Antibrowning Agents Research Articles

7-(Diethylamino) coumarin-3-carboxylic acid as a novel antibrowning agent: Activity and mechanism

Browning caused by polyphenol oxidase (PPO) and microorganisms significantly impacts the nutritional quality of fruits and vegetables. This study identified 7-(Diethylamino) coumarin-3-carboxylic acid (7-DCCA) as an effective inhibitor of both PPO and bacteria. Enzyme assays revealed that 7-DCCA competitively inhibits PPO activity with an IC50 value of 0.275 ± 0.002 mM. Fluorescence and molecular simulation methods demonstrated that 7-DCCA forms a complex with PPO through hydrogen bonding and hydrophobic interactions, altering the enzyme's structure and reducing its activity. Thermogravimetric and differential scanning calorimetry (DSC) assays showed that 7-DCCA stabilizes PPO, delaying its thermal decomposition. Antibacterial tests proved that 7-DCCA inhibits Staphylococcus aureus and Escherichia coli by disrupting cell membranes. Additionally, 7-DCCA suppressed PPO and peroxidase activities, delaying phenolic oxidation and preventing browning in fruits and vegetables. Cytotoxicity assays confirmed its safety, with over 85 % cell viability at concentrations up to 0.1 mM. Stability experiments verified that 7-DCCA had greatly light and thermal stability. This study highlighted 7-DCCA as a promising antibrowning agent with potential application in food preservation.

Pengaruh Jenis dan Konsentrasi Anti-Browning Agent Terhadap Mutu Fisik Tepung Jewawut (Foxtail Millet)

The purpose of this research was to determine the effect of the type and concentration of anti-browning agents (sodium metabisulfit and citric acid) on the physical quality of millet flour, especially the degree of whitness and calor (lightness, redness, yellowness) and determine the best treatment. This study used experimental method. The reseach design used was a Completely Randomized Factorial Design (RALF) with two factors, namely faktor A was the type of anti-browning agent consisting two levels (sodium metabisulfite and citric acid), faktor B was concentration of the anti-browning agent consisting three levels (1,5%, 2%, 2,5%). Fromthe two factors, six treatments were obtained, and each treatment was repeated three times. Data were statistically analyzed using analysis of variance (ANOVA) and then continued with Duncan`s New Multiple Range Test (DNMRT) at 5% level. Results of the research showed that the type of anti-browning agent significantly affected the degree of whiteness, lightness, redness, and yellownes of millet flour. Concentrasion has a significant effect on the lightness value and redness value, but doesn’t have a significat effect on the degree of whitness and yellowness value. The interaction of the two factors (type and concentration) has a significant effect on the lightness value, redness value, and yellowness value, but has no significant effect on the degree of whitness. Based on the physical quality of millet flour produced in this study, namely the degree of whiteness, lightness, redness, and yellowness, the best treatment is sodium metabisulfite soaking.

Inhibitory potential of 7-hydroxycoumarin-3-carboxylic acid against tyrosinase and its effect on the preservation of fresh-sliced apples

Excessive tyrosinase expression leads to pigmented diseases in humans and browning in plants, necessitating effective tyrosinase inhibitors. This study investigated the inhibitory effect and mechanism of 7-hydroxycoumarin-3-carboxylic acid (7-HC-3-CA) on tyrosinase. Using UV–visible absorption spectroscopy, we found that 7-HC-3-CA effectively inhibited tyrosinase activity, with an IC50 value of 364 ± 1.3 μM. Enzyme kinetics, fluorescence methods and molecular simulation techniques revealed that 7-HC-3-CA acted as a reversible and competitive inhibitor, forming a stable complex with tyrosinase through hydrophobic interactions and hydrogen bonding. This altered the microenvironment of Tyr and Trp residues, causing the structural stretching and conformational changes that diminish catalytic activity.Preservation experiments demonstrated that 0.5 mM 7-HC-3-CA significantly reduced mass loss and decreased browning of fresh-sliced apples. It also lowered polyphenol oxidase activity from 0.22 to 0.18 and delayed phenolic oxidation, enhancing total phenolic content from 0.34 to 0.54, thereby controlling browning and extending storage life. Cell assays indicated that 0.5 mM 7-HC-3-CA had no significant impact on cell proliferation, with viability over 80 %. Acute toxicity tests proved that 0.5 mM of 7-HC-3-CA is completely non-lethal to KM mice. In conclusion, this study confirmed 7-HC-3-CA was a viable and safe antibrowning agent and revealed its potential application in the field of food preservation.

Development of Ready to Drink Banana Pseudostem Beverage Incorporated with Pineapple and Grape Extract

Background: Banana pseudostem (Musa acuminata) comprises nearly 30% of plant biomass and carries a substantial quantity of fiber and moisture. Banana pseudostem beverage was developed from banana tender core, natural extracts (Pine apple and Grape) and 2% citric acid used as an antibrowning agent. The present study aimed to develop ready-to-drink banana pseudostem juice incorporated with pineapple and grape extract. The banana pseudostem juice (80%) was incorporated with pineapple (20%) and grape (20%) extracts. Methods: The proximate composition of the ready-to-drink banana pseudostem beverage and the physicochemical properties of banana pseudostem extract were analyzed using standard procedures. Sensory evaluation and microbial quality were analyzed for ready-to-drink banana pseudostem beverages stored at 25°C and 4°C. The beverages were evaluated at 6 days interval period. Result: The ready-to-drink beverages were evaluated at a 6-day interval period. The result of the physicochemical properties of the ready-to-drink banana pseudostem beverage incorporated with pineapple and grape extract during storage at ambient and refrigerated temperature. The banana pseudostem beverage pH value gradually increased and its acidity value decreased. The total soluble solids remained constant, viscosity at 25°C was decreased, at 4°C viscosity was increased during the storage period up to 12 days. During storage conditions, the total soluble solids remain constant, while the viscosity increased at 4! and reduced at 25°C. Minimal substantial changes were observed in the quality of ready-to-drink banana pseudostem beverages during storage conditions. The pineapple extract-flavored pseudostem beverages during storage conditions. The pineapple extract-flavored pseudostem beverage was very well-liked by consumers, according to the organoleptic evaluation. The quality of ready-to-drink banana pseudostem beverages was minimal significant changes were observed. Based on the organoleptic evaluation, the pineapple extract flavored pseudostem beverage was highly accepted by consumer preference. The banana pseudostem beverage incorporated with pineapple extracts was microbiologically safe for 12 days at 25°C and 4°C for human consumption. After 12 days at (25°C) and (4°C), the banana pseudostem beverage incorporated with pineapple extracts proved microbiologically safe.

Insights into inhibitory action and interaction of bisdemethoxycurcumin on tyrosinase: Spectroscopic and docking analysis

Bisdemethoxycurcumin (BDMC), a demethoxy derivative of curcumin, has garnered interest for its potential anti-tyrosinase properties, which are crucial for applications in food preservation and cosmetic industries. Despite its recognized bioactive effects, the detailed inhibitory action and interaction of BDMC on tyrosinase and its application in anti-browning processes remain unclear. This study aims to dissect the molecular interactions of BDMC with tyrosinase, elucidate its inhibition mechanism, and assess its efficacy in preventing browning, thereby underpinning its potential as a natural anti-browning agent. Employing a battery of spectroscopic techniques, we characterized the interaction of BDMC with tyrosinase. The anti-browning properties of BDMC were evaluated on fresh-cut apples, and its effect on enzymatic activities related to browning was also investigated. The results indicate that BDMC interacts with tyrosinase in a reversible mixed-type inhibition manner with an IC50 value of 12.5 ± 0.2 μM. Surface Plasmon Resonance (SPR) results indicated that BDMC presented good binding affinity toward tyrosinase. Fluorescence quenching results showed that BDMC could quench the fluorescence of tyrosinase in a static process. Synchronous fluorescence, circular dichroism spectra, and three-dimensional fluorescence results indicated that interaction of BDMC against tyrosinase resulted in changes of tyrosinase on microenvironment and conformation, thus causing decrease of tyrosinase activity. Copper-chelating results presented that BDMC could chelate to copper with stoichiometric ratio of 1: 2. Molecular docking provided intricate details of how BDMC interacted with tyrosinase. Moreover, BDMC exhibited anti-browning capability on fresh cut apples, and could regulate PPO, POD, and APX activities. The comprehensive analysis proposed in this study consolidated the theoretical basis of BDMC as a tyrosinase inhibitor and supported its potential anti-browning application.

Unlocking the Potential of Hydrosols: Transforming Essential Oil Byproducts into Valuable Resources

The global demand for sustainable and non-toxic alternatives across various industries is driving the exploration of naturally derived solutions. Hydrosols, also known as hydrolates, represent a promising yet underutilised byproduct of the extraction process of essential oils (EOs). These aqueous solutions contain a complex mixture of EO traces and water-soluble compounds and exhibit significant biological activity. To fully use these new solutions, it is necessary to understand how factors, such as distillation time and plant-to-water ratio, affect their chemical composition and biological activity. Such insights are crucial for the standardisation and quality control of hydrosols. Hydrosols have demonstrated noteworthy properties as natural antimicrobials, capable of preventing biofilm formation, and as antioxidants, mitigating oxidative stress. These characteristics position hydrosols as versatile ingredients for various applications, including biopesticides, preservatives, food additives, anti-browning agents, pharmaceutical antibiotics, cosmetic bioactives, and even anti-tumour agents in medical treatments. Understanding the underlying mechanisms of these activities is also essential for advancing their use. In this context, this review compiles and analyses the current literature on hydrosols’ chemical and biological properties, highlighting their potential applications and envisioning future research directions. These developments are consistent with a circular bio-based economy, where an industrial byproduct derived from biological sources is repurposed for new applications.

Identification of novel natural anti-browning agents based on phenotypic and metabolites differences in potato cultivars

This study aimed to elucidate the changes of browning-related metabolite in fresh-cut potato and to identify anti-browning agents. Metabolomics and weighted correlation network analysis (WGCNA) were used to identify metabolites and correlate them with potato browning traits. A total of 79 browning trait-positive-related metabolites and 19 browning trait-negative-related metabolites were obtained from four key modules via WGCNA. The accumulation of metabolites with rich reducing groups and acidic groups were found to enhance anti-browning activity in potatoes. Among these metabolites, only L-pyroglutamic acid (L-PA) and ascorbic acid had variable importance for the projection (VIP) values greater than 1.5. In addition, it was found that L-PA inhibited polyphenol oxidase (PPO) activity by lowering pH and interacting with amino acid residues of PPO. L-PA also inhibited the growth of microorganisms in fresh-cut potato. Our results show that L-AP is an effective novel anti-browning agent with antibacterial activity.

Inhibitory activity and mechanism of thiosemicarbazide derivatives on tyrosinase and their anti-browning activity in fresh apple juice

Exploring tyrosinase inhibitors has been an effective way to find promising anti-browning agents in the food industry. Therefore, a class of thiosemicarbazide derivatives (4a-4m) were synthesized and we investigated the inhibitory mechanism on tyrosinase by fluorescence quenching, copper ion chelating and UV spectra study etc. 2-(2-Chlorobenzyl) hydrazine-1-carbothioamide (4f) (IC50 = 1.21 ± 0.02 μM) is the most active compound of all derivatives, which was defined as a mix-type inhibitor. Additionally, molecular docking and copper ions chelating studies indicated that compound 4f has the ability to inhibit the tyrosinase activity by chelating the copper ions in the active region. Furthermore, compound 4f also exhibited lower cytotoxicity, excellent aqueous solubility and outstanding anti-browning capacity in fresh apple juice. These findings indicated these derivatives could provide more possibility for developing more safer and effective anti-browning agents.

Effect of sodium metabisulfite treatment and storage condition on metabolic profile of young coconut (Cocos nucifera L.)

Young coconuts (Cocos nucifera L.) used for export are trimmed to reduce their size and weight to lower transport costs. However, trimmed coconuts have a shorter shelf life due to microbial spoilage and surface discoloration caused by enzymatic browning. To minimize these effects, trimmed coconuts were dipped in an anti-browning agent, sodium metabisulfite (SMB), and stored under ambient conditions. However, there have been no reports on the effects of SMB treatment on metabolome changes in the flesh and water of young coconuts. Hence, this study investigated the metabolite changes in trimmed young coconuts after SMB treatment under different storage conditions using a gas chromatography (GC)/mass spectrometry (MS) metabolomic profiling approach. Tall young coconut samples were trimmed and treated with a 2% SMB solution for 5min before storage at 25°C or 4°C for 2-4 weeks. Coconut flesh and water samples were collected after storage for 0, 2, and 4 weeks, and were subjected to GC-MS analysis. The results showed that the major metabolites affected by coconut deterioration were amino acids, sugars, and sugar alcohols. SMB treatment and/or refrigeration can help prevent metabolite changes in the flesh and water of young coconuts. In the future, improvements in storage conditions based on metabolite profiles should be explored.

Synthesis and Evaluation of 1,4-Dihydropyridine-Based Urea Derivatives as Polyphenol Oxidase Inhibitors

This study investigated the potential inhibitory effects of nine novel synthesized urea-substituted 1,4-dihydropyridine derivatives (DT-DEN-1-9) on polyphenol oxidase (PPO) activity. The compounds were synthesized via the Hantzsch reaction, providing a series of structurally diverse urea and thiourea-modified 1,4-dihydropyridines. Polyphenol oxidase enzyme was extracted from banana (Musa cavendishii) and purified using affinity chromatography with a Sepharose 4B-L-tyrosine-p-aminobenzoic acid affinity gel. The purified enzyme's activity was measured spectrophotometrically using catechol as the substrate, monitoring the increase in absorbance at 420 nm. The inhibitory effects of the synthesized compounds on PPO activity were evaluated through in vitro assays. Various concentrations of each compound were incorporated into the enzyme reaction mixture, and the residual PPO activity was determined. The percentage of PPO activity was calculated relative to a control reaction without inhibitors. IC50 values, representing the concentration of inhibitor required to reduce enzyme activity by 50%, were determined using Lineweaver-Burk plots. Among the tested compounds, DT-DEN-6, featuring a phenyl thiourea substituent, exhibited the most potent inhibition with an IC50 value of 100.14 μM. DT-DEN-8, containing a 2,5-dichlorophenyl thiourea moiety, also showed strong inhibitory activity with an IC50 below 150 μM. Structure-activity relationships were observed, with electron-withdrawing substituents generally enhancing inhibitory potency. Conversely, DT-DEN-5, bearing a 4-(trifluoromethyl)phenyl thiourea substituent, exhibited the weakest inhibition profile (IC50: 233.33 μM). Our findings provide valuable insights for the design of next-generation PPO inhibitors, potentially leading to the development of novel anti-browning agents for applications in food preservation and other industries where control of enzymatic browning is crucial.

Molecular insights into the anti-spoilage effect of salicylic acid in Favorita potato processing

Salicylic acid is a commonly used anti-spoilage agent to prevent browning and quality degradation during potato processing, yet its precise mechanism remains unclear. This study elucidates the role of StuPPO2, a functional protein in Favorita potato shreds, in relation to the anti-browning and starch degradation effects of 52 SA analogues. By employing molecular docking and Gaussian computing, SA localizes within the hydrophobic cavity of StuPPO2, facilitated by hydroxyl and carboxyl groups. The inhibitory effect depends on the distribution pattern of the maximal electrostatic surface potential, requiring hydroxyl ion potentials of >56 kcal/mol and carboxyl ion potentials of >42 kcal/mol, respectively. Multiomics analysis, corroborated by validation tests, indicates that SA synthetically suppresses activities linked to defense response, root regeneration, starch degradation, glycoalkaloids metabolism, and potato shred discoloration, thereby preserving quality. Furthermore, SA enhances antimicrobial and insect-repellent aromas, thereby countering biotic threats in potato shreds. These collective mechanisms underscore SA's anti-spoilage properties, offering theoretical foundations and potential new anti-browning agents for agricultural preservatives.

Development of novel pyrazole-1,2,4-triazole derivatives as tyrosinase inhibitors: Design, preparation, mechanism of action and anti-browning application

Tyrosinase (Polyphenol oxidase), a key enzyme in enzymatic browning, is an attractive target for developing new anti-browning agents in the food industry. In this work, twenty pyrazole-1,2,4-triazole derivatives (3a-3n, 4a-4f) were synthesized and tested in vitro, most of compounds showed potent anti-tyrosinase activity. Of these, 3c (IC50 = 1.02 ± 0.08 μM) was found to be 14 folds stronger than kojic acid (IC50 = 14.74 ± 1.23 μM) and behaved as a mixed type inhibitor. Besides, the disappeared peak of dopaquinone in the HPLC assay intuitively validated the inhibitory effect of 3c. Copper ions chelating, fluorescence quenching and molecular docking assays showed that coordination with copper is the key to play a role. Furthermore, 3c exhibited excellent anti-browning ability for the Rosa roxburghii Tratt, the non-enzymatic browning experiment showed that 3c could prevent browning in non-enzymatic ways. It is suggested that these derivatives could serve as the leading compounds to find more efficient anti-browning agents in the future.

New Strategy for Browning Prevention in Apple Pomace Processing and Toxicity Tested in a Rodent Model.

Apple pomace (AP) is a byproduct of apple juice industries, which constitutes around 30% of the original fruit and rich in essential compounds like carbohydrates, phenolics, minerals, and dietary fibers. This study is focused on optimizing the combinational utilization of antibrowning agents like l-cysteine and l-ascorbic acid for the sustainable debrowning of AP with response surface methodology and assessment of its acute toxicity in female rats. In addition, the phytochemical content and antioxidant activity of treated AP were investigated and compared with the untreated control AP. The study revealed that the treated AP has higher dietary fiber (p < 0.01), protein (p < 0.0001), and phenolic content (p < 0.001) in comparison to the control AP. Moreover, the treated AP also observed with higher antioxidant activity 37% inhibition and water retention capacity (8.5 g H2O/g solid) along with the debrowning effect. Furthermore, a 4-week in vivo study is conducted to assess the toxicity of treated AP. Results indicated no discernible variations in biochemistry, morphometric, or histology between the supplementation (0.5, 1.5, and 3% AP) and control groups. Thus, adding AP rich in dietary fiber to a range of meals is deemed a safe and valuable food supplement.

Biochemical properties of polyphenol oxidase purified from Sarali plum (Prunus domestica)

Enzymatic browning, catalysed by the enzyme polyphenol oxidase in fruit and vegetables, limits the efficient use of natural resources and promote food waste. Plums are a popular fruit with consumers around the world and are considered an important raw material in the food industry. Plums are very susceptible to enzymatic browning due to their high phenolic compound content and climacteric nature. The aim of this study is to purify the polyphenol oxidase enzyme from Sarali plum (Prunus domestica) and to determine its biochemical properties, kinetic parameters, pH and thermal stability and inhibition. In this study, polyphenol oxidase enzyme was purified 22.54-fold by affinity chromatography using Sepharose-4B-l-Tyr-p-amino benzoic acid affinity gel. The purity and molecular mass of the enzyme were determined by SDS-PAGE and non-denaturing PAGE (native PAGE). The molecular mass of the enzyme was estimated to be 72.44 kDa by SDS-PAGE. The enzyme was confirmed as PPO by native PAGE as a single band. Kinetic characterization studies were conducted for both catechol and 4-methyl catechol substrates. The optimal pH and temperature for both substrates were found to be 7.0 and 20 °C, respectively. The thermal stability of PPO was investigated, and it retained about 90% of its activity for 90 min at 4 °C. The determination of KM and Vmax was carried out using the Lineweaver–Burk plot. The substrate specificity (Vmax/KM) values for catechol and 4-methyl catechol were determined as 790.91 ± 37.34 and 492.06 ± 13.75 respectively. The enzyme exhibited the best activity towards catechol substrate. IC50, Ki constant and inhibition types were determined for various anti-browning agents on PPO enzyme. Ascorbic acid, l-cysteine, citric acid, salicylic acid and tartaric acid effectively inhibited PPO activity.

Potential application of nanoliposomes loaded with complex tannins from the seed shell of Euryale ferox in the anti-browning of fresh-cut asparagus lettuce

Surface browning of plant-derived fresh-cut products is mainly caused by conversion of the phenolic compounds into o-quinones under tyrosinase catalysis. In this study, the rarely reported complex tannins from Euryale ferox seed shell (ECTs) constituted by the units of 35.60% condensed tannins and 64.40% hydrolysable tannins were shown to suppress the activity of tyrosinase efficiently, supporting the exploitation of ECTs into novel anti-browning agents. However, the utilization of ECTs in food preservation is often restricted because of their chemical instability to external environment. Further fabrication of nanoliposomes loaded with ECTs (ECTs-NLs) herein was carried out to improve the stability of ECTs. DLS, TEM, FTIR, DSC and XRD confirmed that ECTs were encapsulated into nanoliposomes successfully, and ECTs-NLs appeared as vesicle-like spherical morphology with favorable encapsulation efficiency, uniform particle size distribution and negative zeta-potential. The resulting ECTs-NLs were relatively stable in the dark at 4 °C. Nanoliposomal encapsulation significantly enhanced ECTs stability, thus protecting inhibitory effect of ECTs against tyrosinase. Furthermore, anti-browning evaluation proved that ECTs-NLs had distinct advantages over free ECTs in alleviating surface browning of fresh-cut asparagus lettuces. These results suggested that nanoliposomes were effective in stabilizing ECTs and ECTs-NLs could be potentially applied to the fresh-cut food industry.

Edible Coating with Encapsulated Antimicrobial and Antibrowning Agents via the Emerging Electrospinning Process and the Conventional Spray Drying: Effect on Quality and Shelf Life of Fresh-Cut Potatoes

Edible Coating with Encapsulated Antimicrobial and Antibrowning Agents via the Emerging Electrospinning Process and the Conventional Spray Drying: Effect on Quality and Shelf Life of Fresh-Cut Potatoes

Mitigation of Surface Browning in Fresh-Cut Banana Blossom by Tamarind (Tamarindus indica L.) Pulp Extract: A Role in Regulating ROS Metabolism

T he surface browning of fresh-cut products not only diminishes their nutritional content but also lowers their market value. Fresh-cut banana blossom (FBB), an increasingly popular vegan food, is prone to browning on the cut surface, which poses a significant challenge for this fresh-cut produce. Chemicals and natural extracts are commonly used to address this issue in fresh-cut produce, offering alternatives to synthetic chemicals. Tamarind (Tamarindus indica L.) pulp extract (TPE), derived from the tamarind fruit, contains compounds such as polyphenols with antioxidant properties, making it an intriguing choice as an anti-browning agent. Therefore, this study investigated the effects of TPE on surface browning and reactive oxygen species (ROS) metabolism in FBB during storage at 30 ± 1 °C. FBB was immersed in 0 % (the control) and 2.5 % TPE for 5 min, then rinsed with distilled water, air-dried, and stored at 30 ± 1 °C for 60 h. The control group showed increasing surface browning and declining overall quality during storage. TPE immersion significantly enhanced antioxidant defense systems during storage compared to the control. The heightened activity of antioxidant enzymes and increased non-enzymatic antioxidant levels corresponded with decreased ROS levels, oxidative membrane damage, and surface browning. These findings suggest that TPE has the potential to effectively reduce browning in FBB and may serve as an effective anti-browning agent for other fresh-cut products.

Karakteristik Sensori Tepung Jewawut dengan Perendaman Anti-browning Agent

The purpose of this study was to determine the sensory properties of jewawut flour by soaking citric acid as an anti-browning agent. The study was an experimental study using a two-factorial Complete Randomized Design three repeats. The variables of the study were concentration (A) consisting of 1.5% (A1), 2% (A2), 2.5% (A3) and soaking duration (B), and soaking duration (B) consisting of 30 minutes (B1), 45 minutes (B2), and 60 minutes (B3). Data collection through observation and measurement of sensory parameters including color, aroma, and texture using the hedonic method. The results showed that the sensory properties of jewawut flour with citric acid soaking both color, texture, and aroma were favored by the panelists, which were on a scale of 4 (likes). The color of the white jewawut flour is slightly yellowish, the texture is very soft (mesh size 60), and the distinctive aroma that remains smelled. The addition of citric acid as an inhibitor of the browning reaction has an effect by producing a brighter flour color as the concentration increases (1.5-2.5%), the texture also gets softer. However, in terms of aroma, the addition of citric acid with a high concentration will affect the aroma of flour to sour.

Synthesis and Characterization of Metronidazole and Heterocycle Ester Dyads for Tyrosinase Inhibitory Activity

Tyrosinase is an important copper-based enzyme mainly involved in skin pigmentation. The inhibition of the tyrosinase enzyme attracts importance in cosmetic and medicinal chemistry industry for its applications in skin whitening and anti-browning agents for humans as well as in food, agriculture industries. Imidazole based Metronidazole and its derivatives are widely accepted drug for wide range of diseases. Therefore, the present report involves the synthesis of heterocyclic derivatives of metronidazole and investigation of its efficacy towards the tyrosinase inhibitory activity. A series of metronidazole esters were synthesized and their chemical structures were confirmed using spectral techniques like, infrared spectroscopy (IR), proton nuclear magnetic resonance (1H-NMR), and liquid chromatography-mass spectrometry (LC-MS). All the compounds were evaluated for its tyrosinase inhibitory activity by oxidation of 3,4-dihydroxyphenylalanine in the presence of the synthesized esters(I-VIII) with kojic acid as standard. Among the synthesized compounds, VII (isonicotinic ester) and VIII (quinoline ester) demonstrated significant activity IC50 values 92.5 and 91.8µM respectively. Further molecular docking experiments were carried out for the synthesized compounds with 2y9w protein exhibited greater number of physical interactions for compounds VII and VIII than the other compounds in the series confirming the mushroom tyrosinase activity.

Natural Antioxidant Extracts as Anti-browning Agents from Algerian Date Palm Fruit

Abstract: Enzymatic browning is a negative change that affects fruits and vegetables. This makes them unfit for consumption or reduces their shelf life and quality. This reaction alters the appearance, texture, fragrance, taste, and nutritional value of the food. In order for these products to be widely accepted by consumers, it is necessary to use natural compounds with anti-browning properties. Objective: The main objective of this study was to select effective extracts for the anti-browning (antipolyphenol oxidase and anti-peroxidase), and antioxidant activities of by-products of Phoenix dactylifera L., Ghars variety, from Algeria. Methods: Hydro-methanolic extracts from the pedicel, perianth, and leaves of date palm were examined to evaluate the phenol and total flavonoid contents. Using spectrophotometric techniques, the antioxidant activities were assessed using 1, 1-diphenyl-2-picrylhydrazyl radical (DPPH●), 2, 2’-azino-bis-(3- ethylbenzthiazoline-6-sulfonic acid) radical (ABTS●+) and Ferric Reducing Antioxidant Power (FRAP) assay, examined the enzyme inhibitory activity against polyphenol oxidase and peroxidase of Phoenix dactylifera L. extract. Results: The range of total phenolic and flavonoid contents was 12.29 to 48.98 mg gallic acid equivalent/ g dry matter and 2.83 to 15.07 mg rutin equivalent/g dry matter, respectively. The pedicel extracts showed significant antioxidant activity in the DPPH and FRAP tests (IC50 = 0.0057 ± 0.0010 mg/ml and FEAC = 1.1961 ± 0.0647) compared to other extracts. However, in the ABTS assay, the leaf extract exhibited an interesting potency (IC50 = 0.0020 ± 0.0001mg/ml). The study on the anti-browning activity of date palm by-product extracts showed that it inhibited the activity of peroxidase enzyme from date palm fruit. Conclusion: This work is the first time the potential of an extract from date palm by-products to enzymatically reduce the browning of date palms is presented. According to the results obtained, the different organs studied from the Ghars date palm, are a powerful natural antioxidant and may include natural compounds that retard browning by enzymes.