Polyphenol oxidase (PPO) is a vital polyphenol-metabolizing enzyme responsible for the enzymatic browning of fruits and vegetables. This study assessed the anti-PPO activity of protocatechualdehyde (PCA), yielding an IC50 value of 94 μM (95% CI: 91.8 to 96.4 μM). Kinetic analysis revealed that PCA acted as a reversible and competitive inhibitor of PPO. Molecular docking indicated that hydrogen bonding and hydrophobic interactions were the main driving forces for PCA-PPO binding. Fluorescence spectroscopy further demonstrated that PCA binding altered the microenvironments around tyrosine and tryptophan residues, leading to conformational rearrangements and partial unfolding of the enzyme, evidenced by significant fluorescence quenching. Molecular dynamics simulation demonstrated that PCA perturbed the secondary structure of PPO and caused stretching of its overall structure, thereby inhibiting the catalytic activity of the enzyme. Furthermore, PCA demonstrated excellent anti-browning activity by regulating phenolic metabolism, reducing membrane lipid peroxidation, enhancing the ascorbic acid-glutathione cycle, and modulating cell wall metabolism to delay cellular senescence. Collectively, these findings offer some valuable insights into the development of PPO inhibitor and anti-browning agent, and provide a theoretical foundation for the potential application of PCA in the area of food preservation.

In this study, hawthorn leaf condensed tannins (HLCTs) were screened for their strong inhibition of both α-glucosidase and nonenzymatic glycosylation. MALDI-TOF MS and HPLC-ESI-MS first confirmed that HLCTs were mainly made up of procyanidins, accompanied by a small amount of propelargonidins and prodelphinidins. Enzymatic experiments demonstrated that HLCTs were effective inhibitors of α-glucosidase with an IC50 of 8.0 ± 1.1 μg mL-1. Inhibitory mechanism analyses showed that the combination of HLCTs to α-glucosidase was propelled by noncovalent interactions, which modified the polarity and hydrophobicity near tyrosine and tryptophan residues in the binding site and induced variation of the enzyme's secondary structure and conformation, leading to an inhibition of enzyme activity. In addition, HLCTs effectively inhibited nonenzymatic glycosylation by reducing glycosylation products, protein carbonylation, protein oxidation, and amyloid cross-β structures. These findings provided a scientific basis for the application of HLCTs as potential type 2 diabetes drugs.

Volatile Organic Compounds (VOCs) are critical determinants of loquat flavor quality and cultivar differentiation, but comprehensive characterization and rapid detection remain challenging. This study aimed to establish a robust approach for discriminating three loquat cultivars and evaluating their flavor quality by integrating electronic nose (E-nose) technology and Comprehensive Two-Dimensional Gas Chromatography-Time-of-Flight Mass Spectrometry (GC × GC-TOF-MS). GC × GC-TOF-MS was used for VOC profiling, while E-nose was applied for rapid fragrance characterization, with orthogonal partial least squares-discriminant analysis (OPLS-DA) and correlation analysis performed to identify discriminatory compounds and sensor-VOC relationships. GC × GC-TOF-MS identified over 2000 volatile compounds across three loquat cultivars. OPLS-DA further screened 22 discriminatory VOCs with variable importance in projection (VIP) values >1, which contributed to aroma hierarchy shifts among cultivars. E-nose sensors W1W and W1S showed high sensitivity to floral-scent-related VOCs, serving as key factors for distinguishing fragrance quality. Notably, E-nose detection results exhibited good consistency with GC × GC-TOF-MS data, and W1W/W1S sensors were significantly positively correlated with key VOCs. These findings demonstrate that the integration of E-nose and GC × GC-TOF-MS offers complementary advantages for comprehensive VOC characterization and cultivar discrimination. The established approach provides a scientific basis for optimizing loquat quality standards by incorporating VOC-driven biochemical authenticity and a potential efficient method for rapid, non-destructive assessment of postharvest flavor quality in loquat cultivars. These results facilitate quality control and cultivar authentication in the fruit industry.

This research investigated the inhibitory effect and mechanism of 6,7-dimethoxy-3H-quinazolin-4-one (DMQ) on polyphenol oxidase (PPO) and bacteria (Escherichia coli and Staphylococcus aureus), as well as its anti-browning properties on fresh-cut apples. The findings demonstrated that DMQ potently inhibited PPO activity with an IC50 of 98 +/- 3 mu mol L-1. Subsequently, the inhibitory mechanism of DMQ against PPO was elucidated through enzyme kinetics, fluorescence analysis, as well as computer molecular simulation. The results revealed that the interaction between DMQ and PPO led to structural elongation and relaxation of the enzyme, and influenced the microenvironment of amino acid residues at the binding region. These changes modified secondary structure and molecular conformation of PPO, ultimately resulting in the reduction of catalytic activity. Antibacterial experiments demonstrated that DMQ exhibited remarkable antibacterial properties by enhancing cell membrane permeability in E. coli and S. aureus, contributing to cellular contents leakage and bacterial cell death. Furthermore, DMQ delayed the enzymatic browning of fresh-cut apples by controlling phenolic metabolism. In particular, it was confirmed by cytotoxicity and stability tests that DMQ was safe at experimental concentrations and had good thermal stability and photostability. These discoveries offered a theoretical framework for the potential application of DMQ in food preservation.

1-(2,5-Dichlorophenyl)-2-thiourea (DCPT) was selected from thiourea due to its extraordinary polyphenol oxidase (PPO) inhibitory activity (IC50 = 33.2 ± 0.2 nmol L-1). The binding of DCPT to PPO affected the microenvironment of amino acid residues at the binding site, subsequently inducing structural stretching and relaxation in PPO, and ultimately altering the secondary structure and conformation of the enzyme. These alterations resulted in a significant suppression of PPO activity. In antibacterial experiments, DCPT exhibited remarkable bacteriostatic properties by enhancing the permeability of cell membrane and cell wall in Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli), leading to cellular content leakage and bacterial cell death. In addition, studies on browning inhibition indicated that DCPT mitigated the browning of fresh-cut apples by inhibiting lipid peroxidation, enhancing antioxidant capacities, and regulating phenolic metabolism. Furthermore, cell assays and oral toxicity tests demonstrated that the concentration of DCPT used in the anti-browning experiment was safe. These findings offered some new insights into the inhibition of DCPT against PPO, bacteria, and browning, providing scientific evidence for its potential application in food preservation.

Condensed tannins (proanthocyanidins) were isolated from the pulp of Chinese hawthorn (Crataegus pinnatifida Bge. var. major N.E.Br.) and fractioned into three subfractions (F1-F3) using 40 %, 60 %, and 80 % ethanol on a macroporous resin column. HPLC-ESI-MS analysis revealed that epicatechin-polymerized procyanidins were the predominant components of the three subfractions, with mean degrees of polymerization (mDP) of 5.78, 10.09, and 3.03, respectively. These subfractions exhibited excellent antioxidant capacity and showed a significant positive correlation (P < 0.05) with mDP. The subfraction F2 was further proven to be an efficient inhibitor of polyphenol oxidase (PPO) and bacteria. In addition, subfraction F2 controlled the browning of fresh-cut apples by regulating phenolic metabolism, enhancing antioxidant system, and reducing lipid peroxidation. Overall, these findings provided a theoretical foundation for utilizing condensed tannins from Chinese hawthorn pulp as an effective anti-browning agent for fruits and vegetables.

Tyrosinase is a biological macromolecule closely related to browning of fruit and vegetables, melanin production, and tyrosinase inhibitors are usually used to prevent browning and pigmentation. In this study, longan shell tannins (LSTs) were screened as tyrosinase inhibitors and their structures were proved to be mixtures of procyanidins (condensed tannins) and ellagitannins (hydrolyzed tannins). Enzymatic experiments verified that LSTs were efficient inhibitors, and the IC50 values for monophenolase and bisphenolase were 176.04 ± 10 and 59.94 ± 5 μg mL-1, respectively. Fluorescence detections and molecular docking revealed that the combination of LSTs to tyrosinase was mainly driven by hydrogen bonding, hydrophobic interaction, as well as van der Waals force, which changed the microenvironment of tyrosine and tryptophan residues as well as enzyme conformation. Circular dichroism and molecular dynamics simulation showed that LSTs affected secondary structures of tyrosinase, resulting in structural stretching and conformational modification of the enzyme. In addition, preservation studies demonstrated that LSTs owned the ability to delay the browning of fresh-cut apples by inhibiting phenolic metabolism, strengthening the antioxidant system, and reducing lipid peroxidation. This paper testified that LSTs are exteaordinary tyrosinase inhibitors, and offered a scientific foundation for the application of LSTs in food industry and medicine.

6,7-Bis-(2-methoxyethoxy)-4(3H)-quinazolinone (BMEQ) was selected from quinazolinones for its strong tyrosinase inhibitory activity (IC50 [ 160 +/- 6 mM). It suppressed tyrosinase activity in a competitive way and quenched the fluorescence of the enzyme through a static mechanism. The binding of BMEQ to tyrosinase increased the hydrophobicity of the latter and facilitated non-radiative energy transfer between them. The formation of BMEQ-tyrosinase complex was driven by hydrogen bonds and hydrophobic interactions, and it loosened the basic framework structure of tyrosinase, affecting the conformation of the enzyme, and leading to a decrease in tyrosinase activity. In addition, the BMEQ postponed the oxidation of phenolics and flavonoids by inhibiting polyphenol oxidase (PPO) and peroxidase (POD), which resulted in the inhibition of the browning of fresh-cut apples. This study identified a novel tyrosinase inhibitor BMEQ and verified its potential application for improving the preservation of postharvest fruits. (c) 2023, The Society for Biotechnology, Japan. All rights reserved.

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.

Condensed tannins were isolated from the bark of Ficus altissima and fractionated into four subcomponents on a Sephadex LH-20 column with 60 %, 80 %, 100 % methanol, and 70 % acetone, separately. Their structures were characterized by MALDI-TOF MS coupled with HPLC-ESI-MS and confirmed to be polymers of B-type procyanidin glucosides, procyanidins, and prodelphinidin glucosides. The degree of polymerization (DP) of these polymers was as high as 21, and the mDPs of the four subcomponents were calculated as 2.4, 6.6, 10.5 and 13.4, respectively. They competitively or noncompetitively suppressed the activities of tyrosinase and α-glucosidase through hydrogen bonding and hydrophobic interaction. And they also showed a powerful antioxidative activity. Correlation analyses verified that the anti-tyrosinase capacity exhibited a significant positive correlation (R2monophenolase = 0.9167 and R2diphenolase = 0.9302) with mDP within the methanol-water system, and the anti-α-glucosidase activity also showed a significant positive correlation with the mDP (R2 = 0.9187). In contrast, the antioxidant capability showed a significant negative correlation with the mDP (R2DPPH = 0.9258, R2ABTS = 0.9372). This study confirmed that condensed tannins from the bark of F. altissima were desirable anti-tyrosinase, anti-α-glucosidase, and antioxidant agents, and elucidated the relationships of their mDP (molecular weight) and activities, which provided a scientific basis for the comprehensive utilization of these polymers in the food, cosmetics, medicine and other fields.

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 mu M. 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.

Longan seed tannins (LSTs) were separated and confirmed to be mixtures of procyanidins, ellagitannins, and gallotannins. Multiple spectroscopy methods and molecular simulation technique demonstrated that LSTs were competitive inhibitors of tyrosinase and formed stable complex with the enzyme. The LSTs influenced the microenvironment of amino acid residues in the catalytic center of tyrosinase by non-covalent interactions, and induced stretching of polypeptide framework and conformational change of the enzyme by altering its secondary structures, generating an intense inhibition in enzyme activity. Moreover, LSTs effectively prevented the enzymatic browning of apples by inhibiting the polyphenol oxidation, enhancing the anti-oxidation system, and preventing the lipid peroxidation of cell membrane. This study demonstrated that LSTs were quality tyrosinase inhibitors and browning resistance agents, and provided novel insights for understanding the suppressive mechanism of LSTs on tyrosinase and browning, as well as scientific evidence for their potential application as food preservative.

The anti-tyrosinase mechanism of esculetin has been systematically investigated by various spectroscopic techniques and molecular simulation. And the outcomes confirmed that esculetin was a competitive and excellent tyrosinase inhibitor (IC50=43 +/- 0.5 mu mol L-1). The binding of esculetin to tyrosinase affected the hydrophobic microenvironment of the enzyme and altered its conformation. Thermodynamic analysis and molecular docking demonstrated that the binding was driven by hydrophobic interaction and hydrogen bonding. Circular dichroism and molecular dynamic analysis revealed that esculetin induced the structural stretching of tyrosinase and slightly impacted the microenvironment of amino acid residues. Cell assays further demonstrated that esculetin inhibited intracellular tyrosinase activity and melanin production but showed no significant effect on cell proliferation. Additionally, studies on browning inhibition indicated that esculetin delayed the browning of fresh-cut apples by suppressing phenolic metabolism, strengthening antioxidant systems, and reducing membrane-lipid peroxidation. The above discoveries offered new viewpoints for understanding the suppressive mechanism of esculetin on tyrosinase and browning, as well as scientific evidence for its potential application in food preservation and medicine.

Dimocarpus longan Lour. is a valuable industrial crop for its broad applications in food, traditional Chinese medicine, and other fields. In this paper, condensed tannins were isolated from the leave of D. longan Lour., and their structure, anti-tyrosinase, anti-melanogenesis, anti-browning, anti-α-glucosidase, and anti-glycation properties were methodically clarified. The joint application of matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF MS), electrospray ionization time-of-flight mass spectrometer (ESI+ TOF MS), and high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS) confirmed that the longan leave condensed tannins (LLCTs) were polymers of procyanidins (majority) and prodelphinidins. The polymers powerfully inhibit tyrosinase (TY) with a competitive mechanism. These compounds altered the microenvironment of the binding site through hydrophobic interaction and hydrogen bond, and caused conformational modification of the enzyme by changing the polypeptide framework and secondary structure, leading to a decrease in TY activity. Cell assays further suggested that LLCTs exhibited a strong inhibition against intracellular TY activity and melanin production, and caused apoptosis in B16F10 cells. Anti-browning studies demonstrated that LLCTs suppress the browning of fresh-cut apples. Furthermore, the LLCTs exhibited an impressive inhibition on both α-glucosidase and nonenzymatic glycation. Therefore, this study confirms the potential of LLCTs as new inhibitors of tyrosinase, melanogenesis, browning, α-glucosidase, and nonenzymatic glycation, which provided a theoretical basis for the potential utilization of these polymers in the cosmetics, pharmaceutical, and food industries.

BACKGROUNDTyrosinase is the key enzyme involved in enzymatic browning of plant-derived foods. Inhibition of tyrosinase activity contributes to the control of food browning. Due to safety regulations or other issues, most identified tyrosinase inhibitors are not suitable for practical use. Therefore, it is necessary to search for novel tyrosinase inhibitors. In this study, the anti-tyrosinase activity and mechanism of albendazole and 2-(2-aminophenyl)-1H-benzimidazole (2-2-A-1HB) were investigated through ultraviolet-visible absorption spectroscopy, fluorescence spectra, molecular docking, and molecular dynamic (MD) simulation. The anti-browning effect of albendazole on fresh-cut apples was then elucidated. RESULTSAlbendazole and 2-2-A-1HB were both efficient tyrosinase inhibitors with IC50 of 51 +/- 1.5 and 128 +/- 1.3 mu mol L-1, respectively. Albendazole suppressed tyrosinase non-competitively and formed tyrosinase-albendazole complex statically. Hydrogen bond and hydrophobic interaction were major driving forces in stabilizing the tyrosinase-albendazole complex. While 2-2-A-1HB inhibited the enzyme competitively and quenched its intrinsic fluorescence through a static mechanism, it generated strong binding affinity with tyrosinase through hydrophobic interaction. MD simulations further validated that albendazole/2-2-A-1HB could form stable complexes with tyrosinase and loosened its basic framework structure, leading to a change in secondary structure and conformation. In addition, albendazole could delay the browning of fresh-cut apples by inhibiting the activity of polyphenol oxidase, peroxidase and phenylalanine ammonia-lyase, and reducing the oxidation of phenolic compounds. CONCLUSIONThis research might provide a deep view of tyrosinase inhibition by benzimidazole derivatives and a theoretical basis for developing albendazole as a potential fresh-keeping agent. (c) 2023 Society of Chemical Industry.

The inhibition of punicalagin on tyrosinase and melanogenesis was investigated through multiple spectroscopic approaches, molecular docking, molecular dynamic simulation, cell assay, and preservation assays. The results confirmed that punicalagin significantly inhibited tyrosinase activity in vitro (IC50 = 0.64 +/- 0.05 mM) and B16F10 cells (IC50 = 16 +/- 0.7 mu M). The binding of punicalagin to tyrosinase changed the conformation of the enzyme by influencing the hydrophobicity and polar environment of the binding site. The results of molecular docking and thermodynamic analysis showed that hydrophobic interaction and hydrogen bond were major driving forces in stabilizing the punicalagin-tyrosinase complex, influencing substrate-binding affinity to tyrosinase and resulting in tyrosinase activity reduction. Molecular dynamic analysis indicated that punicalagin stretched the basic framework structure of tyrosinase and lowered the surface hydrophobicity of the enzyme. Cell analyses further demonstrated that punicalagin inhibited melanogenesis by down-regulating the expressions of MITF and tyrosinase. What's more, preservation assays showed that punicalagin could reducing the oxidation of phenols to melanin by inhibiting the polyphenol oxidase, thereby preventing the browning of fresh-cut apples. These findings provided new perspectives on the inhibition mechanism of punicalagin on tyrosinase/melanogenesis and a theoretical support for its feasible application in the food and medicine industry.

Crataegus pinnatifida Bge. is a worthwhile industrial crop for its extensive application in Chinese herbal pharmaceuticals, food, and other industries. In this study, proanthocyanidins were extracted from the pulp of Crataegus pinnatifida Bge., and the structure, antityrosinase, antimelanogenesis, anti-alpha-glucosidase, and antiglycation activities of these compounds were systematically elucidated. The combined utilization of high-performance liquid chromatography-electrospray ionization-mass spectrometry (HPLC-ESI-MS), matrix-assisted laser desorption/ionization-time of flight mass spectrometry (MALDI-TOF MS), and nuclear magnetic resonance (NMR) demonstrated that the proanthocyanidins were B-type procyanidin polymers consisting of epicatechin. These polymers were efficient, reversible, and competitive inhibitors of both tyrosinase and alpha-glucosidase with IC50 values of 0.10 +/- 0.01 mg/mL (for monophenolase), 0.16 +/- 0.02 mg/mL (for diphenolase), and 0.50 +/- 0.02 mu g/mL, respectively. Moreover, the process of nonenzymatic glycation was also delayed by proanthocyanidins. Further cell assays suggested that these polymers strongly inhibited intracellular tyrosinase activity and melanogenesis and induced apoptosis in mouse melanoma cells. The results of circular dichroism (CD), molecular docking, and molecular dynamics (MD) consistently revealed that the inhibition of procyanidins on the two enzymes was primarily driven by hydrogen bonding and hydrophobic interactions, and the binding of epicatechin caused structural stretching and conformational modification of tyrosinase. Consequently, this study confirms novel tyrosinase, melanogenesis, alpha-glucosidase, and nonenzymatic glycation inhibitors, which might offer scientific evidence for potential applications in the cosmetics and pharmaceutical industries.

In this study, the inhibitory effect and mechanism of omeprazole on α-glucosidase and nonenzymatic glycation were investigated in vitro by using multi-spectroscopic methods and molecular docking. Enzyme kinetic results showed that omeprazole inhibited α-glucosidase in a reversible and noncompetitive manner (IC50= 0.595 ± 0.003 mM). The results from fluorescence quenching and thermomechanical analyses signified that omeprazole reduced the fluorescence intensity of α-glucosidase by forming an omeprazole-α-glucosidase complex primarily driven by hydrogen bonds. Molecular docking further confirmed that hydrogen bonds and hydrophobic forces were the major driving forces for omeprazole binding to α-glucosidase. The nonenzymatic glycation assays revealed that omeprazole had a moderate inhibition against the formation of fructosamine, dicarbonyl compounds, and advanced glycation end products (AGEs). This study provides a new inhibitor of both α-glucosidase and nonenzymatic glycation and provides a practicable candidate for treating diabetes and its complications.

酪氨酸酶是果蔬褐变和黑色素生物合成过程中的关键酶,酪氨酸酶抑制剂在果蔬保鲜和医药领域具有重要意义.该文首次研究了利巴韦林的抗酪氨酸酶活性、机制及其对贡梨鲜切梨块和梨汁的保鲜效果.酶动力学实验的结果表明,利巴韦林是高效、可逆、竞争型的酪氨酸酶抑制剂,其IC50为(0.3±0.05)mmol/L.荧光淬灭和非辐射能量转移实验的结果表明,利巴韦林可静态淬灭酪氨酸酶的内源荧光,且通过1个结合位点与酪氨酸酶形成"利巴韦林-酶"复合物并导致酶的构象发生改变,这一过程伴随着非辐射能量转移.分子对接的结果表明,利巴韦林可以嵌入到酪氨酸酶的活性口袋并与其B链上的6个氨基酸残基(Lys379、Gln356、Gln307、Asp312、Val313、Asn310)形成氢键.贡梨保鲜实验表明,利巴韦林可以有效减少鲜切梨块的失重率和降低梨汁的褐变度.该研究结果为开发新型的果蔬保鲜剂提供了理论依据和实践基础.

Tyrosinase (polyphenol oxidase) is the key enzyme of enzymatic browning in fruits and vegetables. In this research, the impact of ascorbic acid on tyrosinase and its anti-browning effect on fresh-cut Fuji apple were investigated. Ascorbic acid had a dual effect on tyrosinase with a half inhibitory concentration (IC50 ) of 13.40 ± 0.05 µM. Fluorescence assay demonstrated that ascorbic acid interacted with tyrosinase in a dynamic contaction caused by Förster's resonance energy transfer (FRET) and induced a conformational change of the enzyme. Thermodynamic analysis, copper interaction, and molecular docking further confirmed that ascorbic acid could chelate the copper ions located in active center and interact with amino acid residues of tyrosinase via hydrophobic interaction. In addition, ascorbic acid prevented the browning of fresh-cut apples by increasing APX activity and inhibiting PPO and POD activities which reduce the oxidation of total phenolics and flavonoids. PRACTICAL APPLICATIONS: The present study demonstrated that ascorbic acid had a strong inhibitory activity against tyrosinase (IC50 = 13.40 ± 0.05 µM) and anti-browning activity against fresh-cut Fuji apple. It could delay the browning degree of apple juice, increase APX activity, inhibit PPO and POD activities, and reduce the oxidation of total phenolics and flavonoids. These findings provided a basis for the feasible application of ascorbic acid on the preservation of fruits.