KOJIC ACID

The search for modulators of melanogenesis with improved biological compatibility remains an active area of investigation, as existing tyrosinase (TYR) inhibitors are often limited by low potency, instability, or cytotoxicity. Here, we investigated CBD-TSC 1 , a cannabidiol-based thiosemicarbazone derivative, as a TYR-targeting scaffold. Structural characterization confirmed a single, stable E-isomer, and pKa profiling together with kinetic analyses indicated reversible mixed-type inhibition of human TYR, involving interactions with both free enzyme and enzyme-substrate complexes. CBD-TSC 1 exhibited higher inhibitory activity than CBD and kojic acid under the tested conditions while maintaining low cytotoxicity in G361 melanoma and HaCaT keratinocyte cell lines. In addition, CBD-TSC 1 reduced intracellular oxidative stress at low micromolar concentrations. In zebrafish larvae, treatment with CBD-TSC 1 resulted in a dose-dependent reduction in melanin content, comparable to that of kojic acid under identical experimental conditions, supporting an association between thiosemicarbazone modification and the observed biological activity. Overall, CBD-TSC 1 demonstrated consistent activity across biochemical, cellular, and zebrafish-based assays under the tested conditions. Although the mechanistic relationship between TYR inhibition, redox modulation, and melanogenesis regulation remains to be fully clarified, the present findings support further investigation of cannabidiol-based thiosemicarbazone derivatives as modulators of TYR-related pathways.

Hyperpigmentation disorders stem from tyrosinase-catalyzed melanin overproduction, worsened by ultraviolet oxidative stress. The native Chilean species Cryptocarya alba , Laurelia sempervirens , and Peumus boldus are sources of aporphine and benzylisoquinoline alkaloids, known for their antioxidant activity. Boldine derivatives, notably diacetylboldine (DAB, Lumiskin™), demonstrate commercial depigmenting efficacy, yet structure-activity relationship data are limited.​. Systematically evaluate pure alkaloids and boldine derivatives for tyrosinase inhibition via mushroom enzyme assays, molecular docking, human melanocyte (HEMn-DP), and 3D epidermal (MelanoDerm™) models to elucidate depigmenting mechanisms. Boldine (BOL), N -methyllaurotetanine (NMLT), laurolitsine (LTS), laurotetanine (LTT), and reticuline (RET) alkaloids were isolated from authenticated plant material via acid-base partitioning/silica gel chromatography; structures were confirmed by 1 H-NMR/UHPLC-MS/MS (98% HPLC purity). Coclaurine (CC), N -methylcoclaurine (NMCC), and BOL derivatives: 3-bromoboldine (3BrBOL) and DAB were synthesized. Isocorydine (ISO) was obtained commercially. Mushroom tyrosinase (EC 1.14.18.1) inhibition measured spectrophotometrically (475 nm, L-DOPA; IC 50 interpolation). Docking performed on A. bisporus tyrosinase (PDB:2Y9X) with AutoDock Vina (30 × 30 × 30 Å grid). HEMn-DP cells treated (40/250 ppm, 24 h) for MTS viability and alkali-solubilized melanin (450 nm). MelanoDerm™ tissues were dosed topically (0.1% w/v) for 14 days, followed by the Solvable™ melanin assay (490 nm). Data analyzed in GraphPad Prism 8 (Dunnett's test, P < 0.05). LTS (IC 50 = 0.96 mM), an aporphine alkaloid, followed by CC (1.29 mM), a benzylisoquinoline alkaloid, were the most potent mushroom tyrosinase inhibitors, outperforming BOL 6.8- and 5.1-fold (6.56 mM), respectively, yet trailing reference standards such as kojic acid (0.014 mM). Boldine derivatives, including DAB (2.22 mM) and 3BrBOL (1.96 mM), exhibited superior potency relative to the parent compound. Docking revealed LTS's highest affinity (-7.3 kcal/mol; H-bonds: His259 3.4 Å, Asn260 3.2 Å) versus BOL (-5.3 kcal/mol; solely van der Waals), explained by NH-mediated His263 interaction absent in N -methylated boldine. In addition, hemisynthetic alkaloids (3BrBOL and DAB) show interactions and affinity energies similar to those of BOL. In HEMn-DP (40 ppm, 24 h), BOL/3BrBOL achieved 100% tyrosinase inhibition (viability ∼50%), exceeding DAB (62%). MelanoDerm™ (0.1% w/v, 14 days): results confirmed the efficacy of 3BrBOL (-33% melanin, P < 0.05; ∼arbutin), BOL (-10%), and DAB/LTS inactivity, highlighting the superiority of C-3 halogenation. LTS is the premier natural inhibitor; optimization of 3BrBOL validates BOL derivatization for ARB equivalent depigmentation in 3D models. These findings support the development of hydroquinone-free cosmeceuticals from Chilean flora alkaloids and advocate the use of nanoemulsions to enhance delivery and reduce cytotoxicity.

Staphylococcus aureus is a major skin pathogen that causes a broad spectrum of infections, ranging from mild skin infections to severe invasive diseases. In this study, we evaluated antibacterial and antivirulence properties of selected FDA-approved skincare bioactives and antiseptics against multiple virulence factors. Minimum inhibitory concentration analysis of benzalkonium chloride, retinol, hydroquinone, and kojic acid showed strong antimicrobial activity at concentrations from 2 to 1024 µg/mL. Epigallocatechin gallate effectively inhibits biofilm formation by 81.53% and reduces staphyloxanthin production by 68.26%. Retinol exhibited antibiofilm activity, eradicating mature biofilm mass by 79.18%. Furthermore, a combination of skincare bioactives with antibiotics, including oxacillin, ciprofloxacin, tetracycline, and rifampicin, demonstrated synergy and additive effects, enhancing antibacterial efficacy. Molecular docking analysis exhibited strong predicted binding affinities of skincare bioactives and antiseptics against key virulence factors. This study highlights the multitarget antivirulence potential of skincare bioactives and antiseptics as an alternative strategy to mitigate diverse S. aureus infections.

A novel HPLC method was developed and validated for the concurrent measurement of kojic acid, ascorbic acid, and niacinamide in cosmetic formulations. Using methanol and 0.1% acetic acid gradient elution on a C18 column, the method enables efficient separation and quantification of all three active components within 15 min, markedly improving analytical speed and solvent economy compared to previous approaches. Rigorous method validation demonstrated outstanding precision, specificity, linearity (r2 > 0.99), and robustness were developed in accordance with ICH criteria with the system appropriateness factors, like the tailing factor and theoretical plate count, consistently meeting acceptance criteria. The limits of detection were as low as kojic acid (0.06 µg/mL), niacinamide (0.10 µg/mL), and ascorbic acid (0.15 µg/mL), while percent recoveries for all analytes ranged between 98% and 102% at multiple concentration levels, confirming accuracy. Repeatability and intermediate precision (%RSD < 2%) were upheld across replicate assays, underlining the method's reliability for routine quality control. The unique advantage of this method lies in its simultaneous, rapid assessment of multi-functional vitamins and antioxidants common to cosmetics, streamlining regulatory compliance and product development. This robust protocol provides a practical solution for manufacturers and research laboratories seeking fast, precise, and economical analysis of active ingredients in commercial skincare products.

The growing demand for safe and effective natural ingredients in cosmetic formulations has prompted research into marine-derived compounds, particularly phlorotannins from brown algae. These compounds exhibit diverse bioactivities, including tyrosinase inhibition, which is relevant for the treatment of skin hyperpigmentation disorders. This study aimed to optimize the ultrasound-assisted extraction (UAE) of phlorotannins from the brown macroalga Dictyopteris justii and to evaluate the in vitro tyrosinase inhibitory activity of the resulting extract. A Box-Behnken design was employed to optimize the extraction parameters: ethanol concentration, solid-to-liquid ratio, temperature, and time. Total phlorotannin content (TPhC) was quantified using the DMBA colorimetric method, and the optimized extract was evaluated for tyrosinase inhibitory activity using a commercial colorimetric assay. The IC₅₀ of the extract was determined and compared with kojic acid. The optimal extraction conditions were identified as 70% ethanol, a 1:10 solid-to-liquid ratio, 25 °C, and 20 min. Under these conditions, the TPhC reached 2.874 ± 0.069 mg phloroglucinol equivalents per gram of dry extract, with a 9% extraction yield. Chromatographic analysis suggests the presence of hydroxypentafuhalol-B in the extract.The optimized extract showed significant tyrosinase inhibitory activity with an IC₅₀ of 0.51 mg/mL, compared to 46.61 µg/mL for kojic acid. This study demonstrates the successful optimization of UAE for obtaining a phlorotannin-rich extract from D. justii with reproducible extraction efficiency and potent tyrosinase inhibition. These findings support the potential application of D. justii extracts in the development of cosmetic products targeting hyperpigmentation.

This study investigated the phytochemical composition and bioactivities of Vatica diospyroides flower extracts to evaluate their potential for natural product and cosmetic applications. Phytochemical screening confirmed the presence of alkaloids, phenolics, flavonoids, and terpenoids, with ethanol extracts exhibiting the highest abundance of bioactive constituents. In all extracts, total phenolic content was higher than total flavonoid content. The ethanol bud extract showed strong antioxidant activity, with an IC₅₀ value of 0.00050 ± 0.00003 µg/mL in the DPPH assay. Anti-inflammatory activity was demonstrated by 70% inhibition of nitric oxide production in lipopolysaccharide-stimulated macrophages at 2.5 mg/mL. The extract also exhibited potent tyrosinase inhibition (90% at 2.5 mg/mL), comparable to kojic acid, indicating potential for skin-brightening applications. Antimicrobial testing against Cutibacterium acnes showed dose-dependent inhibitory activity. In a scratch wound-healing assay, the ethanol bud extract enhanced fibroblast migration, achieving 46.7% wound closure after 48 h, approaching the effect of vitamin C. Collectively, these results demonstrate that V. diospyroides flower extracts possess multifunctional bioactivities relevant to cosmetic and dermatological applications. Further studies on formulation stability, safety, and clinical efficacy are warranted to support their development as natural cosmetic ingredients.

The skin is constantly exposed to external factors throughout a person's life, ultraviolet (UV) radiation being one of the most harmful. The primary defence against UV-induced damage is skin pigmentation, which is achieved through the synthesis of melanin. However, overproduction of melanin can lead to skin disorders such as pigment spots, melasma, and even melanoma. Therefore, the present study aimed to obtain a new multifunctional bioactive system (MBS) starting from a supramolecular co-assembled gel (SG) based on amino acids and short peptides enhanced with a glycoside-pyrone-based complex (arbutin-kojic acid), presenting an inhibitory effect on peroxidase and implicitly controlling melanin production. The MBS gel was physicochemically analyzed using FTIR to observe changes in its chemical structure after exposure to 4°C and 25°C. The results indicate that MBS remains stable for up to 12 weeks without chemical changes in structure when stored at 4°C. The potential applicability was evaluated by antioxidant activity, where the gel exhibited above 85% scavenging activity of DPPH· free radicals. The MBS displays synergistically strong ability to inhibit the catalytic activity, functioning as an uncompetitive inhibitor that binds specifically to the enzyme-substrate complex. The in vivo biosafety of the MBS was determined at 24 h and 7 days after rat administration. The hematological and biochemical parameters show that the MBS system is safe and biocompatible both after 24 h and after 7 days. The overall findings suggest that the MBS gel has promising potential as a regulator of melanogenesis by inhibiting skin melanin synthesis.

Tyrosinase (TYR) is a copper-containing metalloenzyme involved in melanin biosynthesis and is an important target in the development of treatments for hyperpigmentation disorders, including melasma, post-inflammatory hyperpigmentation, and melanoma. Among the scaffold classes investigated for TYR inhibition, 1,2,4-triazole derivatives have attracted increasing interest. In this study, we evaluated a structurally diverse series of triazole derivatives using an integrated computational workflow that included absorption, distribution, metabolism, excretion and toxicity (ADMET) profiling, molecular docking, molecular dynamics (MD) simulations, and binding free energy calculations based on Linear Interaction Energy (LIE) and Free Energy Perturbation (FEP). Using Bacillus megaterium TYR as the model enzyme, the triazole derivatives generally produced more favorable docking scores than kojic acid and established recurring interactions with hydrophobic residues such as Met215, Val217, Ala221, and Phe227, as well as hydrogen-bonding contacts with Gly216. The free energy calculations reproduced the experimental binding affinities with high accuracy (FEP: R² = 0.91, MAE = 0.20 kcal/mol; LIE: R² = 0.93, MAE = 0.54 kcal/mol). Residue-level energy analysis indicated that interactions involving Arg209, Gly216 and Val218 play a major role in ligand binding across the series, with aromatic and halogenated substituents favoring stronger van der Waals contacts in this region. Overall, these results provide a consistent structural and energetic framework for understanding triazole-based TYR inhibition and may support the rational design of improved inhibitors for cosmetic and therapeutic applications.

Cynara cardunculus subsp. scolymus (L.) Benth. (Asteraceae) is a medicinal and food plant traditionally used in phytotherapy for its hepatoprotective, digestive, and antioxidant properties. While the edible bracts are widely consumed, artichoke leaf-recognized in herbal medicine as a valuable source of bioactive compounds-is largely discarded during industrial processing. "Carciofo Bianco di Pertosa", a traditional artichoke cultivar from Campania region (Italy), also known as "white" artichoke, remains poorly investigated from a phytochemical and pharmacological point of view. The present study aimed at characterizing the phytochemical profile of its leaf and to explore their potential relevance for nutraceutical and cosmetic applications. A 75% ethanolic extract obtained by Solid-Liquid Dynamic Extraction (Naviglio method) was analyzed by Liquid Chromatography coupled with High-Resolution Mass Spectrometry (LC-ESI/LTQOrbitrap/MS/MS) in negative ion mode. Structural elucidation of the main constituents was performed by 1D- and 2D-NMR spectroscopy and Flow Injection Analysis-Mass Spectrometry (FIA-MS). The analysis revealed the presence of caffeoyl-, dicaffeoyl quinic acid derivatives and flavonoids, along with sesquiterpene lactones. A chlorinated guaiane-type sesquiterpene lactone, pertosin A (17), is here described for the first time. Based on the ability to prevent skin photoaging processes reported for cynaropicrin, the tyrosinase inhibitory activity of the 75% ethanolic extract and isolated sesquiterpenes was evaluated by a spectrophotometric assay. The extract inhibited tyrosinase activity with an IC₅₀ value of 55 μg/mL, while the isolated compounds showed IC₅₀ values between 139 and 312 μM. Pertosin A (17) displayed inhibitory activity (IC₅₀ = 139 μM) comparable to that of kojic acid (IC₅₀ = 134 μM).

The demand for natural ingredients in cosmetic and medical applications is steadily increasing, particularly for anti-aging and skin-lightening products. Sterculia populifolia DC, a member of the Sterculia genus, is known to contain diverse bioactive compounds such as flavonoids, phenolics, and terpenoids, which may offer pharmacological benefits. The aim of this study was to evaluate the anti-aging potential of S. populifolia stem bark extract and its solvent-partitioned fractions through enzyme inhibition assays coupled with phytochemical profiling. The stem bark was extracted using 96% ethanol via maceration, followed by sequential liquid-liquid partitioning with n -hexane, ethyl acetate, n -butanol, and water. Phytochemical constituents were characterized using liquid chromatography-tandem mass spectrometry (LC-MS/MS). The inhibitory activities of the extract and fractions against tyrosinase and elastase enzymes were evaluated using spectrophotometric assays, with kojic acid and quercetin as positive controls, respectively. IC 50 values were calculated to quantify enzyme inhibition potency. LC-MS/MS analysis revealed key bioactive compounds, including 4-[(E)-(3,5-diamino-1H-pyrazol-4-yl)diazenyl]phenol, isofraxidin, and (22E)-ergosta-4,6,8(14),22-tetraen-3-one. Among the tested samples, the ethanol extract exhibited the most potent activity, with an IC 50 of 93.35 µg/mL for elastase inhibition and 133.15 µg/mL for tyrosinase inhibition-classified as strong and moderate activity, respectively. Collectively, these findings demonstrate that S. populifolia stem bark extract possesses promising anti-aging and depigmenting properties, supporting its potential development as a natural bioactive ingredient in cosmetic and skincare formulations.

The elevated melanin production within the skin results in a distressing pigmentation disorder called melanoma. This underscores the importance of developing effective therapeutic approaches, such as nano-delivery systems. The primary objective of this research was to create alginate (AL) nanoparticle (NP) in gel dosage for improving targeting of arbutin (ARB) as a lightening substance to cure and manage melanoma cancer. Ionic gelation and ultrasonication method were employed to prepare ARB-AL-NP followed by In-vitro assessment of the NP. Outcomes noticed that the optimum ARB-AL-NP were in the size of 252.333 ± 11.873 nm with zeta potential -14.766 ± 0.862, greater encapsulation 89.831 ± 1.081%, and exhibited sustained release of ARB over 6 h (56%). In vitro MTT analysis confirmed that the optimum formulation had higher cell survival on the HFF cell line than kojic-acid and ARB, however, it showed a greater cytotoxic effect on the B16f10 cell line than other groups. Besides, ARB-AL-NP was established to obstruct melanogenesis to a superior level than kojic-acid and ARB and considerably suppress L-dopa auto-oxidation contrasted to kojic-acid and ARB). The outcomes of this assessment confirmed that the ARB-AL-NP could potentially serve as a prospective nanocarrier for ARB cutaneous application, thus unveiling novel approaches for addressing melanoma complaints.

Tyrosinase (EC 1.14.18.1) is a binuclear copper enzyme responsible for the rate-limiting steps of melanogenesis, catalyzing the hydroxylation of L-tyrosine and oxidation of L-DOPA into o-quinones that polymerize melanin. Beyond its physiological role in pigmentation, tyrosinase is also implicated in food browning and oxidative stress-related disorders, making it a key target in cosmetic, food, and biomedical industries. This systematic review, conducted following PRISMA guidelines, aimed to identify and analyze microbial metabolites with tyrosinase inhibitory potential as sustainable alternatives to conventional inhibitors such as hydroquinone and kojic acid. Literature searches in Scopus and Web of Science (March 2025) yielded 156 records; after screening and applying inclusion criteria, 11 studies were retained for analysis. The inhibitors identified include indole derivatives, phenolic acids, peptides, and triterpenoids, mainly produced by fungi (e.g., Ganoderma lucidum , Trichoderma sp.), actinobacteria ( Streptomyces , Massilia ), and microalgae ( Spirulina , Synechococcus ). Reported IC 50 values ranged from micromolar to milli-molar levels, with methyl lucidenate F (32.23 µM) and p -coumaric acid (52.71 mM). Mechanisms involved competitive and non-competitive inhibition, as well as gene-level regulation. However, methodological heterogeneity, the predominance of mushroom tyrosinase assays, and limited human enzyme validation constrain translational relevance. Computational modeling, site-directed mutagenesis, and molecular dynamics are proposed to overcome these limitations. Overall, microbial metabolites exhibit promising efficacy, stability, and biocompatibility, positioning them as emerging preclinical candidates for the development of safer and more sustainable tyrosinase inhibitors.