferitrin, caffeic acid, and salicylic acid have been confirmed to exhibit anti-inflammatory and antioxidant activity related to the treatment of burns and scalds. HE staining revealed a gradual decrease in the number of inflammatory cells and healing of the wounds with increasing time after Nanocnide lobata extract administration. Compared with the model group, the petroleum ether extract-treated group showed significant differences in the levels of TNF-α (161.67±4.93, 106.33±3.21, 77.67±4.04 pg/mL) and IL-10 (291.77±4.93, 185.09±9.54, 141.33±1.53 pg/mL) on the 7th, 14th, and 21st days; a significant difference in the content of TGF-β1 (75.68±3.06 pg/mL) on the 21st day; and a significant difference in the level of VEGF (266.67±4.73, 311.33±10.50 pg/mL) on the 7th and 14th days respectively. Petroleum ether Nanocnide lobata extract and the volatile oil compounds of Nanocnide lobata might be effective drugs in the treatment of burn and scald injuries, as they exhibited a protective effect on burns and scalds by reducing the expression of TNF-α, IL-10 and TGF-β1 and increasing the expression of VEGF. In addition, these compounds may also exert pharmacological effects that promote wound tissue repair, accelerate wound healing, and reduce scar tissue proliferation, inflammation and pain.

Analisis Kualitatif Metabolit Sekunder dan Aktivitas Antioksidan Jamur Endofit Cangkang Bulu Babi (Diadema setosum)

Endophytic fungi are fungi that live in plant tissues for a certain period and can form colonies in the host's tissues without endangering the host itself. In addition to plants, endophytic fungi are also found in marine biota. Endophytic fungi that live in the internal organs or tissues of marine biota, whether in the form of mold or yeast, can transform the nutrients they obtain from their host animals into metabolite compounds which will then be transferred back to the host organs so that they have the same metabolites as their hosts. This study aimed to analyze and test the antioxidant activity of the secondary metabolites of sea urchins in the Tomini Bay area. The method used from the beginning of the research was endophytic microbial fermentation, production of secondary metabolites, and partitioning of endophytic microbial isolates, namely liquid-liquid; the method used to test antioxidant activity was qualitative using TLC plates, DPPH UV-Vis spectrophotometer method, color reagent, and thin layer chromatography. Two isolates of endophytic fungi were obtained, namely (JBB1, JBB2). The isolate that was active as an antioxidant was JBB2 from sea urchins in the Tomini Bay area with an ICso 50-100 ppm, which was in the strong category. Meanwhile, JBB2 isolate was carried out at a wavelength of 517 nm with a value absorbance of 0,707 A. In accordance with the value of the linear equation, it obtained y = 0,092x+36,95 and an R2 value = 0,945 that the ethyl acetate extract in JBB2 had a moderate ICs of 87.43 µg/mL. Meanwhile, the qualitative test of secondary metabolites using thin layer chromatography with n-hexane eluent: ethyl acetate (8:2) ethyl acetate extract contained alkaloid and terpenoid compounds.

Penentuan Kadar Flavonoid Daun Rumput Knop (Hyptis capitata Jacq.) Menggunakan Spektrofotometri UV-Vis

Knop grass (Hyptis capitata Jacq.) is a weed used as a tradisional medicine, especially for the leaves. Flavonoids are one of the secondary metabolites contained in the Knop Grass (Hyptis capitata Jacq.) leaves, wich function as anti-inflammatory, analgesic, antipyretic and anti-diabetic. The amount of extracted flavonoids is optimized by choosing the right extraction method, as it will determine the amount of substance that can be attracted and obtain a high content of active substansces. This research aimed to compare the flavonoid levels in the methanol extract of Knop Grass (Hyptis capitata Jacq.) leaves in two different maceration methods: multilevel maceration and total maceration. Multilevel maceration employed n-hekxane, ethyl acetat and methanol solvents, while total maceration employed methanol solvent. In the meantime, the qualitative analysis in this reaserch used the color reagent test method, whereas the thin layer chromatography used the eluent, namely n-hexane : ethyl acetate with a ratio (7:3). In addition, the quantitative analysis used the UV-Vis spectrophotometry method at a maximum wavelength of 435 nm with standard quercetin as a comparison. The result signified that the average flavonoid level in the methanol extract of Knop Grass (Hyptis capitata Jacq.) leaves using the multilevel maceration method was 2,9750%. The total maceration method was 4,8822%. Furthermore, the total maceration method donated the highest concentration obtained from the methanol extract of Knop Grass (Hyptis capitata Jacq.) leaves.

Development of a visual detection method for Salmonella based on loop-mediated isothermal amplification using pyrophosphatase.

Salmonella is one of the most widely distributed and harmful food-borne pathogens; thus, the rapid detection of viable Salmonella is important for ensuring food safety. In this study, a rapid visual strategy based on loop-mediated isothermal amplification (LAMP) with the addition of thermal inorganic pyrophosphatase and linked with an ammonium molybdate chromogenic buffer was established to detect Salmonella. Specific primers were designed based on the phoP gene of Salmonella spp. The pyrophosphatase concentration, LAMP time, addition of ammonium molybdate chromogenic buffer, and color reaction time were optimized. Based on the optimal conditions, the sensitivity and specificity of the method were examined. In addition, the ability to detect actual samples was verified using apple juice containing Salmonella. LAMP was performed at 65°C for 45min in the presence of thermal inorganic pyrophosphatase at a final concentration of 4U ml-1, and 20 μl of the LAMP product was reacted with 50 μl of phosphate chromogenic buffer at 25°C for 15min. According to our results, the limit of detection of the LAMP assay for viable Salmonella was 1.83×102 CFU per reaction, and nonspecific amplification was not observed. The detection rates of Salmonella Typhimurium with different concentrations in apple juice were 89.11%-94.80%, which verifies that the visual detection strategy is suitable for actual sample detection.

Standardization of phenol colour reaction test in rice (Oryza sativa) varieties

Standardization of phenol colour reaction test in rice (Oryza sativa) varieties

<i>NOS2</i>, <i>NOS3</i>, <i>SONE</i> gene transcripts levels in peripheral blood leukocytes and their relationship with markers of endothelial dysfunction in hypertension

Objective. The aim of the study was to evaluate the level of expression of the NOS2, NOS3, SONE genes in peripheral blood leukocytes (PBL) of patients with hypertension (HTN) and to study the relationship between the level of transcripts of these genes and the content of nitric oxide metabolites and markers of endothelial dysfunction.Design and methods. The study included healthy people (25 people) and patients with HTN (stages I–II) before prescribing antihypertensive drugs (15 people) and taking cardioselective β-adrenergic receptor blockers for more than a year (metoprolol (25 mg per day) or bisoprolol (5–10 mg per day)) (20 people). The level of gene transcripts was assessed by real-time polymerase chain reaction (PCR). The level of nitric oxide metabolites was determined by the colorimetric method using the Griess reagent. The content of asymmetric dimethylarginine (ADMA), soluble forms of vascular cell adhesion molecule (sVCAM), and intercellular adhesion molecule (sICAM) in blood plasma was determined by ELISA. The content of malondialdehyde (MDA) in blood plasma was determined spectrophotometrically by color reaction with thiobarbituric acid. Statistical processing of the results was carried out using the Statgraphics Centurion XVI software package (version 16.1.11).Results. The level of nitric oxide metabolites in the blood plasma of HTN patients without antihypertensive therapy was 2,1 times higher than in healthy individuals (p = 0,001) and 1,7 times higher than in patients with HTN taking metoprolol or bisoprolol (p = 0,002). The relative content of mRNA of the NOS3 gene in PBL of individuals included in the study did not differ (p > 0,05). The level of NOS2 gene transcripts in PBL of HTN patients before the prescription of antihypertensive drugs exceeded that in healthy individuals (p = 0,0009) and in HTN patients taking metoprolol or bisoprolol (p = 0,0002). The number of SONE transcripts in the PBL of HTN patients was higher than in people with normal blood pressure (p < 0,00001 when comparing patients before the prescription of antihypertensive therapy and individuals from the control group; p = 0,04 when comparing patients with HTN taking antihypertensive drugs and normotensive subjects). The content of MDA, ADMA, sVCAM was higher in the plasma of HTN patients without antihypertensive therapy compared with people from the control group (p = 0,005, 0,003, 0,039, respectively) and patients taking metoprolol or bisoprolol (p = 0,0006, 0,019, 0,016, respectively). The content of nitric oxide metabolites positively correlated with NOS2, SONE, VCAM1 mRNA level in PBL, the content of MDA and ADMA in blood plasma (p < 0,05). A positive correlation was found between the concentration of MDA and ADMA in plasma (p = 0,03).Conclusions. An increase in the level of nitric oxide metabolites in HTN is associated with an increase in the transcriptional activity of the NOS2 gene, a disturbance of the redox balance of the body, and the development of endothelial dysfunction. The SONE gene is probably involved in the modulation of nitric oxide levels in HTN not only as an antisense transcript that destabilizes the mRNA of the NOS3 gene in vascular endothelial cells, but also indirectly, namely, through the regulation of homeostasis of immune system cells through autophagy.

Quantification of total polyphenol content in wine lees by conventional optical and photoacoustic spectroscopy

The He-Ne laser (632.8 nm) and photoacoustic spectroscopy (PAS), a variant of the photothermal methods, were combined with the Folin-Ciocalteu colorimetry method to determine total phenolics in wine lees. Utilising this method we found that the total polyphenol content of the nine selected wine lees varied from 1305 to 3907 mg/L. The gallic acid equivalent was determined by means of spectrophotometry using 765 nm as the analytical wavelength. The original Folin-Ciocalteu colorimetry assay was modified for the PAS measurements. Since the PAS does not need dilution, the filtration steps and the Folin-Ciocalteu reagent were used directly on the wine lees samples. Using the original colour reaction process and the modified reaction, the PAS showed linear behaviour between the total polyphenol content and the PA signal; the results of which gave determination coefficients of 0.9946 and 0.9936, while the limit of detection was 232.6 mg/L in both cases.

Antioxidant isolation and characterization from the plant Tradescantia spathacea Sw. of the Commelinaceae family

A novel bioactive flavan glycoside was isolated by solvent extraction method with the help of Soxhlet apparatus from the methanolic extract of Tradescantia spathacea Sw. Flavan glycoside having molecular formula C20H22O10, melting point 175-1780C, molecular weight by ESI-MS m/z (M + H]+ 423, optical rotation was[α]21 D-45.1(c 0.20 methanol). Its structure was determined (–)-epicatechin 7-O-alpha-L-arabinopyranoside. Various color reactions, chemical degradation (like acid hydrolysis, permethylation, and enzymatic hydrolysis), UV-Visible spectrophotometry, Fourier transforms infrared spectroscopy, electrospray ionization mass spectrometry, and nuclear magnetic resonance spectroscopy were used to establish the structure of compound (–)-(–)-epicatechin 7-O-alpha-L-arabinopyranoside.. A flavan glycoside was also tested with a DPPH assay method for antioxidant activity by using Ascorbic acid as standard. DPPH radical scavenging test data demonstrate that a flavan glycoside possesses potent antioxidant activity so this flavan glycoside can be utilized as a potent antioxidant agent.

Detection of Abnormal Prion Protein by Immunohistochemistry.

Abnormal prion proteins (PrPSc) are the disease-associated isoform of cellular prion protein and diagnostic markers of transmissible spongiform encephalopathies (TSEs). These neurodegenerative diseases affect humans and several animal species and include scrapie, zoonotic bovine spongiform encephalopathy (BSE), chronic wasting disease of cervids (CWD), and the newly identified camel prion disease (CPD). Diagnosis of TSEs relies on immunodetection of PrPSc by application of both immunohistochemistry (IHC) and western immunoblot methods (WB) on encephalon tissues, namely, the brainstem (obex level). IHC is a widely used method that usesprimary antibodies (monoclonal or polyclonal) against antigens of interest in cells of a tissue section. The antibody-antigen binding can be visualized by a color reaction that remains localized in the area of the tissue or cell where the antibody was targeted. As such, in prion diseases, as in other fields of research, the immunohistochemistry techniques are not solely used for diagnostic purposes but also in pathogenesis studies. Such studies involve detecting the PrPSc patterns and types from those previously described to identify the new prion strains. As BSE can infect humans, it is recommended that biosafety laboratory level-3 (BSL-3) facilities and/or practices are used to handle cattle, small ruminants, and cervid samples included in the TSE surveillance. Additionally, containment and prion-dedicated equipment are recommended, whenever possible, to limit contamination. The PrPSc IHC procedure consists of a formic acid epitope-demasking step also acting as a prion inactivation measure, as formalin-fixed and paraffin-embedded tissues used in this technique remain infectious. When interpreting the results, care must be taken to distinguish non-specific immunolabeling from target labeling. For this purpose, it is important to recognize artifacts of immunolabeling obtained in known TSE-negative control animals to differentiate those from specific PrPSc immunolabeling types, which can vary between TSE strains, host species, and prnp genotype, further described herein.

Antibacterial activity of new flavanone glycoside isolated from Tradescantia spathacea Sw.

Here we are reporting a new bioactive flavanone glycoside. The compound having molecular formula C21H22O11, melting point 123-125°C, and ESI-MS m/z 451 was isolated from the methanolic extract of Tradescantia Spathacea Sw. Its characterization and structure elucidation was done with the help of various chemical degradation, color reactions, and spectral data like UV-Visible, FT-IR, electrospray ionization mass spectrometry technique, nuclear magnetic resonance spectroscopy, etc. It was recognized as 5,7,3’4’-tetrahydroxy flavanone 3’-O-D-mannopyranoside. This study was also designed to examine the efficacy of an isolated compound against various bacteria which are responsible for food spoilage and pathogens in humans. The organic flavanone glycoside of methanolic extract exhibited a promising antibacterial activity towards Escherichia coli (gram negative) MTCC 724, Bacillus subtilis MTCC 441, Staphylococcus aureus MTCC 737, Pseudomonas aerugenosa MTCC 424, and Salmonella typhimurium MTCC 3224. A new flavanone glycoside possesses potent anti-bacterial activity so it can be utilized as a potent source of antibacterial agents for food and pharmaceutical interest.

L-DOPA Assay of Polyphenol Oxidase (PPO) for Varietal Identification in Rice (Oryza sativa L.)

A phenol colour response test on the grain is used to identify varieties of wheat and rice. It is a harmful, damaging procedure due to the carcinogenic properties of phenol. The activity of polyphenol oxidase (PPO) provides the basis for the phenol colour reaction. The goal of this research was to assess a method similar to the phenol colour reaction, by determining where the polyphenol oxidase activity threshold lies for classifying rice types into different groups. The new PPO assay was applied to commercially available rice varieties with the intention of classifying those that ranged from extremely high to extremely low PPO levels into manageable categories. Substrates such as phenol, L-tyrosine, catechol and 3,4-dihydroxyphenylalanine (L-DOPA) were tested. Twenty cultivars cultivated under identical conditions were put through a screening using a standard assay [1.5 mL of 10 mM L-DOPA in 50 mM 3-(N-morpholino) propane sulphonic acid (MOPS) buffer, pH 6.5, with 3 to 5 seeds constantly rotated in a 2-mL microcentrifuge tube for 0.5 or 1 hour at room temperature]. At 30 minutes, PPO levels were assessed. Based on the PPO values, the varieties belonging to phenol colour groups such as black, dark brown, brown, light brown or no colour matched perfectly. Considering easiness in estimation and other advantages of PPO activity, L-DOPA is proposed as a means of identifying rice varieties instead of the phenol colour reaction test.

MoO2 and N-Doped Carbon Nano-Octahedron Nanozymes for Sensitive Detection of Alkaline Phosphatase

As a typical biomarker for clinical diagnosis of diseases, alkaline phosphatase (ALP) plays a crucial role in regulating the dephosphorylation of biomolecules. Consequently, it is necessary to develop an effective and simple method for the determination of ALP activity. In this work, we report a catalytic reaction-based colorimetric method to monitor ALP activity by using a nanostructured MoO2@NP-doped carbon nano-octahedron (MoO2@NPC) as a favorable oxidase mimetic. Because the C–O bond generated in the nano-octahedron MoO2@NPC regulates the electronic valence state of Mo between +5 and +6, the as-prepared MoO2@NPC regular octahedron with good peroxide-like (POD-like) properties and colorless 3,3′,5,5′-tetramethylbenzidine dihydrochloride hydrate (TMB) can be catalyzed to dark-blue oxTMB. When ALP hydrolyzes the substrate AAP, the produced AA with a certain reducing ability can not only reduce oxTMB to TMB but also consume hydroxyl radicals (•OH) generated in the MoO2@NPC/H2O2/TMB system, which significantly inhibits the color reaction of TMB. On this basis, a simple and efficient colorimetric method for ALP was constructed based on carbon-based nanozymes. Furthermore, the system goes for the detection of ALP with high sensitivity for the first time. The linearity is good in the range of 0.5–30 U/L, and the detection limit was 0.02 U/L and had good stability and reproducibility. Reliable and accurate measurements of analytes in real samples were also validated by our analytical method, showing that it can provide a reliable, convenient, and efficient nanoplatform for clinical diagnosis of ALP activity.