Depigmenting effect of Kojic acid esters in hyperpigmented B16F1 melanoma cells

Simultaneous delivery of Paclitaxel and Bcl-2 siRNA via pH-Sensitive liposomal nanocarrier for the synergistic treatment of melanoma

pH-sensitive drug carriers that are sensitive to the acidic (pH = ~6.5) microenvironments of tumor tissues have been primarily used as effective drug/gene/siRNA/microRNA carriers for releasing their payloads to tumor cells/tissues. Resistance to various drugs has become a big hurdle in systemic chemotherapy in cancer. Therefore delivery of chemotherapeutic agents and siRNA's targeting anti apoptotic genes possess advantages to overcome the efflux pump mediated and anti apoptosis-related drug resistance. Here, we report the development of nanocarrier system prepared from kojic acid backbone-based cationic amphiphile containing endosomal pH-sensitive imidazole ring. This pH-sensitive liposomal nanocarrier effectively delivers anti-cancer drug (Paclitaxel; PTX) and siRNA (Bcl-2), and significantly inhibits cell proliferation and reduces tumor growth. Tumor inhibition response attributes to the synergistic effect of PTX potency and MDR reversing ability of Bcl-2 siRNA in the tumor supporting that kojic acid based liposomal pH-sensitive nanocarrier as efficient vehicle for systemic co-delivery of drugs and siRNA.

Optical clearing of melanoma in vivo: characterization by diffuse reflectance spectroscopy and optical coherence tomography

Melanoma is the most aggressive type of skin cancer, with significant risk of fatality. Due to its pigmentation, light-based imaging and treatment techniques are limited to near the tumor surface, which is inadequate, for example, to evaluate the microvascular density that is associated with prognosis. White-light diffuse reflectance spectroscopy (DRS) and near-infrared optical coherence tomography (OCT) were used to evaluate the effect of a topically applied optical clearing agent (OCA) in melanoma in vivo and to image the microvascular network. DRS was performed using a contact fiber optic probe in the range from 450 to 650 nm. OCT imaging was performed using a swept-source system at 1310 nm. The OCT image data were processed using speckle variance and depth-encoded algorithms. Diffuse reflectance signals decreased with clearing, dropping by ∼ 90% after 45 min. OCT was able to image the microvasculature in the pigmented melanoma tissue with good spatial resolution up to a depth of ∼ 300 μm without the use of OCA; improved contrast resolution was achieved with optical clearing to a depth of ∼ 750 μm in tumor. These findings are relevant to potential clinical applications in melanoma, such as assessing prognosis and treatment responses. Optical clearing may also facilitate the use of light-based treatments such as photodynamic therapy.

Enzymatic synthesis of bioactive compounds with high potential for cosmeceutical application

Cosmeceuticals are cosmetic products containing biologically active ingredients purporting to offer a pharmaceutical therapeutic benefit. The active ingredients can be extracted and purified from natural sources (botanicals, herbal extracts, or animals) but can also be obtained biotechnologically by fermentation and cell cultures or by enzymatic synthesis and modification of natural compounds. A cosmeceutical ingredient should possess an attractive property such as anti-oxidant, anti-inflammatory, skin whitening, anti-aging, anti-wrinkling, or photoprotective activity, among others. During the past years, there has been an increased interest on the enzymatic synthesis of bioactive esters and glycosides based on (trans)esterification, (trans)glycosylation, or oxidation reactions. Natural bioactive compounds with exceptional theurapeutic properties and low toxicity may offer a new insight into the design and development of potent and beneficial cosmetics. This review gives an overview of the enzymatic modifications which are performed currently for the synthesis of products with attractive properties for the cosmeceutical industry.

Populus nigra (Salicaceae) absolute rich in phenolic acids, phenylpropanoïds and flavonoids as a new potent tyrosinase inhibitor

The purpose of this study was to evaluate the tyrosinase inhibitory capacity of Populus nigra buds absolute (PBA) and compare it to kojic acid (KA), controversial reference tyrosinase inhibitor. Populus nigra buds were extracted with hexane and ethanol to obtain PBA. The inhibitory effect of this absolute was first tested on the mushroom Agaricus bisporus tyrosinase. Then the depigmenting potential of PBA was tested on B16F10 murine melanocytes by assaying the activity of tyrosinase and melanin content. Consecutively, a microscopic analysis of intracellular melanin granules was performed. Finally, melanised reconstructed human epidermis (RHE) were used to assess the lightening potential activity of this PBA on human skin. Results show that PBA inhibits A. bisporus tyrosinase (IC50=77±8ppm) and inhibits melanocytes B16F10 tyrosinase (IC50=27±1ppm). PBA decreases intracellular melanin levels, with 50% loss at 39±9ppm. Finally, PBA at 1000ppm lightens RHE and decreases their melanin content of 20%. PBA is a strong inhibitor of tyrosinase and reduces melanogenesis in melanocytes B16F10. Thus, PBA has potential applications in skin-lightening cosmetics.

In vitro and in silico studies of the inhibitory effects of some novel kojic acid derivatives on tyrosinase enzyme

OBJECTIVES

Tyrosinase is a key enzyme in pigment synthesis. Overproduction of melanin in parts of the skin results in hyperpigmentation diseases. This enzyme is also responsible for the enzymatic browning in fruits and vegetables. Thus, its inhibitors are of great importance in the medical, cosmetic and agricultural fields.

MATERIALS AND METHODS

A series of twelve kojic acid derivatives were designed to be evaluated as tyrosinase activity inhibitors. The potential inhibitory activity of these compounds was investigated in silico using molecular docking simulation method. Four compounds with a range of predicted tyrosinase inhibitory activities were prepared and their inhibitory effect on tyrosinase activity was evaluated. The antioxidant properties of these compounds were also investigated by in vitro DPPH (2,2-diphenyl-1-picrylhydrazyl) and hydrogen peroxide scavenging assays.

RESULTS

Compound IIId exhibited the highest tyrosinase inhibitory activity with an IC50 value of 0.216 ± 0.009 mM which was in accordance with the in silico ΔGbind results (-13.24 Kcal/mol).

CONCLUSION

Based on the docking studies, from the twelve compounds studied, one (IIId) appeared to have the highest inhibition on tyrosinase activity. This was confirmed by enzyme activity measurements. Compound IIId has an NO2 group which binds to both of Cu(2+) ions located inside the active site of the enzyme. This compound appeared to be even stronger than kojic acid in inhibiting tyrosinase activity. The DPPH free radical scavenging ability of all the studied compounds was more than that of BHT. However, they were not as strong as BHT or gallic acid in scavenging hydrogen peroxide.

Optimisation and Characterisation of Lipase-Catalysed Synthesis of a Kojic Monooleate Ester in a Solvent-Free System by Response Surface Methodology

Kojic acid is widely used to inhibit the browning effect of tyrosinase in cosmetic and food industries. In this work, synthesis of kojic monooleate ester (KMO) was carried out using lipase-catalysed esterification of kojic acid and oleic acid in a solvent-free system. Response Surface Methodology (RSM) based on central composite rotatable design (CCRD) was used to optimise the main important reaction variables, such as enzyme amount, reaction temperature, substrate molar ratio, and reaction time along with immobilised lipase from Candida Antarctica (Novozym 435) as a biocatalyst. The RSM data indicated that the reaction temperature was less significant in comparison to other factors for the production of a KMO ester. By using this statistical analysis, a quadratic model was developed in order to correlate the preparation variable to the response (reaction yield). The optimum conditions for the enzymatic synthesis of KMO were as follows: an enzyme amount of 2.0 wt%, reaction temperature of 83.69°C, substrate molar ratio of 1:2.37 (mmole kojic acid:oleic acid) and a reaction time of 300.0 min. Under these conditions, the actual yield percentage obtained was 42.09%, which is comparably well with the maximum predicted value of 44.46%. Under the optimal conditions, Novozym 435 could be reused for 5 cycles for KMO production percentage yield of at least 40%. The results demonstrated that statistical analysis using RSM can be used efficiently to optimise the production of a KMO ester. Moreover, the optimum conditions obtained can be applied to scale-up the process and minimise the cost.

Natural, semisynthetic and synthetic tyrosinase inhibitors

Tyrosinase plays a pivotal role in the synthesis of melanin pigment synthesis on skin utilizing tyrosine as a substrate. Melanin is responsible for the protection against harmful ultraviolet irradiation, which can cause significant pathological conditions, such as skin cancers. However, it can also create esthetic problems when accumulated as hyperpigmented spots. Various skin-whitening ingredients which inhibit tyrosinase activity have been identified. Some of them, especially ones with natural product origins, possess phenolic moiety and have been employed in cosmetic products. Semi-synthetic and synthetic inhibitors have also been developed under inspiration of the natural inhibitors yet some of which have no phenolic groups. In this review, tyrosinase inhibitors with natural, semi-synthetic and synthetic origins are listed up with their structures, activities and characteristics. Further, a recent report on the adverse effect of a natural melanin synthesis inhibitor which was included in skin-whitening cosmetics is also briefly discussed.

Augmenting the antifungal activity of an oxidizing agent with kojic Acid: control of penicillium strains infecting crops

Oxidative treatment is one of the strategies for preventing Penicillium contamination in crops/foods. The antifungal efficacy of hydrogen peroxide (H₂O₂; oxidant) was investigated in Penicillium strains by using kojic acid (KA) as a chemosensitizing agent, which can enhance the susceptibility of pathogens to antifungal agents. Co-application of KA with H₂O₂ (chemosensitization) resulted in the enhancement of antifungal activity of either compound, when compared to the independent application of each agent alone. Of note, heat enhanced the activity of H₂O₂ to a greater extent during chemosensitization, whereby the minimum inhibitory or minimum fungicidal concentrations of H₂O₂ was decreased up to 4 or 13 fold, respectively, at 35–45 °C (heat), when compared to that at 28 °C (normal growth temperature). However, heat didn’t increase the antifungal activity of KA, indicating specificity exists between heat and types of antifungals applied. The effect of chemosensitization was also strain-specific, where P. expansum (both parental and fludioxonil-resistant mutants) or P. italicum 983 exhibited relatively higher susceptibility to the chemosensitization, comparing to other Penicillium strains tested. Collectively, chemosensitization can serve as a potent antifungal strategy to lower effective dosages of toxic antifungal substances, such as H₂O₂. This can lead to coincidental lowering of environmental and health risks.

Quantitative analysis of ligand effects on bioefficacy of nanoemulsion encapsulating depigmenting active

Efficient skin delivery of active molecules is the main challenge to overcome in order to achieve significant therapeutic efficiency of cosmetics or dermo-pharmaceutical products. Nanocarriers such as nanoemulsions have been envisaged to overcome main challenges of active solubilization, protection and transport to their site of biological action. Nonetheless, their skin permeation is still limited and a new approach is required to significantly improve bioavailability. We here explored the possibility of increasing the whitening activity of a model active, licorice, by implementing a targeting approach of nanoemulsions to melanocyte cells. Targeting requires particle surface modification with specific molecules favoring nanoemulsion/cells contact through ligand-receptor interactions. The uniqueness of our strategy is that unlike classical covalent chemical grafting, we propose a self-assembled strategy based on a selection of amphiphilic ligands able to localize at nanoemulsion droplets interface. Four ligand candidates were thus assayed in terms of formulation and in vitro biological evaluation: a palmitoyl-peptide (palmitoyl-GQPR), a lipidized hyaluronic acid (caproyl-HA) and two amphiphilic actives (polydatin and isopilosine). A functional analysis based on a cellular assay of melanin inhibition was realized. The intrinsic properties of ligand candidates were first evaluated. Then, nanoemulsions encapsulating a drug model, licorice, and targeted with the different ligand candidates were assayed. The use of caproyl-HA significantly improved bioefficacy of the encapsulated licorice, suggesting a better interaction with the cells. The improved value observed was not attributed to a synergetic action as caproyl-HA did not evidence intrinsic melanogenesis modulation activity. In this study, we demonstrated the feasibility of targeting nanoemulsion droplets without chemical covalent modification of nanoemulsion droplets to increase bioefficacy of encapsulated drugs in vitro.

Skin delivery of kojic acid-loaded nanotechnology-based drug delivery systems for the treatment of skin aging

The aging process causes a number of changes in the skin, including oxidative stress and dyschromia. The kojic acid (KA) is iron chelator employed in treatment of skin aging, and inhibits tyrosinase, promotes depigmentation. Nanotechnology-based drug delivery systems, such as liquid crystalline systems (LCSs), can modulate drug permeation through the skin and improve the drug activity. This study is aimed at structurally developing and characterizing a kojic acid-loaded LCS, consists of water (W), cetostearyl isononanoate (oil—O) and PPG-5-CETETH-20 (surfactant-S) and evaluating its in vitro skin permeation and retention. Three regions of the diagram were selected for characterization: A (35% O, 50% S, 15% W), B (30% O, 50% S, 20% W) and C (20% O, 50% S, 30% W), to which 2% KA was added. The formulations were subjected to polarized light microscopy, which indicated the presence of a hexagonal mesophase. Texture and bioadhesion assay showed that formulation B is suitable for topical application. According to the results from the in vitro permeation and retention of KA, the formulations developed can modulate the permeation of KA in the skin. The in vitro cytotoxic assays showed that KA-unloaded LCS and KA-loaded LCS didn't present cytotoxicity. PPG-5-CETETH-20-based systems may be a promising platform for KA skin delivery.

Synergism of antifungal activity between mitochondrial respiration inhibitors and kojic acid

Co-application of certain types of compounds to conventional antimicrobial drugs can enhance the efficacy of the drugs through a process termed chemosensitization. We show that kojic acid (KA), a natural pyrone, is a potent chemosensitizing agent of complex III inhibitors disrupting the mitochondrial respiratory chain in fungi. Addition of KA greatly lowered the minimum inhibitory concentrations of complex III inhibitors tested against certain filamentous fungi. Efficacy of KA synergism in decreasing order was pyraclostrobin > kresoxim-methyl > antimycin A. KA was also found to be a chemosensitizer of cells to hydrogen peroxide (H₂O₂), tested as a mimic of reactive oxygen species involved in host defense during infection, against several human fungal pathogens and Penicillium strains infecting crops. In comparison, KA-mediated chemosensitization to complex III inhibitors/H₂O₂ was undetectable in other types of fungi, including Aspergillus flavus, A. parasiticus, and P. griseofulvum, among others. Of note, KA was found to function as an antioxidant, but not as an antifungal chemosensitizer in yeasts. In summary, KA could serve as an antifungal chemosensitizer to complex III inhibitors or H₂O₂ against selected human pathogens or Penicillium species. KA-mediated chemosensitization to H₂O₂ seemed specific for filamentous fungi. Thus, results indicate strain- and/or drug-specificity exist during KA chemosensitization.