Melanin Pigment Research Articles

Clinico-histopathological profile of acral hyperpigmentation in skin of colour- A case series and review of literature

Acral melanosis refers to increase in melanin pigmentation, in a diffuse, reticulate or focal pattern over the distal portions of the limbs and the head. The underlying causes are broadly classified as genetic or acquired, including various causes like hereditary, infections, inflammatory conditions, traumatic, neoplasms, drug induced and miscellaneous causes. We present seven cases of acral pigmentation with their clinical features, dermoscopy and histopathological findings. Here is an attempt to understand the subject better with the etiological classification and review of literature.

AYURVEDIC MANAGEMENT OF SHWITRA (VITILIGO)- A CASE STUDY.

The Sanskrit term Shweta, which meaning "white patch," is the root of the name Shwitra. Shwitra (Vitiligo) is a condition that is referenced in the classic Kushta Roga Chikitsa and affects a significant section of the pediatric population as a result of poor dietary and lifestyle choices. Shwitra "Shweta Bhava Michanti Shwitram" is what the Kashyapa Samhita says. Kilasa, Daruna, Aruna, and Shweta Kushta are some more names for it. In contemporary medicine, vitiligo is referred to as an auto immune illness and manifests as a white patch on the skin. A widespread, progressive, chronic skin illness called vitiligo is characterized by patches of skin with sharp, frequently hyperpigmented edges caused by a lack of melanin pigments. Approximately 1% of people worldwide suffer from this illness. This condition is included under the general topic of Shwitra in Ayurveda. Every Acharya has the same opinion that the two primary therapeutic modalities mentioned in the classics—Samshodhan Karma and Samshaman Karma—should be used to treat Shwitra or Kushtha first. In their various Samhitas, Acharyas have specified a variety of internal and external uses, as well as sun exposure, for Shaman Chikitsa in the Shwitra Roga. Samhitas discuss a wide range of single and combination medications; among them, Shwitrahar Kashaya and lepa are mentioned in detail. One of them is chosen and shown to be useful for the investigation.

Bioproduction and characterization of melanin pigment produced by the fungal strain Gliocephalotrichum sp. DSGB2

Introduction and Aim: The biosynthetic method of naturally occurring pigment melanin production has become a predominant technique in recent years owing to its cost-effectiveness, low chemical usage, and reduced purification procedure. This study aimed to investigate the significant production, characterization, and biological applications of fungal melanin pigment. Materials and Methods: Melanin production in Gliocephalotrichum sp. DSGB2 strain was carried out by submerged fermentation in tyrosine broth and further purified by acidification and precipitation methods. The purified melanin was characterized by analytical methods such as ultraviolet-visible absorbance, TLC, FTIR spectroscopy, and LC-MS. The DPPH (2,2-diphenyl-1-picrylhydrazyl) radical scavenging analysis was performed to evaluate antioxidant properties of melanin. Results: Pigment was confirmed as melanin based on tyrosinase enzyme assay, UV-visible spectroscopy absorbance, TLC, FTIR, and LC-MS analysis. The biosynthesis of melanin was optimized by varying the culture conditions, and the highest yield was obtained under pH 6 at 30ºC. The strain produced about 3.82 gL-1 of melanin in 5 days under optimum conditions and exhibited antioxidant activity. Conclusion: The study provides new ideas into the biosynthesis of water-soluble melanin by the fungal strain Gliocephalotrichum sp. DSGB2 has broad potential applications as an efficient biomaterial in the biopolymer, pharmaceutical sectors, cosmetic, and environmental.

Analysis of the experimental absorption spectrum of the rabbit lung and identification of its components.

The broadband absorption coefficient spectrum of the rabbit lung presents some particular characteristics that allow the identification of the chromophores in this tissue. By performing a weighted combination of the absorption spectra of water, hemoglobin, DNA, proteins and the pigments melanin and lipofuscin, it was possible to obtain a good match to the experimental absorption spectrum of the lung. Such reconstruction provided reasonable information about the contents of the tissue components in the lung tissue, and allowed to identify a similar accumulation of melanin and lipofuscin.

Effect of Sargassum polycystum on Expression of Tyrosinase and Production of Melanin

Introduction: Melanogenesis, the process responsible for producing melanin pigment, hinges on the activation of the amino acid L-tyrosine by the pivotal enzyme tyrosinase. In cases of hyperpigmentation induced by ultraviolet radiation, there's a surge in both tyrosinase enzyme levels and melanin production. Sargassum polycystum is currently under active investigation for its potential in this regard. This review aims to delve deeper into the properties of Sargassum polycystum and its impact on tyrosinase expression and melanin production. Literature Review: Sargassum polycystum, a brown seaweed commonly found in coastal regions with abundant coral reefs, harbors active compounds like flavonoids, fucoidan, fucoxanthin, and phloroglucinol. Fucoidan, an extract from brown seaweed, exhibits promising anti-inflammatory and antioxidant properties. Recent studies have revealed its ability to impede the melanogenesis process. Specifically, it was observed that fucoidan from brown seaweed extract could dampen α-MSH stimulation while enhancing the activation of the ERK-MAPK pathway, thereby acting as a negative regulator for melanogenesis. Fucoxanthin, another component, showcases antioxidant capabilities. Furthermore, phloroglucinol, found in Sargassum polycystum, exerts tyrosinase inhibitory effects by chelating copper within the enzyme. Flavonoids like catechin, hesperidin, kaempferol, and baicalein in Sargassum polycystum demonstrate inhibitory effects on melanogenesis activation pathways, including suppression of the Erk1/2 pathway, MiTF, and direct inhibition of tyrosinase. Consequently, this leads to reduced tyrosinase expression and melanin production, ultimately attenuating the melanogenesis process. Conclusion: Sargassum polycystum emerges as a promising candidate for combating hyperpigmentation induced by exposure to ultraviolet B radiation.

Streptomyces tagetis sp. nov., a chromomycin producing bacteria isolated from the roots of Tagetes patula.

A novel halotolerant actinobacterium, designated as RG38T, capable of producing black extracellular melanin pigment on SP2 agar, was isolated from the roots of Tagetes patula. Comparative analysis of the 16S rRNA gene sequence revealed the highest similarity to Streptomyces collinus NBRC 12759T (99.3%). Phylogenetic analysis showed that strain RG38T clustered within the genus Streptomyces forming a monophyletic cluster with its close relatives. The average nucleotide identity (ANI), digital DNA-DNA hybridization (dDDH), and amino-acid identity (AAI) values between strain RG38T and related species within the genus Streptomyces were below the standard threshold for prokaryotic species delineation. The DNA G + C content of the strain RG38T was determined to be 73.3%. The genome size measured 7,150,598 bp comprising 17 contigs and encompassed 6,053 protein coding genes. AntiSMASH analysis of the whole genome revealed 35 putative biosynthetic gene clusters (BGCs) responsible for various secondary metabolites. Among these clusters, two gene clusters exhibited 100% similarity to the chromomycin A3, albaflavenone, and anthracimycin, respectively. These compounds were reported to possess significant anticancer and antibacterial activities. LC-MS-based analysis, coupled with further isolation studies, confirmed the production of chromomycins A2 (1), A3 (2), and their derivatives, along with their antibiotic activities. These findings underscore the potential of this novel strain as a novel resource for the discovery of diverse antimicrobial compounds. This study is the first to report an antimicrobial compound producing Streptomyces species isolated from medicinal plant T. patula. Based on a polyphasic study, the strain RG38T isolated from an unexplored habitat with a high potential for new natural products represents a novel species within the genus Streptomyces. Accordingly, we propose the name Streptomyces tagetis sp. nov. for this novel species, with the type strain is RG38T (=KCTC 49624T = TBRC 15113T).

Production and characterization of melanin pigment from black fungus Curvularia soli AS21 ON076460 assisted gamma rays for promising medical uses

Owing to the growing need for natural materials in different fields, studying melanin production from biological sources is imperative. In the current study, the extracellular melanin pigment was produced by the fungus Curvularia soli AS21 ON076460. The factors that affect the production of melanin were optimized by the Plackett-Burman design (P-BD). The effect of gamma irradiation on melanin productivity was investigated. The maximum melanin yield (3.376 mg/L) was elicited by a stimulus of gamma irradiation at 1.0 kGy. The results evoked that, Curvularia soli AS21 ON076460 melanin exhibited excellent antimicrobial activity against all tested bacteria and fungi. Klebsiella pneumoniae ATCC 13883 and P. digitatum were mostly affected by melanin registering the inhibition zone diameters of 37.51 ± 0.012 and 44.25 ± 0.214 mm, respectively. Moreover, Curvularia soli AS21 ON076460 melanin indicated a significant antiviral efficacy (77% inhibition) of Herpes simplex virus (HSV1). The melanin pigment showed antioxidant activities with IC50 of 42 ± 0.021 and 17 ± 0.02 µg/mL against DPPH and NO, respectively. Melanin had cytotoxic action against human breast cancer and skin cancer cell lines (Mcf7and A431) as well as exerting a low percentage of cell death against normal skin cell lines (Hfb4). Melanin was effective in wound management of human skin cells by 63.04 ± 1.83% compared with control (68.67 ± 1.10%). The novelty in the study is attributed to the possibility of using gamma rays as a safe method in small economic doses to stimulate melanin production from the fungi that have been isolated. In summary, melanin produced from fungi has significant biological activities that encourage its usage as a supportive medical route.

A Swine Burn Model for Investigating the Healing Process in Multiple Depth Burn Wounds.

Burn wound healing is a complex and long process. Despite extensive experience, plastic surgeons and specialized teams in burn centers still face significant challenges. Among these challenges, the extent of the burned soft tissue can evolve in the early phase, creating a delicate balance between conservative treatments and necrosing tissue removal. Thermal burns are the most common type, and burn depth varies depending on multiple parameters, such as temperature and exposure time. Burn depth also varies in time, and the secondary aggravation of the "shadow zone" remains a poorly understood phenomenon. In response to these challenges, several innovative treatments have been studied, and more are in the early development phase. Nanoparticles in modern wound dressings and artificial skin are examples of these modern therapies still under evaluation. Taken together, both burn diagnosis and burn treatments need substantial advancements, and research teams need a reliable and relevant model to test new tools and therapies. Among animal models, swine are the most relevant because of their strong similarities in skin structure with humans. More specifically, Yucatan minipigs show interesting features such as melanin pigmentation and slow growth, allowing for studying high phototypes and long-term healing. This article aims to describe a reliable and reproducible protocol to study multi-depth burn wounds in Yucatan minipigs, enabling long-term follow-up and providing a relevant model for diagnosis and therapeutic studies.

Unraveling the mystery of ocular retinoid turnover: Insights from albino mice and the role of STRA6

A delicate balance between photon absorption for vision and protection of photoreceptors from light damage is pivotal for ocular health. This equilibrium is governed by the light-absorbing 11-cis-retinylidene chromophore of visual pigments, which, upon bleaching, transforms into all-trans-retinal and undergoes regeneration through an enzymatic pathway, named the visual cycle. Chemical side reactions of retinaldehydes during the recycling process can generate byproducts that may result in a depletion of retinoids. In our study, we have clarified the crucial roles played by melanin pigmentation and the retinoid transporter STRA6 in preventing this loss and preserving the integrity of the visual cycle. Our experiments initially confirmed that consecutive green and blue light bleaching of isolated bovine rhodopsin produced 9-cis and 13-cis retinal. The same unusual retinoids were found in the retinas of mice exposed to intense light, with elevated concentrations observed in albino mice. Examining the metabolic fate of these visual cycle byproducts revealed that 9-cis-retinal, but not 13-cis-retinal, was recycled back to all-trans-retinal through an intermediate called isorhodopsin. However, investigations in Stra6 knockout mice unveiled that the generation of these visual cycle byproducts correlated with a light-induced loss of ocular retinoids and visual impairment. Collectively, our findings uncover important novel aspects of visual cycle dynamics, with implications for ocular health and photoreceptor integrity.

Study of the localization of pigment cells in the skin of scaly carp of various ages (Cyprinus carpio L.)

Morphological methods of fish research provide an opportunity to study their biological systems – cells, tissues, and organs in normal and pathological conditions – in depth at all levels of structural organization. The work aimed to investigate the morphological features of localization of skin pigment cells in scaly carp (Cyprinus carpio L.) of different ages. The study was conducted in the laboratory of complex ichthyopathological studies at the Department of Ichthyology and Zoology of the Belotserkiv National Agrarian University. One-, two-, and three-year-old scaly carp from the feeding ponds of PJSC “Chernigivrybhosp” were used. From which the scales were removed, skin samples of scaly carp (Cyprinus carpio L.) were used as material for research. Tissue samples were taken from freshly caught fish for the research. Our study established that pigment cells in carp of different ages were localized in the upper and lower layers of the dermis and hypodermis and in the lateral connective tissue septum at the level of the lateral line that divides the lateral muscles. In addition, in the carp of the same age, in contrast to the older age groups, isolated clusters of pigment cells were observed in the loose connective tissue between the muscle fibers of the superficial lateral muscle. During the histological examination, we also discovered the presence of pigment cells in the skin, particularly melanophores. Thus, the skin of peers of scaly carp was located in single clusters and had a rounded shape and a concentrated distribution of melanin pigment. Many melanophores were observed in the lower layer of the dermis at the border with the hypodermis. In the area of the lateral line, in the connective tissue septum, at the level of the deep lateral muscle, large strands of melanophores were detected.

A critique of the use of colour lightness in animal studies

Abstract Colour lightness has received considerable attention owing to its diverse functional aspects, such as in thermoregulation, pathogen resistance, and photoprotection. However, the theoretical basis underlying the function of colour lightness is closely related to melanin pigments. Therefore, here we discuss that neglecting other colour-producing mechanisms may bias interpretation of the results. In general, colour lightness is indiscriminately employed as a measure of melanization. Nevertheless, animals may exhibit colours that derive from several pigmentary and structural mechanisms other than melanin. Our primary argument is that colour lightness should not be used indiscriminately before knowing the colour-producing mechanism and validating correlated physiological parameters. For instance, the use of colour lightness as a proxy for thermal or photoprotection function must be validated for pterins, ommochromes, and structural colours.

Skin histopathological responses of Oreochromis niloticus (Nile tilapia) to transportation in water with and without salt

Oreochromis niloticus (Nile tilapia) is a well-known economic fish species that can thrive under the right environmental circumstances. The transport of live fish, either for food or as companion animals, presents a big issue for animal welfare at the same time it is considered one of stressful conditions. Hence, the present study investigated the skin histopathological responses of O. niloticus that were attributed to stress and salt addition during transportation. Three experimental groups of O. niloticus the 1st is the control non-transported group (CG), the 2nd is transport in water without salt (PT-S) and the 3rd is transport in water containing 5gL− 1salt (PT + S), the last 2 groups were transported in 5 h transport model. Results indicate that the skin of PT-S fish showed a marked decrease in epidermal thickness, decreased number of goblet cells, and an increase in the sub-epidermal and dermal pigments with the presence of large edematous vacuoles. Fish skin from PT + S demonstrated mild hydropic swelling in epidermal cells with normal goblet (mucous) cells density, and more or less normal melanin pigment distribution in sub epidermis and on the dermis layers, however, dermis showed mild edematous spaces. Scanning microscopy of PT-S skin tissue showed few scratched white patches among normal regions that may represent a thickened surface with the decreased number of goblets cell opening, while the PT + S group showed moderate preservation of surface skin architectures with the presence of goblet (mucous) cells opening in spite of presence of slight thickened white patches. The estimated total lesion changes present in PT-S group showed a significant increase (P < 0.001) compared with the control (CG) group. On the other hand, PT + S showed significant (P < 0.001) improvement in the overall previously recorded changes compared with the PT-S group, and a non- significant change in the histological architectures compared with the control group. Our findings underlined the importance of skin and its mucous cover health during transportation. The use 5 gL− 1salt during O. niloticus transportation appears to preserve the surface skin features, and keep the goblet (mucous) cells open to the external surface, and may act as a deterrent for the release of mucus from goblet (mucous) cells in response to stress and lessen the stress of transportation.

CRISPR/Cas9-mediated ebony knockout causes melanin pigmentation and prevents moth Eclosion in Ectropis grisescens

Ectropis grisescens (Lepidoptera: Geometridae) is a destructive tea pest in China. Mimesis, characterized by changing body color, is an important trait of E. grisescens larvae. Hence, identifying melanin pathway-related genes may contribute to developing new pest control strategies. In the present study, we cloned Egebony, a gene potentially involved in melanin pigmentation in E. grisescens, and subsequently conducted CRISPR/Cas9-mediated targeted mutagenesis of Egebony to analyze its role in pigmentation and development. At the larvae, prepupae, and pupae stages, Egebony-knockout individuals exhibited darker pigmentation than the wild-type. However, Egebony knockout did not impact the colors of sclerotized appendants, including ocelli, setae, and claws. While mutant pupae could successfully develop into moths, they were unable to emerge from the puparium. Notably, embryo hatchability and larval survival of mutants remained normal. Further investigation indicated that mutant pupae exhibited significantly stronger shearing force than the wild-type, with the pigmented layer of mutant pupae appearing darker and thicker. Collectively, these results suggest that the loss of Egebony might increase the rigidity of the puparium and prevent moth eclosion. This study provides new insights into understanding the function and diversification of ebony in insect development and identifies a lethal gene that can be manipulated for developing effective pest control strategies.

(2-Methylbutyryl)shikonin Naturally Occurring Shikonin Derivative Ameliorates the α-MSH-Induced Melanogenesis via ERK1/2 and p38 MAP Kinase-Mediated Down-Regulation of the MITF Transcription Factor.

Cutaneous pigmentation is an important phenotypic trait whose regulation, despite recent advances, has yet to be completely elucidated. Melanogenesis, a physiological process of melanin production, is imperative for organism survival as it provides protection against the environmental insults that majorly involve sunlight-induced skin photodamage. However, immoderate melanin synthesis can cause pigmentation disorders associated with a psychosocial impact. In this study, the hypopigmentation effect of (2-methylbutyryl)shikonin, a natural product present in the root extract of Lithospermum erythrorhizon, and the underlying mechanisms responsible for the inhibition of melanin synthesis in α-MSH-stimulated B16F10 cells and C57BL/6J mice was studied. Non-cytotoxic concentrations of (2-methylbutyryl)shikonin significantly repressed cellular tyrosinase activity and melanin synthesis in both in vitro and in vivo models (C57BL/6J mice). (2-Methylbutyryl)shikonin remarkably abolished the protein expression of MITF, tyrosinase, tyrosinase-related protein 1, and tyrosinase-related protein 2, thereby blocking the production of pigment melanin via modulating the phosphorylation status of MAPK proteins, viz., ERK1/2 and p38. In addition, specific inhibition of ERK1/2 attenuated the inhibitory effects of (2-methylbutyryl)shikonin on melanin synthesis, whereas selective inhibition of p38 augmented the inhibitory effect of BSHK on melanin synthesis. Moreover, topical application of (2-methylbutyryl)shikonin on C57BL/6J mouse tails remarkably induced tail depigmentation. In conclusion, with these findings, we, for the first time, report the hypopigmentation effect of (2-methylbutyryl)shikonin via inhibition of cellular tyrosinase enzyme activity, subsequently ameliorating the melanin production, thereby indicating that (2-methylbutyryl)shikonin is a potential natural therapy for hyperpigmentation disorders.

Phototoxic Reactions Inducted by Hydrochlorothiazide and Furosemide in Normal Skin Cells-In Vitro Studies on Melanocytes and Fibroblasts.

Hypertension is known to be a multifactorial disease associated with abnormalities in neuroendocrine, metabolic, and hemodynamic systems. Poorly controlled hypertension causes more than one in eight premature deaths worldwide. Hydrochlorothiazide (HCT) and furosemide (FUR), being first-line drugs in the treatment of hypertension, are among others the most frequently prescribed drugs in the world. Currently, many pharmacoepidemiological data associate the use of these diuretics with an increased risk of adverse phototoxic reactions that may induce the development of melanoma and non-melanoma skin cancers. In this study, the cytotoxic and phototoxic potential of HCT and FUR against skin cells varied by melanin pigment content was assessed for the first time. The results showed that both drugs reduced the number of metabolically active normal skin cells in a dose-dependent manner. UVA irradiation significantly increased the cytotoxicity of HCT towards fibroblasts by approximately 40% and melanocytes by almost 20% compared to unirradiated cells. In the case of skin cells exposed to FUR and UVA radiation, an increase in cytotoxicity by approximately 30% for fibroblasts and 10% for melanocytes was observed. Simultaneous exposure of melanocytes and fibroblasts to HCT or FUR and UVAR caused a decrease in cell viability, and number, which was confirmed by microscopic assessment of morphology. The phototoxic effect of HCT and FUR was associated with the disturbance of redox homeostasis confirming the oxidative stress as a mechanism of phototoxic reaction. UVA-irradiated drugs increased the generation of ROS by 10-150%, and oxidized intracellular thiols. A reduction in mitochondrial potential of almost 80% in melanocytes exposed to HCT and UVAR and 60% in fibroblasts was found due to oxidative stress occurrence. In addition, HCT and FUR have been shown to disrupt the cell cycle of normal skin cells. Finally, it can be concluded that HCT is the drug with a stronger phototoxic effect, and fibroblasts turn out to be more sensitive cells to the phototoxic effect of tested drugs.

Redox modulation of oxidatively-induced DNA damage by ascorbate enhances both in vitro and ex-vivo DNA damage formation and cell death in melanoma cells

Elevated genomic instability in cancer cells suggests a possible model-scenario for their selective killing via the therapeutic delivery of well-defined levels of further DNA damage. To examine this scenario, this study investigated the potential for redox modulation of oxidatively-induced DNA damage by ascorbate in malignant melanoma (MM) cancer cells, to selectively enhance both DNA damage and MM cell killing. DNA damage was assessed by Comet and ɣH2AX assays, intracellular oxidising species by dichlorofluorescein fluorescence, a key antioxidant enzymatic defence by assessment of catalase activity and cell survival was determined by clonogenic assay. Comet revealed that MM cells had higher endogenous DNA damage levels than normal keratinocytes (HaCaT cells); this correlated MM cells having higher intracellular oxidising species and lower catalase activity, and ranked with MM cell melanin pigmentation. Comet also showed MM cells more sensitive towards the DNA damaging effects of exogenous H2O2, and that ascorbate further enhanced this H2O2-induced damage in MM cells; again, with MM cell sensitivity to induced damage ranking with degree of cell pigmentation. Furthermore, cell survival data indicated that ascorbate enhanced H2O2-induced clonogenic cell death selectively in MM cells whilst protecting HaCaT cells. Finally, we show that ascorbate serves to enhance the oxidising effects of the MM therapeutic drug Elesclomol in both established MM cells in vitro and primary cell cultures ex vivo. Together, these results suggest that ascorbate selectively enhances DNA damage and cell-killing in MM cells. This raises the option of incorporating ascorbate into clinical oxidative therapies to treat MM.

Bioproduction and optimization of newly characterized melanin pigment from Streptomyces djakartensis NSS-3 with its anticancer, antimicrobial, and radioprotective properties

BackgroundMelanin is a natural pigment that is considered a promising biomaterial for numerous biotechnological applications across several industries. Melanin has biomedical applications as antimicrobial, anticancer, and antioxidant properties. Additionally, in the pharmaceutical and cosmetic industries, it is used in drug delivery and as a radioprotective agent. Also, melanin has environmental uses in the fields of bioremediation and the food industry. The biosynthesis of melanin pigment is an area of interest for researchers due to its multifunctionality, high compatibility, and biodegradability. Therefore, our present work is the first attempt to characterize and optimize the productivity of melanin pigment from Streptomyces djakartensis NSS-3 concerning its radioprotection and biological properties.ResultsForty isolates of soil actinobacteria were isolated from the Wadi Allaqui Biosphere Reserve, Egypt. Only one isolate, ACT3, produced a dark brown melanin pigment extracellularly. This isolate was identified according to phenotypic properties and molecular phylogenetic analysis as Streptomyces djakartensis NSS-3 with accession number OP912881. Plackett–Burman experimental design (PBD) and response surface methodology (RSM) using a Box-Behnken design (BBD) were performed for optimum medium and culturing conditions for maximum pigment production, resulting in a 4.19-fold improvement in melanin production (118.73 mg/10 mL). The extracted melanin pigment was purified and characterized as belonging to nitrogen-free pyomelanin based on ultraviolet–visible spectrophotometry (UV–VIS), Fourier transform infrared (FT-IR), Raman spectroscopy, scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDX), and NMR studies. Purified melanin demonstrated potent scavenging activity with IC50 values of 18.03 µg/mL and revealed high potency as sunscreens (in vitro SPF = 18.5). Moreover, it showed a nontoxic effect on a normal cell line (WI38), while it had a concentration-dependent anticancer effect on HCT116, HEPG, and MCF7 cell lines with IC50 = 108.9, 43.83, and 81.99 µg/mL, respectively. Also, purified melanin had a detrimental effect on the tested MDR bacterial strains, of which PA-09 and SA-04 were clearly more susceptible to melanin compared with other strains with MICs of 6.25 and 25 µg/mL, respectively.ConclusionOur results demonstrated that the newly characterized pyomelanin from Streptomyces djakartensis NSS-3 has valuable biological properties due to its potential photoprotective, antioxidant, anticancer, antimicrobial, and lack of cytotoxic activities, which open up new prospects for using this natural melanin pigment in various biotechnological applications and avoiding chemical-based drugs.

Designing bioinspired multifunctional nanoplatforms to support wound healing and skin regeneration: Mg-hydroxyapatite meets melanins

Melanin is a multifunctional biological pigment that recently emerged as endowed with anti-inflammatory, antioxidant, and antimicrobial properties and with high potentialities in skin protection and regenerative medicine. Here, a biomimetic magnesium-doped nano-hydroxyapatite (MgHA) was synthesized and decorated with melanin molecules starting from two different monomeric precursors, i.e. 5,6-dihydroxyindole-2-carboxylic acid (DHICA) and dopamine (DA), demonstrating to be able to polymerize on the surface of MgHA nanostructures, thus leading to a melanin coating. This functionalization was realized by a simple and green preparation method requiring mild conditions in an aqueous medium and room temperature. Complementary spectroscopy and electron imaging analyses were carried out to define the effective formation of a stable coating, the percentage of the organic compounds, and the structural properties of resulting melanin-coated nanostructures, which showed good antioxidant activity. The in vitro interaction with a cell model, i.e. mouse fibroblasts, was investigated. The excellent biocompatibility of all bioinspired nanostructures was confirmed from a suitable cell proliferation. Finally, the enhanced biological performances of the nanostructures coated with melanin from DHICA were confirmed by scratch assays. Jointly our findings indicated that low crystalline MgHA and melanin pigments can be efficiently combined, and the resulting nanostructures are promising candidates as multifunctional platforms for a more efficient approach for skin regeneration and protection.

Efficient production and characterization of melanin from Thermothelomyces hinnuleus SP1, isolated from the coal mines of Chhattisgarh, India.

In the present study, fungi were isolated and screened from barren land in south-eastern Coalfields limited (SECL) in Chhattisgarh, India. Out of 14 isolated fungi, only three fungal isolates exhibited pigmentation in screening studies. The isolated fungal strain SP1 exhibited the highest pigmentation, which was further utilized for in vivo production, purification, and characterization of melanin pigment. The physical and chemical properties of the fungal pigment showed insolubility in organic solvents and water, solubility in alkali, precipitation in acid, and decolorization with oxidizing agents. The physiochemical characterization and analytical studies of the extracted pigment using ultraviolet-visible spectroscopy and Fourier transform infrared (FTIR) confirmed it as a melanin pigment. The melanin-producing fungus SP1 was identified as Thermothelomyces hinnuleus based on 18S-rRNA sequence analysis. Furthermore, to enhance melanin production, a response surface methodology (RSM) was employed, specifically utilizing the central composite design (CCD). This approach focused on selecting efficient growth as well as progressive yield parameters such as optimal temperature (34.4°C), pH (5.0), and trace element concentration (56.24 mg). By implementing the suggested optimal conditions, the production rate of melanin increased by 62%, resulting in a yield of 28.3 mg/100 mL, which is comparatively higher than the actual yield (17.48 ± 2.19 mg/100 mL). Thus, T. hinnuleus SP1 holds great promise as a newly isolated fungal strain that could be used for the industrial production of melanin.

Rodents show darker and redder coloration in warm and rainy environments

AbstractAimAnimal coloration varies in response to environmental conditions. One well‐known principle, Gloger's rule, suggests that warmer and wetter environments lead to more pigmented animals. Yet, the original formulation lacks differentiation between the two primary melanin pigments: eumelanin and pheomelanin. We examined spatial eumelanin and pheomelanin variation to unravel the impact of various ecological factors on pigment deposition, and to assess support for the complex version of Gloger's rule.LocationSouth America.Time PeriodContemporary.Major Taxa StudiedSigmodontine rodents.MethodsWe extracted pelage color data from 231 species and quantified the geographic variation in eu‐ and pheomelanin deposition. We performed linear multiple regression to investigate the influence of temperature, precipitation, predator diversity, and UVA‐B radiance in eumelanin (lightness) and pheomelanin (redness).ResultsOur findings support the original formulations of Gloger's rule. Rodents in warmer and rainier regions, which also entails greater exposure to UV radiation and a diverse range of predators, exhibit darker‐colored pelage. In addition, redder rodents prevail in warmer environments. However, contrary to the rule predictions, we observe a reversal for reddish patterns in relation to precipitation, with rainier regions showcasing more intense red rodents.Main ConclusionsOur study breaks new ground by investigating previously unexplored facets of Gloger's rule in a continental mammalian group. We discovered compelling evidence that darker and redder coloration aligns closely with temperature and rainfall gradients. Although we found support for eumelanin–pelage predictions, expectations for pheomelanin pigmentation were only partially met. Our results might suggest that selective pressures act differently on dark and reddish coloration, revealing that coloration patterns in response to climate are more intricate than previously formulated.