Search Results (103)

Tomato processing generates large amounts of by-products, with seeds representing an underutilized yet protein-rich fraction. This study investigated direct enzyme-assisted protein extraction from non-defatted tomato seeds. Various enzymes, enzyme/substrate ratios, pre-treatments, and incubation temperatures were evaluated and optimized. An enzyme/substrate ratio of 5% (w/w) was found to be optimal, with proteases alone outperforming cell wall-degrading enzymes and two-step extraction strategies. Bromelain, Protamex, and Trypsin, for the first time applied directly to non-defatted tomato seeds, achieved the highest protein recoveries (average 110.56 mg BSA eq/g DW). Among them, Trypsin also produced the highest reducing sugar content (25.07 mg GLU eq/g DW), indicating effective cell wall disruption. Digestates obtained from defatted and non-defatted tomato seeds showed comparable protein contents, demonstrating that defatting was unnecessary. Avoiding the defatting step improved process sustainability by reducing solvent use and energy consumption without significantly affecting protein extraction efficiency. Incubation at 37 °C was preferred over 60 °C, as similar yields were achieved under milder conditions while also reducing energy consumption by approximately three-fold (54,340 kJ vs 150,480 kJ for a 1000 L water-based scale-up simulation). These digestates showed significantly higher antioxidant and, for the first time in tomato seed extracts, anti-tyrosinase activities compared with controls. Protamex-derived samples exhibited the highest bioactivities (7.40 mg AA eq/g DW; 101.36 μg KA eq/g DW). Compared to conventional alkaline–acid extraction followed by enzymatic digestion, the direct enzymatic approach provided higher protein recovery. Overall, this method represents a sustainable strategy for producing bioactive peptide-rich extracts for food and non-food applications. Full article

The invasive plant Tithonia diversifolia is a promising source of botanical insecticides, yet the mechanisms by which its active compounds impair insect physiology remain incompletely characterized. This study investigated the effects of 6-methoxyluteolin (6-ML), a flavonoid isolated from T. diversifolia, on melanization and cuticle integrity in Spodoptera litura larvae. Cuticle melanization, mediated by tyrosinase-catalyzed oxidation of tyrosine-derived substrates, is essential for cuticle sclerotization and immune defense in insects. Whether 6-ML directly targets this pathway has not been previously examined at the biochemical and histological level. Tyrosinase activity and melanin content were measured across 3rd–6th-instar larvae exposed to a concentration gradient of 6-ML (1.625–100 μg/mL). Histological sections of 4th- and 5th-instar larvae were prepared by paraffin embedding and hematoxylin and eosin (H&E) staining. 6-ML significantly reduced tyrosinase activity and melanin content in a concentration-dependent manner across all instars examined. Histological analysis revealed progressive cuticle thinning and loss of pigmentation granules with increasing 6-ML concentration. These findings provide the first biochemical and histological evidence that 6-ML targets the melanization pathway in S. litura, supporting its potential as a melanization-inhibiting botanical insecticide. Full article

The ability of enzymes to recognize and process structurally diverse substrates is fundamental to metabolic flexibility and biological regulation. In melanin biosynthesis, human tyrosinase (Tyr) catalyzes the oxidation of several chemically distinct intermediates, including L-tyrosine, L-DOPA, DHICA, and DHI. Although its catalytic chemistry is well established, the structural basis of substrate selectivity and how it is altered by disease-associated mutations remains unclear. Using molecular docking and molecular dynamics simulations, we mapped the Tyr active site and identified 23 evolutionarily conserved residues that mediate multi-substrate recognition and binding. Across all substrates, binding induces coordinated conformational responses, particularly within an anchoring region (334–347) that provides electrostatic and hydrophobic steering, and a flexible gating loop (374–386) that modulates access and stabilizes bound intermediates. The OCA1B-associated P406L mutation, although distant from the catalytic core, disrupts long-range dynamic coupling and impairs loop flexibility, while 25 ClinVar-listed genetic variants at substrate-interacting residues weaken active-site organization, underscoring the sensitivity of Tyr’s dynamic network to perturbation. Integrating these findings, we propose an ordered multi-substrate binding mechanism in which substrates are first guided by the anchoring region, then aligned by the universal triad, and finally refined through loop-mediated, substrate-specific contacts. Our work suggests a dynamic framework that could be useful for understanding human tyrosinase catalysis, genetic mutation impact, and future engineering strategies. Full article

Strain-promoted azide–alkyne cycloaddition (SPAAC) is widely used in solution-phase bioconjugation. However, its application in surface chemistry remains limited because substrate-independent azide films that remain stable upon reaction with bulky strained alkynes have not yet been developed. In this study, we address this challenge using a melanin-inspired coating based on tyrosine–azide derivatives with different linkers. In particular, we investigated how differences in linker length and hydrophilicity affect the hydrophobic interactions within the film network and, ultimately, determine film stability. Specifically, Tyr-3-N₃, a tyrosine–azide derivative having an azide group tethered to tyrosine through a short three-carbon alkyl linker, was identified as optimal, forming azide-presenting films via tyrosinase-mediated oxidation and retaining integrity during SPAAC with external dibenzocyclooctyne (DBCO) ligands. The optimized poly(Tyr-3-N₃) coatings enabled efficient methoxypolyethylene glycol (mPEG) immobilization, thereby exhibiting excellent antifouling performance against protein adsorption, and further supported spatially controlled protein patterning through soft lithography techniques such as micromolding in capillaries (MIMIC) and microcontact printing (µCP). The approach was broadly applicable with a range of inorganic and polymeric substrates, as well as living cell surfaces; even after encapsulation and SPAAC-based functionalization, the cells remained viable. Collectively, these findings establish a substrate-independent and biocompatible coating platform that preserves film stability through SPAAC functionalization, supporting applications in antifouling coatings, biosensing, and cell surface engineering. Full article

The metabolism of hydroquinone (HQ) by tyrosinase presents significant biochemical and dermatological challenges, particularly due to its association with adverse effects such as exogenous ochronosis (EO). Despite its widespread use in skin-lightening products, the detailed mechanistic pathways of HQ metabolism by tyrosinase remain inadequately understood. This study aims to elucidate the mechanistic insights into the tyrosinase-catalyzed metabolism of HQ, leading to the production of HQ-eumelanin (HQ-EM) and HQ-pheomelanin (HQ-PM). We employed HPLC analysis to detect key intermediates and final metabolites. Results show that mushroom tyrosinase catalyzes the hydroxylation of HQ to 2-hydroxyhydroquinone (HHQ) via the 2-hydroxybenzoquinone (HBQ) pathway, giving rise to HQ-EM. However, in the presence of cysteine, a shift from HBQ to the benzoquinone (BQ) pathway occurs, giving rise to HQ-PM. Hydroiodic acid hydrolysis of HQ-PM and subsequent HPLC-electrochemical analysis identified 4-aminophenol (AP) as degradation product, thereby serving as a novel marker to monitor HQ oxidation in vitro. These results indicate that HQ functions both as a “pseudo” substrate for tyrosinase—undergoing redox exchange with dopaquinone to form BQ—and as a true substrate, yielding HBQ. This dual role contributes to the formation of HQ-EM and HQ-PM. It would be possible that EO is caused by a continuous oxidation of HQ mediated by tyrosinase activity in the skin. Full article

Electrospun fibers serve as a medium for the targeted release of active compounds, facilitating the desired therapeutic effects in drug administration. The point of this study was to find the best conditions for making electrospun fibers from cellulose acetate (CA) and poly(ε-caprolactone) (PCL), mixed with pure oxyresveratrol extract from Artrocarpus lakoocha Roxberg (Moraceae). Additionally, the study focused on evaluating the antioxidant properties, antityrosinase activity, and freeze–thaw stability of the resulting fibers. We incorporated a concentration of oxyresveratrol at 0.1% w/w into various mass ratios of CA/PCL blended fiber sheets (1:0, 3:1, 1:1, 1:3), utilizing mixed solvents of acetone/DMF (2:1% v/v) and chloroform/DMF (9:1% v/v) for preparation. The fiber sheets displayed a continuous and uniform structure, with fiber diameters ranging from 300 to 1000 nanometers. We investigated the release kinetics of oxyresveratrol from the fibrous substrates using the total immersion technique, specifically in phosphate-buffered saline at a pH of 7.4. The results showed that the fiber sheet with a 3:1 w/w ratio of CA to PCL and a 0.1 w/w loading of oxyresveratrol showed the most significant release of oxyresveratrol at the 2 h mark, and it continued to release consistently at this peak value for up to 24 h. The antioxidant and anti-tyrosinase properties of oxyresveratrol in fiber sheets were more stable than those of free oxyresveratrol at the same concentrations. The fiber sheet presents a promising avenue for a user-friendly transdermal patch application. Full article

This study explores the valorization of agro-industrial by-products—riceberry broken rice (RBR) and soybean meal (SBM)—as cost-effective substrates for enhancing exopolysaccharide (EPS) production by Bacillus tequilensis PS21. Eight Bacillus strains were screened, and B. tequilensis PS21 demonstrated the highest EPS yield (2.54 g/100 mL DW). The EPS displayed a strong antioxidant capacity with 65.5% DPPH and 80.5% hydroxyl radical scavenging, and a FRAP value of 6.51 mg Fe²⁺/g DW. Antimicrobial testing showed inhibition zones up to 10.07 mm against Streptococcus agalactiae and 7.83 mm against Staphylococcus aureus. Optimization using central composite design (CCD) and the response surface methodology (RSM) revealed the best production at 5% (w/v) RBR, 3% (w/v) SBM, pH 6.66, and 39.51 °C, yielding 39.82 g/L EPS. This EPS is a moderate-molecular-weight (11,282 Da) homopolysaccharide with glucose monomers. X-ray diffraction (XRD) showed an amorphous pattern, favorable for solubility in biological applications. Thermogravimetric analysis (TGA) demonstrated thermal stability up to ~250 °C, supporting its suitability for high-temperature processing. EPS also exhibited anticancer activity with IC₅₀ values of 226.60 µg/mL (MCF-7) and 224.30 µg/mL (HeLa) at 72 h, reduced colony formation, inhibited cell migration, and demonstrated anti-tyrosinase, anti-collagenase, and anti-elastase effects. This study demonstrates the successful valorization of agro-industrial by-products—RBR and SBM—for the high-yield production of multifunctional EPS with potent antioxidant, antimicrobial, and anticancer properties. The findings highlight the sustainable potential of these low-cost substrates in supporting the development of green and value-added bioproducts, with promising utilizations across the food, pharmaceutical, and cosmetic sectors. Full article

Alpine plants face intense ultraviolet (UV) radiation in high-altitude ecosystems, necessitating adaptive mechanisms like tyrosinase-mediated phenolic metabolism for UV protection. This study aimed to characterize the phenolic profile of Corallodiscus flabellatus (or C. flabellata) and elucidate its mechanistic interactions with tyrosinase under high-altitude environments with intense ultraviolet (UV) radiation. Two novel phenylethanoid glycosides (PhGs) and seven known compounds were isolated using silica gel, ODS, and preparative HPLC, with structures determined via NMR, HR-ESI-MS, and acid hydrolysis. Tyrosinase (EC 1.14.18.1) inhibition assays revealed divergent effects: compound 7 (containing a caffeoyl moiety) exhibited potent inhibition (IC₅₀ = 0.23 μM), comparable to arbutin, while other PhGs displayed activation or biphasic responses. Molecular docking analysis demonstrated that compound 7 stabilized tyrosinase via π-π stacking with Phe264 and Cu²⁺ coordination, whereas activating compounds likely acted as substrates. These findings elucidate the dual regulatory function of PhGs, which activate tyrosinase to counteract acute ultraviolet-induced stress and inhibit its activity to attenuate oxidative overload, thereby advancing our understanding of alpine plant adaptation mechanisms. Full article

Selecting suitable crop species is crucial for optimizing the productivity and nutritional content of microgreens. In this study, twenty-three diverse microgreen species, grown under controlled conditions, were analyzed for yield, bioactive compounds, and antioxidant activities. The microgreens were cultivated on a peat substrate in a controlled environment, with a growth period of 6 to 20 days from planting to harvest. Conditions were maintained at 25 ± 2 °C, a 16 h photoperiod, CO₂ concentration of 1000 ppm, relative humidity of 60 ± 2%, and the LED light was set at 330 μmol/m²/s PPFD. Results from the analysis revealed that the yield, bioactive compounds, and antioxidant potential differed significantly among the twenty-three microgreen species. Unfortunately, the superior microgreens exhibiting greater values for all studied traits could not be identified. However, the principal component analysis (PCA) clustered red radish, rat-tailed radish, and Chinese kale microgreens, which were high in both yield and bioactive compounds. In contrast, red holy basil and lemon basil microgreens had high levels of these compounds but low yields. Additionally, a high level of anti-tyrosinase activity was observed in garland chrysanthemum, Chinese mustard, and Chinese cabbage microgreens. Therefore, these microgreen species can be utilized individually or in varying ratios to produce bioactive compounds in different concentrations that are suitable for various applications. The information presented in this study provides valuable insights for health-conscious consumers and growers for selecting superior species with functional implications. Full article

Hyperpigmentation can be prevented by regulating melanin synthesis through tyrosinase inhibition. As such, tyrosinase inhibitors like arbutin, kojic acid, and hydroquinone are commonly used for skin lightening. Recent studies suggest that certain pyrazole derivatives with tyrosinase activity may also have anticancer potential by influencing melanocyte transformation and tumor progression, positioning them as promising candidates for both cosmetic and therapeutic uses. The aim of this study was to evaluate the tyrosinase inhibitory activity of carbothioamidopyrazole derivatives. Inhibition was determined using the Dixon method, leveraging in silico molecular docking and circular dichroism (CD) spectroscopy to analyze fluorescence quenching. Carbothioamidopyrazole derivatives at the C-3 and C-5 positions in the pyrazole ring may be effective alternatives to traditional skin-lightening agents. These derivatives can induce structural changes in tyrosinase, thus altering its activity, and influence melanocyte transformation. Their dual action as tyrosinase inhibitors and potential anticancer agents makes them valuable for future research. Two compounds exhibited stronger inhibitory activity than kojic acid. Molecular docking suggests that these derivatives may block tyrosinase activity by preventing substrate access to its active site. These results underscore the potential of pyrazole derivatives for both cosmetic and therapeutic applications. Full article

Background/Objectives: Conjugation techniques are increasingly valued in food chemistry for enhancing sensory properties, nutritional profiles, and bioactivity, with potential applications in cosmeceuticals. This study aimed to investigate the potential of Glycine max (L.) Merrill oligopeptide–monosaccharide conjugates as active ingredients in cosmeceuticals, emphasizing their biological activities and stability. Methods: G. max isolate was prepared and subsequently hydrolyzed using alcalase to obtain the oligopeptide (OP). The OP was then conjugated with allulose (AL) or mannose (MN) through a controlled humid-dry heating process to produce the conjugates, OPA and OPM, respectively. Their biological activities, including antioxidant, anti-tyrosinase, anti-collagenase, anti-elastase, and anti-hyaluronidase properties, were assessed and compared to the individual components. Additionally, the irritation potential was evaluated using the hen’s egg test on chorioallantoic membrane (HET-CAM). The stability was examined under varying pH levels, temperatures, and light conditions based on their biological activity profiles. Results: OPA demonstrated the highest antioxidant activity, showing the lowest DPPH^• IC₅₀ value of 198.6 ± 2.7 µg/mL along with a strong ferric reducing power of 1.37 ± 0.04 µg FeSO₄/g sample. Besides, OPM showed superior tyrosinase inhibition on both L-tyrosine and L-DOPA substrates, highlighting its potential for skin whitening. Both OPA and OPM significantly enhanced collagenase inhibition, supporting their anti-aging potential. All samples were non-irritating in the HET-CAM test. The conjugates (OPA and OPM) demonstrated enhanced stability against pH, heat, and light compared to OP, AL, and MN. Conclusions: Oligopeptide–monosaccharide conjugation not only improved bioactivity but also enhanced biological stability, suggesting their potential for use in cosmeceutical applications. Full article

The 2,4-dihydroxyphenyl group is commonly present in the chemical structures of potent tyrosinase inhibitors. Based on this observation, a series of 6-(substituted phenyl)-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]thiazole compounds 1–13 were designed and synthesized as potential tyrosinase inhibitors. Among these, compounds 5 and 9 strongly inhibited mushroom tyrosinase activity. Particularly, compound 9 exhibited nanomolar IC₅₀ values regardless of the substrate used, whereas kojic acid yielded IC₅₀ values of 15.99–26.18 μM. Kinetic studies on mushroom tyrosinase revealed that compounds 5 and 9 competitively inhibited tyrosinase activity, findings further corroborated by in silico docking analysis. In B16F10 cell-based experiments, both compounds effectively inhibited the cellular tyrosinase activity and melanin formation. These inhibitory effects were confirmed through in situ cellular tyrosinase activity assays. Compound 9 exhibited strong antioxidant activity by scavenging radicals, suggesting that its ability to reduce melanin production may be attributed to a combination of its antioxidant and tyrosinase inhibitory properties. Additionally, five compounds, including compound 5, demonstrated effective depigmentation activity in vivo in zebrafish embryos, and their depigmentation efficacy was similar to that of kojic acid, even at concentrations hundreds of times lower. These findings suggest that 6-(substituted phenyl)-[1,3]dioxolo[4′,5′:4,5]benzo[1,2-d]thiazole compounds may be promising anti-melanogenic agents. Full article

Pterostilbene (PTS), which is abundant in blueberries, is a dimethyl derivative of the natural polyphenol resveratrol (RES). Several plant species, including peanuts and grapes, also produce PTS. Although RES has a wide range of health benefits, including anti-cancer properties, PTS has a robust pharmacological profile that includes a better intestinal absorption and an increased hepatic stability compared to RES. Indeed, PTS has a higher bioavailability and a lower toxicity compared to other stilbenes, making it an attractive drug candidate for the treatment of various diseases, including diabetes, cancer, cardiovascular disease, neurodegenerative disorders, and aging. We previously reported that RES serves as a substrate for tyrosinase, producing an o-quinone metabolite that is highly cytotoxic to melanocytes. The present study investigated whether PTS may also be metabolized by tyrosinase, similarly to RES. PTS was oxidized as a substrate by tyrosinase to form an o-quinone, which reacted with thiols, such as N-acetyl-L-cysteine, to form di- and tri-adducts. We also confirmed that PTS was taken up and metabolized by human tyrosinase-expressing 293T cells in amounts several times greater than RES. In addition, PTS showed a tyrosinase-dependent cytotoxicity against B16BL6 melanoma cells that was stronger than RES and also inhibited the formation of melanin in B16BL6 melanoma cells and in the culture medium. These results suggest that the two methyl groups of PTS, which are lipophilic, increase its membrane permeability, making it easier to bind to intracellular proteins, and may therefore be more cytotoxic to melanin-producing cells. Full article

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

Phenolic compounds with a position ortho to the free phenolic hydroxyl group occupied can be tyrosinase substrates. However, ortho-substituted compounds are usually described as inhibitors. The mechanism of action of tyrosinase on monophenols is complex, and if they are ortho-substituted, it is more complicated. It can be shown that many of these molecules can become substrates of the enzyme in the presence of catalytic o-diphenol, MBTH, or in the presence of hydrogen peroxide. Docking studies can help discern whether a molecule can behave as a substrate or inhibitor of the enzyme. Specifically, phenols such as thymol, carvacrol, guaiacol, eugenol, isoeugenol, and ferulic acid are substrates of tyrosinase, and docking simulations to the active center of the enzyme predict this since the distance of the peroxide oxygen from the oxy-tyrosinase form to the ortho position of the phenolic hydroxyl is adequate for the electrophilic attack reaction that gives rise to hydroxylation occurring. Full article