Search Results (407)

Tyrosinase is a key enzyme that catalyzes the rate-limiting step in melanogenesis. Although numerous mushroom-derived tyrosinase inhibitors have been identified, many exhibit limited efficacy against human tyrosinase. In this study, in silico approaches were employed to evaluate the inhibitory potential of aminonaphthoquinone–chalcone hybrids against human tyrosinase. Molecular docking analysis revealed that all 10 hybrids showed higher binding affinity than kojic acid. Among them, six hybrids (3, 4, 5, 7, 9, and 10) displayed higher binding affinity than the others and interacted with amino acid residues within the active site of tyrosinase. Molecular dynamics simulations revealed that the six selected hybrids maintained stable binding to human tyrosinase throughout the simulations. Among them, compound 9 exhibited the highest structural stability, consistent with its most favorable MM/PBSA-predicted binding free energy and the greatest number of key residue interactions (K306, K334, S358, S360, N364, H367, I368, S375, Q376, and V377). Van der Waals interactions were identified as the predominant driving force governing ligand–protein binding in all complexes. These findings provide atomistic insights into the interactions between aminonaphthoquinone–chalcone hybrids and human tyrosinase and may facilitate the future development of novel human tyrosinase inhibitors. Full article

A key factor that regulates melanogenesis is the activity of tyrosinase, and inhibitors of this enzyme are used as skin-whitening and lightening agents in the skincare and cosmetics industries. The methanolic extract from male inflorescences of Artocarpus altilis (Parkinson) Fosberg (breadfruit) was investigated for its bioactivities which are important for the skincare industry, including anti-tyrosinase activity. Bioassay-guided fractionation led to the isolation of a geranylated dihydrochalcone, 2-Geranyl-2’,3,4,4’-tetrahydroxydihydrochalcone (hereinafter referred to as Artochalcone), present at 1.64% of the inflorescence dry weight. Its structure was determined by a combination of 1D and 2D-NMR and HR-ESI-MS analysis. Artochalcone was found to inhibit tyrosinase with an IC₅₀ value of 28.4 μM, making it sixteen times more effective than the leading commercial skin-whitening agent, arbutin. In addition, Artochalcone displayed significant antioxidant activity determined by 2,2-diphenyl-1-picrylhydrazyl (IC₅₀ = 20.4 μM) and nitric oxide scavenging assays (IC₅₀ = 20.7 μM). Full article

Background: Conventional tyrosinase (TYR) inhibitors irritate skin and trigger rebound pigmentation, necessitating safer and more effective depigmenting agents. Methods: Biocompatibility was assessed by cell viability. Melanin content and TYR activity were measured spectrophotometrically. Reactive oxygen species (ROS), adenosine triphosphate (ATP), and inflammatory cytokines were detected by fluorescence, luminescence, and ELISA. Western blot and RT-qPCR assessed oxidative stress, inflammatory, and melanogenic targets. Molecular docking simulated Ganoderic Acid A (GAA) interactions with key proteins. Results: GAA exhibits good biocompatibility, inhibits melanin synthesis and TYR activity in B16-F10 cells, and reverses ultraviolet B-induced pigmentation. Mechanistically, GAA restores mitochondrial homeostasis by scavenging ROS, replenishing ATP, activating the nuclear factor erythroid 2-related factor 2 (Nrf2) axis, and inhibiting nuclear factor kappa-B (NF-κB) and cytokines such as tumor necrosis factor-α (TNF-α) and interleukin-6 (IL-6) to regulate the inflammatory microenvironment. This synergistic regulation inhibits the mitogen-activated protein kinase (MAPK) signaling pathway and down-regulates the microphthalmia-associated transcription factor (MITF) transcriptional network and the expression of TYR, tyrosinase-related protein 1 (TRP-1), and tyrosinase-related protein 2 (TRP-2). Conclusion: GAA eliminates ultraviolet B-induced hyperpigmentation through a multi-target mechanism of mitochondrial repair, inflammation inhibition, and direct binding to tyrosinase, and is a potential natural candidate drug for the treatment of skin diseases. Full article

Agro-industrial residues have emerged as promising sources of bioactive compounds for dermo-cosmetic applications, particularly as inhibitors of collagenase, elastase, hyaluronidase, and tyrosinase. However, the interpretation of reported inhibitory activities is frequently complicated by variations in extraction strategies, matrix composition, assay design, and methodological rigor. This critical narrative review examines how these factors collectively influence the reliability, comparability, and translational relevance of enzyme inhibition data obtained from residue-derived extracts. The literature was analyzed using a framework-oriented approach based on representative peer-reviewed studies selected according to their methodological quality, experimental design, and mechanistic relevance. The analysis integrates three complementary dimensions: extraction and processing strategies, compositional complexity of the recovered matrices, and evidence quality supporting the reported bioactivities. The reviewed literature demonstrates that enzyme inhibition is rarely an intrinsic property of isolated compounds but rather an emergent behavior arising from complex physicochemical systems in which synergistic interactions, matrix effects, and assay-dependent artefacts frequently influence the observed responses. The widespread reliance on simplified in vitro screening methods, often without dose–response evaluation, kinetic characterization, or adequate control of assay interference, remains a major obstacle to reproducibility and cross-study comparison. Based on this analysis, an integrative framework is proposed to guide the interpretation of enzyme inhibition in complex botanical extracts by explicitly linking process design, matrix composition, and methodological evidence. This perspective provides a more robust basis for the identification, validation, and industrial translation of sustainable bioactive ingredients obtained from agro-industrial residues for next-generation dermo-cosmetic formulations. Full article

Background/Objectives: mRNA display technology has emerged as a powerful platform for discovering macrocyclic peptides against intractable proteins. However, direct screening against the “undruggable” transcription factor MYC using this approach remains largely unexplored. In this study, we aimed to integrate tyrosinase-mediated cyclization with mRNA display to identify novel macrocyclic peptide inhibitors targeting MYC. Methods: We performed mRNA display combined with tyrosinase-mediated cyclization to generate macrocyclic peptides targeting MYC. Antiproliferative activity was assessed in MYC-dependent tumor cells using CCK8 assay. C-terminal fusions with a TAT-derived cell-penetrating peptide were generated to enhance cell membrane permeability. Binding affinities were measured by bio-layer interferometry (BLI). MYC transcriptional activity was evaluated by RNA sequencing (RNA-seq) analysis of canonical MYC target genes. Results: The identified macrocyclic peptides exhibited potent antiproliferative activity against MYC-dependent tumor cells, with half-maximal inhibitory concentration (IC₅₀) values in the micromolar range. Fusion with the TAT peptide improved antiproliferative potency, yielding IC₅₀ values of 1–3 μM in MYC-dependent cell lines. BLI assays confirmed dose-dependent binding of the peptides to MYC, with dissociation constants (Kd) in the micromolar range. Furthermore, RNA-seq analysis revealed significant downregulation of canonical MYC target genes upon treatment with the TAT-fusion macrocyclic peptide, indicating specific suppression of MYC transcriptional activity. Conclusions: This work establishes the feasibility of using mRNA display to target the “undruggable” protein MYC and identifies a panel of macrocyclic peptides as promising lead candidates for further optimization toward targeted therapies for MYC-driven cancers. Full article

Tyrosinase is a pivotal therapeutic target for hyperpigmentation disorders, yet current inhibitors frequently exhibit limited potency and suboptimal safety. Here, we employed structure-based virtual screening of an FDA-approved drug library against a refined human tyrosinase homology model, identifying methotrexate and selinexor as potent anti-melanogenic candidates. Both compounds markedly suppressed cellular tyrosinase activity and melanin synthesis (IC₅₀ < 1 µM) in MNT-1 melanoma cells. Mechanistically, they orchestrate a multi-pronged downregulation of microphthalmia-associated transcription factor (MITF) by attenuating cAMP/PKA/CREB signaling, promoting β-catenin degradation, and accelerating MITF proteolysis via AKT/ERK activation. Additionally, they bolster the intracellular antioxidant defense system. These findings unveil a sophisticated regulatory network and suggest that with strict control of systemic exposure through optimized topical formulations, these FDA-approved agents could be further investigated as potential localized treatments for pigmentary disorders. Full article

Life expectancy in high-income countries is increasing, leading to a higher incidence of age-related neurodegenerative diseases. To address this urgent medical need, several molecular targets have been identified, including advanced glycation end products (AGEs) and tyrosinase. Given the well-established role of diet in counteracting degenerative processes, this study aimed to identify a potential food ingredient with combined anti-tyrosinase and anti-glycative properties. Acanthus mollis L. was selected based on its inclusion in the BelFrIt list and its known content of tyrosinase inhibitors, such as benzoxazinones and verbascoside. Extraction of A. mollis leaves was optimized using a design of experiments approach, comparing microwave- and ultrasound-assisted techniques. Optimal conditions were achieved using microwave-assisted extraction with ethanol 80%, 80 °C, one cycle, drug-to-solvent ratio of 10 mL/g. The optimized extract (at 5 mg/mL) inhibited tyrosinase activity by approximately 47%, increasing to 58% after chlorophyll removal. Moreover, the extract reduces AGEs formation in presence of methylglyoxal, with an activity at 1 mg/mL comparable with that of a well-known anti-glycative agent. A similar trend was observed in the reduction in methylglyoxal and glyoxal levels. Overall, these results support the potential of the optimized A. mollis extract as a functional food ingredient to counteract aging-related neurodegeneration. Full article

Equisetum ramosissimum Desf. Subsp. debile (Roxb. ex Vaucher) Hauk (E. ramosissimum), exhibits anti-tyrosinase and antioxidant activities. However, identifying the key compounds exhibiting anti-tyrosinase effects and establishing effective protocols for their extraction have not been accomplished. Herein, we investigate and establish an effective extraction method and identify the key bioactive compounds responsible for tyrosinase inhibition. E. ramosissimum was extracted using the microwave-assisted extraction (MAE) method. The MCW4 extract exhibited the highest antioxidant activity (IC₅₀: 90.96 ± 0.515 µg/mL) and TPC (27.23 ± 1.180 mg of GAE/g-crude extract), while the MCW5 extract showed the strongest anti-tyrosinase activity (IC₅₀: 126.48 ± 6.668 µg/mL). LC-MS/MS analysis identified resveratrol isomers, protocatechuic acid, cis-ETRA acid, KF-3-GBS, 1-16:0-lysoPC, and 1-16:0-lysoPE as potential anti-tyrosinase compounds, detected only in MCW4 and MCW5 under the applied extraction and analytical conditions. Molecular docking indicated favorable predicted binding toward human tyrosinase (hTyr) for resveratrol isomers, KF-3-GBS, and 1-16:0-lysoPE. KF-3-GBS was uniquely detected in MCW5. These results suggest that MAE using a solid-to-solvent ratio of 1:16 at 40 °C for 15 min produced an E. ramosissimum extract that exhibited strong tyrosinase inhibitory activity. Kaempferol-3-gentiobioside (KF-3-GBS) demonstrated favorable binding to hTyr in molecular docking analysis, supporting its potential role as a direct tyrosinase inhibitor. Full article

Lippia origanoides Kunth (Verbenaceae family), popularly known in northern Brazil as “Salva-de-Marajó”, is a native plant widely used in traditional medicine and cooking. While previous studies have addressed its antimicrobial and insecticidal properties, its ability to inhibit disease-related enzymes has received limited attention. This study investigated the essential oil (EO) of L. origanoides as a source of enzyme inhibitors relevant to Alzheimer’s disease, metabolic disorders and skin pigmentation disorders. The EO showed strong inhibitory activity against acetylcholinesterase (IC₅₀: 22.9 μg/mL) and α-glucosidase (IC₅₀: 14.6 μg/mL), indicating potential for managing neurodegenerative conditions and diabetes, respectively. Moderate inhibition was observed for lipase, butyrylcholinesterase and tyrosinase. Although carvacrol, the major EO constituent, contributed significantly to these effects, it did not fully explain the observed bioactivity. Bio-guided fractionation revealed that oxygenated compounds were mainly responsible for inhibiting cholinesterases and lipase, whereas α-glucosidase inhibition was associated with hydrocarbon compounds. Both fractions contributed to tyrosinase inhibition, reinforcing the EO’s relevance for treating hyperpigmentation. Furthermore, the EO demonstrated strong antioxidant activity, largely linked to carvacrol and oxygenated constituents. Chemical characterization by GC-MS, GC-FID and enantiomeric analysis strengthened the relationship between composition and bioactivity. Overall, L. origanoides EO emerged as a promising multifunctional natural product for therapeutic and cosmetic applications. Full article

Tyrosinase promotes excessive deposition of melanin, which may lead to severe skin diseases. Passiflora edulis f. edulis seeds have been reported to be rich in diverse bioactive constituents exhibiting potential tyrosinase inhibitory activity. However, the principal bioactive constituents responsible for tyrosinase inhibitory activity and its underlying mechanisms remain largely unclear. Therefore, this study aimed to: (1) optimize SC-CO₂ extraction of Passiflora edulis f. edulis seed oil (PFSO) for maximum yield and bioactive preservation; (2) comprehensively characterize its physicochemical and phytochemical profile; (3) elucidate the tyrosinase inhibition mechanism through kinetic, spectroscopic, and computational approaches; and (4) validate its safety, antioxidant, and anti-pigmentation efficacy in a zebrafish model. PFSO exhibited a yield of 24.96%, with a high content of unsaturated fatty acids (88.03%, mainly linoleic acid at 74.40%). The oil inhibited tyrosinase via a reversible mixed-type mechanism (IC₅₀ = 1.12 mg/mL). Fluorescence spectroscopy and molecular docking revealed that linoleic acid binds to LYS180 and β-sitosterol binds to TYR78, mainly driven by hydrogen bonding and hydrophobic interaction, which changed the microenvironment of tryptophan residues and indicated static quenching. Further validation experiments revealed that the major constituent, linoleic acid, exhibited only weak inhibitory activity against tyrosinase (IC₅₀ = 29.44 mg/mL), whereas the key component β-sitosterol markedly suppressed tyrosinase activity (IC₅₀ = 46.43 μg/mL). In vitro assays demonstrated PFSO’s significant efficacy in reducing the melanin content and tyrosinase activity in α-MSH-stimulated B16F10 murine melanoma cells. In vivo experiments in zebrafish that received dietary supplementation with PFSO confirmed that PFSO (≤5 mg/mL) reduced ROS production, suppressed melanin deposition, inhibited tyrosinase activity, and downregulated the expression of melanogenesis-related genes (TYR, TYRP1, TYRP2, MITF). This study provides, for the first time, a comprehensive elucidation of PFSO’s potential as a natural tyrosinase inhibitor, integrating extraction optimization, multicomponent characterization, multimodal inhibition analysis, and in vivo validation. Full article

The increasing interest in valorizing agricultural by-products has positioned grape pomace as a rich source of bioactive compounds. This study developed an effect-directed extraction (EDE) approach guided by bioactivity quantification on thin layer chromatography (TLC). Twelve grape pomaces were screened based on antioxidant and tyrosinase inhibitory properties. Using hydroalcoholic solvent (ethanol:water, 1:1), the two most promising sources (Malbec from San Rafael) were subjected to response surface methodology (RSM) to optimize extraction of anti-browning and antioxidant compounds visualized as TLC spots. Temperature and time were optimized (76 °C, 45 min), and samples were analyzed using TLC coupled with DPPH and laccase inhibition bioautography. Antioxidant compounds showed retention factor values on TLC plates of 0.37 and 0.75 (DPPH/ABTS-active), while laccase inhibition occurred at Rf 0.35, coinciding with the primary tyrosinase inhibition zone. However, subsequent bioassay-guided HPLC fractionation and HRMS/MS analysis revealed that tyrosinase and laccase inhibitions are mediated by distinct compounds within this bioactive zone, highlighting a synergistic multi-target effect in the optimized extract that is retained throughout the process. The primary tyrosinase inhibitor at Rf ~0.35 was tentatively elucidated as an acylated anthocyanin, consistent with malvidin-3-O-(p-coumaroyl)glucoside. Optimized extracts were evaluated on Pink Lady apple slices at different timepoints. The browning index was reduced by 25% versus the control at 15 h, confirmed by significantly lower ΔE values (p < 0.05). The process requires only food-grade solvents and conventional equipment, facilitating scale-up for grape pomace generated worldwide. Validating the EDE strategy, this TLC-guided approach successfully tracked and preserved the primary anti-tyrosinase activity from the crude waste matrix down to the tentatively identified molecule, contributing to circular economy objectives in the wine industry. Full article

Background: Glabridin, a natural compound derived from Glycyrrhiza glabra L., possesses skin-lightening effects. This study aims to further elucidate the depigmentation mechanism of glabridin by investigating its effects on melanogenesis and melanin transfer. Methods: We initially confirmed the anti-melanogenic effects of glabridin in MNT-1 human melanoma cells. Then, we investigated the mechanism of its anti-melanogenic effect by evaluating the protein expression of β-catenin and MITF via Western blot. To investigate melanin transfer, we compared glabridin’s efficacy with that of niacinamide, a recognized inhibitor of melanosome transfer and employed two complementary experimental models: (1) α-melanocyte-stimulating hormone (α-MSH)-stimulated MNT-1 cells to analyze dendrite formation, and (2) a UVB-irradiated co-culture system of MNT-1 cells and HaCaT keratinocytes to evaluate melanin transfer. Results: By measuring glabridin’s effects on melanin content, tyrosinase activity, and melanogenesis-related protein expression confirmed its inhibition of melanin synthesis. Further investigation demonstrated that glabridin suppresses melanogenesis by downregulating β-catenin and MITF, indicating inhibition of the Wnt/β-catenin pathway. Furthermore, in α-MSH-treated MNT-1 cells, both glabridin and niacinamide were found to suppress dendrite formation and elongation. In a UVB-exposed co-culture system, both glabridin and niacinamide inhibited melanin transfer to keratinocytes. Mechanistically, these effects were linked to the regulation of Rho GTPases (Rac1, RhoA, Cdc42) and suppression of F-actin reorganization. Conclusions: This study provides, for the first time, evidence that the skin-lightening effect of glabridin involves two complementary mechanisms: inhibition of melanogenesis through suppression of the Wnt/β-catenin pathway, and attenuation of both dendricity and melanin transfer via the influence of Rho family GTPases expression. Full article

Species of the genus Stachys (Lamiaceae) are recognized for their ethnobotanical importance and chemical diversity. In this study, the essential oil (EOS) and solvent extracts of the endemic species Stachys sparsipilosa were investigated using integrated GC–MS and LC–ESI–QTOF/MS approaches. GC–MS analysis showed that identified constituents accounted for 94.62% of the total oil, with caryophyllene oxide, kauran-16-ol, and cubebol as major components. Targeted LC–MS analysis quantified prominent phenolic compounds, including chlorogenic acid, rutin, and hesperidin, while untargeted metabolomics tentatively annotated 168 metabolites belonging to phenolics, terpenoids, and other classes. Antioxidant capacity was evaluated using complementary in vitro assays, and enzyme inhibitory activities against α-amylase, α-glucosidase, tyrosinase, acetylcholinesterase, and butyrylcholinesterase were assessed in comparison with standard inhibitors. The extracts demonstrated measurable but generally moderate activities relative to the corresponding positive controls. The essential oil exhibited moderate, non-selective cytotoxic effects at relatively high concentrations, whereas solvent extracts showed limited activity within the tested range. Molecular docking analyses were performed as supportive tools to explore possible enzyme–ligand interactions. Overall, S. sparsipilosa displays a chemically diverse metabolite profile associated with composition-dependent bioactivities, providing a basis for further mechanistic and in vivo studies. Full article

Tyrosinase is a key enzyme in melanin biosynthesis, and natural inhibitors have potential therapeutic and cosmetic applications. Lysinibacillus sp. JNUCC 52, a member of the Bacillaceae family, shows potential for producing bioactive secondary metabolites. However, the tyrosinase inhibitory potential of metabolites from this strain has not been previously reported. This study investigates its genomic features, secondary metabolites, and tyrosinase inhibitory activity to identify promising enzyme inhibitors. Integrated COG, GO, and KEGG annotation revealed a metabolically robust network supporting secondary metabolite biosynthesis. Chemical investigation of the ethyl acetate extract yielded five known compounds, among which cyclo(L-Pro-L-Leu) displayed the strongest tyrosinase inhibition (IC₅₀ = 79.5 ± 2.3 μM), whereas uracil showed weaker activity. In silico ADMET and drug-likeness analyses suggested favorable pharmacokinetic properties and compliance with major drug-likeness rules for cyclo(L-Pro-L-Leu). Molecular docking and molecular dynamics simulations demonstrated stable binding to mushroom tyrosinase (mTYR) and human TYRP1, supported by MM/GBSA and residue decomposition analyses identifying key stabilizing residues. Together, these results provide mechanistic insight into tyrosinase inhibition and highlight cyclo(L-Pro-L-Leu) as a minimal lead-like scaffold, while establishing strain JNUCC 52 as a promising microbial source of bioactive metabolites. Full article

Mussaenda pubescens Dryand. is a medicinal plant widely used in traditional medicine in Southeast Asia for the treatment of inflammation, skin-related disorders, and other health conditions. Despite its ethnopharmacological significance, scientific evidence regarding its bioactive constituents remains limited. In particular, no comprehensive study has been reported on the chemical constituents of M. pubescens in relation to tyrosinase-associated activity. In the present study, one new compound (1) and six known compounds (2–7) were isolated from the ethanol extract of the aerial parts of M. pubescens using various chromatographic techniques. Their structures were elucidated on the basis of extensive spectroscopic analyses, including NMR and HR-ESI-MS data. All isolated compounds were evaluated for their tyrosinase inhibitory activity. The results showed that compounds 1, 4, and 5 exhibited significant inhibitory effects, with IC₅₀ values of 62.39 ± 0.48, 62.55 ± 0.49, and 178.06 ± 0.89 µM, respectively. The underlying inhibitory mechanisms against tyrosinase were further investigated through enzyme kinetic studies and molecular docking simulations. Enzyme kinetic analysis revealed that compound 1 acted as a competitive inhibitor of tyrosinase, with an inhibition constant (K_i) value of 22.28 ± 0.73 µM. Overall, M. pubescens was found to contain a diverse range of secondary metabolites, including iridoid glucosides, saponins, and flavonoids, which exhibited notable tyrosinase inhibitory activity. These findings provide the first chemical insight into the tyrosinase-related bioactivity of M. pubescens and support its potential application as a natural source of tyrosinase inhibitors for pharmaceutical and cosmetic purposes. Full article