Disposable biosensor based on nanodiamond particles, ionic liquid and poly-l-lysine for determination of phenolic compounds.

This study describes the development of a highly sensitive amperometric biosensor for the analysis of phenolic compounds such as catechol. The biosensor architecture is based on the immobilization of tyrosinase (Tyr) on a screen-printed carbon electrode (SPE) modified with nanodiamond particles (ND), 1-butyl-3-methylimidazolium hexafluorophosphate (IL) and poly-l-lysine (PLL). Surface morphologies of the electrodes during the modification process were evaluated by scanning electron microscopy (SEM) and energy-dispersive X-ray spectroscopy (EDX). Cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) were used to investigate the electrochemical characteristics of the modified electrodes. Owing to the synergistic effect of the modification materials, the Tyr/PLL/ND-IL/SPE exhibited high sensitivity (328.2 µA mM-1) towards catechol with a wide linear range (5.0 × 10-8 - 1.2 × 10-5 M) and low detection limit (1.1 × 10-8 M). Furthermore, the method demonstrated good reproducibility and stability. The amperometric response of the biosensor towards other phenolic compounds such as bisphenol A, phenol, p-nitrophenol, m-cresol, p-cresol and o-cresol was also investigated. The analytical applicability of the biosensor was tested by the analysis of catechol in tap water. The results of the tap water analysis showed that the Tyr/PLL/ND-IL/SPE can be used as a practical and effective method for catechol determination.

Microbial synthesis of antimony sulfide to prepare catechol and hydroquinone electrochemical sensor by pyrolysis and carbonization.

The application of antimony sulfide sensors, characterized by their exceptional stability and selectivity, is of emerging interest in detection research, and the integration of graphitized carbon materials is expected to further enhance their electrochemical performance. This study represents a pioneering effort in the synthesis of carbon-doped antimony sulfide materials through the pyrolysis of the mixture of microorganisms and their synthetic antimony sulfide. The prepared materials are subsequently applied to electrochemical sensors for monitoring the highly toxic compounds catechol (CC) and hydroquinone (HQ) in the environment. Via cyclic voltammetry (CV) and impedance testing, we concluded that the pyrolytic product at 700 °C (Sb-700) demonstrated the best electrochemical properties. Differential pulse voltammetry (DPV) revealed impressive separation when utilizing Sb-700/GCE for simultaneous detection of CC and HQ, exhibiting good linearity within the concentration range of 0.1-140 µM. The achieved sensitivities of 24.62 µA µM-1 cm-2 and 22.10 µA µM-1 cm-2 surpassed those of most CC and HQ electrochemical sensors. Meanwhile, the detection limits for CC and HQ were as low as 0.18 µM and 0.16 µM (S/N = 3), respectively. Additional tests confirmed the good selectivity, reproducibility, and long-term stability of Sb-700/GCE, which was effective in detecting CC and HQ in tap water and river water, with recovery rates of 100.7%-104.5% and 96.5%-101.4%, respectively. It provides a method that combines green microbial synthesis and simple pyrolysis for the preparation of electrode materials in CC and HQ electrochemical sensors, and also offers a new perspective for the application of microbial synthesized materials.

Storage Conditions Influence the Quality of Ginger - A Stability Study Inspired by Clinical Trials.

Ginger has traditionally been used to treat and prevent nausea and vomiting; however, the results of clinical trials are ambiguous. The efficacy of ginger is attributed to gingerols and their metabolites, shogaols. Since these compounds have different pharmacological profiles, the clinical efficacy of ginger products is largely dependent on their chemical composition. The goal of our study was to examine the stability of ginger, determining the 6-gingerol contents in order to assess the effects of different storage conditions. We have performed a 6-month stability test with dry ginger rhizome samples stored in a constant climate chamber in three different storage containers (uncovered glass container, glass container sealed with rubber stopper, and plastic container). The 6-gingerol contents were measured by HPLC method. The concentration of 6-gingerol decreased in all samples. In the sealed glass container, the decrease in 6-gingerol content was significantly lower than in the unsealed glass container and in the plastic container. These results demonstrate that storage conditions have a significant impact on the quality of ginger, which may also affect efficacy.

Red-emitting 4-methyl coumarin fused barbituric acid as an electrochemical sensor for catechol detection and probe for latent fingerprints.

Herein, we have reported a red-emitting 4-methyl coumarin fused barbituric acid azo dye (4-MCBA) synthesized by conventional method. Density functional theory (DFT) studies of tautomer compounds were done using (B3LYP) with a basis set of 6-31G(d,p). NLO analysis has shown that tautomer has mean first-order hyperpolarisabilities (ß) value of 1.8188 × 10-30 esu and 1.0470 × 10-30 esu for azo and hydrazone forms, respectively, which is approximately nine and five times greater than the magnitude of urea. 4-MCBA exhibited two absorption peaks in the range of 290-317 and 379-394 nm, and emission spectra were observed at 536 nm. CV study demonstrated that the modified 4-MCBA/MGC electrode exhibited excellent electrochemical sensitivity towards the detection of catechol and the detection limit is 9.39 µM under optimum conditions. The 4-MCBA employed as a fluorescent probe for the visualisation of LFPs on various surfaces exhibited Level-I to level-II LFPs, with low background interference.

Simultaneous Electrochemical Detection of Catechol and Hydroquinone Based on a Carbon Nanotube Paste Electrode Modified with Electro-Reduced Graphene Oxide.

Effectively detecting catechol (CC) and hydroquinone (HQ) simultaneously is crucial for environmental protection and human health monitoring. In the study presented herein, a novel electrochemical sensor for the sensitive simultaneous detection of CC and HQ was constructed based on an electrochemically reduced graphene oxide (ERGO)-modified multi-walled carbon nanotube paste electrode (MWCNTPE). Scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy and electrochemical techniques were utilized to characterize the sensing interface and investigate the sensing mechanism. Under the optimal detection conditions, the oxidation peak currents of CC and HQ show a good linear relationship with their concentrations in the range of 0.4-400 µM with a detection limit of 0.083 µM for CC and 0.028 µM for HQ (S/N = 3). Moreover, the sensor exhibits good performance and can be applied successfully in the simultaneous detection of CC and HQ in tap water samples and urine samples with satisfactory results, indicating its promising application prospects.

Purification and Biochemical Characterization of Polyphenol Oxidase Extracted from Wheat Bran (Wan grano).

Currently, little is known about the characteristics of polyphenol oxidase from wheat bran, which is closely linked to the browning of wheat product. The wheat PPO was purified by ammonium sulfate precipitation, DEAE-Sepharose ion-exchange column, and Superdex G-75 chromatography column. Purified wheat PPO activity was 11.05-fold higher, its specific activity was 1365.12 U/mg, and its yield was 8.46%. SDS-PAGE showed that the molecular weight of wheat PPO was approximately 21 kDa. Its optimal pH and temperature were 6.5 and 35 °C for catechol as substrate, respectively. Twelve phenolic substrates from wheat and green tea were used for analyzing the substrate specificity. Wheat PPO showed the highest affinity to catechol due to its maximum Vmax (517.55 U·mL-1·min-1) and low Km (6.36 mM) values. Docking analysis revealed strong affinities between catechol, gallic acid, EGCG, and EC with binding energies of -5.28 kcal/mol, -4.65 kcal/mol, -4.21 kcal/mol, and -5.62 kcal/mol, respectively, for PPO. Sodium sulfite, ascorbic acid, and sodium bisulfite dramatically inhibited wheat PPO activity. Cu2+ and Ca2+ at 10 mM were considered potent activators and inhibitors for wheat PPO, respectively. This report provides a theoretical basis for controlling the enzymatic browning of wheat products fortified with green tea.

6-Gingerol contents of several ginger varieties of Northeast India and correlation of their antioxidant activity in respect to phenolics and flavonoids contents.

INTRODUCTION: Ginger constitutes the rhizome part of the plant Zingiber officinale from the Zingiberaceae family. A large number of ginger varieties with high sensorial and functional quality are found in Northeast India. Hence, phytopharmacological screening of different ginger varieties is essential that will serve as a guideline in applied research to develop high-end products and improve economical margins. OBJECTIVE: To determine the variation in total phenolics content (TPC), total flavonoids content (TFC), and antioxidant activities and correlate that with 6-gingerol contents of different ginger varieties collected from Northeast India using Pearson's correlation analysis. MATERIALS AND METHODS: The TPC and TFC values were determined using standard methods. Antioxidant activities were measured using the 2,2-diphenyl-1-picrylhydrazyl (DPPH) and hydroxyl radical scavenging assays, while reversed-phase high-performance liquid chromatography (RP-HPLC) analysis was utilised for quantitative determination of 6-gingerol content. RESULTS: The result revealed that ginger variety 6 (GV6) contains the highest 6-gingerol content and TPC value showing maximum antioxidant activity, followed by GV5, GV4, GV9, GV3, GV2, GV8, GV1, and GV7. The findings also suggested that the antioxidant activity has much better correlations with TPC as compared with TFC values. Pearson's correlation analysis showed a significant correlation between 6-gingerol contents and TPC values. CONCLUSION: This work underlines the importance of ginger varieties from Northeast India as a source of natural antioxidants with health benefits.

Inhibition of benzo[a]pyrene formation in charcoal-grilled pork sausages by ginger and its key compounds.

BACKGROUND: Ginger and its extracts have been frequently used in food processing and pharmaceuticals. However, the influence of ginger and its key compounds on benzo[a]pyrene (BaP) production in meat processing has not been investigated. The purpose of this study was to explore the effect of application of ginger and its important active ingredients on BaP formation and the mechanism of inhibiting BaP formation in charcoal-grilled pork sausages. RESULTS: The DPPH scavenging (23.59-59.67%) activity and the inhibition rate of BaP (42.1-68.9%) were significantly increased (P < 0.05) with increasing ginger addition. The active components extracted by supercritical carbon dioxide from ginger were identified by gas chromatography-mass spectrometry and 14 representative compounds (four terpenes, two alcohols, two aldehydes, four phenols and two other compounds, totaling 77.57% of the detected compounds) were selected. The phenolic compounds (eugenol, 6-gingerol, 6-paradol and 6-shogaol, accounting for 29.73% of the total composition) in ginger played a key role and had the strongest inhibitory effect on BaP (61.2-68.2%), whereas four other kinds of compound showed obviously feeble inhibitory activity (6.47-17.9%). Charcoal-grilled sausages with phenolic substances had lower values of thiobarbituric acid-reactive substances, carbonyl and diene (three classic indicators of lipid oxidation) (P < 0.05). CONCLUSION: Ginger and its key compounds could effectively inhibit the formation of BaP in charcoal-grilled pork sausages. Phenolic compounds make the strongest contribution to the inhibition of Bap formation, and the inhibitory mechanism was related to the inhibition of lipid oxidation. © 2023 Society of Chemical Industry.

New carbon black-based conductive filaments for the additive manufacture of improved electrochemical sensors by fused deposition modeling.

The development of a homemade carbon black composite filament with polylactic acid (CB-PLA) is reported. Optimized filaments containing 28.5% wt. of carbon black were obtained and employed in the 3D printing of improved electrochemical sensors by fused deposition modeling (FDM) technique. The fabricated filaments were used to construct a simple electrochemical system, which was explored for detecting catechol and hydroquinone in water samples and detecting hydrogen peroxide in milk. The determination of catechol and hydroquinone was successfully performed by differential pulse voltammetry, presenting LOD values of 0.02 and 0.22 µmol L-1, respectively, and recovery values ranging from 91.1 to 112% in tap water. Furthermore, the modification of CB-PLA electrodes with Prussian blue allowed the non-enzymatic amperometric detection of hydrogen peroxide at 0.0 V (vs. carbon black reference electrode) in milk samples, with a linear range between 5.0 and 350.0 mol L-1 and low limit of detection (1.03 µmol L-1). Thus, CB-PLA can be successfully applied as additively manufactured electrochemical sensors, and the easy filament manufacturing process allows for its exploration in a diversity of applications.

Qualitative analysis on chemical constituents from different polarity extracted fractions of the pulp and peel of ginger rhizomes by ultra-high-performance liquid chromatography coupled with electrospray ionization quadrupole time-of-flight tandem mass spectrometry.

RATIONALE: Ginger pulp is the dried rhizome scraped off the skin which originates from Zingiber officinale Rosc., a Zingiberaceae plant. Ginger peel is the dried rhizome skin of Zingiber officinale Rosc. (Zingiberaceae). The present work aims to investigate the different chemical constituents that are related to the medicinal properties of the ginger pulp and ginger peel. METHODS: A rapid ultra-high-performance liquid chromatography/electrospray ionization quadrupole time-of-flight tandem mass spectrometry (UHPLC/ESI-QTOF/MS) method was developed for qualitative analysis of the constituents in different polarity extracted fractions of the pulp and peel of ginger rhizomes. RESULTS: A total of 83 compounds were identified from the pulp and peel of ginger rhizomes, including 36 diarylheptanoids, 25 gingerols and 22 other compounds. Nine of these were new compounds. In total, 46, 27, 65 and 51 compounds were identified from the crude extract, petroleum ether, ethyl acetate, and n-butanol fractions of the ginger pulp, respectively, and 60, 30, 70 and 62 compounds were identified from the crude extract, petroleum ether, ethyl acetate, n-butanol fractions of the ginger peel, respectively. Each identified compound is marked on the corresponding chromatogram. CONCLUSIONS: The integrated method is sensitive and reliable for searching the different chemical constituents from different polarity extracted fractions of the ginger pulp and ginger peel. This work may provide a significant contribution to research into the medicinal properties of the ginger pulp and ginger peel.

Enhancing electrochemical sensing for catechol by biomimetic oxidase covalently functionalized graphene oxide.

Catechol level is an important indicator for evaluating the quality of tea. Therefore, the exploration of a simple and efficient quantitative detection method for catechol has an important significance. In this study, functionalized graphene oxide was synthesized by chemically modifying the surface of graphene oxide. The prepared carrier was covalently combined with biomimetic oxidase iron porphyrin (FePP, the active center of horseradish peroxidase). Ionic liquid as covalent coupling agents was designed as electronic bridge between biomimetic oxidase and graphene oxide. The novel biomimetic biosensor provided a detection range of 50.0-1600.0 µmol/L by modulating under the optimal conditions of the reaction system (FePP concentration is 1.5 × 10-3 mol/L, pH 3.0, Nafion solution dosage 1% and temperature 25 °C), the detection limit is 0.09 µmol/L. The biosensor has excellent stability, repeatability and reproducibility, and is expected to be applied to the rapid detection of catechol in actual tea sample..

Quality control and long-term stability study of ginger from different geographical origins using chemometrics.

BACKGROUND: Ginger rhizome (Zingiber officinale) is a well-known spice and medicinal plant that is widely used in the Egyptian market as a spice, flavor and medicinal herb for different diseases. Since it is not cultivated as rhizomes in Egypt, ginger is imported from other countries, which may impact its quality. In this study, UV spectroscopy and high-performance liquid chromatography (HPLC) were applied as efficient available techniques for the discrimination and quality control of ginger collected from different geographical origins in combination with chemometrics. In addition, HPLC was applied to investigate the stability of ginger samples upon storage for 3 years to trace the changes in their main active constituents. RESULTS: Data obtained from both UV and HPLC in combination with Principal Component Analysis (PCA) displayed proper discrimination of the samples according to their geographical origins. Regarding the stability study, ginger samples showed a significant decrease in quality after storage for 3 years, in which significant variation in the main pungent principles (6-, 8-, 10-gingerols and 6-shogaol) were observed. PCA failed to discriminate between ginger samples after long-time storage, so the applied model could discriminate between ginger samples before and after storage. CONCLUSION: UV and HPLC in combination with chemometrics can be applied as a successful tool for the study of quality, stability and geographical discrimination of ginger. © 2020 Society of Chemical Industry.

A rapid liquid chromatography/tandem mass spectrometry method for simultaneous determination of levodopa, carbidopa, entacapone and their six related compounds in film-coated tablets.

RATIONALE: A liquid chromatography/tandem mass spectrometry (LC/MS/MS) method has been developed and validated to determine levodopa, carbidopa, entacapone, and corresponding six related substances - levodopa impurity B, levodopa impurity C, methyldopa, methylcarbidopa, entacapone impurity C, and entacapone impurity A - in film-coated tablets for the first time. METHODS: Chromatographic separation was achieved with a gradient elution by using a C18 column, a mobile phase containing 0.5% formic acid in water and 0.5% formic acid in methanol. The mobile phase flow rate was 0.5 mL min-1 . The UV detector was set at 280 nm and the triple quadrupole mass spectrometer was used in multiple reaction monitoring (MRM) mode. RESULTS: The limit of detection (LOD) and limit of quantification (LOQ) results were 1.3 and 3.94 ng mL-1 for levodopa impurity B; 5.26 and 15.9 ng mL-1 for levodopa impurity C; 0.833 and 2.53 ng mL-1 for methyldopa; 3.31 and 10.0 ng mL-1 for methylcarbidopa; 1.67 and 5.06 ng mL-1 for entacapone impurity C; and 0.61 and 1.86 ng mL-1 for entacapone impurity A. CONCLUSIONS: The method was rapid, linear, accurate, and reproducible. The LC/MS/MS method that was developed to determine the related substances and assay of levodopa, carbidopa, and entacapone can be used to evaluate the quality of regular samples in the pharmaceutical industry. It can be also used to test the stability of samples.

Biosensors Platform Based on Chitosan/AuNPs/Phthalocyanine Composite Films for the Electrochemical Detection of Catechol. The Role of the Surface Structure.

Biosensor platforms consisting of layer by layer films combining materials with different functionalities have been developed and used to obtain improved catechol biosensors. Tyrosinase (Tyr) or laccase (Lac) were deposited onto LbL films formed by layers of a cationic linker (chitosan, CHI) alternating with layers of anionic electrocatalytic materials (sulfonated copper phthalocyanine, CuPcS or gold nanoparticles, AuNP). Films with different layer structures were successfully formed. Characterization of surface roughness and porosity was carried out using AFM. Electrochemical responses towards catechol showed that the LbL composites efficiently improved the electron transfer path between Tyr or Lac and the electrode surface, producing an increase in the intensity over the response in the absence of the LbL platform. LbL structures with higher roughness and pore size facilitated the diffusion of catechol, resulting in lower LODs. The [(CHI)-(AuNP)-(CHI)-(CuPcS)]2-Tyr showed an LOD of 8.55∙10-4 µM, which was one order of magnitude lower than the 9.55·10-3 µM obtained with [(CHI)-(CuPcS)-(CHI)-(AuNP)]2-Tyr, and two orders of magnitude lower than the obtained with other nanostructured platforms. It can be concluded that the combination of adequate materials with complementary activity and the control of the structure of the platform is an excellent strategy to obtain biosensors with improved performances.

From Graphite to Laccase Biofunctionalized Few-Layer Graphene: A "One Pot" Approach Using a Chimeric Enzyme.

A chimeric enzyme based on the genetic fusion of a laccase with a hydrophobin domain was employed to functionalize few-layer graphene, previously exfoliated from graphite in the presence of the hydrophobin. The as-produced, biofunctionalized few-layer graphene was characterized by electrochemistry and Raman spectroscopy, and finally employed in the biosensing of phenols such as catechol and dopamine. This strategy paves the way for the functionalization of nanomaterials by hydrophobin domains of chimeric enzymes and their use in a variety of electrochemical applications.

Colorimetric paper bioassay by horseradish peroxidase for the detection of catechol and resorcinol in aqueous samples.

Phenolic compounds such as catechol and resorcinol are toxic and persistent pollutants in the aqueous environment. Detection procedures such as chromatographic and spectrophotometric methods are time-consuming and require sophisticated instruments with skilled manpower. Development of a simple, cost effective, portable and disposable paper based biosensor could be a better alternative to the conventional methods. The present study attempted to develop a paper based biosensor by immobilizing horseradish peroxidase enzyme to detect catechol and resorcinol in aqueous samples. Horseradish peroxidase catalyzes the oxidation of phenolic compounds to semiquinones, which on reaction with a chromogen, 3-methyl 2-benzothiazolinone hydrazine (MBTH) gives faint pink to red color depending on the compound and its concentration in the sample is the basis for biosensing application. Different methods of enzyme immobilization on filter paper like physical adsorption, covalent coupling, and polysaccharide entrapment were executed. The performance of the various enzyme immobilization methods was evaluated by analyzing the developed color intensity using ImageJ software. Entrapment technique is the most effective method of immobilizing enzyme on the filter paper that produces the highest color intensity with better stability. The visible limit of detection (LoD) was observed as 0.45 mM (50 mg/L) for catechol and 0.09 mM (10 mg/L) for resorcinol in aqueous samples.

i-Propylammonium Lead Chloride Based Perovskite Photocatalysts for Depolymerization of Lignin Under UV Light.

Lignin depolymerization for the purpose of synthesizing aromatic molecules is a growing focus of research to find alternative energy sources. In current studies, the photocatalytic depolymerization of lignin has been investigated by two new iso-propylamine-based lead chloride perovskite nanomaterials (SK9 and SK10), synthesized by the facile hydrothermal method. Characterization was done by Powder X-Ray Diffraction (PXRD), Scanning Electron Microscopy (SEM), UV-Visible (UV-Vis), Photoluminescence (PL), and Fourier-Transform Infrared (FTIR) Spectroscopy and was used for the photocatalytic depolymerization of lignin under UV light. Lignin depolymerization was monitored by taking absorption spectra and catalytic paths studied by applying kinetic models. The %depolymerization was calculated for factors such as catalyst dose variation, initial concentration of lignin, and varying temperatures. Pseudo-second order was the best suited kinetic model, exhibiting a mechanism for lignin depolymerization that was chemically rate controlled. The activation energy (Ea) for the depolymerization reaction was found to be 15 kJ/mol, which is remarkably less than conventional depolymerization of the lignin, i.e., 59.75 kJ/mol, exhibiting significant catalytic efficiencies of synthesized perovskites. Products of lignin depolymerization obtained after photocatalytic activity at room temperature (20 °C) and at 90 °C were characterized by GC-MS analysis, indicating an increase in catalytic lignin depolymerization structural subunits into small monomeric functionalities at higher temperatures. Specifically, 2-methoxy-4-methylphenol (39%), benzene (17%), phenol (10%) and catechol (7%) were detected by GC-MS analysis of lignin depolymerization products.

Co-biodegradation studies of naphthalene and phenanthrene using bacterial consortium.

Degradation studies of phenanthrene and naphthalene as a mixture was carried out using a developed bacterial consortium. The isolates used in consortium were identified as Chryseobacterium sp., Sphingobacterium sp., Stenotrophomonas sp., Agromyces sp. and Pseudomonas sp. Limited work is done on genus Agromyces in degradation studies of PAHs. Catechol production was detected using Arnow's assay suggested that the pathway used for degradation is the meta-cleavage pathway. Results showed that Tween 80, as a surfactant, had maximum effect on the growth of isolates during PAH degradation. This suggests that use of Tween 80 as a surfactant enhanced the uptake of PAH by bacterial isolates during degradation. The study further revealed that, bacterial consortium was successfully utilized in the treatment of water contaminated with PAH in a laboratory-scale biofilm bioreactor. The bacterial consortium was able to degrade 99.9% of naphthalene and 92.9% of phenanthrene as a mixture at a high concentration of 2000 mg/L within 6 days. Further scaling up of the biofilm bioreactor can prove beneficial in large scale treatment of PAH contaminated water. This study showed promising results and these bacterial strains can be used as potential tools for bioremediation of PAH in contaminated sites.

Immobilization of tyrosinase on Fe3o4@Au core-shell nanoparticles as bio-probe for detection of dopamine, phenol and catechol.

An optical bio-probe based on the immobilized tyrosinase on the surface of Fe3O4@Au was described for the detection of dopamine, phenol and catechol. The prepared bio-probe (Fe3O4@Au@tyrosinase) was characterized by means such as TEM, SEM, VSM, DLS and TGA. In the presence of the bio-probe, the phenol, catechol and dopamine were converted to benzoquinone, o-quinone and dopaquinone, and the fluorescence spectra appeared at 308 nm, 329 nm and 336 nm with ex = 270 nm, respectively. However, by increasing the concentration of phenolic compounds in the bio-probe, the amount of products (benzoquinone, o-quinone and dopaquinone) was increased which was the reason for the increase in fluorescence intensity. Using this mechanism, a bio-probe was designed such that the intensity of the fluorescence spectra increased proportionally with the increase of the substrate concentrations after different time periods. The 0.003 mg/mL of tyrosinase was loaded on 1.65 mg/mL of the Fe3O4@Au. The highest performance for a bio-probe was demonstrated at room temperature and pH 6.8. By investigating the characteristics of the response of the bio-probe to different phenolic compounds, it was found that the bio-probe had a linear response in the concentration range 5.0-75.0 µM, 10.0-100.0 µM for phenol and dopamine and 50.0-500.0 M for catechol. The Michaelis-Menten constant (Km) of the bio-probe was calculated as 0.6 µM. Finally, the bio-probe seems to be stable and efficient even after about 2 months. A novel and easy method for the detection of dopamine, phenol and catechol by florescence that uses oxide capability to identify the phenolic compounds was introduced.

4-Ethylphenol, 4-ethylguaiacol and 4-ethylcatechol in red wines: Microbial formation, prevention, remediation and overview of analytical approaches.

The presence of 4-ethylphenol, 4-ethylguaiacol and 4-ethylcatechol in red wines affect negatively their aroma conferring horsy, barnyard, smoky and medicinal aromatic notes. These volatile phenols formed from free hydroxycinnamic acids and their ethyl esters by Dekkera/Brettanomyces yeasts, can contaminate wines. Their formation can cause serious negative economic impact to the wine industry worldwide as consumers tend to reject these wines. For these reasons various preventive and remedial treatments have been studied. This review summarises the wine microbial volatile phenols formation, preventive measures during winemaking and remedial treatments in finished wines along with their advantages and limitations for dealing with this sensory defect and impact on wine quality. Also it is important to control the levels of volatile phenols in wines using fast and convenient analytical methods namely with a detection limit below their olfactory perception threshold. The analytical methods available for quality control and performance characteristics as well their advantages and disadvantages when dealing with a complex matrix like wine are discussed in detail.