Microorganisms as a source of tyrosinase inhibitors: a review

The Role of Probiotics in Skin Care: Advances, Challenges, and Future Needs

The skin, being the largest organ in the human body, plays a pivotal role in safeguarding the body against invasive pathogens. Therefore, it is essential to reinforce and protect this vital organ. Current research supports the impact of probiotics on skin health and their ability to alleviate various skin disorders. However, the effectiveness and probable side effects of probiotics in skin care remain a subject of debate, necessitating further investigation and analysis. Hence, this study aims to highlight existing gaps and future needs in the current research on probiotics in skin care and pave the way for future investigations. Therefore, we scrutinized the effects of oral (fermented foods and dietary supplements) and non-oral/topical probiotics on skin care, and the mechanism of probiotics that affect skin health. The results of most studies showed that fermented foods containing probiotics, particularly dairy products, positively impact skin health. The research results regarding the efficacy of probiotic supplements and live strains in treating skin disorders show promising potential. However, safety evaluations are crucial, to identify any potential adverse effects. While research has identified numerous potential mechanisms by which probiotics may influence skin health, a complete understanding of their precise mode of action remains elusive. However, it seems that probiotics can exert their positive effects through the gut-skin and gut-skin-brain axis on the human body. Therefore, following the identification of safe probiotics, additional studies should be carried out to establish optimal dosages, potential side effects, suitable regulatory guidelines, and validation methods.

Cyclo(l-Pro-l-Tyr) Isolated from the Human Skin Commensal Corynebacterium tuberculostearicum Inhibits Tyrosinase

Melanin is produced by melanocytes to protect human skin from harmful ultraviolet radiation. During skin cell renewal, melanin and dead skin cells are disposed of. However, prolonged exposure to ultraviolet rays or aging can disturb this cycle, leading to skin hyperpigmentation due to melanin accumulation. Tyrosinase is a crucial enzyme involved in melanin biosynthesis. Although various compounds, including tyrosine inhibitors, that counteract melanin accumulation have been reported, some, such as hydroquinone, are toxic and can cause vitiligo. Meanwhile, the skin is the largest organ and the outermost layer of the immune system, containing a diverse range of bacteria that produce low-toxicity compounds. In the current study, we aim to identify metabolites produced by skin microbiota that inhibit tyrosinase. Specifically, mushroom tyrosinase served as the study model. Following commensal skin bacteria screening, Corynebacterium tuberculostearicum was found to inhibit tyrosinase activity. The active compound was cyclo(l-Pro-l-Tyr); commercially available cyclo(l-Pro-l-Tyr) also exhibited inhibitory activity. Docking simulations suggested that cyclo(l-Pro-l-Tyr) binds to the substrate-binding site of mushroom tyrosinase, obstructing the substrate pocket and preventing its activity. Hence, cyclo(l-Pro-l-Tyr) might have potential applications as a cosmetic agent and food additive.

Virulent-MDR-ESBL E. coli and Klebsiella pneumoniae report from North Sinai calves diarrhea and in vitro antimicrobial by Moringa oleifera

The health of calves has a significant impact on the production of cows and livestock. Some desert plants have pharmacological importance, as they can be used to reduce antibiotic resistance. Our hypothesis is designed to detect Virulent- Multidrug-Resistant and Extended- spectrum Beta- lactamase Enterobacteriaceae (Virulent-MDR-ESBL Enterobacteriaceae and to determine whether Moringa oleifera has antibacterial activity against the detected isolates. A total of 39 Enterobacteriaceae isolates from 28 diarrheic samples were collected from calves aged between 20 days and 20 months from 3 different flocks in North Sinai, Sahl-Eltina region, Egypt. E.coli 46% (18/39), O157 13% (5/39), Klebsiella pneumoniae 41% (16/39). MDR members accounted for 87%, while ESBL isolates accounted for 43%. The antibacterial activity is represented by microdilution. Minimum inhibition concentration (MIC) for the methanol extract of Moringa oleifera ranged from 2.5,5,10, and 25mg/ ml among E.coli isolates, and O157 was susceptible to (2.5mg/ ml), Klebsiella pneumoniae isolates were susceptible to (5-50mg/ ml). Analysis of the methanol extract revealed that ferulic acid was the dominant phenolic compound with a concentration of 29,832 parts per million (ppm). In silico docking study expected the active site of ferulic acid to act on the tyrosine bacterial enzyme through Pi-alkyl, Pi-anion, Carbon hydrogen bonds, and extra ionic attractive interactions with copper ions which can stabilize ferulic acid inside the targeted pocket Diverse virulent gene profiles were observed in E. coli. The Shiga toxin-producing Escherichia coli (STEC) was reported in 83% of the isolated E. coli, while the DNA gyrase (gyrA) was harbored in 100% of Klebsiella pneumoniae isolates. Various profiles of antibiotic resistance genes for both E. coli and Klebsiella pneumoniae isolates were distinguished. blaTEM genes were detected in 99% of E. coli and 100% of Klebsiella pneumoniae. Sequence analysis for E. coli strain DRC-North Sinai-Eg was placed in accession numbers (OP955786) for the Shiga toxin 2 gene (Stx2A), (OP997748) and (OP997749) for the Adhesion to host cell gene (Eae). For the hemolysine gene (hylA), the accession number was (OP946183). Klebsiella pneumoniae strain DRC-North Sinai-Eg was placed in (OP946180) for (gyrA). This study has proven the broad range of Moringa oliefera's antibacterial effects in vitro against the virulent-MDR- ESBL E. coli and Klebsiella pneumoniae isolated from North Sinai calves diarrhea. These are congruent with the disability effect on bacterial tyrosinase enzyme through docking study therefore, we recommend the usage of this desert plant as a prospective feed additive, we endorse this as an antibacterial new insight natural source and for the medication of considered pathogens with zoonotic impacts.

Chemical Compounds, Bioactivities, and Potential Applications of the Mushroom Species of Genus Suillus (Agaricomycetes): A Review

The genus Suillus, also known as "Song mo," falls under the order Boletales and consists of various higher fungi. It establishes mycorrhizae primarily with pine trees and has a good taste and medicinal values. Herein, we reviewed the chemical compounds present in the genus Suillus, including polysaccharides, steroids, phenols, polyprenyl phenol derivatives, fatty acids, organic acids, and amino acids, and their reported bioactivities and potential applications. This review aims to promote the utilization of the resources belonging to the genus Suillus and serves as a theoretical basis for their future studies and clinical applications.

Potent inhibition of human tyrosinase inhibitor by verproside from the whole plant of Pseudolysimachion rotundum var. subintegrum

Affinity-based ultrafiltration-mass spectrometry coupled with ultraperformance liquid chromatography-quadrupole time-of-flight mass spectrometry was utilised for the structural identification of direct tyrosinase ligands from a crude Pseudolysimachion rotundum var. subintegrum extract. False positives were recognised by introducing time-dependent inhibition in the control for comparison. The P. rotundum extract contained nine main metabolites in the UPLC-QTOF-MS chromatogram. However, four metabolites were reduced after incubation with tyrosinase, indicating that these metabolites were bound to tyrosinase. The IC50 values of verproside (1) were 31.2 µM and 197.3 µM for mTyr and hTyr, respectively. Verproside showed 5.6-fold higher efficacy than that of its positive control (kojic acid in hTyr). The most potent tyrosinase inhibitor, verproside, features a 3,4-dihydroxybenzoic acid moiety on the iridoid glycoside and inhibits tyrosinase in a time-dependent and competitive manner. Among these three compounds, verproside is bound to the active site pocket with a docking energy of -6.9 kcal/mol and four hydrogen bonding interactions with HIS61 and HIS85.

Ratiometric electrochemical detection of kojic acid based on glassy carbon modified MXene nanocomposite

The significance of developing a selective and sensitive sensor for quality control purposes is underscored by the prevalent use of kojic acid (KA) in cosmetics, pharmaceuticals, and food items. KA's utility stems from its ability to inhibit tyrosinase activity. However, the instability of KA and its potential adverse effects have created a pressing need for accurate and sensitive sensors capable of analyzing real samples. This research introduces an electrochemical ratiometric sensor designed to accurately detect KA in actual cosmetic and food samples. The ratiometric sensor offers distinct advantages such as enhanced selectivity, reproducibility, and sensitivity. It achieves this by leveraging the ratio between two output signals, thereby producing reliable and undistorted results. The sensor is constructed by modifying a Glassy Carbon Electrode (GCE) with a nanocomposite consisting of Ti3C2 MXene, Prussian blue, and gold nanoparticles. The incorporation of MXene and gold nanoparticles heightens sensitivity and reduces impedance. Meanwhile, the Prussian blue signal diminishes proportionally with increasing KA concentration, forming the basis for the ratiometric sensing mechanism. The outcomes of the study reveal a broad linear range (1-600 μM), a low detection limit (1 μM), and strong selectivity for KA. These findings suggest the sensor's potential efficacy in quality control across cosmetics, pharmaceuticals, and food products.

Trichoderma asperellum Extract Isolated from Brazil Nuts (Bertholletia excelsa BONPL): In Vivo and In Silico Studies on Melanogenesis in Zebrafish

Endophytic fungi are those that present part of their life cycle in healthy tissues of different plant hosts in symbiosis without causing harm. At the same time, fungus-plant symbiosis makes it possible for microorganisms to synthesize their own bioactive secondary metabolites while in the stationary stage. To accomplish this, the endophytic fungus Trichoderma asperellum was isolated from Bertholletia excelsa (Brazil nut) almonds. The fungus was cultivated and extracted with ethyl acetate, obtaining AM07Ac. Then, using HPTLC (High-performance thin-layer chromatography) and nuclear magnetic resonance (¹H NMR), β-amyrin, kaempferol, and brucine were identified as major compounds. Further in vivo assays in zebrafish demonstrated the activity of AM07Ac on melanogenesis by producing a concentration-response inhibitory effect, which, through an in silico study, proved to be related to the noted major compounds known to inhibit tyrosinase activity. The inhibition of tyrosinase prevents melanin accumulation in skin. Therefore, these results imply the importance of investigating microorganisms and their pharmacological activities, in particular the endophytic fungus Trichoderma asperellum as a generator of active metabolites for melanogenesis modulation.

Tyrosinase Immobilization Strategies for the Development of Electrochemical Biosensors-A Review

The development of enzyme biosensors has successfully overcome various challenges such as enzyme instability, loss of enzyme activity or long response time. In the electroanalytical field, tyrosinase is used to develop biosensors that exploit its ability to catalyze the oxidation of numerous types of phenolic compounds with antioxidant and neurotransmitter roles. This review critically examines the main tyrosinase immobilization techniques for the development of sensitive electrochemical biosensors. Immobilization strategies are mainly classified according to the degree of reversibility/irreversibility of enzyme binding to the support material. Each tyrosinase immobilization method has advantages and limitations, and its selection depends mainly on the type of support electrode, electrode-modifying nanomaterials, cross-linking agent or surfactants used. Tyrosinase immobilization by cross-linking is characterized by very frequent use with outstanding performance of the developed biosensors. Additionally, research in recent years has focused on new immobilization strategies involving cross-linking, such as cross-linked enzyme aggregates (CLEAs) and magnetic cross-linked enzyme aggregates (mCLEAs). Therefore, it can be considered that cross-linking immobilization is the most feasible and economical approach, also providing the possibility of selecting the reagents used and the order of the immobilization steps, which favor the enhancement of biosensor performance characteristics.

Anti-Melanogenic Potential of Natural and Synthetic Substances: Application in Zebrafish Model

Melanogenesis is a biosynthetic pathway for the formation of the pigment melanin in human skin. A key enzyme in the process of pigmentation through melanin is tyrosinase, which catalyzes the first and only limiting step in melanogenesis. Since the discovery of its methanogenic properties, tyrosinase has been the focus of research related to the anti-melanogenesis. In addition to developing more effective and commercially safe inhibitors, more studies are required to better understand the mechanisms involved in the skin depigmentation process. However, in vivo assays are necessary to develop and validate new drugs or molecules for this purpose, and to accomplish this, zebrafish has been identified as a model organism for in vivo application. In addition, such model would allow tracking and studying the depigmenting activity of many bioactive compounds, important to genetics, medicinal chemistry and even the cosmetic industry. Studies have shown the similarity between human and zebrafish genomes, encouraging their use as a model to understand the mechanism of action of a tested compound. Interestingly, zebrafish skin shares many similarities with human skin, suggesting that this model organism is suitable for studying melanogenesis inhibitors. Accordingly, several bioactive compounds reported herein for this model are compared in terms of their molecular structure and possible mode of action in zebrafish embryos. In particular, this article described the main metabolites of Trichoderma fungi, in addition to substances from natural and synthetic sources.

Structure and inhibition mechanism of some synthetic compounds and phenolic derivatives as tyrosinase inhibitors: review and new insight

Safety concerns are the primary consideration to identify and detection of enzyme inhibitors. In this regard, safe and potent tyrosinase inhibitors play important role in enhancing nutritional quality, health promotion and also prevent further damages. The present review focuses on the recent and efficient tyrosinase inhibitors discovered from both synthetic sources and synthesized phenolic compounds, including flavonoid, carvacrol, thymol, cinnamic acid and resorcinol derivatives. The inhibitory activity of these compounds was analyzed according to chemical structure, IC₅₀, K_i and their binding energy. Further, inhibition mechanism and the biological effects of some these inhibitors with potential application in food, agricultural, cosmetic and pharmaceutical industries were briefly discussed. Molecular docking procedure was performed on some derivatives and demonstrated favorable binding affinity with amino acid residues of mushroom tyrosinase (PDB ID: 2Y9X). The information offered showed that the substitution pattern of hydroxyl groups at the phenyl ring is an important factor of tyrosinase inhibitory activity. The results confirmed that understanding structural modification of inhibitors is a key role in finding novel and efficacious tyrosinase inhibitors.Communicated by Ramaswamy H. Sarma.

Laccases and Tyrosinases in Organic Synthesis

Laccases (Lac) and tyrosinases (TYR) are mild oxidants with a great potential in research and industry. In this work, we review recent advances in their use in organic synthesis. We summarize recent examples of Lac-catalyzed oxidation, homocoupling and heterocoupling, and TYR-catalyzed ortho-hydroxylation of phenols. We highlight the combination of Lac and TYR with other enzymes or chemical catalysts. We also point out the biological and pharmaceutical potential of the products, such as dimers of piceid, lignols, isorhamnetin, rutin, caffeic acid, 4-hydroxychalcones, thiols, hybrid antibiotics, benzimidazoles, benzothiazoles, pyrimidine derivatives, hydroxytyrosols, alkylcatechols, halocatechols, or dihydrocaffeoyl esters, etc. These products include radical scavengers; antibacterial, antiviral, and antitumor compounds; and building blocks for bioactive compounds and drugs. We summarize the available enzyme sources and discuss the scalability of their use in organic synthesis. In conclusion, we assume that the intensive use of laccases and tyrosinases in organic synthesis will yield new bioactive compounds and, in the long-term, reduce the environmental impact of industrial organic chemistry.

Kojic Acid Showed Consistent Inhibitory Activity on Tyrosinase from Mushroom and in Cultured B16F10 Cells Compared with Arbutins

Kojic acid, β-arbutin, α-arbutin, and deoxyarbutin have been reported as tyrosinase inhibitors in many articles, but some contradictions exist in their differing results. In order to provide some explanations for these contradictions and to find the most suitable compound as a positive control for screening potential tyrosinase inhibitors, the activity and inhibition type of the aforementioned compounds on monophenolase and diphenolase of mushroom tyrosinase (MTYR) were studied. Their effects on B16F10 cells melanin content, tyrosinase (BTYR) activity, and cell viability were also exposed. Results indicated that α-arbutin competitively inhibited monophenolase activity, whereas they uncompetitively activated diphenolase activity of MTYR. β-arbutin noncompetitively and competitively inhibited monophenolase activity at high molarity (4000 µM) and moderate molarity (250–1000 µM) respectively, whereas it activated the diphenolase activity of MTYR. Deoxyarbutin competitively inhibited diphenolase activity, but could not inhibit monophenolase activity and only extended the lag time. Kojic acid competitively inhibited monophenolase activity and competitive–noncompetitive mixed-type inhibited diphenolase activity of MTYR. In a cellular experiment, deoxyarbutin effectively inhibited BTYR activity and reduced melanin content, but it also potently decreased cell viability. α-arbutin and β-arbutin dose-dependently inhibited BTYR activity, reduced melanin content, and increased cell viability. Kojic acid did not affect cell viability at 43.8–700 µM, but inhibited BTYR activity and reduced melanin content in a dose-dependent manner. Therefore, kojic acid was considered as the most suitable positive control among these four compounds, because it could inhibit both monophenolase and diphenolase activity of MTYR and reduce intercellular melanin content by inhibiting BTYR activity without cytotoxicity. Some explanations for the contradictions in the reported articles were provided.

Design, Synthesis, In Vitro, and In silico Evaluation of N-phenylacetamide-oxindole-thiosemicarbazide hybrids as New Potential Tyrosinase Inhibitors

A novel series of N-phenylacetamide-oxindole-thiosemicarbazide hybrids were synthesized and evaluated for their tyrosinase inhibitory activity. According to tyrosinase inhibition results, all the synthesized compounds showed high tyrosinase inhibitory activity with IC50 values ranging from 0.8 to 3.88 µM in comparison to positive control kojic acid with IC50 value of 36.32 µM. Among tested compounds, analog 7o, containing the 2-methyl-4-nitrophenyl on N-phenylacetamide moiety displayed superior tyrosinase inhibition. This compound was around 45-fold more potent than kojic acid. The kinetic analysis of compound 7o demonstrated that this compound is a competitive inhibitor against tyrosinase. Docking study of this compound demonstrated that compound 7o interacted with critical histidine residues within tyrosinase active site.

In vitro anti-melanogenic effect of Perilla frutescens leaf extracts

Introduction: Perilla frutescens (L.) Britt leaves contain various phenolic compounds, especially flavonoids, which potentially inhibit tyrosinase, the key enzyme catalyzing the melanin synthesis pathway. This work aimed to investigate the anti-melanogenic effect of Perilla frutescens extracts through the inhibition of non-cellular as well as cellular tyrosinase activities. Methods: The total extract from Perilla frutescens leaves was obtained by percolation method with 50% ethanol followed by liquid–liquid partition with ethyl acetate (EA) and chloroform (CF) to obtain the EA, CF and EA/CF extracts. The mushroom tyrosinase inhibitory effect of the obtained extracts was screened by dopachrome formation reactions from its substrate 3,4-dihydroxy-L-phenylalanine. The extracts with potential activity were further evaluated for the anti-melanogenic effects in the B16F10 melanoma cell line. Results: EA and EA/CF extracts significantly inhibited mushroom tyrosinase activity with the IC50s of 0.14 and 0.07 mg/mL, respectively, in the same range of that from kojic acid (0.12 mg/mL). Consistently, in B16F10 cells, these extracts inhibited tyrosinase enzyme; their IC50 values were 2 times lower than that of kojic acid. Moreover, both EA and EA/CF extracts remarkably reduced melanin levels in a concentration-dependent manner. Conclusion: The EA and EA/CF extracts from Perilla frutescens leaves were able to inhibit melanogenesis by reducing tyrosinase activity.

Functional Genomic Insights into Probiotic Bacillus siamensis Strain B28 from Traditional Korean Fermented Kimchi

Bacillus siamensis strain B28 was previously isolated from traditional Korean fermented kimchi and inhibited expression of the microphthalmia-associated transcription factor and β-catenin in human embryonic kidney 293 cells. Here, we determined the complete genome sequence of strain B28 and compared it with other strains to elucidate its potential probiotic properties. Strain B28 does not contain antibiotic resistance-, hemolysin- or enterotoxin-encoding genes. The genome includes genes related to survival in extreme conditions, adhesion in the gut, and synthesis of the bacteriocin. Considering the potential for enhancement of human health, the strain B28 genome encodes genes related to production of eight essential amino acids, γ-aminobutyric acid, branched-chain fatty acids, γ-glutamyltransferase, and subtilisin. There are genes for the synthesis of uracil, lipoteichoic acid, glutathione, and several reactive oxygen species-scavenging enzymes. Experimentally, strain B28 exhibited sensitivity to eight antibiotics and antibacterial activity against seven foodborne pathogens. B. siamensis B28 is a safe strain with potential for development as a probiotic.

Fungal-fungal and fungal-bacterial interactions in aquatic decomposer communities: bacteria promote fungal diversity

Fungi produce a variety of extracellular enzymes making recalcitrant substrates bioavailable. Thus, fungi are central for decomposition of dead organic matter such as leaf litter. Despite their ecological importance, our understanding of relationships between fungal species diversity and ecosystem functioning is limited, especially with regard to aquatic habitats. Moreover, fungal interactions with other groups of microorganisms such as bacteria are rarely investigated. This lack of information may be attributed to methodological limitations in tracking the biomass of individual fungal species in communities, impeding a detailed assessment of deviations from the overall performance expected from the sum of individual species' performances, so-called net diversity effects (NDEs). We used fungal species-specific biomolecular tools to target fungal-fungal and fungal-bacterial interactions on submerged leaves using four cosmopolitan aquatic fungal species and a stream microbial community dominated by bacteria. In microcosms, we experimentally manipulated fungal diversity and bacterial absence/presence and assessed functional performances and fungal community composition after 14 days of incubation. Fungal community data was used to evaluate NDEs on leaf colonization. The individual fungal species were functionally distinct and fungal cultures were on average more efficient than the bacterial culture. In absence of bacteria, NDEs correlated with growth rate (negatively) and genetic divergence (positively), but were predominantly negative, suggesting that higher fungal diversity led to a lower colonization success (niche overlap). In both absence and presence of bacteria, the overall functional performances of the communities were largely defined by their composition (i.e., no interactions at the functional level). In presence of bacteria, NDEs correlated with genetic divergence (positively) and were largely positive, suggesting higher fungal diversity stimulated colonization (niche complementarity). This stimulation may be driven by a bacteria-induced inhibition of fungal growth, alleviating competition among fungi. Resulting feedback loops eventually promote fungal coexistence and synergistic interactions. Nonetheless, overall functional performances are reduced compared to bacteria-free cultures. These findings highlight the necessity to conduct future studies, investigating biodiversity-ecosystem functioning relationships using artificial systems, without exclusion of key organisms naturally co-occurring in the compartment of interest. Otherwise, study outcomes might not reflect true ecological relationships and ultimately misguide conservation strategies.

Isolation and Identification of Tyrosinase Inhibitors from Marine Algae Enteromorpha sp

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The extract of marine green algae Enteromorpha sp. was evaluated in vitro for inhibitory activity against mushroom tyrosinase enzyme. The principle active agents i.e. coumarin; 4-hydroxycoumarin (1) and two sterols; ergosta-5,7,22-trien-3β-ol (2) & ergosterol peroxide (3) were isolated for the first time, from a crude methanol extract of Enteromorpha sp. showing anti-tyrosinase activity. Their structures were elucidated by IR, extensive NMR spectroscopy, LC-ESI-MS, Single crystal X-ray diffraction techniques. Thus, Enteromorpha sp. can be an alternative edible anti-tyrosinase agent.

Biochemical Properties of Tyrosinase from Aspergillus terreus and Penicillium copticola; Undecanoic Acid from Aspergillus flavus, an Endophyte of Moringa oleifera, Is a Novel Potent Tyrosinase Inhibitor

Tyrosinase is a copper-containing monooxygenase catalyzing the O-hydroxylation of tyrosine to 3,4-dihydroxyphenylalanine then to dopaquinone that is profoundly involved in melanin synthesis in eukaryotes. Overactivation of tyrosinase is correlated with hyperpigmentation that is metabolically correlated with severe pathological disorders, so, inhibition of this enzyme is the most effective approach in controlling the overproduction of melanin and its hazardous effects. Thus, searching for a powerful, selective inhibitor of human tyrosinase to limit the hyper-synthesis of melanin is a challenge. Unlike the difficulty of overexpression of human tyrosinase, using fungal tyrosinase as a model enzyme to the human one to evaluate the mechanistics of enzyme inhibition in response to various compounds is the most feasible strategy. Thus, the purification of highly catalytic-efficient fungal tyrosinase, exploring a novel inhibitor, and evaluating the mechanistics of enzyme inhibition are the main objectives of this work. Aspergillus terreus and Penicillium copticola were reported as the most potential tyrosinase producers. The biochemical properties suggest that this enzyme displays a higher structural and catalytic proximity to human tyrosinase. Upon nutritional bioprocessing by Plackett–Burman design, the yield of tyrosinase was increased by about 7.5-folds, compared to the control. The purified tyrosinase was strongly inhibited by kojic acid and A. flavus DCM extracts with IC₅₀ values of 15.1 and 12.6 µg/mL, respectively. From the spectroscopic analysis, the main anti-tyrosinase compounds of A. flavus extract was resolved, and verified as undecanoic acid. Further studies are ongoing to unravel the in vivo effect and cytotoxicity of this compound in fungi and human, that could be a novel drug to various diseases associated with hyperpigmentation by melanin.

Review on druggable targets of key age-associated properties regulated by therapeutic agents

Aging is a biological process which accounts for the deterioration of effective physiological functions. The malfunctioning of vital organ systems leads to the onset of neurodegenerative, cardiovascular, and immunomodulatory diseases in the elder population. Age-dependent mitochondrial dysfunctions trigger the production of reactive oxygen species, which serve as a major contributing factor for the onset of age-associated diseases. The increasing burden of age-related pathologies explicates the relevance of identifying novel therapeutic agents with enhanced potency and bioavailability. Key information on the biological mechanisms of significant age-related diseases aids in understanding relevant druggable targets essential for the initiation and progression of the disease. This review provides detailed insights into the druggable targets of key anti-aging properties of therapeutic agents such as anti-oxidant, immunomodulation, cardioprotection, anti-melanogenic, and anti-elastase properties. This information aids in the development of novel therapeutic agents/ supplements with enhanced efficacy.

A comprehensive review on tyrosinase inhibitors

Tyrosinase is a multi-copper enzyme which is widely distributed in different organisms and plays an important role in the melanogenesis and enzymatic browning. Therefore, its inhibitors can be attractive in cosmetics and medicinal industries as depigmentation agents and also in food and agriculture industries as antibrowning compounds. For this purpose, many natural, semi-synthetic and synthetic inhibitors have been developed by different screening methods to date. This review has focused on the tyrosinase inhibitors discovered from all sources and biochemically characterised in the last four decades.

A highly sensitive electrochemical biosensor for phenol derivatives using a graphene oxide-modified tyrosinase electrode

The fabrication, characterization and analytical performance were investigated for a phenol biosensor based on the covalent bonding of tyrosinase (TYR) onto a graphene oxide (GO)-modified glassy carbon electrode (GCE) via glutaraldehyde (GA). The surface morphology of the modified electrode was studied by atomic force microscope (AFM) and field-emission scanning electron microscopy (FE-SEM). The fabricated TYR/GA/GO/GCE biosensor showed very good stability, reproducibility, sensitivity and practical usage. The catechol biosensor exhibited a wide sensing linear range from 5×10^-8M to 5×10^-5M, a lower detection limit of 3×10^-8M, a current maximum (I_max) of 65.8μA and an apparent Michaelis constant (K_m^app) of 169.9μM.

Wine Phenolic Compounds: Antimicrobial Properties against Yeasts, Lactic Acid and Acetic Acid Bacteria

Microorganisms play an important role in the conversion of grape juice into wine. Yeasts belonging the genus Saccharomyces are mainly responsible for the production of ethanol, but members of other genera are known as producers of off-flavors, e.g., volatile phenols. Lactic acid and acetic acid bacteria also occur regularly in must and wine. They are mostly undesirable due to their capacity to produce wine-spoiling compounds (acetic acid, biogenic amines, N-heterocycles, diacetyl, etc.). In conventional winemaking, additions of sulfite or lysozyme are used to inhibit growth of spoilage microorganisms. However, there is increasing concern about the health risks connected with these enological additives and high interest in finding alternatives. Phenols are naturally occurring compounds in grapes and wine and are well known for their antimicrobial and health-promoting activities. In this study, we tested a selection of phenolic compounds for their effect on growth and viability of wine-associated yeasts and bacteria. Our investigations confirmed the antimicrobial activities of ferulic acid and resveratrol described in previous studies. In addition, we found syringaldehyde highly efficient against wine-spoiling bacteria at concentrations of 250–1000 µg/mL. The promising bioactive activities of this aromatic aldehyde and its potential for winemaking deserves further research.