Mushroom tyrosinase: recent prospects

Enzymatic assays for the assessment of toxic effects of halogenated organic contaminants in water and food. A review

Halogenated organic compounds are a particular group of contaminants consisting of a large number of substances, and of great concern due to their persistence in the environment, potential for bioaccumulation and toxicity. Some of these compounds have been classified as persistent organic pollutants (POPs) under The Stockholm Convention and many toxicity assessments have been conducted on them previously. In this work we provide an overview of enzymatic assays used in these studies to establish toxic effects and dose-response relationships. Studies in vivo and in vitro have been considered with a particular emphasis on the impact of halogenated compounds on the activity of relevant enzymes to the humans and the environment. Most information available in the literature focuses on chlorinated compounds, but brominated and fluorinated molecules are also the target of increasing numbers of studies. The enzymes identified can be classified as enzymes: i) the activities of which are affected by the presence of halogenated organic compounds, and ii) those involved in their metabolisation/detoxification resulting in increased activities. In both cases the halogen substituent seems to have an important role in the effects observed. Finally, the use of these enzymes in biosensing tools for monitoring of halogenated compounds is described.

Catalysis-based specific detection and inhibition of tyrosinase and their application

Tyrosinase is an important enzyme in controlling the formation of melanin in melanosome, and plays a key role in the pigmentation of hair and skin. The abnormal expression or activation of tyrosinase is associated with several diseases such as albinism, vitiligo, melanoma and Parkinson disease. Excessive deposition of melanin could cause diseases such as freckles and brown spots in the human body, and it is also closely related to browning of fruits and vegetables and insect molting. Detecting and inhibiting the activity of tyrosinase is of extraordinary value in the progress of diagnosis and treatment of these diseases. Therefore, many selective optical detection probes and small molecular inhibitors have been developed, and have made significant contributions to the basic and clinical research on these diseases. In this paper, the detection and inhibition of tyrosinase and their application in whitening products are reviewed, with special emphasis on development of fluorescent probes and inhibitors. Hopefully, this review will help design more efficient and sensitive tyrosinase probes and inhibitors, as well as shed light on novel treatment of diseases such as melanoma.

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The abnormal expression or activation of tyrosinase is the pathogenesis of several diseases such as albinism, vitiligo, and melanoma.

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Detecting and inhibiting tyrosinase activity is of great value in the diagnosis and treatment of these diseases.

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The detection/inhibition of tyrosinase and its application in whitening products are reviewed, with special emphasis on probes/inhibitors.

Antioxidant and enzyme-inhibitory activity of peppermint extracts and essential oils obtained by conventional and emerging extraction techniques

Peppermint is widely used medicinal plant with distinguished bioactive potential, therefore, the aim of present work was to develop novel peppermint extracts with high activity by application of traditional and emerging separation techniques. Conventional hydrodistillation and microwave-assisted hydrodistillation (MWHD) were applied for recovery of essential oil (EO), while organic solvent extraction using Soxhlet apparatus, microwave-assisted and ultrasound-assisted process and supercritical fluid extraction (SFE) were applied for non-selective recovery of peppermint lipophilic extracts. Extracts were characterized in terms of terpenoids profile with special emphasis on content of major compounds (mentol, menthone, isomenthol and eucalyptol). Antioxidant activity (DPPH, ABTS, CUPRAC, FRAP, chelating and phosphomolybdenum assay) and enzyme-inhibitory assays (acetylcholinesterase, butyrylcholinesterase, tyrosinase, amylase and glucosidase inhibition) were used for screening of peppermint bioactivity. MWHD was recognized as alternative for traditional process in EO recovery, while SFE extracts were useful for green production of solvent-free peppermint extracts rich in terpenoids and other lipophilic bioactives.

Inhibitory Effect of Azamacrocyclic Ligands on Polyphenol Oxidase in Model and Food Systems

Enzymatic browning is one of the main problems faced by the food industry due to the enzyme polyphenol oxidase (PPO) provoking an undesirable color change in the presence of oxygen. Here, we report the evaluation of 10 different azamacrocyclic compounds with diverse morphologies as potential inhibitors against the activity of PPO, both in model and real systems. An initial screening of 10 ligands shows that all azamacrocyclic compounds inhibit to some extent the enzymatic browning, but the molecular structure plays a crucial role on the power of inhibition. Kinetic studies of the most active ligand (L2) reveal a S-parabolic I-parabolic noncompetitive inhibition mechanism and a remarkable inhibition at micromolar concentration (IC₅₀ = 10 μM). Furthermore, L2 action has been proven on apple juice to significantly reduce the enzymatic browning.

1,2,3-Triazole-linked 5-benzylidene (thio)barbiturates as novel tyrosinase inhibitors and free-radical scavengers

In this study, benzyl-1,2,3-triazole-linked 5-benzylidene (thio)barbiturate derivatives 7a-d and 8a-h were designed as potential tyrosinase inhibitors and free-radical scavengers. The twelve derivatives were synthesized via the [3+2] cycloaddition reaction of the corresponding benzyl azide as a dipole and the corresponding alkyne as a dipolarophile in the presence of copper(I) species, generated in situ from copper(II)/ascorbate. The thiobarbiturate derivative 8h and the barbiturate derivative 8b bearing 4-fluoro and 4-bromo groups on the benzyl-triazole moiety were found to be the most potent tyrosinase inhibitors with IC₅₀ values of 24.6 ± 0.9 and 26.8 ± 0.8 μM, respectively. Almost all the compounds showed a good radical scavenging activity with EC₅₀ values in the range of 29.9-324.9 μM. Derivatives 7a, 8f, and 8h were the most potent free-radical scavengers with EC₅₀ values of 29.9 ± 0.8, 36.8 ± 0.9, and 39.2 ± 1.1 μM, respectively. The kinetic analysis revealed that compound 8h was a mixed-type tyrosinase inhibitor. The molecular docking analysis indicated that 8b and 8h were well accommodated in the active site of the tyrosinase enzyme and possessed the most negative binding energy values of -8.55 and -8.81 kcal/mol, respectively. Moreover, it was found that the two residues, Asn81 and Glu322, played a significant role in forming stable enzyme-inhibitor complexes.

Identification of new arylsulfide derivatives as anti-melanogenic agents in a zebrafish model

A series of aryl sulfide derivatives was synthesized and evaluated for their anti-melanogenic activities. Several compounds, including 3e, 3i and 3q exhibited good anti-melanogenic activities. Among the derivatives, compound 3i showed good inhibitory effects against melanin synthesis and showed no toxicity in reconstituted human eye and skin tissues.

Effectivity of tyrosinase purification by membrane techniques versus fractionation by salting out

The main goal of this study was to select micro- and ultrafiltration membranes that can be used for the purification of mushroom tyrosinase, replacing salting-out dual-step processes followed by centrifugations. In experiments, a raw extract from white mushrooms was used with high level of ballast proteins and brownish impurities. Four microfiltration membranes for the removal of undesired high molecular weight compounds were screened and that made of nitrocellulose was selected due to high recovery of enzymatic activity. Then diafiltration and concentration on the membrane made of polyethersulphone (300 kDa) was selected to recover 8% of proteins and 58% of tyrosinase activity with five- to seven purification fold, 10% of proteases, and 8% of brown impurities. It was shown that tyrosinase can be pre-purified by selected membranes yielding the enzyme quality at least comparable to that after double salting-out method but in one device. In both cases, subsequent purification by ion-exchange chromatography slightly increased purification degree of the enzyme and brown impurity removal. The surplus of membrane pre-purification is substantially higher thermal stability of the enzyme, enlarged after the chromatographic step, due to very low content of proteolytic enzymes.

Kojic acid-natural product conjugates as mushroom tyrosinase inhibitors

As part of our effort to develop potential tyrosinase inhibitors, we have conjugated the well-known tyrosinase inhibitor kojic acid (KA) with several phenolic natural products such as umbelliferone, sesamol, thymol, carvacrol, eugenol, isoeugenol, vanillin, isovanillin, and apocynin that some reports have shown their activity on tyrosinase enzyme. The designed compounds were synthesized using click reaction and 1,2,3-triazole formation. All compound showed potent anti-tyrosinase activity significantly higher than KA. The best activities were observed with apocynin and 4-coumarinol analogs (10c and 16c) displaying IC₅₀ values of 0.03 and 0.02 μM, respectively. The potency of 16c was >460-times more than that of KA. Cell-based assays against B16F10 and HFF cells revealed that the representative compounds can efficiently suppress the melanogenesis without significant toxicity on cells.

Lectins from the Edible Mushroom Agaricus bisporus and Their Therapeutic Potentials

The mushroom Agaricus bisporus secretes biologically active compounds and proteins with benefits for human health. Most reported proteins from A. bisporus are tyrosinases and lectins. Lectins are of therapeutic or pharmaceutical interest. To date, only limited information is available on A. bisporus lectins and lectin-like proteins. No therapeutic products derived from A. bisporus lectin (ABL) are available on the market despite its extensive exploration. Recently, A. bisporus mannose-binding protein (Abmb) was discovered. Its discovery enriches the information and increases the interest in proteins with therapeutic potential from this mushroom. Furthermore, the A. bisporus genome reveals the possible occurrence of other lectins in this mushroom that may also have therapeutic potential. Most of these putative lectins belong to the same lectin groups as ABL and Abmb. Their relationship is discussed. Particular attention is addressed to ABL and Abmb, which have been explored for their potential in medicinal or pharmaceutical applications. ABL and Abmb have anti-proliferative activities toward cancer cells and a stimulatory effect on the immune system. Possible scenarios for their use in therapy and modification are also presented.

Tyrosinase-Targeting Gallacetophenone Inhibits Melanogenesis in Melanocytes and Human Skin-Equivalents

Demands for safe depigmentation compounds are constantly increasing in the pharmaceutical and cosmetic industry, since the numerous relevant compounds reported to date have shown undesirable side effects or low anti-melanogenic effects. In this study, we reported three novel inhibitors of tyrosinase, which is the key enzyme in melanogenesis, identified using docking-based high throughput virtual screening of an in-house natural compound library followed by mushroom tyrosinase inhibition assay. Of the three compounds, gallacetophenone showed high anti-melanogenic effect in both human epidermal melanocytes and a 3D human skin model, MelanoDerm. The inhibitory effect of gallacetophenone on tyrosinase was elucidated by computational molecular modeling at the atomic level. Binding of gallacetophenone to the active site of tyrosinase was found to be stabilized by hydrophobic interactions with His367, Ile368, and Val377; hydrogen bonding with Ser380 and a water molecule bridging the copper ions. Thus, our results strongly suggested gallacetophenone as an anti-melanogenic ingredient that inhibits tyrosinase.

Inhibition of Tyrosinase by Mercury Chloride: Spectroscopic and Docking Studies

Inorganic mercury compounds have been used in skin-lightening products since ancient times. Although a previous study demonstrated that mercury impeded the transfer of Cu²⁺ to the apotyrosinase, the effect of mercury on tyrosinase is still unclear. In the present study, the mechanism of mercury chloride (HgCl₂) induced inactivation of tyrosinase was investigated for the first time. The IC₅₀ values were 29.97 and 77.93 μmol/L for monophenolase and diphenolase, respectively. A kinetic analysis revealed that HgCl₂ inhibited tyrosinase activity in an irreversible non-competitive manner. The strong intrinsic fluorescence quenching suggested that the formation of the HgCl₂-tyrosinase complex induced conformational changes of the enzyme, and HgCl₂ had only one single binding site or a single class of binding site on tyrosinase. The molecular docking and further experiments demonstrated that HgCl₂ bound to the amino residuals (His) in the catalytic center of tyrosinase. To our knowledge, these findings presented in this paper were the first evidence of the direct interactions between HgCl₂ and tyrosinase, which provided a deep understanding of the inhibition mechanism of mercury on tyrosinase.

Gadolinium-based MRI contrast agent for the detection of tyrosinase

Tyrosinase is a key enzyme that has long been considered as a biomarker for melanoma as it catalyzes the oxidation of tyrosine and l-DOPA in melanogenesis. Recent studies also suggest a link between tyrosinase activity and Parkinson's disease; however, the mechanism of tyrosinase-mediated melanin formation in the brain is poorly understood. To better understand this connection, more advanced tools for the detection of tyrosinase in the brain are required. Herein, we successfully designed and synthesized a tyrosinase-targeting Gd(iii)-based MR contrast agent Tyr-GBCA 1. Tyr-GBCA 1 was synthesized by linking m-hydroxyphenyl to Gd-DOTA via a self-immolative linker. Tyr-GBCA 1 shows a 21% increase in the T1 relaxation rate (R1) in the presence of tyrosinase in artificial cerebral spinal fluid. Furthermore, Tyr-GBCA 1 is unreactive to hydrogen peroxide, which is a potential interferent in oxidation-based tyrosinase sensing systems. The reaction mechanism of the probe was studied by electrospray ionization (ESI) mass spectrometry and supports the cleavage of a reaction site.

Phloretin as both a substrate and inhibitor of tyrosinase: Inhibitory activity and mechanism

Tyrosinase is the rate-limiting enzyme for controlling the production of melanin in the human body, and overproduction of melanin can lead to a variety of skin disorders. In this paper, the inhibitory kinetics of phloretin on tyrosinase and their binding mechanism were determined using spectroscopy, molecular docking, antioxidant assays and chromatography. The spectroscopic results indicate that phloretin reversibly inhibits tyrosinase in a mix-type manner through a multiphase kinetic process with the IC₅₀ of 169.36 μmol/L. It is shown that phloretin has a strong ability to quench the intrinsic fluorescence of tyrosinase mainly through a static quenching procedure, suggesting that a stable phloretin-tyrosinase complex is generated. Molecular docking results suggest that the dominant conformation of phloretin binds to the gate of the active site of tyrosinase. Moreover, the antioxidant assays demonstrate that phloretin has powerful antioxidant capacity and has the ability to reduce o-dopaquinone to l-dopa just like ascorbic acid. Interestingly, the results of spectroscopy and chromatography indicate that phloretin is a substrate of tyrosinase but also an inhibitor. The possible inhibitory mechanism is proposed, which will be helpful to design and search for tyrosinase inhibitors.

Comparative transcriptomic analysis reveals novel insights into the response to Cr(VI) exposure in Cr(VI) tolerant ectomycorrhizal fungi Pisolithus sp. 1 LS-2017

Chromium (Cr) is one of the most toxic heavy metals and a health hazard to millions of people worldwide. Ectomycorrhizal (ECM) fungi can assist plants in phytoremediation of heavy metal contaminated soil. Cr tolerance differs among ECM fungal varieties, but the underlying molecular mechanisms of Cr tolerance in ECM fungi are not clear. This study identified, analysed and compared the Cr(VI)-induced transcriptional changes between Cr(VI)-tolerant strain (Pisolithus sp. 1 LS-2017) and Cr(VI)-sensitive strain (Pisolithus sp. 2 LS-2017) by de novo transcriptomic analysis. The results showed that 93,642 assembled unique transcripts representing the 22,353 (46.76%) unigenes matched the proteins we have known in the Nr database and 47,801 unigenes were got from the Pisolithus spp. For DEGs between the control and 10 mg/L Cr(VI) treatment, cyanoamino acid metabolic, type I diabetes mellitus metabolism, nitrogen metabolism and beta-Alanine metabolism pathways were significantly enriched (p < 0.05) in Pisolithus sp. 1 LS-2017. Two nitrate reductase family genes (nidD, niiA) provide Cr(VI) tolerance for Pisolithus sp. 1 LS-2017 by regulating Cr(VI) reduction. In addition, NO produced by nidD, niiA regulated denitrification can alleviate Cr(VI) induced oxidative stress. In Pisolithus sp. 2 LS-2017, the alcC, aldA and lcf2 gene may alleviate Cr(VI) induced oxidative stress by protecting SH groups and increasing secondary metabolism, reducing detoxify aldehydes to carboxylic acids and producing LCPUFAs respectively; .T gene regulate Cr(VI) induced wound healing by pigmentation and stability of melanin in spore; MKP2 gene accelerate Cr(VI) induced cell death and gpmA gene regulated Cr(VI) induced energy emergency.

Inhibition of melanin production and tyrosinase activity by flavonoids isolated from Loranthus acutifolius

Activity-guided fractionations of leaves and stems from Loranthus acutifolius led to the isolation of 2',4',6-trimethoxyflavone (1), 3',4',5-trihydroxy-6,7,8-trimethoxyflavone (2), 2'4'-dihydroxy-6'-methoxy-chalcone (3) and 4',5-dihydroxy-6,7,8-trimethoxyflavone (4). The potential for inhibition against melanin production and tyrosinase activity of these 4 compounds was tested in B16-F10 cells. 2',4',6-trimethoxyflavone, 3',4',5-trihydroxy-6,7,8-trimethoxyflavone, 2'4'-dihydroxy-6'-methoxy-chalcone and 4',5-dihydroxy-6,7,8-trimethoxyflavone showed an inhibitory activity of melanin production with IC₅₀ of 3.6 ± 0.05 μM, 8.1 ± 0.05 μM, 1.6 ± 0.03 μM and 6.5 ± 0.05 μM, respectively. In addition, 2',4',6-trimethoxyflavone, 3',4',5-trihydroxy-6,7,8-trimethoxyflavone, 2'4'-dihydroxy-6'-methoxy-chalcone and 4',5-dihydroxy-6,7,8-trimethoxyflavone were able to inhibit tyrosinase activity with IC₅₀ of 4.0 ± 0.03 μM, 11.3 ± 0.05 μM, 5.7 ± 0.02 μM and 8.6 ± 0.04 μM, respectively. This is the first time that these compounds are reported in the L. acutifolius species showing anti-melanogenic activities.

Edible mushrooms as a novel protein source for functional foods

Fast demographic growth has led to increasing interest in low-cost alternative protein sources to meet population needs.

Insect Hemolymph Immune Complexes

Insects possess powerful immune systems that have evolved to defend against wounding and environmental pathogens such as bacteria, fungi, protozoans, and parasitoids. This surprising sophistication is accomplished through the activation of multiple immune pathways comprised of a large array of components, many of which have been identified and studied in detail using both genetic manipulations and traditional biochemical techniques. Recent advances indicate that certain pathways activate arrays of proteins that interact to form large functional complexes. Here we discuss three examples from multiple insects that exemplify such processes, including pathogen recognition, melanization, and coagulation. The functionality of each depends on integrating recognition with the recruitment of immune effectors capable of healing wounds and destroying pathogens. In both melanization and coagulation, protein interactions also appear to be essential for enzymatic activities tied to the formation of melanin and for the recruitment of hemocytes. The importance of these immune complexes is highlighted by the evolution of mechanisms in pathogens to disrupt their formation, an example of which is provided. While technically difficult to study, and not always readily amenable to dissection through genetics, modern mass spectrometry has become an indispensable tool in the study of these higher-order protein interactions. The formation of immune complexes should be viewed as an essential and emerging frontier in the study of insect immunity.

Novel Amide Derivatives as Potent Tyrosinase Inhibitors; In-vitro, In-vivo Antimelanogenic Activity and Computational Studies

BACKGROUND

Tyrosinase is involved in the melanin biosynthesis and the abnormal accumulation of melanin pigments leading to hyperpigmentation disorders. Controlling the melanogenesis could be an important strategy for treating abnormal pigmentation.

METHODS

In the present study, a series of amide derivatives (3a-e and 5a-e) were synthesized aiming to inhibit tyrosinase activity and melanin production. All derivatives were screened for tyrosinase inhibition in a cell-free system. The possible interactions of amide derivatives with tyrosinase enzyme and effect of these interactions on tyrosinase structure were checked by molecular docking in silico and by Circular Dichroism (CD) studies, respectively. The most potent amide derivative (5c) based on cell-free experiments, was further tested for cellular ROS inhibition and for tyrosinase activity using mouse skin melanoma (B16F10) cells.

RESULTS

The tyrosinase inhibitory concentration (IC50) for tested compounds was observed between the range of 68 to 0.0029 µg/ml with a lowest IC50 value of compound 5c which outperforms the reference arbutin and kojic acid. The cellular tyrosinase activity and melanin quantification assay demonstrate that 15µg/ml of 5c attenuates 36% tyrosinase, 24% melanin content of B16F10 cells without significant cell toxicity. Moreover, the zebrafish in vivo assay reveals that 5c effectively reduces melanogenesis without perceptible toxicity. Furthermore, the molecular docking demonstrates that compound 5c interacts with copper ions and multiple amino acids in the active site of tyrosinase with best glide score (-5.387 kcal/mol), essential for mushroom tyrosinase inhibition and the ability to diminish the melanin synthesis in-vitro and in-vivo.

CONCLUSION

Thus, we propose compound 5c as a potential candidate to control tyrosinase rooted hyperpigmentation in the future.

Functional Analysis of Macromolecular Polysaccharides: Whitening, Moisturizing, Anti-Oxidant, and Cell Proliferation

In this research we utilized extracts from two different nature products, Achatina fulica and Heimiella retispora, to enhance skin moisturizing abilities, anti-oxidative properties, and cell proliferations. It was observed that two polysaccharides with anti-oxidative effects by chelating metal ions reduced oxidative stress and further blocked the formation of reactive oxygen species syntheses. To detect whether there was a similar effect within the cellular mechanism, a flow cytometry was applied for sensing the oxidative level and it was found that both materials inhibited the endogenous oxidative stress, which was induced by phorbol-12-myristate-13-acetate (PMA). Both polysaccharides also stimulated the production of collagen to maintain skin tightness and a moisturizing effect. In summary, we developed two macromolecular polysaccharides with potential applications in dermal care.

A New Natural Antioxidant Biomaterial from Cinnamomum osmophloeum Kanehira Leaves Represses Melanogenesis and Protects against DNA Damage

Cinnamomoum osmophloeum Kanehira (COK) is an indigenous tree species in Taiwan. Chemical compositions, antioxidant activity, mushroom tyrosinase inhibition, melanin synthesis repression, and protection against DNA damage of hydrosol from the COK leaves by steam distillation were examined. We performed 1,1-diphenyl-2-picrylhydrazyl radical scavenging, metal ion chelating, reducing power, and Trolox equivalent antioxidant capacity (TEAC) assays and determined the correlations between total phenolic contents and antioxidant activities. The findings showed that the anti-oxidative properties of COK hydrosol are closely correlated with their phenol contents. Additionally, the major constituents of hydrosol, i.e., cinnamaldehyde and benzaldehyde, had dose-dependent anti-tyrosinase effects against both monophenolase and diphenolase activities. GC-MS analysis revealed that the major bioactive components of hydrosol were trans-cinnamaldehyde (87.7%), benzaldehyde (7.0%), and cinnamyl acetate (5.3%). Moreover, we found that the hydrosol with the presence of benzaldehyde is more potent than pure cinnamaldehyde, and enhances the tyrosinase inhibitory activity of hydrosol. In kinetic analyses, Lineweaver-Burk plots and replots showed that COK hydrosol is a mixed-type inhibitor. Additionally, we found that very low doses of COK hydrosol repressed α-melanocyte-stimulating hormone-induced synthesis of microphthalmia-associated transcription factor, leading to decreased melanin synthesis in B16-F10 melanoma cells. These results demonstrated that production of hydrosol from COK leaves using steam distillation may provide a safe and efficacious source of skin-whitening agents for cosmetic and pharmaceutical applications, with antioxidant, anti-tyrosinase, anti-melanogenesis, and DNA protective activities.

Isolation of a tyrosinase inhibitor from unripe grapes juice: A spectrophotometric study

Grapes are known to contain high quantity of polyphenolic compounds, including caffeic, coumaric and ferulic acids esterified with tartaric acid, to yield caftaric, coutaric and fertaric acids, respectively. These acids are more abundant in unripe grapes, which can be processed into verjuice, a product that shows intrinsic resistance against microbial growth and significant antioxidant activity. In the present work, the isolation of hydroxycinnamoyl tartaric acids from unripe grape juice by chromatographic techniques was described. Moreover, the capability of caftaric acid to inhibit tyrosinase activity was evaluated by spectrophotometric assays. According to the kinetics parameters calculated, caftaric acid was shown to be a competitive inhibitor of tyrosinase, more potent than the related caffeic and chlorogenic acids, suggesting that it can be used in cosmetic and food industries for the development of natural skin whitening formulations and as an agent able to counteract the enzymatic browning of food.

Anti-Melanogenic Effects of Hydroxyectoine via MITF Inhibition by JNK, p38, and AKT Pathways in B16F10 Melanoma Cells

Melanin plays a role in determining human skin color of a person, and a large amount of melanin makes the skin color look darkened. The proper amount of melanin formation protects our skin from UV radiation, but excessive melanin production causes hyperpigmentation and leads to freckles, melasma, and lentigo. In this study, we investigated the inhibitory effect of hydroxyectoine on melanogenesis and its mechanism in B16F10 cells. Melanin content and cellular tyrosinase activity were determined. The expression of microphthalmia-associated transcription factor (MITF), and the activities of tyrosinase and other melanogenesis-related enzymes, such as tyrosinase-related protein 1 (TRP-1) and tyrosinase-related protein 2, were also examined. Hydroxyectoine treatment significantly inhibited melanin production and intracellular tyrosinase activity in a dose-dependent manner. Western blot analysis showed that hydroxyectoine also reduced the expressions of tyrosinase and TRP-1. In addition, hydroxyectoine significantly reduced the expression of MITF, a major regulator of melanin production, and inhibited the phosphorylation of p38, c-Jun N-terminal kinase, and activated the protein kinase B. The results demonstrated that hydroxyectoine inhibits the expression of MITF through the inhibition or activation of melanin-related signaling pathways and downregulates melanogenesis by inhibiting melanogenic enzyme expression and tyrosinase activity. Hydroxyectoine has potential value in functional cosmetics applications, such as whitening.

Verification of the Functional Antioxidant Activity and Antimelanogenic Properties of Extracts of Poria cocos Mycelium Fermented with Freeze-Dried Plum Powder

Here we examine the effects of extracts of Poria cocos mycelium fermented with freeze-dried plum powder (PPE) on the α-melanocyte stimulating hormone (α-MSH)-stimulated melanogenesis in cultured murine B16 melanoma cells (B16 cells), relative to the effects of Prunus extract. We found that an extract of Prunus fermentation showed significant inhibition of melanogenesis and tyrosinase activity with no effect on cell proliferation and was more active compared to Prunus extract alone. Furthermore, we confirmed that medium containing 3% Prunus was the optimal culture substrate for fermentation with Poria cocos. These results provide evidence that Prunus fermentation extract affects skin whiting in murine B16 melanoma cells (B16 cells). Prunus contains rutin, oxalic acid, succinic acid, and fumaric acid, which help in digestion and fatigue recovery. The rutin of Prunus mume is reported to have antioxidant and anti-inflammatory effects. Also, Prunus extract has a tyrosinase inhibitory activity for skin whiting through its antioxidant activity. Therefore, we believe the Prunus extract for Poria cocos fermentation can be provided as a potential mediator to induce skin whiting.

Aptitude of Oxidative Enzymes for Treatment of Wastewater Pollutants: A Laccase Perspective

Natural water sources are very often contaminated by municipal wastewater discharges which contain either of xenobiotic pollutants and their sometimes more toxic degradation products, or both, which frustrates the universal millenium development goal of provision of the relatively scarce pristine freshwater to water-scarce and -stressed communities, in order to augment their socioeconomic well-being. Seeing that both regulatory measures, as regards the discharge limits of wastewater, and the query for efficient treatment methods remain unanswered, partially, the prospects of enzymatic treatment of wastewater is advisable. Therefore, a reconsideration was assigned to the possible capacity of oxidative enzymes and the respective challenges encountered during their applications in wastewater treatment, and ultimately, the prospects of laccase, a polyphenol oxidase that oxidizes aromatic and inorganic substrates with electron-donating groups in treatment aromatic contaminants of wastewater, in real wastewater situations, since it is assumed to be a vehicle for a greener community. Furthermore, the importance of laccase-driven catalysis toward maintaining mass-energy balance, hence minimizing environmental waste, was comprehensibly elucidated, as well the strategic positioning of laccase in a model wastewater treatment facility for effective treatment of wastewater contaminants.

Enzyme Modification and Oxidative Cross-linking Using Carboxylate-, Phenol- and Catechol-Conjugated 1,8-Naphthalimides

The ground- and excited-state interactions of β-alanine, tyrosine and l-dopa substituted 1,8 naphthalimides (NI-Ala, NI-Tyr and NI-Dopa) with lysozyme and mushroom tyrosinase were evaluated to understand the mechanism of oxidative modification. Photooxidative cross-linking of lysozyme was observed for all three conjugates. The yield was significantly reduced for NI-Tyr and NI-Dopa due to intramolecular electron transfer to the excited singlet state of the 1,8-naphthalimide. Incubation of NI-Tyr and NI-Dopa with mushroom tyrosinase resulted in an increased fluorescence from the naphthalimide, suggesting that the phenol and catechol portion of the conjugates are oxidized by the enzyme. This result demonstrates that the compounds bind in the active site of mushroom tyrosinase. The catalytic activity of mushroom tyrosinase to oxidize both tyrosine (monophenolase) and l-dopa (diphenolase) was modified by NI-Tyr and NI-Dopa. Monophenolase activity was inhibited, and the diphenolase activity was enhanced in the presence of these conjugates. Detailed Michaelis-Menten studies show that both V_max and K_m are modified, consistent with a mixed inhibition mechanism. Collectively, the results show that the compounds interact in the enzyme's active site, but also modify the distribution of the enzyme's oxidation states that are responsible for catalysis.

Extraction conditions for Rosa gallica petal extracts with anti-skin aging activities

The anti-skin inflammatory activities of rose petal extracts have been described in our previous study. Because skin inflammation is closely linked to skin aging, our study investigated the effects of Rosa gallica petals on skin aging-related activities such as skin whitening and anti-wrinkle properties. Each sample was prepared via extraction using different ethanol ratios with the objective of evaluationg optimal extraction conditions for industrial application. Aqueous 50% (v/v) EtOH extract of R. gallica petal significantly suppressed tyrosinase activity, melanin production, and solar UV-induced matrix metalloproteinase-1, a hall mark of wrinkle formation. In addition, the aqueous 50% (v/v) EtOH extract showed the highest antioxidative effect and had highest flavonoid contents, consistent with the reported anti-aging effects. Overall, our findings suggest that R. gallica petals extracts exhibit anti-aging effects. Furthermore, 50% EtOH extraction, in particular, was optimal for the highest anti-aging, and anti-oxidative effects as well as to obtain the highest flavonoid content.

Secondary metabolite profiling, cytotoxicity, anti-inflammatory potential and in vitro inhibitory activities of Nardostachys jatamansi on key enzymes linked to hyperglycemia, hypertension and cognitive disorders

ETHNOPHARMACOLOGICAL RELEVANCE

Nardostachys jatamansi (D. Don) DC., 'Spikenard' or 'Jatamansi', a highly valued, aromatic herb from alpine Himalayas has a long history of use as ethnomedicine and dietary supplements in Ayurveda, Unani and Chinese system of medicine since Vedic ages (1000-800 BC). In Ayurveda and traditional system of medicine, the species is used as stimulant, sedative, brain tonic or mind rejuvenator, antidiabetic, cardio tonic, and in the treatment of various neurological disorders such as insomnia, epilepsy, hysteria, anxiety and depression. It is considered as Sattvic herb in Ayurveda and is now commercially marketed either as single or poly-herbal formulations by many companies in national and international markets.

AIM OF THE STUDY

The species has become threatened in its natural habitats due to over exploitation and illegal trade of its rhizomes for drug preparation in herbal and pharmaceutical industries. Considering the increasing demand and tremendous medicinal importance of this threatened plant species, a detailed study was undertaken to evaluate its antioxidant potential, secondary metabolite profiling, cytotoxicity, anti-inflammatory potential and in vitro enzyme inhibitory activities on key enzymes linked to hyperglycemia, hypertension and cognitive disorders in different plant parts of wild and in vitro-raised plants with respect to different solvent systems for its sustainable utilization.

MATERIALS AND METHODS

Anti-cholinesterase activity of leaves and rhizome of wild and cultured plant extracts was investigated against both acetylcholinesterase (AChE) and butyrylcholinesterase (BuChE) enzymes. In vitro anti-hyperglycemic (α-amylase and PTP1B), anti-hypertensive (angiotensin-converting enzyme), anti-tyrosinase and anti-inflammatory potential (5-lipoxygenase and hyaluronidase) of different plant parts of wild and in vitro-raised plants with respect to different solvent systems were also evaluated. In vitro cytotoxic effect of rootstock extracts of wild and in vitro-derived plants were against cancer (HCT-116, MCF-7 and OE33) and two normal (HEK and MEF) cell lines. Secondary metabolite profiling of rhizome segments of wild and in vitro-derived plants was carried out by quantitative gas chromatography-mass spectrometry (GC-MS).

RESULTS

In vitro-raised plantlets showed comparative higher yield of various secondary metabolites with a significantly high antioxidant activity as compared to the wild plants. Methanolic rootstock extracts of both wild and in vitro-derived plants of N. jatamansi exhibited significant AChE (IC₅₀ 36.46 ± 2.1 and 31.18 ± 2.6 µg/ml, respectively) and BuChE (IC₅₀ 64.6 ± 3.5 and 60.12 ± 3.6 µg/ml, respectively) inhibitory potential as compared to standard inhibitor galanthamine (IC₅₀ 0.94 ± 0.03 and 4.45 ± 0.5 µg/ml). Methanolic rootstock extract of in vitro-derived plants showed significant α-amylase (IC₅₀ 90.69 ± 2.1 µg/ml), PTP1B (IC₅₀ 24.56 ± 0.8 µg/ml), angiotensin-converting enzyme (IC₅₀ 42.5 ± 3.6 µg/ml) and tyrosinase (IC₅₀ 168.12 ± 3.6 µg/ml) inhibitory potential as compared to standard acarbose (IC₅₀ 52.36 ± 3.1 µg/ml), ursolic acid (IC₅₀ 5.24 ± 0.8 µg/ml), captopril (IC₅₀ 32.36 ± 2.5 µg/ml) and kojic acid (IC₅₀ = 54.44 ± 2.3 µg/ml). Both the methanolic rootstock and leaf extracts of tissue culture-derived plants exhibited promising anti-5-LOX and anti-hyaluronidase activities against the known inhibitor of 5-LOX and hyaluronidase. Furthermore, methanolic rootstock extracts of both wild and in vitro-derived plants exhibited promising cytotoxic effects to HCT-116, MCF-7 and OE33 cell lines as compared to the normal HEK and MEF after 12 h of treatment. Secondary metabolite profiling of wild and in vitro-derived plants by quantitative GC-MS analysis revealed the presence of different classes of terpenoids and phenolic acids might be responsible for its effective biological activities.

CONCLUSION

In vitro-derived plants revealed a substantial anti-cholinesterases, anti-hyperglycemic anti-inflammatory, anti-hypertensive and anti-tyrosinase potential with higher yield of various bioactive metabolites and significantly higher antioxidant activity which substantially explain medicinal importance of N. jatamansi in traditional medicine, used for centuries in different Ayurvedic formulations. The present findings suggest that cultured plants could be a promising alternative for the production of bioactive metabolites with comparative biological activities to the wild plants.

Mushroom Tyrosinase-Based Enzyme Inhibition Assays Are Not Suitable for Bioactivity-Guided Fractionation of Extracts

Tyrosinase (Tyr) catalyzes the rate-limiting step of melanogenesis in human skin and is thus the main target for treating pigmentation disorders today. This has led to an increased research interest in Tyr inhibitors during the last decades, with a frequent focus on polyphenols. In the early stages of drug discovery, it is typical to avoid the high costs of human Tyr by using the more economic mushroom tyrosinase (mh-Tyr). Since some polyphenols are accepted as substrates by mh-Tyr, the present study aimed to more generally investigate this enzyme's specificity toward polyphenols and to discuss its significance in the context of bioactivity-guided fractionation. Mh-Tyr substrates can change the sample color during an inhibition assay, leading to unreliable inhibition constants or to the discontinuation of a bioactivity-guided fractionation campaign. A data set of 56 natural products was investigated and classified into assay interferers (AIs) and noninterferers, using a spectrophotometric and an LC-ESIHRMS assay. Based on these experimental findings, structure-activity relationships defining AIs were deduced and implemented into an in silico tool that will allow for rapid prescreening in the future. We anticipate that these results will aid in the search for new Tyr inhibitors and contribute to the understanding of this enzyme, as well as its optimal use in pharmacological research.

Anti-Oxidant and Anti-Melanogenic Properties of Essential Oil from Peel of Pomelo cv. Guan Xi

Here, we investigated the anti-oxidant and anti-melanogenic effects of pomelo peel essential oil (PPEO) from pomelo cv. Guan Xi. The volatile chemical composition of PPEO was analyzed with gas chromatography–mass spectrometry (GC/MS). The most abundant component of PPEO was limonene (55.92%), followed by β-myrcene (31.17%), and β-pinene (3.16%). PPEO showed strong anti-oxidant activities against 2,2-diphenyl-2-picryhydrazyl (DPPH), 2,2′-azinobis-(3-ethylbenzthiazoline-6-sulphonate (ABTS) and superoxide anion free radicals. Based on the B16 melanoma cell system, the effects of PPEO on the viability and morphology of B16 cells and the production of melanin were evaluated. The results revealed that PPEO at concentrations below 50 μg/mL could decrease the melanin content without affecting cell viability and morphology. Intracellular tyrosinase (TYR) activity and Western blot analysis showed that PPEO could down-regulate the expression level of TYR in B16 cells and dose-dependently inhibit TYR activity (by a maximum of 64.54%). In conclusion, PPEO has good anti-oxidant and anti-melanogenic activity, and thus can be widely used as a natural antioxidant in the food, pharmaceutical, and cosmetic industries.

Pyruvic acid/ethyl pyruvate inhibits melanogenesis in B16F10 melanoma cells through PI3K/AKT, GSK3β, and ROS-ERK signaling pathways

Melanin is the main product of human melanocytes and functions to protect skin from ultraviolet (UV) radiation while conferring color to skin and hair. Tyrosinase is the rate-limiting enzyme for melanin synthesis along with tyrosinase-related protein (TRP)-1 and TRP-2. Microphthalmia-associated transcription factor regulates tyrosinase gene expression and is in turn regulated by extracellular signal-regulated kinase (ERK), phosphoinositide 3-kinase (PI3K)/AKT, and glycogen synthase kinase (GSK)3β signaling pathways. Pyruvic acid (PA) is an energy source for ATP synthesis in the tricarboxylic acid cycle that also acts as a reactive oxygen species (ROS) scavenger. As UV irradiation induces melanin synthesis and ROS generation, we speculated that PA or ethyl pyruvate (EP), a stable form of pyruvate, regulates melanogenesis. B16F10 melanoma cells served as a melanin synthesis model. Treatment with PA or EP suppressed melanin synthesis while increasing intracellular ROS levels, which was accompanied by increased ERK phosphorylation in the case of EP treatment. PA and EP induced GSK3β phosphorylation and activated PI3K/AKT signaling, leading to decreased melanin synthesis. These results indicate that PA and EP inhibit melanogenesis via PI3K/AKT and GSK3β signaling and targeting the ERK and GSK3β pathways, respectively. Thus, PA and EP can potentially be used for treatment of hyperpigmentation disorders.

Anti-melanogenesis potential of a new series of Morita-Baylis-Hillman adducts in B16F10 melanoma cell line

Melanin is a natural polymer pigment which provides skin photoprotection against ultraviolet radiation. An excessive synthesis of melanin leads to hyperpigmentation disorders. Tyrosinase catalyzes the rate limiting steps on melanogenesis. Therefore, tyrosinase inhibitors have potential applications in medicine and cosmetic fields. We carried out herein the screening of a family of cyclic Morita-Baylis-Hillman adducts (MBH) to find out their effects on tyrosinase activity and on melanogenesis in murine melanoma B16F10 cell line. Kinetic analysis of tyrosinase inhibition showed that compounds 1a (2-hydroxymethyl) cyclohex-2-enone) and 3f (diethyl (1-(6-oxocyclohex-1-en-1-yl) ethyl-phosphonate) were competitive inhibitors, whereas the compound 2b (6-oxocyclohex-1-en-1-yl) ethyl acetate) was a non-competitive one. Additionally we have found that (1a, 2b and 3f) compounds had a strong melanogenesis inhibition effect in isobutylmethylxanthine (IBMX)-treated murine melanoma B16F10 cells when tested at low and non cytotoxic dose (10-50 µM), by attenuating the melanin production, intracellular tyrosinase activity and tyrosinase expression. Thus, we suggest that these compounds could be used as effective skin-whitening agents.

Tyrosinase-Treated Hydroxytyrosol-Enriched Olive Vegetation Waste with Increased Antioxidant Activity Promotes Autophagy and Inhibits the Inflammatory Response in Human THP-1 Monocytes

Treatment of olive vegetation waste with tyrosinase immobilized on multiwalled carbon nanotubes increased the antioxidant activity as a consequence of the conversion of phenols to corresponding catechol derivatives, as evaluated by DPPH, Comet assay, and micronucleus analyses. During this transformation, 4-hydroxyphenethyl alcohol (tyrosol) was quantitatively converted to bioactive 3,4-dihydroxyphenethyl alcohol (hydroxytyrosol). The hydroxytyrosol-enriched olive vegetation waste also promoted autophagy and inhibited the inflammatory response in human THP-1 monocytes.

Novel Piperazine Amides of Cinnamic Acid Derivatives as Tyrosinase Inhibitors

Background:

A series of novel cinnamic acid piperazine amide derivatives has been designed and synthesized, and their biological activities were also evaluated as potential tyrosinase inhibitors.

Methods:

Compounds 9, 11 and 17 showed the most potent biological activity (IC50 = 66.5, 61.1 and 66 &#181;M, respectively). In silico docking simulation was performed to position compound 11 into the Agaricus bisporus mushroom tyrosinase’s active site to determine the putative binding interactions.

Results and Conclusion:

The results indicated that compound 11 could serve as a promising lead compound for further development of potent tyrosinase inhibitors.

1,2,3-Triazole-based kojic acid analogs as potent tyrosinase inhibitors: Design, synthesis and biological evaluation

A series of kojic acid-derived compounds 6a-p bearing aryloxymethyl-1H-1,2,3-triazol-1-yl moiety were designed by modifying primary alcoholic group of kojic acid as tyrosinase inhibitors. The target compounds 6a-p were synthesized via click reaction. All compounds showed very potent anti-tyrosinase activity (IC₅₀s = 0.06-6.80 µM), being superior to reference drug, kojic acid. In particular, the naphthyloxy analogs 6o and 6p were found to be 31-155 times more potent than kojic acid. The metal-binding study of selected compound 6o revealed that the prototype compound possesses metal-chelating ability, particularly with Cu²⁺ ions. The promising compounds 6o and 6p had acceptable safety profile as demonstrated by cytotoxicity assay against melanoma (B16) cell line and Human Foreskin Fibroblast (HFF) cells.

Kinetic, spectroscopic and computational docking study of the inhibitory effect of the pesticides 2,4,5-T, 2,4-D and glyphosate on the diphenolase activity of mushroom tyrosinase

The inhibitory effect of 2,4,5-T, 2,4-D, glyphosate and paraquat on the diphenolase activity of mushroom tyrosinase for oxidation of L-DOPA has been investigated by kinetic measurements, fluorescence spectroscopy and computational docking analysis. 2,4,5-T and 2,4-D inhibit the diphenolase activity of the enzyme following a competitive mechanism, while glyphosate is a mixed inhibitor according to Lineweaver-Burk kinetic analysis. The inhibitory activity follows the order glyphosate >2,4,5-T > 2,4-D with IC50 values of 65, 90 and 106 μM, respectively. Intrinsic tyrosinase fluorescence quenching and computational docking analysis suggest that 2,4,5-T and 2,4-D interact with the active site of the enzyme through hydrophobic interactions, while glyphosate also interacts with external residues of the active site of the enzyme by hydrogen bonding and hydrophilic interactions inducing conformational changes in the protein structure.

Synthesis of cinnamic amide derivatives and their anti-melanogenic effect in α-MSH-stimulated B16F10 melanoma cells

Of the three enzymes that regulate the biosynthesis of melanin, tyrosinase and its related proteins TYRP-1 and TYRP-2, tyrosinase is the most important because of its ability to limit the rate of melanin production in melanocytes. For treating skin pigmentation disorders caused by an excess of melanin, the inhibition of tyrosinase enzyme is by far the most established strategy. Cinnamic acid is a safe natural product with an (E)-β-phenyl-α,β-unsaturated carbonyl motif that we have previously shown to play an important role in high tyrosinase inhibition. Since cinnamic acid is relatively hydrophilic, which hinders its absorption on the skin, fifteen less hydrophilic cinnamic amide derivatives (1-15) were designed as safe and more potent tyrosinase inhibitors and were synthesized through a Horner-Wadsworth-Emmons reaction. The use of conc-HCl and acetic acid for debenzylation of the O-benzyl-protected cinnamic amides 40-54 produced the following three results. 1) Cinnamic amides 43, 48, and 53 with a 2,4-dibenzyloxyphenyl group, irrespective of the amine type of the amides, produced complex compounds with high polarity. 2) Cinnamic amides 40-42, 44, 50-52, and 54 with a benzylamino, or diethylamino group produced the desired debenzylated cinnamic amides 1-3, 5, 10-13, and 15. 3) Cinnamic amides 45-47, and 49 with an anilino moiety provided 3,4-dihydroquinolinones 16-19 through intramolecular Michael addition of the anilide group. Notably, the use of BBr₃ as an alternative debenzylating agent for debenzylation of cinnamic amides 45-49 with the anilino moiety provided our desired cinnamic amides 6-10 without inducing the intramolecular Michael addition. Debenzylation of cinnamic amides 43, 48, and 53 with a 2,4-dibenzyloxyphenyl group was also successfully accomplished using BBr₃ to give 4, 9, and 14. Among the nine compounds that inhibited mushroom tyrosinase more potently at 25 μM than kojic acid, four cinnamic amides 4, 5, 9, and 14 showed 3-fold greater tyrosinase inhibitory activity than kojic acid. The docking simulation using tyrosinase indicated that these four cinnamic amides (-6.2 to -7.9 kcal/mol) bind to the active site of tyrosinase with stronger binding affinity than kojic acid (-5.7 kcal/mol). All four cinnamic amides inhibited melanogenesis and tyrosinase activity more potently than kojic acid in α-MSH-stimulated B16F10 melanoma cells in a dose-dependent manner without cytotoxicity. The strong correlation between tyrosinase activity and melanin content suggests that the anti-melanogenic effect of cinnamic amides is due to tyrosinase inhibitory activity. Considering that the cinnamic amides 4, 9, and 14, which exhibited strong inhibition on mushroom tyrosinase and potent anti-melanogenic effect in B16F10 cells, commonly have a 2,4-dihydroxyphenyl substituent, the 2,4-dihydroxyphenyl substituent appears to be essential for high anti-melanogenesis. These results support the potential of these four cinnamic amides as novel and potent tyrosinase inhibitors for use as therapeutic agents with safe skin-lightening efficiency.

Fast and direct amperometric analysis of polyphenols in beers using tyrosinase-modified screen-printed gold nanoparticles biosensors

In this work it is explored a real applicability of miniaturised and portable biosensing technology for the estimation of total phenolic content in 15 different commercial beers by applying direct amperometry. Gold nanoparticles screen-printed electrodes were thoroughly modified with tyrosinase (Tyr-AuNPS-SPCEs), which was immobilised on the surface by crosslinking with glutaraldehyde. All chemical and instrumental variables involved in the electrochemical method were optimised to develop a reliable and powerful tool to estimate rapidly the content of phenolic compounds in complex beer samples. Catechol, phenol, caffeic acid and tyrosol were analysed individually using the proposed methodology and good analytical and kinetic performances were obtained. Total phenolic content in tested beers (high fermented, low fermented and non-alcoholic) were expressed as mg L^-1 of tyrosol, which is one of the major phenolic compound reported in beer. Moreover, the developed amperometric methodology was successfully benchmarked against standardised Folin-Ciocalteau spectrophotometric method with a good Pearson correlation (r = 0.821, p < 0.01). Hierarchical Cluster Analysis (HCA) was also applied on electrochemical results and a good capability to group tested beers based on their tyrosol concentration was demonstrated.