Color Reaction Research Articles

Simple and rapid photometry for measuring low dosage of periodate with bromide ion-catalyzed oxidation of ABTS

A new method for the quantification of trace periodate (PI) concentration was developed. The Br--ABTS method was based on the oxidation coloration reaction. Under Br- catalysis, the PI rapidly oxidized ABTS to the green ABTS•+, which could be accurately determined by UV-Vis spectrophotometer. The absorbance of ABTS•+ was remarkably correlated linearly with the concentration of PI at 415 nm, and the slope of standard curve was (3.77 ± 0.01)× 104 M−1·cm−1. The proposed method had high sensitivity and the slope at different optical paths showed a good multiplicative relationship for concentration values as low as 0.02 μM to be measured. The existence of different solutes in river and lake water did not affect the accuracy of Br--ABTS method, the generated ABTS•+ could maintain good stability within 30 min, and the recovery of PI was between 95%− 105%. The stoichiometric coefficient between PI and ABTS•+ was 1.12 at pH 3.0. In addition, a common reductant (hydroxylamine), transition metal ions and inorganic anions (Cl-, SO42- and HCO3-) did not affect the Br--catalyzed oxidation of ABTS for the measurement of PI concentration. Consequently, Br--ABTS is a feasible method to determine the concentration of PI.

Soft Sub-Structured Multi-Material Biosensor Hydrogels with Enzymes Retained by Plant Viral Scaffolds.

An all-soft multi-material combination consisting of a hydrogel based on poly(ethylene glycol) (PEG) coated with spatially defined spots of gelatin methacryloyl (GM) containing selectively addressable viral nanorods is presented, and its basic application as a qualitative biosensor with reporter enzymes displayed on the tobacco mosaic virus (TMV) bioscaffolds within the GM is demonstrated. Biologically inert PEG supports are equipped with GM spots serving as biological matrix for enzymes clustered on TMV particles preventing diffusion out of the gel. For this multi-material combination, i) the PEG-based hydrogel surface is modified to achieve a clear boundary between coated and non-coated regions by introducing either isothiouronium or thiol groups. ii) Cross-linking of the GM spots is studied to achieve anchoring to the hydrogel surface. iii) The enzymes horseradish peroxidase or penicillinase (Pen) are conjugated to TMV and integrated into the GM matrix. In contrast to free enzymes, enzyme-decorated TMVs persist in GM spots and show sustained enzyme activity as evidenced by specific color reaction after 7 days of washing, and for Pen after 22 months after dry storage. Therefore, the integration of enzyme-coupled TMV into hydrogel matrices is a promising and versatile approach to obtaining reusable and analyte-specific sensor components.

Nanomesh‐YOLO: Intelligent Colorimetry E‐Skin Based on Nanomesh and Deep Learning Object Detection Algorithm

AbstractPerspiration is an important physiological process that maintains thermal homeostasis and water–salt balance. However, the collection and analysis of perspiration currently rely on microfluidic technology and colorimetric assays. The complexity and high cost of fabricating microfluidic channels and the insecurity of chemical reagents for color reactions should be optimized. In this work, a colorimetry electronic skin (e‐skin) for intelligent perspiration monitoring has been realized. The colorimetry e‐skin system consists of the polyurethane (PU) nanomesh and the object detection algorithm You Only Look Once version 3 (YOLOv3). Due to the 44% porosity of the PU nanomesh and capillary action, the low‐cost PU nanomesh (<1 cent) can be used as the colorimetric indicator. The volume of the PU nanomesh expands to 362.37% as a result of perspiration being absorbed and changes the optical transmittance (up to 277.78%). A finite element model based on capillary action has been proposed to explain the change in optical transmittance. Finally, a database containing 735 images has been built, and the object detection algorithm YOLOv3 is used to analyze the perspiration absorbed by the PU nanomesh. The detection results can identify the perspiration volume with a high accuracy of 97%. These results show that this work has great potential in healthcare field.

Phytochemical study and characterization of the fixed oil, extracted from the fruits of Gardenia ternifolia

This present study concerns the phytochemical study and the characterization of the fixed oil of the fruits of Gardenia ternifolia which is a plant recognized in several African pharmacopoeias for its therapeutic virtues. Its fruits, leaves and roots are used for the treatment of several infections. Thus, the overall objective of this study is to contribute to the valorization of Gardenia ternifolia fruits in phytomedicine and agri-food. Phytochemical screening is carried out using standard methods, based on coloring and precipitation reactions. The extraction of the fixed oil was done using a Soxhlet, providing an estimated yield of 3%. The evaluation of the chemical parameters of this oil according to the AFNOR standards (French Association for Standardization) made it possible to obtain the following results: iodine index (𝐼𝐼) = 5.6 ± 0.07 𝑔𝐼 /100 𝑔𝑐𝑔; acid value (𝐼𝐴) = 137.2 ± 0.001 𝑚𝑔𝐾𝑂𝐻/𝑔𝑐𝑔; saponification index (𝐼𝑆) = 201.6 ± 0.04 𝑚𝑔𝐾𝑂𝐻/𝑔𝑐𝑔; peroxide index (𝐼𝑃) = 8.4 ± 0.03 𝜇𝑔𝑂2/𝑔𝑐𝑔 and ester index (𝐼𝐸) = 64.4 ± 0.039 𝑚𝑔𝐾𝑂𝐻/𝑔𝑐𝑔. Ultimately, with much higher extraction quantities, the fruit oil of Gardenia ternifolia can present an interesting and valuable pharmaco-nutritional potential in the food industry and in pharmacology.

Rapid colorimetric and fluorescence identification of Pinelliae Rhizoma and adulterate Rhizoma Typhonii Flagelliformis using direct-LAMP assay

Pinelliae Rhizoma, renowned for its medicinal benefits against cough, insomnia and inflammation, is frequently utilized in botanical dietary supplements and herbal products. However, due to high demand, there is a risk of adulteration. This study introduced Direct-Loop-Mediated Isothermal Amplification (Direct-LAMP), a rapid colorimetric technique, for distinguishing Pinelliae Rhizoma from its primary adulterant, Rhizoma Typhonii Flagelliformis. This method comprises three parts: DNA extraction-free direct lysis, isothermal amplification and prompt color development. The direct lysis process allows for release of genomic DNA within 2 min. The isothermal amplification reaction exhibits excellent analytical performance, detecting Pinelliae Rhizoma at levels as low as 0.1 pg and Rhizoma Typhonii Flagelliformis at 0.08 ng, while also demonstrating good linearity across a wide range, making it suitable for quantitative analysis. Two different color reagents are employed for these two different plant materials, resulting in dual-color changes for captivating visual detection. The developed direct-LAMP was also successfully validated across 48 actual samples.

Phenolic compounds profile of macerates of different edible parts of carob tree (Ceratonia siliqua L.) using UPLC-ESI-Q-TOF-MSE: Phytochemical screening and biological activities

Locust bean pulp and gum extracts were prepared, and phytochemical tests based on color reactions and chromatographic analyzes were performed. A profile of seventy-six phenolic compounds was obtained by the ultra-high performance liquid chromatography with electrospray ionization and quadrupole time-of-flight mass spectrometry. The main groups of phenolic compounds identified in the both extracts of Ceratonia siliqua L., were flavonoids, tannins and phenolic acids.Moreover, carob pulp and gum extracts were tested for their antimicrobial activity using disk diffusion tests which showed sensitivity of the different strains to the analyzed extracts at a concentration of 100 mg/mL. Additionally, the antioxidant activity of Ceratonia siliqua L. extracts was assessed by the 2,2-diphenyl-1-picrylhydrazyl acid test, which confirmed stronger antioxidant properties in the case of the pulp extract.To sum up, carob pulp and gum extracts present promising alternatives to synthetic additives within the medicinal industry, serving as potential antioxidant agents and preservatives that combat bacterial contamination, thereby offering a more natural approach to enhancing product safety and efficacy.

PHYTOCHEMICAL ANALYSIS AND ANTIOXIDANT ACTIVITY OF EXTRACTS OF PLANTS OF THE GENUS VITEX L. (LAMIACEAE)

A comparative phytochemical study of selected species of the genus Vitex L. (Lamiaceae) (V. agnus-castus, V. canescens, V. negundo, V. tripinnata) from the flora of Russia and Vietnam out was carried. The largest amount of extractive compounds was obtained from the leaves of V. agnus-castus when extracted with 60 % ethanol. Color reactions with Trim Hill and Stahl reagents, as well as thin-layer chromatography data, showed a high content of iridoids in extracts of leaves of V. agnus-castus and V. negundo and their low content (or absence) in V. tripinnata and V. canescens leaf extracts. The greatest amount of polyphenols and flavonoids is contained in the extract of the leaves of V. agnus-castus. The smaller amount of polyphenols is found in the leaves of V. canescens, and least amount of flavonoids is found in the leaves of V. tripinnata. All Vitex samples studied are characterized by an increased content of essential trace elements – iron, copper and zinc, and the leaves of V. tripinnata are also high in cobalt. High antiradical activity of all leaf samples of Vitex species was established. The relationship between the content of secondary metabolites and the position of species on the molecular phylogenetic tree of the genus Vitex is shown, which makes it possible to develop a chemotaxonomic forecast for search species of this genus with an increased content of biologically active compounds of a certain class (iridoids, polyphenols, phytoecdysteroids) for further pharmacological studies.

SKRINING FITOKIMIA INFUSA DAUN SUNGKAI (Peronema canescens Jack.) DENGAN METODE REAKSI WARNA

Sungkai (Peronema canescens Jack) was used traditionally as a medicine to help relieve fever, malaria and flu. In general, people was used sungkai leaves in the form as infusion. This study was aimed to screening of secondary metabolite of Sungkai leaf infusion using the color reaction method. The sample in this study was sungkai leaf that obtained from Bengkulu city. The infusion was obtained by boiling 10 gram of sungkai leaf simplicia with 100 ml of distilled water for 15 minutes at 90 0C until a concentration of 10% (w/v) was obtained. Secondary metabolite screening was carried out using the color reaction method to identify alkaloids, flavonoids, saponins, tannins and steroids. Phytochemical screening using specific reagents with the test was repeated three times. The results were showed that sungkai leaves infusion was positive in alkaloid test as evidenced by the presence of white precipitate with Mayer reagent, brown precipitate with Wagner reagent, and orange precipitate with Dragendorff reagent. Positive results were also shown in flavonoid, saponin and tannin tests. While, negative result was seen in steroid test using Liebermann Burchard reagent. In this study it can be concluded that sungkai leaf infusion positively contains alkaloids, flavonoids, saponins and tannins.

Phytochemical screening and evaluation of antiradical and antibacterial activities of stem and root barks of Gardenia ternifolia Schumach. (Rubiaceae): A plant traditionally used in northern Côte d'Ivoire

Gardenia ternifolia is an Ivorian plant species used to treat tooth decay, hemorrhoidal crises, leprosy, skin diseases and rheumatism. The present study is based on phytochemical screening and evaluation of the antiradical and antibacterial activities of aqueous, hydroethanolic and ethanolic extracts of G. ternifolia stem and root barks. Phytochemical screening of secondary metabolites was carried out using tube color reaction methods and Thin Layer Chromatography (TLC). Phytochemical screening revealed the presence of polyphenols (flavonoids, coumarins, tannins), saponins, steroids and terpenoids in G. ternifolia stem and root extracts. Phenolic acids were revealed only in stems, while alkaloids were absent in both organs studied. Anti-radical activities were highlighted in both organs by qualitative and quantitative methods with respect to the DPPH free radical. However, quantitative spectrophotometric analysis showed better antioxidant activity in stems than in roots. Antibacterial activity assessed against 05 bacterial strains using the solid-medium diffusion and liquid-medium dilution methods showed that only the aqueous and ethanolic extracts of G. ternifolia stems were absolutely bactericidal against the Staphylococcus aureus strains tested (S.a ATCC 29213, S.a 06 UB/22 and S.a 27 UB/22). The results obtained could give the stems the ability to treat infections caused by S. aureus bacteria.

A specific purple–blue color reaction between tryptophan and tyrosine in concentrated acidic medium

Electron transfer between tryptophan (Trp) and tyrosine (Tyr) is often accompanied with transient emission of visible blue-purple light, which is very common in numerous laser-induced photolysis experiments. However, recent experiments have shown that in the absence of pulse radiolysis, by mixing Trp and Tyr in concentrated aqueous hydrochloric acid can also produce a blue–purple color as it was observed in photolysis experiments. Unexpectedly, this color is quite stable in strong acid media (it can be kept at room temperature for at least a week). It is proposed that after initial formation of Trp radical products (TrpH▪+/Trp▪) by the solvent radical oxidation, charge-transfer complexes were generated via electron transfer reactions between Trp radical products and phenol of Tyr or their directly hole-trapping mechanism, which exhibit a blue-purple color. In this work, HPLC analysis and density functional calculations show that there are loosely reversible associations in the charge-transfer complexes which can be stabilized by strong hydrogen bonding. A Trp radicals signal was observed but the intensity was not so strong as expected. This color reaction exhibits high selectivity towards Trp and Tyr, and thus it can be a convenient method for naked-eye identifying the coexistence of these two amino acids or protein modifications of related to them.

Peroxidase-like activity of microrocket for efficient and directional glutathione detection

Glutathione (GSH) is an important reducing molecule in organisms, and its abnormal levels are closely related to certain diseases. Thus, developing a fast and simple strategy to detect GSH, especially in complex channels such as blood vessels, is of great significance for disease prevention and diagnosis. In this work, a novel peroxidase-like catalytic activity tubular microrocket (FeOx/Pt/PEDOT) with efficient propulsion and steerable motion has been successfully developed for GSH detection. The microrocket fueled by H2O2 exhibits strong propulsion for solution self-stirring and effective reactive oxygen species (ROS) generation to GSH color reaction. Combining these advantages, the catalytically propelled microrocket-treated sample can greatly shorten a half time of detecting reactions and realize efficient GSH detection. In addition, the microrocket shows effective directional detection of GSH in a designed complex channel due to its excellent magnetically navigation, which is of great significance in GSH detection in the microenvironment. This attractive catalytic microrocket has strong propulsion, effective direction control and excellent GSH detection performance, which shows great potential in biodetection and biomedical applications, especially in visual detection of vessels microenvironment.

Identifikasi Sakarin Dalam Sediaan Jamu Instan Beras Kencur Yang Beredar Di Pasar Gede Kota

Saccharin is a synthetic chemical substance that is classified as a food or beverage additive. Excessive consumption of saccharin can cause side effects, including migraines and headaches, memory loss, confusion, insomnia, irritation, asthma, hypertension, diarrhea, stomach pain, allergies, impotence and sexual disorders, baldness, and brain and bladder cancer. The purpose of this study was to identify saccharin in beras kencur instant herbal preparations circulating in Pasar Gede, Surakarta. This research was conducted to determine the content of saccharin in instant herbal medicine using the color reaction method, Thin Layer Chromatography (TLC) and FTIR Spectroscopy. This research is an experimental descriptive research. The results of this study were 10 samples of instant herbal beras kencur MF, JM, SPA, IE, MR, BK, SP, BC, AG on the color reaction test, the negative TLC test contained saccharin. The FTIR spectral profile contains functional groups in the standard saccharin N-H (Stretching) secondary amine, C-H aromatic, C=O (stretching) carbonyl, C=C (stretching) cyclic aromatic, S=O sulfoksida, C-N (stretching) amine, C-H (bending) 1,2- substituted benzene (ortho) with wave numbers respectively 3402.68 cm-1, 3093.74 cm-1, 1718.84 cm-1, 1592.92 cm-1, 1358.84 cm-1, 1054.60 cm-1, 758.43 cm-1 which is in accordance with the literature. From the results of the analysis, it can be concluded that of the 10 samples of instant herbal medicine, beras kencur that was examined tested negative for the artificial sweetener saccharin. This shows that the beras kencur instant herbal medicine in market is safe for public

Some properties of fruit juice produced by black raisins by traditional methods in Erbil region and changes during storage

Grape (Vitis vinifera) is one of the most grown fruits in Iraq and is evaluated in different ways. This study aimed to determine some properties of the fruit juice that is traditionally produced from dried black grapes in the Erbil region and consumed directly, to make it durable by various methods, as well as to examine the changes that may occur during storage. For this purpose, some of the grape juices were pasteurized and the other part was stored using Na-benzoate in 500 ml glass bottles, at room temperature, under dark and light conditions for 6 months. In the stored products, pH, acidity, total dry matter, soluble dry matter, ash, color, total antioxidant (DPPH), Hydroxymethylfurfural (HMF) and browning reaction and total phenolic substance (folin-ciocalteu) analyzes as well as sensory evaluations were made periodically. As a result of the statistical evaluations, There is no difference between the applications in terms of color, but there is a slight decrease in the L value after the 4th month, depending on the storage period, while the pasteurized samples show higher values in terms of HMF and browning levels, the browning levels increase significantly in all samples after the 2nd month, and TFM values were decreased. It has been determined that all products are highly appreciated in terms of sensory properties, pasteurized samples are more appreciated, and the storage time does not have a significant effect on the sensory properties of the samples. In addition, it has been determined that beverages can be easily stored for a long time at room temperature with or without the addition of preservatives, only by pasteurization, and such a product will be in demand.

Elucidating the effects on polyphenol oxidase activity and allelic variation of polyphenol oxidase genes on dough and whole wheat-derived product color parameters

ABSTRACT Polyphenol oxidase (PPO) activity is a primary cause of the development of unattractive dark brown discoloration of wheat-based end products. The present study aims to evaluate a set of 41 diverse wheat genotypes grown at three different locations in India for grain phenol color reaction, PPO activity and molecular marker-based characterization of alleles of PPO genes. Relationships among these parameters were analyzed along with the effects of grain PPO activity on dough and chapati color at different time intervals. The mean PPO activity ranged from 7.42 to 27.57 min−1 g−1 10−3 among the genotypes and it showed a significant negative correlation with color brightness (L*) of dough rested for 0 min (r = -0.406), 15 min (r = -0.406), 2 h (r = -0.502) and 4 h (r = -0.551) and whole wheat flour-derived chapati rested for 2 h (r = -0.267) and 4 h (r = -0.424). The overall quality color score was negatively correlated with PPO activity (r = -0.863) and showed a positive correlation with both dough and chapati visual color measured at different time intervals. PPO activity in the genotypes carrying different alleles was found to be Ppo-A1a>Ppo-A1b; Ppo-B2d>Ppo-B2a; and Ppo-D1b>Ppo-D1a. The allelic constitution Ppo-A1bPpo-B2aPpo-D1a and Ppo-A1bPpo-B2dPpo-D1 was found to produce the lowest PPO activity, and thus these alleles are recommended to be used in marker assisted breeding for low PPO activity genotypes to minimize the discoloration of wheat-based end-products.

Sensitive and Direct Analysis of Pseudomonas aeruginosa through Self-Primer-Assisted Chain Extension and CRISPR-Cas12a-Based Color Reaction.

Pseudomonas aeruginosa (P. aeruginosa) is a common opportunistic Gram-negative pathogen that may cause infections to immunocompromised patients. However, sensitive and reliable analysis of P. aeruginosa remains a huge challenge. In this method, target recognition assists the formation of a self-primer and initiates single-stranded chain production. The produced single-stranded DNA chain is identified by CRISPR-Cas12a, and consequently, the trans-cleavage activity of the Cas12a enzyme is activated to parallelly digest Ag+ aptamer sequences that are chelated with silver ions (Ag+). The released Ag+ reacted with 3,3',5,5'-tetramethylbenzidine (TMB) for coloring. Compared with the traditional color developing strategies, which mainly rely on the DNA hybridization, the color developing strategy in this approach exhibits a higher efficiency due to the robust trans-cleavage activity of the Cas12a enzyme. Consequently, the method shows a low limit of detection of a wide detection of 5 orders of magnitudes and a low limit of detection of 21 cfu/mL, holding a promising prospect in early diagnosis of infections. Herein, we develop a sensitive and reliable method for direct and colorimetric detection of P. aeruginosa by integrating self-primer-assisted chain production and CRISPR-Cas12a-based color reaction and believe that the established approach will facilitate the development of bacteria-analyzing sensors.

Phytochemical screening, total phenolic content and antioxidant activities of Marrubium vulgare L. collected in three development stages

The change of phenolic compounds and antioxidant activities of plants extracts are widely attributed to numerous conditions and parameters viz. geographical conditions, type of extraction, and type of extract. Thus, this study was the first one conducted to evaluate the phenolic composition, the content of total polyphenols, flavonoids, and proanthocyanidins, and the antioxidant activities of methanolic extract of M. vulgare aerial part collected in three development stages (before flowering, during flowering, and after flowering periods). Phytochemical screening was carried out using standard methods of precipitation and coloration reactions. The total polyphenol, flavonoid, and proanthocyanidins contents were determined using the Folin-Ciocalteu method, aluminum chloride colorimetric method, and vanillin method, respectively. The antioxidant activity was assessed by two methods: DPPH and ABTS scavenging activity. Preliminarily phytochemical screening revealed the presence of saponins, essential oil, cardiac glucosides, sterols and triterpenes, and the absence of alkaloids. In addition, tannins were absence in March and present in May and July. The total phenol content of M. vulgare extracts showed a highest flavonoid and proanthocyanidin contents during flowering period (1.644 mg QE.g-1 extract, and 0.195 mg CE.g-1 extract, respectively) while polyphenol content was highest before flowering period (0.043 mg GAE.g-1 extract). Afterward, M. vulgare methanolic extract exhibited a potent antioxidant activity during flowering period with an IC50 value of 2.23 mg.ml-1. From the current study, this plant contains natural antioxidant substances which can be used as antioxidant agents to treat several diseases.

New and rapid visual detection assay for Trogoderma granarium Everts based on recombinase polymerase amplification and CRISPR/Cas12a.

Khapra beetle (Trogoderma granarium Everts), one of the most important quarantine pests globally, is capable of causing severe infestation and huge economic loss to stored grain, and its interception rate has increased in major global trade countries over the past few years. However, difficulties remain in distinguishing this species with similar ones. In order to assist border ports and warehouses in khapra beetle's effective rapid identification as well as pest control at the early stages of monitoring or interception, we herein developed a new and rapid visual detection assay for T. granarium based on recombinase polymerase amplification (RPA) and CRISPR/Cas12a system. We designed and selected the first khapra beetle-specific RPA primers and crRNA, and optimized the visualization reaction system (Cas12a/CrRNA=100 nM/500 nM). With only a 37°C-heat-source and a blue light torch, RPA and CRISPR/CAS12a-based visualization assays can be completed within 40 min to differentiate among khapra beetle and other nine similar Dermestidae species. After DNA extraction using a kit (4-5 h) or a simple method (5 min), the specific amplicons were obtained after a 15 min-RPA-reaction at 37°C, followed by a 15 min-color-reaction under 37°C in dark using CRISPR/CAS12a system and a fluorescent probe (5'-FAM/3'-BHQ1 labeled). This method is ingenious to low levels of DNA (10-1 ng/μL) and meets the sensitivity requirements for detecting a single khapra beetle's egg (about 0.7 mm). Our specificity and sensitivity analysis inferred that the present visualization system is effective to quickly and uniquely detect khapra beetle at room temperature (37°C), thereby preventing this species before they spread widely. Our study is suitable for being pushed forward in storage pest management and provides value as a reference for monitoring and identification of other pests. This article is protected by copyright. All rights reserved.

Effect of MoS2-PEG nanozymes on tumor cell multiplication

Molybdenum disulfide (MoS2), as a nanozyme, can effectively kill tumor cells by catalyzing H2O2 to produce extremely poisonous hydroxyl radical (*OH). In this work, spherical MoS2-PEG nanozymes were prepared by hydrothermal synthesis under the modification of polyethylene glycol (PEG). Firstly, XRD, XPS, SEM, TEM, and BET were used to analyze the phase, morphology, oxidation state, and distribution of each element of nanozyme. Secondly, the determination and verification of *OH as the main reactive oxygen species (ROS) in the MoS2-PEG nanozyme catalyzed Fenton reaction based on 3,3′,5,5′-tetramethyldiphenylamine (TMB) color reaction and electron spin resonance (ESR). Interestingly, MoS2-PEG nanozymes exhibited cytostatic rates of 43.9 % and 47.2 % in vitro in mouse breast cancer cell (4 T1) and mouse glioma cell (GL261) tumor cell models. In mouse fibroblast (L929) models, MoS2-PEG nanozymes showed excellent cytocompatibility and safety. Therefore, MoS2-PEG nanozyme may serve as an impactful drug to inhibit cancer cell growth.

2D nanoplate-shaped CaCo2O4 spinel as an oxidase nanozyme for the colorimetric sensing of sodium dodecyl benzene sulfonate under nearly neutral pH

Nanozymes are outstanding candidates of natural enzymes and have been aroused lasting interest. However, the development of oxidase mimics with highly and robust catalytic activity is still a challenge. Also, the activity of most nanozymes were restricted by pH condition, significantly limiting their extensive applications. Here, the spinel CaCo2O4 nanoplates with high oxidase-mimicking activity at nearly neutral pH were prepared by a simple hydrothermal-calcination method. Relative to the Co3O4 and CaO, the spinel CaCo2O4 exhibited lower electron transfer resistance and enhanced electron transfer rate. This endows the CaCo2O4 to maintain superior catalytic activity even in neutral pH condition (pH = 6.5). The oxidase-like activity of CaCo2O4 is 17.0-fold and 31.5-fold times that of Co3O4 and CaO, respectively. CaCo2O4 exhibited good affinity to TMB with a Km of 0.111 mM and Vmax value of 1.34 × 10−7 M·S−1. Based on the inhibition effect of sodium dodecyl benzene sulfonate (SDBS) on the TMB/CaCo2O4 color reaction, a colorimetric platform for the SDBS detection has been developed under nearly neutral pH. The linear range for SDBS determination was 0.2–70.0 μM, with a detection limit of 0.12 μM (3σ). The TMB/CaCo2O4 system was successfully applied to the determination of SDBS in real water samples. This work provided a new strategy to design spinel oxide-based high activity nanozyme at neutral pH media for colorimetric sensing of pollutant.

Evaluation of xanthine oxidase inhibitory activity of sinapyl alcohol diacetate and stigmasterol compounds and phytochemical screening stem of Etlingera rubroloba A.D Poulsen

Etlingera rubroloba A.D Poulsen is a genus Etlingera found in Southeast Sulawesi. This plant is widely used in local communities to relieve joint pain and increase stamina. Previous researchers isolated and identified this plant to obtain the compounds sinapyl alcohol diacetate and stigmasterol. However, these two compounds have never been reported on the Xanthine Oxidase (XO) inhibitory activity in vitro. The results of phytochemical screening have also not been reported in this plant. Therefore, in this study, a phytochemical screening test was conducted using colour reagents, and an in vitro test for XO inhibitory activity was carried out using the XO Kit. The results showed that E. rubroloba contains secondary metabolites of flavonoids, alkaloids, tannins, saponins, terpenoids, and the value of the percent XO inhibitory activity at a concentration of 320 µg/mL, namely sinapyl alcohol diacetate 85.52%, stigmasterol 90.42%, and allopurinol 97.63%, as a positive control. This research will be a reference in the development of antihyperuricemia medicine of nature.