No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Final Report of the Safety Assessment of Kojic Acid as Used in Cosmetics
Abstract
Kojic acid functions as an antioxidant in cosmetic products. Kojic acid was not a toxicant in acute, chronic, reproductive, and genotoxicity studies. While some animal data suggested tumor promotion and weak carcinogenicity, kojic acid is slowly absorbed into the circulation from human skin and likely would not reach the threshold at which these effects were seen. The available human sensitization data supported the safety of kojic acid at a use concentration of 2% in leave-on cosmetics. Kojic acid depigmented black guinea pig skin at a concentration of 4%, but this effect was not seen at 1%. The Cosmetic Ingredient Review (CIR) Expert Panel concluded that the 2 end points of concern, dermal sensitization and skin lightening, would not be seen at use concentrations below 1%; therefore, this ingredient is safe for use in cosmetic products up to that level.
... Tyrosinase is widely distributed and can be isolated Since a tyrosinase-catalysed reaction is highly associated with hyperpigmentation, discovering tyrosinase inhibitors is of great importance in medicinal, cosmetic and cosmeceutical products for the treatment and prevention of pigmentation disorders [14]. Unfortunately, the capacity of commercially available tyrosinase inhibitors as whitening agents is not completely satisfactory [14][15][16][17][18][19][20]. Although they can efficiently inhibit tyrosinase activity, their exploitation for this purpose has been limited due to the side effects and the lack of safety regulations governing their use [20]. ...
... Although they can efficiently inhibit tyrosinase activity, their exploitation for this purpose has been limited due to the side effects and the lack of safety regulations governing their use [20]. For example, hydroquinone (2), one of the most potent and frequently prescribed tyrosinase inhibitors, causes significant pathological conditions, such as skin irritation, contact dermatitis and ochronosis, and might have cytotoxic effects on melanocytes [14][15][16][17][18][19][20][21]. Because of the risks of adverse effects, the European Committee banned hydroquinone, its derivative formulation has been withdrawn from cosmetics and it is only available through prescription [1]. ...
... Because of the risks of adverse effects, the European Committee banned hydroquinone, its derivative formulation has been withdrawn from cosmetics and it is only available through prescription [1]. Unfortunately, none of the alternatives to hydroquinone (2), such as arbutin (3) or kojic acid (4), are offered as a safe and effective replacement ( Figure 2) [14,[16][17][18][19][20]. Recently, the plant extracts and isolated compounds from natural sources have been extensively utilized for searching new, safe and effective products with antityrosinase activity, as a novel approach for the treatment of pigmentary disorders [14,[22][23][24]. ...
Tyrosinase is a multifunctional, copper-containing and rate-limiting oxidase that catalyses crucial steps in the melanogenesis pathway and is responsible for skin-pigmentation abnormalities in mammals. Numerous tyrosinase inhibitors derived from natural and synthetic sources have been identified as an objective for the development of anti-melanogenesis agents. However, due to side effects and lack of expected efficiency, only a small percentage of them are used for medical and cosmetic purposes. This critical review focuses on searching for novel active substances and recently discovered plant-derived anti-tyrosinase inhibitors from the Morus genus (Moraceae family). A detailed analysis of their structure–activity relationships is discussed. The information contained in this article is crucial for the cosmetics and medical industries, in order to show new directions for the effective search for natural anti-melanogenesis products (with satisfactory efficiency and safety) to treat and cure hyperpigmentation.
... Some cosmetic substances can disrupt the functioning of the endocrine system or have carcinogenic, mutagenic and reprotoxic effects [4][5]. Others are sources of irritation, allergies [6][7][8], dyschromia and stretch marks [2,3]. In 2017, more than 140 cosmetic products were withdrawn from the French market by the competent authorities because of the presence of prohibited substances [9]. ...
... Apart from these substances prohibited by European regulation 2009, kojic acid was also common on the labels of no rinse cosmetics products on the market with a rate of 13.11%. It can be used in cosmetic products at a maximum threshold of 1% in the EU [8]. It was only 4.09% of the labels that specified the concentration used in this study. ...
... It was between 2% to 3%. This result is close to that of Burnett et al., In 2010 where the concentration of 4% was reported by the competent authorities on 79 cosmetic products [8]. While above 1%, it depigments the skin and is extremely irritating, allergenic to the skin and eyes [8]. ...
Introduction: Several substances used in cosmetic products can be dangerous for human health. These substances can induce a public health problem, especially in developing countries such as Togo; where there is no strict control regarding cosmetic products. The objectives of this study were to verify the presence of hazardous ingredients on the labels of cosmetics products. Method: This study was a cross-sectional descriptive study, which focused on body and hygiene cosmetics, intended for children and adults, sold in pharmacies and in a market in Lomé. Results: In total, 800 cosmetics products were studied, including 400 in pharmacies and 400 in the market. At the pharmacy as in the market, 244 no-rinse cosmetics products (milks, creams, serums, oils and lotions) and 156 rinse-off cosmetics products (bar and gel soaps) were evaluated. Hazardous ingredients were present both on the labels of cosmetic products collected at the pharmacy as well as at the market. But some hazardous ingredients were more frequent on the labels of the market cosmetic than on those of the pharmacy. Substances banned by the European Union such as hydroquinone and clobestasol propionate; allergenic and prohibited perfumes such as hydroxyisohexyl-3-cyclohexene carboxaldehyde; regulated preservatives as methylparaben and banned ingredients such as methylisothiazolinone and isobutylparaben; and unclassified dangerous depigmenting substances such as kojic acid and glutathione were the main families of hazardous ingredients identified on the labels of cosmetic products. Conclusion: This study confirms the absence of a control and regulatory system concerning cosmetic products marketed in Lome (Togo).
... Several studies have been conducted to evaluate the safety and efficiency of tyrosinase inhibitors in the cosmeceutical and medicinal industries [2,23]. These inhibitors are important due to their ability to prevent pigmentation disorders. ...
... KA is listed as an 'additive' in the Inventory of Cosmetic Ingredients database of Europe, and in countries such as Switzerland, there is a ban on the use of KA as a cosmetic ingredient [13]. Other skin sensitization data have reinforced the safety of KA at a dosage of 2% in leave-on products [1,23,24] KA depigmented black guinea pig skin at a dosage of 4%, but these results were not observed at 1%. The CIR Expert Panel also concluded that at concentrations below 1%, dermal sensitization and skin lightening would not be seen, thus recommending the usage at 1% [9,25]. ...
... KA was also not found to be toxic in chronic, reproductive, genotoxicity, and acute studies [23] Another study on acute, chronic, reproductive, and genotoxic aspects by Aytemir and Karakay (2012), revealed that KA was not toxic, as it is slowly released into the human skin; it would not reach the limit of tumor promotion and low carcinogenicity [1]. ...
This article reviews the use of Kojic Acid (KA) as a skin-lightening ingredient in the cosmetics industry. In 1907, Saito discovered KA, a natural product; it has since become one of the most investigated skin-lightening agents. This paper highlights the findings of the research conducted on this agent. It has been found that KA has certain disadvantages, and researchers have attempted to mitigate these disadvantages by designing new equivalents of KA that are more efficient in tyrosinase inhibition. These equivalents are also safe to use and have improved properties and solubility. The Cosmeceutical Ingredient Review (CIR) indicates that this ingredient can be safely used at a concentration not higher than 1% due to its cytotoxicity. Other scientific data also support its safety at a concentration of 2% or less. It was shown to be helpful in the treatment of hyper pigmentary disorders, such as freckles, age spots, post-inflammatory hyperpigmentation, and melasma, which has been proven clinically.
... 25 Other topical products commonly used in hyperpigmentation disorders such as arbutin and kojic acid, have low systemic absorption, no reported fetomaternal risk in animal and no data available on human reproductive system. [27][28][29] These drugs have not been approved and classi ed by the US FDA. As a glycosylated hydroquinone, arbutin has lower toxicity than its main metabolite and considered safe to be used in pregnancy. ...
... 27 In mice study, kojic acid was reported to have no maternal risks or fetal damage. 29 No data available on reproductive system. 29 -Still not recommended and further studies are required. ...
... 29 No data available on reproductive system. 29 -Still not recommended and further studies are required. ...
Objective:
We sought to know the efficacy and safety profile of topical products for use during pregnancy.
Methods:
We used PubMed, Embase, and Cochrane Library to review literature on topical products and pregnancy.
Results:
A majority of pregnant women develop skin changes, including physiological or hormonal changes, worsening of preexisting skin conditions, or the appearance of new dermatoses during pregnancy. Most pregnant women are concerned about the availability of treatments options with good safety profiles, especially for skin and hair treatments, to maintain their appearance and health. Although most of the treatments are recommended to be used after delivery, there are some alternatives to prevent and treat skin lesions during pregnancy.
Conclusion:
The most current and comprehensive information about the efficacy and safety profile of topical products in pregnancy are necessary.
... These effects have also been observed in mice exposed to kojic acid for 26 weeks [47]. Long-term exposure (13 weeks) will increase liver mass [48]. ...
... High kojic acid doses (over 1 g/kg body weight) administered to rodents caused diuresis and kidney pallor [47]. Long-term exposure (13 weeks) will increase kidney mass [48]. Kojic acid-exposed rats (2% of food, 55 weeks) exhibited urinary cylinders and damage to the urinary tract [51]. ...
... After being exposed to fungi that produce kojic acid, rodent myocardium exhibited hemorrhagic lesions [57]. Exposed to doses of 900 mg/kg body weight kojic acid, pregnant female mice experienced a reduction in heart mass compared to the control group [48]. ...
Machine learning is a branch of artificial intelligence that allows computer systems to learn directly from examples, data, and experience. Statistical modeling is more about finding connections between variables and consequently the impact of these relationships, while also catering for prediction. It should be clear that these two methodologies are different in terms of their purpose, despite the fact that they use similar means to get there. The evaluation of the machine learning algorithm uses a set of tests to validate its accuracy. Although, for a statistical model, the analysis of regression parameters by confidence intervals, significance tests and other tests can be used to assess the legitimacy of the model. To demonstrate the applications and usefulness of this theory, an experimental study was conducted on zebrafish exposed to mycotoxin. Methods: Patulin (70 µg/L) and kojic acid (100 mg/L, 204 mg/L, and 284 mg/L) were administered by immersion to zebrafish once daily for a period of 7 days before the behavior testing. The following behavioral tests were performed: a novel tank test (NTT) (to assess the explorative behavior and anxiety); and a Y-maze test (which measures the spontaneous explorative behavior). Behavioral tests were performed on separate days. For the behavior tests, the statistical analysis was performed using ANOVA variation analysis (two-way ANOVA). All results are expressed as the mean ± standard error of the mean. The values of the general index F for which p < 0.05 were considered statistically significant. Results: Y-maze—patulin exposure led to an intensification of the locomotor activity and an increased traveled distance and number of arm entries. By increasing the spontaneous alternation between the aquarium’s arms, patulin has shown a stimulating effect on spatial memory. In the case of zebrafish exposed to 100 mg/L kojic acid, the traveled distance was shorter by 27% than the distance attained by those in the control group. The higher doses of kojic acid (204 mg/L and 284 mg/L) led to an increased locomotor activity, distance traveled, number of arm entries, and the spontaneous alternation. The increase in spontaneous alternation demonstrates that 204 mg/L and 284 mg/L kojic acid doses had a stimulating effect on spatial memory. Novel tank test—compared to the control group, the traveled distance of the patulin-exposed fish is slightly reduced. Compared to the control group, the traveled distance of the kojic acid-exposed fish is reduced, due to a shorter mobile time (by 25–27% in the case of fish exposed to 204 mg/L and 284 mg/L kojic acid). Patulin and kojic acid exhibit toxic effects on zebrafish liver, kidney, and myocardium and leads to severe alteration. We continued the analysis by trying some machine learning algorithms on the classification problems in the case of the two behavioral tests MAZE and NTT, after which we concluded that the results were better in the case of the NTT test relative to the MAZE test and that the use of decision tree algorithms leads to amazing results, knowing that their hierarchical structure allows them to learn signals from both classes. Conclusions: The groups exposed to patulin and kojic acid show histological changes in the liver, kidneys, and myocardial muscle tissue. The novel tank test, which assesses exploratory behavior, has been shown to be conclusive in the behavioral analysis of fish that have been given toxins, demonstrating that the intoxicated fish had a decreased explorative behavior and increased anxiety. We were able to detect a machine learning algorithm in the category of decision trees, which can be trained to classify the behavior of fish that were given a toxin in the category of those used in the experiment, only by analyzing the characteristic features of the NTT Behavior Test.
... Hydroquinone and kojic acid, 12 known components of anti-pigmentation cosmetics, have been reported to be unsafe in concentrations required for a substantial skin-lightening effect. 13,14 Therefore, there is a need to search for novel effective and safe tyrosinase inhibitors. ...
... The results show that melanogenesis in B16F0 cells was inhibited by all the synthetic compounds 1-15 (except for compound 11), kojic acid, and DMSO in a dose-dependent manner. Almost all compounds (3)(4)(5)(6)(7)(8)(9)(10)(11)(12)(13)(14) inhibited 0-3% of melanogenesis at the concentration of 10 mM, and 4-13% at 40 mM, which does not place them among the most potent melanogenesis inhibitors. Only TSC 1-3 and the tripeptide conjugate 15 inhibited melanogenesis more than kojic acid at these two concentrations. ...
The development of skin-care products is recently growing. Cosmetic formulas containing active ingredients with proven efficacy, namely cosmeceuticals, are based on various compounds, including peptides. Different whitening agents featuring anti-tyrosinase activity have been applied in the cosmeceutical field. Despite their availability, their applicability is often limited due to several drawbacks including toxicity, lack of stability, and other factors. In this work, we present the inhibitory effect on diphenolase activity of thiosemicarbazone (TSC)-peptide conjugates. Tripeptides FFY, FWY, and FYY were conjugated with three TSCs bearing one or two aromatic rings via amide bond formation in a solid phase. Compounds were then examined as tyrosinase and melanogenesis inhibitors in murine melanoma B16F0 cell line, followed by the cytotoxicity assays of these cells. In silico investigations explained the differences in the activity, observed among tested compounds. Mushroom tyrosinase was inhibited by TSC1-conjugates at micromolar level, with IC50 lower than this for kojic acid, a widely used reference compound. Up to now, this is the first report regarding thiosemicarbazones conjugated with tripeptides, synthesised for the purpose of tyrosinase inhibition.
... KA has been used as an ingredient in cosmetics, i.e., for a whitening agent and a protective against UV light [21]. KA is also widely used clinically as an anti-fungal and anti-bacterial agent, painkiller and anti-inflammation drug, and cytotoxic agent; as an ...
... KA has been used as an ingredient in cosmetics, i.e., for a whitening agent and a protective against UV light [21]. KA is also widely used clinically as an anti-fungal and anti-bacterial agent, painkiller and anti-inflammation drug, and cytotoxic agent; as an anti-melanosis agent, an anti-browning agent for fruits Xanthan gum, a precursor for flavor enhancers in the food industry field [22], a reagent for an ion determination substrate for comenic acid synthesis in the chemical industry, and as an insecticidal mycotoxin, chelating agent, and pesticides in agriculture [23]. ...
Our previous work showed that citrinin (CTN) produced bay Penicillium citrinum inhibited the production of aflatoxin by Aspergillus parasiticus. We also reported that CTN was non-enzymatically converted to a novel CTN-KA adduct with kojic acid (KA) in aqueous condition. We herein observed that unlike CTN, the CTN-KA adduct does not show antimicrobial activity against Escherichia coli or Bacillus subtilis or any cytotoxic effect on HeLa cells, suggesting that CTN was detoxified by KA by the formation of the CTN-KA adduct. To examine the function of KA production by fungi, we isolated A. parasiticus mutants with impaired KA production. When the mutants were incubated in either liquid or agar medium supplemented with CTN, they were more susceptible to CTN than the wild KA-producing strain. The same results were obtained when we used the A. oryzae KA-producing strain RIB40 and KA-non-producing strains. When KA was added to the CTN-containing agar medium, the inhibition of growth by CTN was remarkably mitigated, suggesting that the production of KA protected the fungal growth from CTN’s toxicity. We also observed that CTN enhanced the production of KA by A. parasiticus as well as A. oryzae strains. Reverse transcription-PCR showed that CTN enhanced the expression of KA biosynthetic genes (kojA, kojR, and kojT) of A. parasiticus. However, the enhancement of KA production with CTN was repressed by the addition of α-tocopherol or butylated hydroxy anisole, suggesting that KA production is enhanced by oxidative stress via the formation of reactive oxygen species caused by CTN. In contrast, α−tocopherol did not affect inhibition of AF production as well as fungal growth by CTN, suggesting that the regulation of these inhibitions with CTN might be different from that of KA production. We propose a regulation scheme of CTN for each of KA production, AF production, and fungal growth in A. parasiticus.
... On the other hand, in November 2005, the Japanese Ministry of Health, Labor, and Welfare conducted a toxicity test of kojic acid and confirmed that there was no particular problem in safety. And although the use of kojic acid in cosmetics is now permitted, it is still controversial for its use [18,19]. In addition, kojic acid is not oil-soluble and is unstable at high temperature when stored for a long period of time. ...
... In addition, kojic acid is not oil-soluble and is unstable at high temperature when stored for a long period of time. Thus, because of these disadvantages, it cannot be added to cosmetic products that are oil-soluble as raw materials [12,18]. ...
Although melanogenesis is a defense mechanism against ultraviolet (UV)-induced skin damage, abnormally excessive melanin production causes pigmentation disorders. Tyrosinase, as a key factor for melanin synthesis, plays an important role in inducing skin pigmentation. Therefore, the inhibition of tyrosinase is crucial in preventing skin pigmentation in the cosmetics and medicine fields. However, the majority of well-known tyrosinase inhibitors have been discontinued due to toxic effects on the skin or lack of selectivity and/or stability. In this study, we evaluated possible anti-melanogenic effects of catechin-7-O-α-L-rhamnopyranoside (C7R) isolated from the stem bark of Ulmus parvifolia, to discover a new tyrosinase inhibitor that has both safety and stability. When C7R was pretreated in B16F10 melanoma cells stimulated by α-melanocyte-stimulating hormone, this compound reduced melanin accumulation and murine tyrosinase activity. In line with these results, C7R inhibits tyrosinase purified from a mushroom in vitro like kojic acid and arbutin. Furthermore, C7R exhibited a competitive inhibition on a Lineweaver-Burk plot. Next, the underlying mechanisms of the C7R-mediated tyrosinase inhibitory effect were sought through docking simulation and pharmacophore analysis between tyrosinase residues and C7R. The results of these analyses showed that C7R had binding energy of -14.5kcal/mol, and indicated that C7R interacts with tyrosinase through an aromatic ring and various hydrophobic and hydrogen bonds. Together, our results suggest that C7R can be applied as a novel natural anti-melanogenic agent that inhibits tyrosinase.
... [32,83] In the preparations for skincare, the optimal concentration of kojic acid is 1.0%. [87] Percutaneous absorption of kojic acid in healthy postmenopausal women was tested before and after applying a cream containing kojic acid (1.0%). The data have shown that kojic acid concentration in plasma was slightly above the limit of 1 ng/ml, and thus, it was clearly proven that kojic acid does not play a role in its transdermal penetration into the blood. ...
... [86,93] According to the U.S. Food and Drug Administration reports, kojic acid can be used at concentrations ranging from 0.1% to 2.0% in 16 products. [87] As a matter of fact, there has never been reported a fatal event of human poisoning by kojic acid. [85] 8 | CONCLUSIONS Kojic acid is produced predominantly biologically by various types of fungal strains in the aerobic fermentation process by using carbon, nitrogen, and minerals containing substrates. ...
This review traces the road leading to the demonstration of a variety of kojic acid chemical and biological properties. It illustrates the biological effects of several synthetic kojic acid derivatives. Besides the main capability of kojic acid to inhibit the activity of tyrosinase in melanin synthesis, the focus is also on antibacterial, antifungal, antiproliferative, anti-inflammatory, and other biological activities of kojic acid derivatives, which may be applicable in medicine. Kojic acid derivatives manifest antiparasitic effects and its metal complexes may serve as potential radioprotective agents. Several kojic acid derivatives exert antidiabetic therapeutic potential as nuclear peroxisome proliferator-activated receptor alpha/gamma dual agonists. Kojic acid derivatives show pancreatic lipase inhibitor properties and some of its derivatives are cognate ligands for the histamine H3 receptor. Recently, "KojoTacrines" were reported as novel perspective preparations for the therapy of Alzheimer's disease. Kojic acid derivatives possess insecticidal or pesticidal activity, and they are powerful chelators, able to form iron(III) containing nanocomposites, as well. Toxicology and health aspects of products containing kojic acid produced by the cosmetic, health care, or food industry are summarized. Kojic acid thus represents a highly attractive molecule containing a skeleton that allows the synthesis of new kojic acid derivatives to create a novel class of effective and specific pharmaceutical preparations.
... Kojik asit melazma tedavisinde genellikle %1-4 oranında kullanılmaktadır. Ancak, yüksek konsantrasyonlarda irritan özelliğinden dolayı SCCS tarafından topikal olarak %1 konsantrasyonda kullanılması önerilmektedir [27,28]. ...
... Ancak, yüksek konsantrasyonlarda postinflamatuvar hiperpigmentasyona neden olduğundan paradoksal bir pigment koyulaşması oluşturabilir. Arbutinin sentetik formu olan deoksiarbutinin arbutine göre daha fazla tirozinaz inhibisyonu sağladığı belirlenmiştir [13,28]. Arbutin ve deoksiarbutin, reçetesiz satılan birçok cilt aydınlatma kreminde bulunmasına rağmen melazma tedavisindeki etkinliği net olarak kanıtlanamamıştır. ...
... The U.S. Food and Drug Administration (FDA) classifies A. oryzae (koji) as generally regarded as safe (GRAS), despite the fact that its safety has not been properly investigated (Hamajima et al., 2016). The FDA has not authorized KA for use in medicinal products for skin-lightning purposes (Belsito et al., 2009). ...
The cosmetic industry makes extensive use of kojic acid (KA); however, the toxicity of KA in humans is not well known. By monitoring oxidative stress, mitogen-activated protein kinase (MAPK) and nuclear factor kappa B (NFκB) signalling in human hepatoma (HepG2) cells after a 24 h exposure, this study aimed to identify the toxicity of KA. KA toxicity [4.22, 8.02 and 12.67 mM] was assessed using mitochondrial output, antioxidant responses, macromolecule damage, MAPK signalling, inflammation, and cell death markers, using spectrophotometry, luminometry, Western blot and qPCR. Apoptosis was confirmed by reduced cell viability and increased caspases -9 (p < 0.0001), -8 (p = 0.0003), and -3/7 (p < 0.0001) activities at 4.22 mM & 8.02 mM. LDH leakage was present at 12.67 mM, providing significant evidence of necrosis. Malondialdehyde (MDA) levels significantly increased at 4.22 mM (p < 0.0001). There was an increase of phosphorylated nuclear factor erythroid-2 factor-2 (p-Nrf2) at 4.22 mM & 8.02 mM, whilst at 12.67 mM decreased p-Nrf2 (p < 0.0001) was observed. KA increased p38 expression (p = 0.0011). The findings point to significant suppression of the NFκB inflammatory pathway at 8.02 mM (p < 0.0001). This study showed that KA initiated MAPK signalling due to oxidative stress and suppressed inflammation. HepG2 cells showed minimal toxicity to KA.
... Other skin pigmentation ingredients in the current marketplace include kojic acid, which is effective; however, it too has toxicity concerns; thus, the European and Asian markets have banned use of this ingredient. 11 Arbutin is a common skin pigmentation ingredient derived from the Indian Hawthorne plant, but it is a naturally occurring hydroquinone derivative. It is also available as the synthetic deoxyarbutin, but may have some of the same issues as hydroquinone. ...
Background:
The recent removal of hydroquinone from the over-the-counter market has created a need for modern skin lightening formulations. An effective pigment lightening formulation must be non-irritating to prevent skin darkening from post-inflammatory hyperpigmentation, penetration enhanced to reach the epidermal/dermal junction, contain anti-inflammatory ingredients, and address multiple mechanisms of pigment production.
Objective:
The objective of this research was to demonstrate the efficacy of a topical multimodal pigment lightening preparation containing tranexamic acid, niacinamide, and licorice.
Methods:
Fifty female subjects 18+ years of all Fitzpatrick skin types with mild to moderate facial dyspigmentation were enrolled. Subjects were provided with the study product for twice daily use on the entire face and an SPF50 sunscreen with evaluations occurring at Week 4, Week 8, Week 12, and Week 16. The investigator used a face map to identify a pigmented target site on the face for dermaspectrophotometer (DSP) measurement. The dermatologist investigator completed a baseline facial efficacy and tolerability assessment. The subjects completed a tolerability assessment.
Results:
48/50 subjects completed the study without tolerability issues. The DSP readings demonstrated a statistically significant reduction in target spot pigmentation at Week 16. The investigator assessed a 37% decrease in pigment intensity, a 31% decrease in pigment extent, a 30% decrease in pigment homogeneity, a 45% improvement in brightness, a 42% improvement in clarity, and a 32% improvement in overall facial skin dyspigmentation at Week 16.
Conclusion:
The combination of penetration enhanced tranexamic acid, niacinamide, and licorice was effective in inducing facial pigment lightening.
... However, this difference in activity is not necessarily a problem, as the use of kojic acid in cosmetics is controversial due to its toxicity and mutagenicity. [35,36] Similar concerns are raised for another strong and widely used tyrosinase inhibitor, hydroquinone. [37] It seems that high tyrosinase inhibitory activity is often correlated with higher toxicity, therefore there is still much room left to find tyrosinase inhibitors with good physico-chemical properties, with the tyrosinase inhibitory itself not being the most important parameter. ...
... Unfortunately, neither substance offers a safe and effective alternative. Kojic acid is likely a carcinogen [32] while arbutin shares a toxicity profile with dihydroquinone [33]. In this context there is an urgent need for new strategies for the rational conception of Ty-inhibitors. ...
In human, Tyrosinase enzyme (TyH) is involved in the key steps of protective pigments biosynthesis (in skin, eyes and hair). The use of molecules targeting its binuclear copper active site represents a relevant strategy to regulate TyH activities. In this work, we targeted 2-Hydroxypyridine-N-oxide analogs (HOPNO, an established chelating group for the tyrosinase dicopper active site) with the aim to combine effects induced by combination with a reference inhibitor (kojic acid) or natural substrate (tyrosine). The HOPNO-MeOH (3) and the racemic amino acid HOPNO-AA compounds (11) were tested on purified tyrosinases from different sources (fungal, bacterial and human) for comparison purposes. Both compounds have more potent inhibitory activities than the parent HOPNO moiety and display strictly competitive inhibition constant, in particular with human tyrosinase. Furthermore, 11 appears to be the most active on the B16-F1 mammal melanoma cells. The investigations were completed by stereospecificity analysis. Racemic mixture of the fully protected amino acid 10 was separated by chiral HPLC into the corresponding enantiomers. Assignment of the absolute configuration of the deprotected compounds was completed, based on X-ray crystallography. The inhibition activities on melanin production were tested on lysates and whole human melanoma MNT-1 cells. Results showed significant enhancement of the inhibitory effects for the (S) enantiomer compared to the (R) enantiomer. Computational studies led to an explanation of this difference of activity based for both enantiomers on the respective position of the amino acid group versus the HOPNO plane.
... For years, only a few naturally occurring compounds, including arbutin, kojic acid and rhododendrol (Figure 2A), have been used as cosmetic additives since most of the proposed melanogenesis inhibitors and skin whitening agents have generated concern due to their toxicity, scarce membrane crossing, or low inhibitory activity [7][8][9][10][11]. Recently, several nature-inspired tyrosinase inhibitors have been prepared and proposed as an alternative to those commercially available [12][13][14][15][16]. The crystal structure of Bacterium megaterium tyrosinase, containing or not one molecule of kojic acid, was obtained at high resolution [17,18], allowing to shed some light on the mechanism of the inhibitor/substrate reaction since the catalytic site of tyrosinase is well-conserved in human, animals, bacteria, fungi and plants [19]. ...
Tyrosinase is a well-known copper-containing metalloenzyme typically involved in the synthesis of melanin. Recently, curcumin and several synthetic derivatives have been recognized as tyrosinase inhibitors with interesting anti-melanogenic therapeutic activity. In this study, three curcumin-inspired compounds 1, 6 and 7 were prepared in yields ranging from 60 to 88 % and spectrophotometric, electrochemical, in vitro and in silico analyses were carried out. The viability of PC12 cells, a rat pheochromocytoma derived-cell line, with compounds 1, 6 and 7, showed values around 80% at 5 µM concentration. In cell proliferation assays, compounds 1, 6 and 7 did not show significant toxicity on fibroblasts nor melanoma cells up to 10 µM with viability values over 90%. The inhibition of tyrosinase activity was evaluated both by a UV-Vis spectroscopic method at two different concentrations, 0.2 and 2.0 µM, and by amperometric assay with IC50 for compounds 1, 6 and 7 ranging from 11 to 24 nM. Melanin content assays on human melanoma cells were performed to test the capability of compounds to inhibit melanin biosynthesis. All compounds exerted a decrease in melanin content, with compound 7 being the most effective by showing a melanogenesis inhibition up to four times greater than arbutin at 100 µM. Moreover, the antioxidant activity of the selected inhibitors was evaluated against H2O2 in amperometric experiments, whereby compound 7 was about three times more effective compared to compounds 1 and 6. The tyrosinase X-ray structure of Bacterium megaterium crystal was used to carry out molecular docking studies in the presence of compounds 1, 6 and 7 in comparison with that of kojic acid and arbutin, two conventional tyrosinase inhibitors. Molecular docking of compounds 6 and 7 confirmed the high affinity of these compounds to tyrosinase protein.
... This compound is frequently used in docking studies and was one of the first inhibitors to be identified. However, this compound has high carcinogenesis [28], which limits it to cosmetic uses. All these undesirable side effects restrict its human use. ...
Overexpression of melanin contributes to darkening of plant and fruit tissues and skin hyperpigmentation, leading to melasma or age spots. Although melanin biosynthesis is complex and involves several steps, a single enzyme known as tyrosinase is key to regulating this process. The melanogenesis pathway is initiated by oxidation of the starting material l-tyrosine (or l-DOPA) to dopaquinone by tyrosinase; the resulting quinone then serves as a substrate for subsequent steps that eventually lead to production of melanin. Medicinal plants are considered a good source of tyrosinase inhibitors. This study investigated the tyrosinase inhibitory activity of A. mollis leaf extracts and their phytochemicals. Significant activity was verified in the ethanol extract –EEt (IC50 = 1.21 µg/mL). Additionally, a kinetic study showed that this tyrosinase inhibition occurs by DIBOA (2,4-dihydroxy-1,4-benzoxazin-3-one) and verbascoside contribution through a non-competitive reaction mechanism. A synergistic effect on tyrosinase inhibition was observed in the binary combination of the compounds. In conclusion, both EEt and a mixture of two of its phytochemicals can be effective tyrosinase inhibitors and can be used as a bleaching agent for cosmetic formulations in the future.
... Kojic acid is a fungal metabolite that exhibits inhibitory activity against tyrosinase. Kojic acid is often used as a positive control to discover new tyrosinase inhibitors [33,34]. ...
... A standard compound kojic acid is a fungal metabolite exhibited tyrosinase enzyme inhibitory activity, it is effect mediated via copper chelating mechanism to the active site of the enzyme, because of it is efficacy it is used as positive control in tyrosinase inhibition assay and in cosmetic and food industry. But it is applications have been limited due to many recorded side effects (Burnett et al., 2010). ...
Context: Sage (Salvia officinalis) is an ancient valuable plant used in the treatment of variant health issues. Aims: To evaluate the depigmentation activity of S. officinalis leaf chloroformic (SOCF) and ethanolic (SOMF) extracts via its efficacy to inhibit tyrosinase enzyme using in vitro model and bioassay-guided identification and quantification of the main active constituents. Methods: Plant extracts efficacy as a depigmentation agent has been studied via mushroom tyrosinase inhibition using in vitro model at two concentrations (100 and 200 µg/mL). Extracts were analyzed for phenolic compounds that could be responsible for the biological activity using LC-MS/MS analysis. Results: Significant potency at a high concentration of 200 µg/mL for the methanolic extract were recorded (p≤0.05). The LC-MS/MS analysis of S. officinalis leaf extracts revealed the presence of eight and fourteen analytes of origin of thirty-seven analytes in both SOCF and SOMF, respectively. Analytes’ quantification recorded the highest amount for rosmarinic acid (46 016 µg/g) in SOMF and the lowest was hesperidin (0.6 µg/g) in SOCF. Conclusions: S. officinalis extracts recorded significant tyrosinase inhibition potency could control the melanin synthesis process and exhibit beneficiary effect in hyperpigmentation issues.
... Kojic acid, a fungal metabolite, is the most widely used tyrosinase inhibitor today. However, animal experiments have shown that kojic acid has weak carcinogenicity; thus, its usage in humans is limited up to a concentration of 1% [11]. Hydroquinone is also a tyrosinase inhibitor that has been used clinically in the treatment of hyperpigmentation in leading cosmetics [12]. ...
The tyrosinase enzyme plays an essential role in the pigmentation of human skin, fruits, and vegetables. It has been tied with several human skin diseases and post-harvest problems. Hence, the tyrosinase enzyme becomes an excellent therapeutic target to overcome these issues. This study aimed to screen tyrosinase inhibitors by synthesizing halogen-substituted pyrazolopyridine derivatives. The pyrazolopyridine compound was obtained through two stages of synthesis. First, the intermediate compound, a derivative of 3,5-bis(arylidene)-4-piperidone, was synthesized through the Cleisen-Schmidt condensation reaction of 4-piperidone and benzaldehyde derivatives. Furthermore, the intermediate compound was reacted with phenylhydrazine through a cyclocondensation reaction to produce the titled compound with an 11% yield. The chemical structure of the target compound was identified through the interpretation of UV, FTIR, NMR, and HRMS spectra. Then an in vitro assay was conducted on the tyrosinase enzyme of the fungus Agaricus bisporus by detecting the presence of dopachrome at a wavelength of 492 nm. As a result, the in vitro assay showed that the titled compound had a weak inhibitory activity, and the IC50 value was > 500 µM. Thus, the synthesized compound is considered inactive.
... The concentration of KA in dermal lightening creams is typically between 1 and 4% [3]. Owing to the inability of KA to penetrate the dermal layer, skin irritation, cytotoxicity, and instability during storage, its use in topical formulations has been restricted [3][4][5]. Various approaches have been developed to obtain effective medication delivery systems for medicinal or cosmetic local application. ...
The local treatment of kojic acid (KA) as a tyrosinase inhibitor results in inadequate skin absorption and a number of side effects. The current study aims to maximize KA skin delivery. To produce KA-hydrogel, 1% KA was injected into a Chitosan/alginate hydrogel. The impacts of biopolymer proportion on the KA-hydrogel preparations were investigated. Swelling analysis, weight loss analysis, differential scanning calorimetry (DSC), scanning electron microscopy (SEM), UV absorption spectroscopy, attenuated total reflectance-Fourier transform infrared (ATR-FTIR) spectroscopy were used to evaluate the KA-hydrogel. The swelling percentages of KA-hydrogel increased significantly after 4 hours. After two weeks, up to 60% of the primary mass of the KA- hydrogel has been removed. By alternation in biopolymer proportion, the drug release profile of KA-hydrogel demonstrated a sustained pattern. According to the skin absorption experiment, KA-hydrogel had higher skin deposition (25.630 ± 3.350 %) than KA-plain gel (5.170 ± 0.340 %). Moreover, an in vitro cytotoxicity analysis for the modified KA-hydrogel preparations revealed no cytotoxic effects on HFF cell line (90%). Moreover, KA hydrogel had inhibitory effect on melanin synthesis and are comparable with KA. Furthermore, KA-hydrogel had higher inhibitory effect on L-dopa auto oxidation (94.84 ± 2.41%) in comparison KA solution (73.95 ± 3.28%). Also, the dermal irritation study on Wistar rat revealed that the hydrogel constituent used did not irritate the skin. These results revealed that the KA-hydrogel might be employed as KA local administration, thus opening up new prospects for the therapies of hyperpigmentation problems.
... L'acide kojique a été commercialisé en 1955 mais montre peu d'efficacité et provoque des réactions allergiques. Il a donc été modifié afin de diminuer sa cytotoxicité et de palier à son instabilité (Burnett et al. 2010). Par exemple, en 2006, une équipe a mis en évidence une molécule constituée de deux acides kojiques. ...
L’entreprise SEPROSYS est une société spécialisée dans le développement de solutions d’extraction, de séparation et de purification de molécules d’intérêts. Au cours de l’année 2011, l’entreprise a développé un procédé innovant et éco-compatible de séparation et de purification fractionnée de biomolécules issues de macroalgues marines dont l’objectif est de valoriser une biomasse locale, via un procédé de fractionnement ne faisant pas intervenir de solvant ou d’acide. Ces travaux de thèse ont pour objectif d’identifier des applications potentiellement commercialisables pour les différentes fractions de macroalgues marines extraites selon le procédé développé par la société SEPROSYS, et en particulier, dans deux domaines distincts : en dermocosmétique pour leur activité anti-âge et anti-tâche, et en nutraceutique pour leur activité anti-inflammatoire. La première partie de nos travaux concerne l’amélioration du procédé, la caractérisation des fractions protéiques ainsi que la production de fractions peptidiques et oligosaccharidiques provenant d’Ulva rigida et Ulva intestinalis. La deuxième partie est consacrée à l’évaluation du potentiel « anti-âge » et du potentiel « anti-tâche » des différentes fractions provenant d’Ulva rigida et Ulva intestinalis. Dans ce but, l’impact des différentes fractions sur la biosynthèse de collagène et d’acide hyaluronique de lignées fibroblastiques, puis par la suite l’effet des fractions sur la production in vitro de mélanine par des mélanocytes murins ont été étudié. De plus, l’objectif de ce travail consiste également à mieux comprendre la relation structure-fonction de l'activité anti-âge des fractions protéiques. La troisième partie s’intègre au sein d’un projet dénommé Neuronalg, dont l’objectif est le développement d’actifs nutritionnels algo-sourcés, ciblant l’inflammation et les mécanismes d’altérations du comportement émotionnel liés aux troubles métaboliques. Pour cela, les activités anti-inflammatoires des fractions produites sur des macrophages murins à travers la quantification de monoxyde d’azote produit, associée au niveau transcription de protéines cibles comme iNOS (NO synthase inductible) et de cytokines pro- et anti-inflammatoires.
... When comparing the effects between the positive control kojic acid and our herbal formula extracts, we demonstrated that our modified Qi Bai San F3 exerted beneficial effects on hyperpigmentation which appeared comparable or even carried a better trend in potency than kojic acid. Although kojic acid has been proven to be a potent hypopigmentation agent and is used widely by various cosmetic company as agents for the control of pigmentation in the market, increasing concerns are arising since some animal data suggest kojic acid is weakly carcinogenic [26]. Furthermore, the European Commission's Scientific Committee on Consumer Products (SCCP) had also determined that based on a margin of safety calculation, the use of kojic acid at 1.0% in skin care formulations poses a risk to human health due to potential systemic effects. ...
... 15 However, KA reportedly exhibits weak carcinogenicity in certain animals and has significant side effects, such as redness, itchiness and exfoliation of the human skin. 16 In the R&D of new substances, in vitro experiments on 2D monolayer cell cultures are standard methods of preliminary pharmacological testing. 17 However, they cannot completely predict the actual activity of compounds in vivo due to the lack of a complex structure of tissues and extracellular substances. ...
Skin hyperpigmentation is commonly treated by topical drug application. Several naturally occurring compounds exhibit attractive biological effects including anti‐melanogenic activity. Chemically modified derivatives of those compounds are expected to be more efficient. However, efficacy and safety testing processes are of significant consideration to identify the most effective compound among them. Herein, we demonstrated a tiered approach to investigate the antipigmentation activity of 17 trans‐N‐coumaroyltyramine derivatives. First, we evaluated the in chemico antityrosinase activity, then the cytotoxicity of the most potent derivatives using a mitochondrial activity‐based assay, followed with the in vitro anti‐melanogenic activity in two dimensional (2D) monolayer human melanocytes. The selected derivatives were topically applied on a three dimensional (3D) pigmented‐reconstructed human epidermis (pRhE) containing melanocytes and keratinocytes to evaluate their depigmenting activity. Two of the 17 derivatives displayed a significant reduction in pigmentation in the 3D pRhE, comparable to kojic acid, a known tyrosinase inhibitor. In addition, a molecular docking experiment indicated an interaction of the three derivatives and tyrosinase, suggesting that these derivatives have potent anti‐melanogenic activity through tyrosinase inhibition. Our findings provide an alternative approach for investigating skin‐whitening agents, thereby facilitating the research and development of skin‐whitening products that need not be tested on animals.
... The active ingredients chosen re ected the above mentioned OTC products, except for kojic acid, which was replaced by resveratrol considering the safety assessment by Cosmetic Ingredient Review (CIR) Expert Panel. 40 The test formulation (a lipophilic dispersion as opposed to an emulsion) employed an oil thickener (plant-based triglycerides). Each of the ve preparations included one active ingredient, except for the negative control. ...
Objective:
Skin lightening agents are popular in southern Asia, but there is dearth of evidence on their effectiveness on Fitzpatrick IV/V skin types. This study was designed to assess the depigmenting efficacy of commercially available and specifically formulated ointments using the Mexameter® (MX 18).
Methods:
This single center prospective study was performed to test five commercially available preparations (Eldopaque®, Aziderm®, Garnier Dark Spot Corrector®, Ban a Tan Cream® and Neostrata Pigment Lightening Gel) on 28 healthy female volunteers in Phase 1, while five single active ingredients in lipophilic dispersion (hydroquinone 4%, ascorbyl palmitate 1%, resveratrol 1% arbutin 5% and azelaic acid 20%) were tested on a different group of 26 healthy female volunteers in Phase 2. The test agents were applied twice a day for five days per week and continued for six weeks in both study phases. Weekly Mexameter® measurements were obtained from test sites and negative controls.
Results:
Significant hypopigmentation when compared to untreated controls was observed with Aziderm cream (p<0.05, MWU) and the Neostrata Pigment Lightening Gel (p<0.05, MWU). All formulated preparations showed significant reduction in pigmentation; however, only the arbutin (5%) containing formulation revealed significant attenuation of pigmentation in comparison to the inactive control (p<0.05, MWU).
Conclusion:
All applications containing active ingredients showed significant skin lightening; however, only arbutin was able to demonstrate significant diminution of pigmentation when compared to the inactive control.
... Kojic acid (1) or hydroquinone (3) which used to be applied as the ingredients of skin-lightning cosmetics [24] have been reported to be unsafe for human skin in concentrations required for depigmenting effect [25]. Kojic acid also triggers carcinogenicity and instability issues [26], and its use has been restricted to 1% in cosmetic preparations in the EU [27]. ...
A novel series of twenty-seven cinnamides constituted by cinnamic acid derivatives liked to 1-aryl piperazines were synthesized and evaluated for their potential inhibitory diphenolase activity of mushroom tyrosinase. Among them, the presence of a 3-chloro-4-fluorophenyl moiety at the N-1 position of piperazine ring was essential for a potent tyrosinase inhibitory effect, with the 3-nitrocinnamoyl (19p) and 2-chloro-3-methoxycinnamoyl (19t) derivatives as the most potent compounds of the series, with IC50 of 0.16 and 0.12 μM, respectively, resulting much active than kojic acid, whose IC50 value was 17.76 μM. In general, all compounds characterized by the presence of a 1-(3-chloro-4-fluorophenyl)piperazine moiety showed an excellent potency, and the nature, position and number of the substituents on the aryl of the cinnamic acid did not affect significantly the anti-tyrosinase activity. The molecular docking to the active site of the enzyme has been also performed to investigate the nature of enzyme-inhibitor interactions. Furthermore, for selected highly active compounds, their ability to inhibit melanogenesis in the A375 human melanoma cells and in vivo zebrafish model was also evaluated. One of the most potent compounds of series (19t) significantly reduced the pigmentation of zebrafish at 50 μM, unfortunately showing 100% mortality in the Fish Embryo Acute Toxicity (FET) test at the same concentration, Moreover, the zebrafish assay reveals that also compound 19r (IC50:0.51 μM against mushroom tyrosinase) effectively reduces melanogenesis with no acute toxicity effects and it could be proposed as potential candidate to treat tyrosinase-mediated hyperpigmentation.
... have evolved metabolic detoxification mechanisms to increase their tolerance to kojic acid. Essentially nothing is known about the metabolism of kojic acid in insects, although it is substantially metabolised to sulfate and glucuronide conjugates in rats ( Burnett et al., 2010 ), suggesting similarly conjugationheavy metabolism -such as phosphorylation via EcKLs -could also occur in insects. ...
A unique aspect of metabolic detoxification in insects compared to other animals is the presence of xenobiotic phosphorylation, about which little is currently understood. Our previous work raised the hypothesis that members of the taxonomically restricted ecdysteroid kinase-like (EcKL) gene family encode the enzymes responsible for xenobiotic phosphorylation in the model insect Drosophila melanogaster (Diptera: Ephydroidea)—however, candidate detoxification genes identified in the EcKL family have yet to be functionally validated. Here, we test the hypothesis that EcKL genes in the rapidly evolving Dro5 clade are involved in the detoxification of plant and fungal toxins in D. melanogaster. The mining and reanalysis of existing data indicated multiple Dro5 genes are transcriptionally induced by the plant alkaloid caffeine and that adult caffeine susceptibility is associated with a novel naturally occurring indel in CG31370 (Dro5-8) in the Drosophila Genetic Reference Panel (DGRP). CRISPR-Cas9 mutagenesis of five Dro5 EcKLs substantially decreased developmental tolerance of caffeine, while individual overexpression of two of these genes—CG31300 (Dro5-1) and CG13659 (Dro5-7)—in detoxification-related tissues increased developmental tolerance. In addition, we found Dro5 loss-of-function animals also have decreased developmental tolerance of the fungal secondary metabolite kojic acid. Taken together, this work provides the first compelling functional evidence that EcKLs encode detoxification enzymes and suggests that EcKLs in the Dro5 clade are involved in the metabolism of multiple ecologically relevant toxins in D. melanogaster. We also propose a biochemical hypothesis for EcKL involvement in caffeine detoxification and highlight the many unknown aspects of caffeine metabolism in D. melanogaster and other insects.
... Even though there are many tyrosinase inhibitors known today, the binding modes and mechanisms of inhibition are still unclear for the vast majority of them. Furthermore, most of the commonly known and widely used inhibitors are accompanied by undesirable side effects, such as kojic acid being a possible weak carcinogen and hydroquinone being responsible for ROS formation [14,15]. Therefore, finding new potent tyrosinase inhibitors and exploring the structural aspects of their inhibitory action is still of great importance. ...
Numerous natural products and designed molecules have been evaluated as tyrosinase inhibitors that impede enzymes’ oxidation activity. In the present study, new potent natural inhibitors were retrieved from the ZINC database by the similarity-screening of 37 previously reported tyrosinase inhibitors. The screening resulted in 42 candidate inhibitory molecules that were categorized into five groups. Molecular-docking analysis for these compounds, as well as for three others known for their inhibition activity (caffeic acid, naringenin, and gallic acid), was carried out against the tyrosinase structure from Agaricus bisporus (AbTYR). The top-scoring compounds were used for further comparative analysis with their corresponding naturally occurring glycosides. The results suggested that the glycosylated inhibitors could interact better with the enzyme than their aglycon forms. In order to further examine the role of the sugar side group of potent tyrosinase inhibitors, the dynamic behavior of two such pairs of glycosidic/aglycol forms (naringin–naringenin and icariin–icaritin) in their complexes with the enzyme were studied by means of 20-ns MD simulations. The increased number of intermolecular hydrogen bonds and their augmented lifetime between AbTYR and the glycosidic analogues showed that the naringin and icariin molecules form more stable complexes than naringenin and icaritin with tyrosinase, and thus are more potent inhibitors.
The skin containing melanin pigment acts as a protective barrier and counteracts the UVR and other environmental stressors to maintain or restore disrupted cutaneous homeostasis. The production of melanin pigment is dependent on tyrosine levels. L-tyrosine and L-dihydroxyphenylalanine (L-DOPA) can serve both as a substrates and intermediates of melanin synthetic pathway and as inducers and positive regulators of melanogenesis. The biosynthesis of melanin is stimulated upon exposure to UVR, which can also stimulate local production of hormonal factors, which can stimulate melanoma development by altering the chemical properties of eu- and pheomelanin. The process of melanogenesis can be altered by several pathways. One involves activation of POMC, with the production of POMC peptides including MSH and ACTH, which increase intracellular cAMP levels, which activates the MITF, and helps to stimulate tyrosinase (TYR) expression and activity. Defects in OCA1 to 4 affects melanogenic activity via posttranslational modifications resulting in proteasomal degradation and reducing pigmentation. Further, altering, the MITF factor, helps to regulate the expression of MRGE in melanoma, and helps to increase the TYR glycosylation in ER. CRH stimulates POMC peptides that regulate melanogenesis and also by itself can stimulate melanogenesis. The POMC, P53, ACTH, MSH, MC1R, MITF, and 6-BH4 are found to be important regulators for pigmentation. Melanogenesis can affect melanoma behaviour and inhibit immune responses. Therefore, we reviewed natural products that would alter melanin production. Our special focus was on targeting melanin synthesis and TYR enzyme activity to inhibit melanogenesis as an adjuvant therapy of melanotic melanoma. Furthermore, this review also outlines the current updated pharmacological studies targeting the TYR enzyme from natural sources and its consequential effects on melanin production.
SCCS Opinion on Kojic Acid – SCCS/1637/21 – Final version and Corrigendum
U. Bernauer, L. Bodin, Q. Chaudhry, P.J. Coenraads, M. Dusinska, J. Ezendam, E. Gaffet, C. L. Galli, B. Granum, E. Panteri, V. Rogiers, Ch. Rousselle, M. Stepnik, T. Vanhaecke, S. Wijnhoven, A. Koutsodimou, W. Uter, N. von Goetz
The SCCS adopted this document at its plenary meeting on 15–16 March 2022 and the CORRIGENDUM by written procedure on 10 June 2022
Mise en ligne le 30 Août 2023
Ed. Publications Office of the European Union, Luxembourg, Luxembourg
ISSN : 1831-4767
ISBN : 978-92-68-06161-9
doi:10.2875/373705
Catalog Number : EW-AQ-23-003-EN-N
https://op.europa.eu/en/publication-detail/-/publication/04c88769-46f0-11ee-bbdc-01aa75ed71a1/language-en/format-PDF/source-291551344
The term cosmeceutical refers to a category of skincare products that are purported to have active ingredients whose physiological or pharmacological actions are capable of inducing cosmetic enhancements to the skin. Given a demand for brighter, healthier, younger‐appearing skin, and relatively limited regulatory control, thousands of different cosmeceutical formulations have found their way onto store shelves and onto the skin of hopeful consumers, despite a lack of scientific evidence. This chapter summarizes new and old, common and rare cosmeceutical ingredients; their uses and side effects; and the science, where available, behind the claims.
In the current study, an ultrasonic approach (as green method) was utilized to prepared kojic acid niosome (kojisome) which aimed to increase the dermal delivery and improving anti-melanogenesis properties. The study's findings demonstrated that increasing cholesterol enhanced the mean particle size from 68.333 ± 5.686nm to 325.000 ± 15.099nm and entrapment efficiency 0% to 39.341 ± 4.126% of the kojisome. Cholesterol may enhance the number and rigidity of bilayers that induced a size enhancement and entrapment efficiency. The skin permeability test revealed that kojisome gel had more kojic acid in dermal layers (437.563 ± 29.857 μg/cm2 or 16.624 ± 1.379%) than kojic acid plain gel (161.290 ± 14.812 μg/cm2 or 6.128 ± 0.672%). The niosome's lipophilicity allowed for gradual penetration, possibly due to better contact with the skin layers. Also, the extended-release behavior of improved kojisome exhibited high safety profile and low side effect in In vitro cytotoxicity assay, dermal irritation test, and Histo-pathological evaluation. Furthermore, optimum kojisome inhibited melanin formation (53.093 ± 2.985% at 1000 µM) higher than free kojic acid (62.383 ± 1.958%) significantly (p < 0.05). In addition, Kojisome 6 inhibited L-dopa auto-oxidation greater extent (94.806 ± 2.411%) than pure kojic acid solution (72.953 ± 2.728%). Kojisome by delivering and targeting large amount of kojic acid on specific site causes high efficacy in inhibition of melanin synthesis. The observations of this study revealed that the produced kojisome might be used as a potential nano-vehicle for kojic acid dermal administration, thereby opening up innovative options for the treatment of hyperpigmentation problems.
Melanogenesis involves a synthesis of melanin pigment and is regulated by tyrosinase. The addition of whitening agents with tyrosinase-inhibiting properties in cosmetics is becoming increasingly important. In this study, the ethanolic extracts from twelve seaweeds were assessed for tyrosinase-inhibiting activity using mushroom tyrosinase and melanin synthesis in B16F10 melanoma cells. The highest mushroom tyrosinase inhibition (IC50) was observed with Lobophora challengeriae (0.15 ± 0.01 mg mL−1); treatment was more effective than kojic acid (IC50 = 0.35 ± 0.05 mg mL−1), a well-known tyrosinase inhibitor. Three seaweeds, Caulerpa racemosa, Ulva intestinalis, and L. challengeriae, were further investigated for their ability to reduce melanogenesis in B16F10 cells. The ethanolic extracts of C. racemosa, U. intestinalis, and L. challengeriae showed inhibitory effects by reducing melanin and intracellular tyrosinase levels in B16F10 cells treated with α-melanocyte stimulating hormone in a dose-dependent manner. C. racemosa (33.71%) and L. challengeriae (36.14%) at 25 µg mL−1 reduced melanin production comparable to that of kojic acid (36.18%). L. challengeriae showed a stronger inhibition of intracellular tyrosinase (decreased from 165.23% to 46.30%) than kojic acid (to 72.50%). Thus, ethanolic extracts from C. racemosa, U. intestinalis, and L. challengeriae can be good sources of natural tyrosinase inhibitors and therapeutic or cosmetic agents in the future.
Arbutin và axit kojic được biết đến là chất ức chế tyrosinase thường được sử dụng trong mỹ phẩm sản phẩm làm trắng da. Tuy nhiên, axit kojic gây ra nhạy cảm da, trong khi arbutin có khả năng gây độc tế bào. Do đó, việc tìm ra chất ức chế tyrosinase có nguồn gốc thiên nhiên đang rất được quan tâm. Nghiên cứu này nhằm đánh giá tác động ức chế enzyme tyrosinase của các cao chiết từ lá nho Vitis vinifera L.. Cao toàn phần của lá nho được chiết bằng phương pháp ngâm với chloroform, cồn 96o và nước. Tác động ức chế tyrosinase của các cao lá nho được đánh giá thông qua phản ứng với L-DOPA (3,4-dihydoxy-L-phenylalanin), từ đó tính IC50 (giá trị nồng độ có khả năng ức chế 50% hoạt tính enzyme tyrosinase) của các cao tiềm năng. Kết quả cho thấy, tất cả các cao khảo sát đều có hoạt tính ức chế tyrosinase, trong đó cao cồn 96o của lá nho xanh và lá nho đỏ thể hiện rõ nhất tác động ức chế tyrosinase. Cao cồn 96o của lá nho đỏ có hoạt tính mạnh nhất với IC50 = 0,197 mg/mL so với 0,072 mg/mL của axit kojic.
Background
Phytochemicals utilization in the cosmetics are the current trend in the beauty and fashion. Most women prefer the cosmetics derived from natural products over synthetic chemicals, as the natural products are devoid of undesirable side effects. Skin protection has become not only aesthetic, but also linked to health. Therefore, exploring the use of phytochemicals in cosmetic dermatology is essential.
Objective
In the current in vitro studies, we investigated the skin-protection properties of capsanthin 50%w/w crystals (CAP-50CR) and capsanthin 1.5% w/w soft extract (CAP-1.5SE) obtained from red bell pepper fruits, out of which one is an industrial by-product on sunburn, melanin inhibition, tyrosinase inhibition, anti-fungal activity and, gene expression of Aquaporin 3 (AQP-3) in the human keratinocyte cell line.
Methodology
The two extracts, obtained by solvent extraction, super critical extract purification, saponification, characterized, and examined on their dermatological activities.
Results
Capsanthin 50%w/w crystals (CAP-50CR) showed a sun protection factor (SPF) value of 34.44 whereas capsanthin 1.5% w/w soft extract (CAP-1.5SE) showed a value of 20.63. Minimal inhibitory concentration (MIC) of CAP-50CR against Malassezia furfur was 0.625 mg/mL and CAP-1.5SE showed a MIC of 5mg/mL. Both CAP-50CR and CAP-1.5SE showed the same MIC against Candida albicans which is 2.5 mg/mL. In the MTT assay on mouse skin melanoma cells (B16F10), the test substance CAP-50CR showed a CTC50 value of 98.44±2.55 µg/mL whereas the test substance CAP-1.5SE exhibited a CTC50 value greater than 1000 µg/mL. Further, the non-toxic concentrations of the test items were evaluated for forskolin-induced melanin inhibition activity. For CAP-50CR, the non-toxic concentration of 7 and 3 µg/mL showed the melanin inhibition of 48.73±0.75% and 42.29±5.2% and for CAP-1.5SE the melanin inhibition was found to be 55.84%±1.47 and 46.44%±1.05 for the non-toxic concentration of 50 and 25µg/mL. The CAP-50CR extract showed 43.78% and 39.37% tyrosinase inhibition at the tested concentrations of 7 and 3 µg/mL. Similarly, CAP-1.5SE showed the tyrosinase inhibitions as 34.6% and 22.9% for the concentrations of 50 and 25 µg/mL. The test substances CAP-50CR and CAP-1.5SE exhibited a CTC50 value of 76.59±3.25 μg/mL and 664.95±2.88 µg/mL on the HaCaT cells. In the gene expression study, both the test substances showed an increase in the levels of AQP-3 mRNAs at lower and higher concentrations as compared to the control in the semi-quantitative RT-PCR procedure.
Conclusion
CAP-50CR and CAP-1.5SE showed skin protection from UV radiation and hyperpigmentation. Also exhibits anti-fungal, skin brightening, anti-wrinkle and moisturizing properties. These results suggests that capsanthin from red bell pepper fruit can be employed as cosmetic active ingredient in skin guard formulations and as a potential therapeutic agent for variety of dermatological disorders. This study breaks new ground by investigating the potential of capsanthin in the management of skin protection for the first time.
As one of the representative secondary metabolites in fermentation processes and common additives in modern industry, kojic acid (KA) has been mired in controversy in recent years due to its potential toxicity and carcinogenicity. Hence, it is of high importance to develop novel analysis strategies for KA to surveil its rational utilization and ensure public health. Based on enzyme modulated sensitization of TiO2 NPs and the inhibition effect of KA towards tyrosinase (Tyr), we report a facile and sensitive photoelectrochemical (PEC) sensor for KA in food samples. On an operational level, this protocol excluded the tedious immobilization process of traditional PEC enzyme sensors, allowing the crucial catalysis and sensitization process to take place in a small centrifuge tube, making the experimental process concise and fast. Under optimized conditions, a linear detection range of 10-7 M to 10-3 M was achieved, with a detection limit of 3.2 × 10-8 M. Furthermore, the feasibility of the strategy in food samples was validated in vinegar and wheat flour. This protocol would hold great promise for real application in diverse food products, and offer a general prototype for future immobilization-free and quick analysis of other enzyme inhibitors.
Background:
Melanin is a skin pigment that gives color to the skin, hair and eyes, the accumulation or over production of melanin can lead to aesthetic problems as well as serious diseases associated with hyperpigmentation. Skin lightening is described as the procedure of using natural or synthetic products to lighten the skin tone, or provide an even skin complexion by reducing the amount of melanin in the skin, therefore skin lightening products help people to treat their skin problems. Ingredients such as hydroquinone, ascorbic acid and retinoic acid were used as whitening agents to lighten the skin. However, they have many adverse effects on the skin and body health, such as skin irritation.
Aim:
In this review, firstly, discuss on the directly/indirectly target melanogenesis-related signal pathways. Secondly, summarize potential natural bioactive ingredients with skin lightening properties from plants, marine organisms, microorganisms. Finally, the remaining problems and future challenges are also discussed.
Methods:
For relevant literature, a literature search was conducted using Google Scholar and Web of Science. Natural bioactive compounds, tyrosinase inhibitors, and other related topics were researched and evaluated.
Results:
Natural products isolated from plant and animal resources are potential active cosmetic candidates for lightening the skin tone and skin whitening and protection against UV irradiation. Natural bioactive ingredients as cosmetic whitening additives have attracted increasingly attention due to their safety and cost effectiveness, with few side effects.
Conclusion:
Although natural active substances have been advocated for use in whitening cosmetics in recent years, there are still many challenges due to the fact that traditional inhibitors are used perennial in cosmetics which cannot be easily changed and the research on natural active substances is still in its infancy. In the future, by improving the extraction technique of natural extracts, it is achieved to give a qualitative and quantitative analysis of the active ingredients of the extracts, to determine the effect of the active components of action, and to find the substances that have the best possible whitening effect in natural organisms.
In this study, a new magnetic molecularly imprinted polymer Fe3O4@MIP is prepared via a surface molecularly imprinting technique; it is first applied as a magnetic solid phase extraction (MSPE) adsorbent for the selective and rapid extraction of kojic acid (KA) in cosmetic products. The as-prepared Fe3O4@MIP is characterized systematically, and is found to exhibit good monodispersity and high magnetic susceptibility in favor of fast separation. The adsorption capacity and equilibrium time of KA on the Fe3O4@MIP adsorbent are 314.0 mg/g and 30 min, respectively. In addition, the imprinting factor of Fe3O4@MIP is 2.09 for KA, which indicates that the prepared Fe3O4@MIP exhibits good selectivity for KA. Under the optimum experimental conditions, the KA in cosmetic products was successfully extracted with Fe3O4@MIP adsorbent and determined by ultraviolet-visible (UV–vis) spectrophotometry. Validation experiment shows that the developed method presents good linearity (50–500,000 μg/L), satisfactory precision (RSD, 2.5–4.6 %), and high recovery (92.4–104.6 %). The limit of detection (LOD) is 21.4 μg/L, and the enrichment factor is 299. These results suggest that this MSPE method coupled with UV–vis spectrophotometry holds great potential for efficient sample pretreatment and target molecule determination in real samples.
Kojic acid presents a variety of applications for human use, especially as a depigmenting agent. Its derivatives are also proposed in order to prevent chemical degradation, prevent adverse effects and improve efficacy. The aim of this study was to peer review the current scientific literature concerning the biological activities and safety data of kojic acid or its derivatives, aiming at human use, and trying to elucidate the action mechanisms. Three different databases were assessed and the word “kojic” was crossed with “toxicity”, “adverse effect”, “efficacy”, “effect”, “activity” and “safety”. Articles were selected according to pre‐defined criteria. Besides the depigmenting activity, kojic acid and derivatives can act as antioxidant, antimicrobial, anti‐inflammatory, radioprotector, anticonvulsant and obesity management agents, and present potential as antitumor substances. Depigmenting activity is due to the molecules, after penetrating the cell, binding to tyrosinase active site, regulating melanogenesis factors, leucocytes modulation and free radical scavenging activity. Hence, polarity, size and ligands are also important factors for activity. Kojic acid and derivatives present cytotoxicity to some cancerous cell lines, including melanoma, hepatocellular carcinoma, ovarian cancer, breast cancer and colon cancer. Regarding safety, kojic acid or its derivatives are safe molecules for human use in the concentrations tested. Kojic acid and its derivatives have great potential for cosmetic, pharmaceutical and medical applications.
SCCS Opinion on Kojic Acid – Corrigendum - SCCS/1637/21 – Final version and Corrigendum
U. Bernauer, L. Bodin, Q. Chaudhry, P.J. Coenraad, M. Dusinska, J. Ezendam, E. Gaffet, C. L. Galli, B. Granum, E. Panteri, V. Rogiers, Ch. Rousselle, M. Stepnik, T. Vanhaecke, S. Wijnhoven, A. Koutsodimou, W. Uter, N. von Goetz
The SCCS adopted this document at its plenary meeting on 15–16 March 2022 and the CORRIGENDUM by written procedure on 10 June 2022
Mise en ligne le 13 Juin 2022 (86 pages)
https://ec.europa.eu/health/publications/kojic-acid_en
The Chemistry inside Spices and Herbs: Research and Development brings comprehensive information about the chemistry of spices and herbs with a focus on recent research in this field. The book is an extensive 2-part collection of 20 chapters contributed by experts in phytochemistry with the aim to give the reader deep knowledge about phytochemical constituents in herbal plants and their benefits. The contents include reviews on the biochemistry and biotechnology of spices and herbs, herbal medicines, biologically active compounds and their role in therapeutics among other topics. Chapters which highlight natural drugs and their role in different diseases and special plants of clinical significance are also included. Part II continues from the previous part with chapters on the treatment of skin diseases and oral problems. This part focuses on clinically important herbs such as turmeric, fenugreek, ashwagandha (Indian winter cherry), basil, Terminalia chebula (black myrobalan). In terms of phytochemicals, this part presents chapters that cover resveratrol, piperine and circumin.
It is of great importance to integrate two kinds of fluorescent probes in one system to construct ratiometric sensing platform. Inspired by the efficient overlapped spectrum of glutathione-stabilized copper nanoclusters (GSH-CuNCs) and 2, 3-diaminophenazine (DAP), a novel and label-free ratiometric fluorescent sensor has been developed for Cu ²⁺ and kojic acid (KA) detection on the basis of in situ converting o -phenylenediamine (OPD) into DAP by the catalytic oxidation ability of Cu ²⁺ . The Cu ²⁺ catalytically generated DAP was served as an energy acceptor to inhibit the fluorescence emission of GSH-CuNCs (energy donor). As a result, the sensitivity and accuracy of the strategy were greatly improved due to the dual-emission reverse change ratiometric profile. The sensing system showed high sensitivity toward Cu ²⁺ in a range of 0.1–50 μ M and with a limit of detection of 20 nM. Furthermore, based on the specific coordination interaction between Cu ²⁺ and KA, the ratiometric sensor displayed the range of detection of KA from 0.2 μ M to 300 μ M with a limit of detection of 50 nM. Thus, the ratiometric method paved a new way for the effective quantification of Cu ²⁺ and KA in real samples, which were closely concerned with human health.
SCCS Opinion on Kojic Acid - SCCS/1637/21 - Final version (85 pages)
U. Bernauer, L. Bodin, Q. Chaudhry, P.J. Coenraad, M. Dusinska, J. Ezendam, E. Gaffet, C. L. Galli, B. Granum, E. Panteri, V. Rogiers, Ch. Rousselle, M. Stepnik, T. Vanhaecke, S. Wijnhoven, A. Koutsodimou, W. Uter, N. von Goetz
The SCCS adopted this document at its plenary meeting on 15 and 16 March 2022 (85 Pages)
Mise en ligne 17 Mars 2022
https://ec.europa.eu/health/publications/kojic-acid_en
Skin lightening is a popular practice across the world, especially in India, the Philippines and other Asian countries, and some Caribbean nations. It is a dangerous trend, as some of the products used to achieve a lighter skin tone have been shown to often contain unsafe chemicals. In this article, we examine trends in consumer interest in skin lightening using a Google Trends query of 4 search terms: “skin lightening,” “skin brightening,” “skin whitening,” and “skin bleaching,” across the United States from 2015 to 2020, and demonstrate that it is most popular in states with diverse populations, including a high percentage of black and Asian Americans.
The Chemistry inside Spices & Herbs: Research and Development brings comprehensive information about the chemistry of spices and herbs with a focus on recent research in this field. The book is an extensive 2-part collection of 20 chapters contributed by experts in phytochemistry with the aim to give the reader deep knowledge about phytochemical constituents in herbal plants and their benefits. The contents include reviews on the biochemistry and biotechnology of spices and herbs, herbal medicines, biologically active compounds and their role in therapeutics among other topics. Chapters which highlight natural drugs and their role in different diseases and special plants of clinical significance are also included.
Part II continues from the previous part with chapters on the treatment of skin diseases and oral problems. This part focuses on clinically important herbs such as turmeric, fenugreek, ashwagandha (Indian winter cherry), basil, Terminalia chebula (black myrobalan). In terms of phytochemicals, this part presents chapters that cover resveratrol, piperine and circumin.
Audience: This book is an ideal resource for scholars (in life sciences, phytomedicine and natural product chemistry) and general readers who want to understand the importance of herbs, spices and traditional medicine in pharmaceutical and clinical research.
The SCCS adopted this document at its plenary meeting on 26 and 27 October 2021
Mise en ligne le 6 Novembre 2021
https://ec.europa.eu/health/sites/default/files/scientific_committees/consumer_safety/docs/sccs_o_259.pdf
The mutagenicity of kojic acid was studied by means of reversion mutation test in bacteria (Ames test), forward mutation test in cultured Chinese hamster cells and dominant lethal test in mice. A positive result was obtained only in Ames test (TA 98, 1535 and 100) which was not modified by the presence of S-9 fraction. Thus, it is concluded that although kojic acid is a weak mutagen in bacteria, it is nonmutagenic in eukaryotic systems either in vivo or in vitro.
Tyrosinase is responsible for the molting process in insects, undesirable browning of fruits and vegetables, and coloring of skin, hair, and eyes in animals. To clarify the mechanism of the depigmenting property of hydroxystilbene compounds, inhibitory actions of oxyresveratrol and its analogs on tyrosinases from mushroom and murine melanoma B-16 have been elucidated in this study. Oxyresveratrol showed potent inhibitory effect with an IC(50) value of 1.2 microm on mushroom tyrosinase activity, which was 32-fold stronger inhibition than kojic acid, a depigmenting agent used as the cosmetic material with skin-whitening effect and the medical agent for hyperpigmentation disorders. Hydroxystilbene compounds of resveratrol, 3,5-dihydroxy-4'-methoxystilbene, and rhapontigenin also showed more than 50% inhibition at 100 microm on mushroom tyrosinase activity, but other methylated or glycosylated hydroxystilbenes of 3,4'-dimethoxy-5-hydroxystilbene, trimethylresveratrol, piceid, and rhaponticin did not inhibit significantly. None of the hydroxystilbene compounds except oxyresveratrol exhibited more than 50% inhibition at 100 microm on l-tyrosine oxidation by murine tyrosinase activity; oxyresveratrol showed an IC(50) value of 52.7 microm on the enzyme activity. The kinetics and mechanism for inhibition of mushroom tyrosinase exhibited the reversibility of oxyresveratrol as a noncompetitive inhibitor with l-tyrosine as the substrate. The interaction between oxyresveratrol and tyrosinase exhibited a high affinity reflected in a K(i) value of 3.2-4.2 x 10(-7) m. Oxyresveratrol did not affect the promoter activity of the tyrosinase gene in murine melanoma B-16 at 10 and 100 microm. Therefore, the depigmenting effect of oxyresveratrol works through reversible inhibition of tyrosinase activity rather than suppression of the expression and synthesis of the enzyme. The number and position of hydroxy substituents seem to play an important role in the inhibitory effects of hydroxystilbene compounds on tyrosinase activity.
In order to evaluate the tumorigenic potential of kojic acid (KA), used as a food additive for preventing enzymatic browning of crustaceans and a cosmetic agent for the purpose of skin whitening, heterozygous p53-deficient CBA [p53(+/-)] mice, which are recognized as useful for detecting genotoxic carcinogens, and wild-type littermates [p53(+/+) mice] were fed diet containing 0, 1.5, and 3% KA for 26 weeks. KA induced diffuse hypertrophy and hyperplasia of thyroid follicular epithelial cells with decreased serum thyroxine levels in both p53 (+/-) and p53 (+/+) mice, but caused no thyroid tumors. In the liver, the incidence of altered hepatocellular foci was significantly increased at 1.5 and 3% in p 53(+/-) and 1.5% in p53 (+/+) mice, and that of hepatocellular adenomas was increased at 1.5 and 3% in p 53(+/-) and 3% in p53 (+/+) mice. p53 (+/-) mice thus appeared to be more susceptible in terms of the tumorigenic dose of KA with a greater prevalence of hepatic proliferative lesions. The results of the present study indicate tumorigenic potential of KA in the liver, but not thyroid follicular epithelial cells in CBA mice and a contribution of genotoxicity on hepatocellular tumor development cannot be ruled out.
Although humans have been exposed to airborne nanosized particles (NSPs; < 100 nm) throughout their evolutionary stages, such exposure has increased dramatically over the last century due to anthropogenic sources. The rapidly developing field of nanotechnology is likely to become yet another source through inhalation, ingestion, skin uptake, and injection of engineered nanomaterials. Information about safety and potential hazards is urgently needed. Results of older biokinetic studies with NSPs and newer epidemiologic and toxicologic studies with airborne ultrafine particles can be viewed as the basis for the expanding field of nanotoxicology, which can be defined as safety evaluation of engineered nanostructures and nanodevices. Collectively, some emerging concepts of nanotoxicology can be identified from the results of these studies. When inhaled, specific sizes of NSPs are efficiently deposited by diffusional mechanisms in all regions of the respiratory tract. The small size facilitates uptake into cells and transcytosis across epithelial and endothelial cells into the blood and lymph circulation to reach potentially sensitive target sites such as bone marrow, lymph nodes, spleen, and heart. Access to the central nervous system and ganglia via translocation along axons and dendrites of neurons has also been observed. NSPs penetrating the skin distribute via uptake into lymphatic channels. Endocytosis and biokinetics are largely dependent on NSP surface chemistry (coating) and in vivo surface modifications. The greater surface area per mass compared with larger-sized particles of the same chemistry renders NSPs more active biologically. This activity includes a potential for inflammatory and pro-oxidant, but also antioxidant, activity, which can explain early findings showing mixed results in terms of toxicity of NSPs to environmentally relevant species. Evidence of mitochondrial distribution and oxidative stress response after NSP endocytosis points to a need for basic research on their interactions with subcellular structures. Additional considerations for assessing safety of engineered NSPs include careful selections of appropriate and relevant doses/concentrations, the likelihood of increased effects in a compromised organism, and also the benefits of possible desirable effects. An interdisciplinary team approach (e.g., toxicology, materials science, medicine, molecular biology, and bioinformatics, to name a few) is mandatory for nanotoxicology research to arrive at an appropriate risk assessment.
Two novel species from Aspergillus section Flavi from different species of Arachis (peanuts) in Argentina are described as Aspergillus arachidicola sp. nov. and Aspergillus minisclerotigenes sp. nov. Their novel taxonomic status was determined using a polyphasic taxonomic approach with phenotypic (morphology and extrolite profiles) and molecular (beta-tubulin and calmodulin gene sequences) characters. A. minisclerotigenes resembles Aspergillus flavus and Aspergillus parvisclerotigenus in producing aflatoxins B(1) and B(2), cyclopiazonic acid, kojic acid and aspergillic acid, but in addition it produces aflatoxins G(1) and G(2), aflavarins, aflatrem, aflavinines, parasiticolides and paspaline. This species also includes several isolates previously assigned to A. flavus group II and three Australian soil isolates. A. arachidicola produces aflatoxins B(1), B(2), G(1) and G(2), kojic acid, chrysogine and parasiticolide, and some strains produce aspergillic acid. The type strain of A. arachidicola is CBS 117610(T) =IBT 25020(T) and that of A. minisclerotigenes is CBS 117635(T) =IBT 27196(T). The Mycobank accession numbers for Aspergillus minisclerotigenes sp. nov. and Aspergillus arachidicola sp. nov. are respectively MB 505188 and MB 505189 (http://www.mycobank.org).
In order to examine whether kojic acid (KA) exerts a promoting effect on thyroid carcinogenesis, male F344 rats were initiated with N-bis(2-hydroxypropyl)nitrosamine (BHP; 2800 mg/kg body wt, single s.c. injection) and, starting 1 week later, received pulverized basal diet containing 2 or 0% KA for 12 weeks. Untreated control rats were given basal diet for 13 weeks. As an additional experiment, two groups without BHP initiation received basal diet or diet containing 2% KA for 20 weeks. The serum triiodothyronine (T3) and thyroxine (T4) levels were significantly decreased (half to one-third of values of the BHP alone group) and serum thyroid-stimulating hormone (TSH) was markedly increased (13‐19 times higher than the values of the BHPalone group) in the BHP F KA group at weeks 4 and 12. Similar changes in serum thyroid-related hormones were observed in the group with 2% KA alone at week 4, but not at week 20. Thyroid weights were significantly increased in the BHP F KA and KA-alone groups. Focal thyroid follicular hyperplasias and adenomas were observed in 4/5 and 3/ 5 rats in the BHP F KA group at week 4, respectively. At weeks 12, these lesions were observed in all rats in the BHP F KA group. Animals of the KA alone group showed marked diffuse hypertrophy of follicular epithelial cells at weeks 4 and 20. No changes in thyroid-related hormone levels or thyroid histopathological lesions were observed in either the BHP alone or the untreated control groups. Measurement of liver T4-uridine diphosphate glucuronosyltransferase (UDP-GT) activity at week 4 revealed no significant intergroup differences. These results suggest that thyroid proliferative lesions were induced by KA administration due to continuous serum TSH stimulation through the negative feedback mechanism of the pituitary‐thyroid axis, with decreases of T3 and T4 caused by a mechanism independent of T4-UDP-GT activity.
To clarify the mechanism of tumorigenesis by kojic acid (KA), dose and time dependence of iodine uptake in the thyroid gland and serum thyroid stimulating hormone (TSH) and thyroid hormone levels were investigated in F344 rats fed a diet containing 2% KA. After 4 weeks, thyroid hyperplasia was apparent in males, associated with a decrease in 125 I uptake into the thyroid gland to only 3% of that in controls. The serum triiodothyronine (T 3 ) and thyroxine (T 4 ) levels dropped to 0.36 ng/ml, 1.7 μg/dl from the initial values of 0.61 ng/ml, 4.0 μg/dl and TSH increased seven times to 15 ng/ml. In females, the effects on thyroid weight and 125 I uptake were less prominent, although the changes in serum T 3 , T 4 and TSH levels were similar to those in males. Time-dependent changes in serum T 3 , T 4 and TSH levels correlated with the inhibition of iodine uptake in the thyroid. Inhibition of organic iodine formation was only observed after 3 weeks treatment. On return to the control diet, normal serum T 3 , T 4 and TSH levels became evident within 48 h in both sexes. These data suggest that KA interrupts thyroid function, primarily by inhibiting iodine intake, consequently causing a decrease in serum T 3 and T 4 . Increased TSH from the pituitary gland in turn stimulates thyroid hyperplasia, which is reversible on withdrawal of KA.
Background:
Melasma is difficult to clear. Many agents have been used, such as hydroquinone, and glycolic acid and glycolic acid peels, kojic acid, a tyrosinase inhibitor in the fungus Aspergilline oryzae.
Objective:
To see if the addition of 2% kojic acid in a gel containing 10% glycolic acid and 2% hydroquinone will improve melasma further.
Methods:
Forty Chinese women with epidermal melasma were treated with 2% kojic acid in a gel containing 10% glycolic acid and 2% hydroquinone on one half of the face. The other half was treated with the same application but without kojic acid. The side receiving the kojic acid was randomized. Determination of efficacy was based on clinical evaluation, photographs and self-assessment questionnaires at 4 weekly intervals until the end of the study at 12 weeks. The non-parametric Wilcoxon's rank sum test was used for statistical analysis.
Results:
All patients showed improvement in melasma on both sides of the face. The side receiving the kojic acid did better. More than half of the melasma cleared in 24/40 (60%) patients receiving kojic acid compared to 19/40 (47.5%) patients receiving the gel without kojic acid. In 2 patients, there was complete clearance of melasma, and this was on the side where kojic acid was used. Side effects include redness, stinging, and exfoliation. These were seen on both sides of the face, and they settled by the third week.
Conclusion:
The addition of kojic acid to a gel containing 10% glycolic acid and 2% hydroquinone further improves melasma.
In our previous study in which diets containing 0, 1.5 or 3% Kojic acid (KA) were administered to heterozygous p53-deficient mice of the CBA strain [p53 (+/-) mice] and their wild-type littermates [p53 (+/+) mice] for 26 weeks, the incidences of hepatocellular adenomas as well as altered hepatocellular foci were increased in p53 (+/-) and p53 (+/+) mice of the KA treated groups without initiation, as compared to those in the untreated control mice. In order to confirm the reproducibility of the induction of hepatocellular proliferative lesions in p53 (+/+) mice given KA, male CBA mice were given dietary administration of 0, 0.5, 1 or 2% KA for 26 weeks. Body weight gain in the 2% KA group was depressed after week 20 as compared to the corresponding control group. Significant increases of absolute and relative liver weights were observed in the groups treated with 1% and 2% KA. The incidences of hepatocellular adenomas in the control and 0.5, 1 and 2% KA groups were 5, 17, 10 and 21%, respectively, and those of hepatocellular foci in these groups were 15, 39, 45 and 47%, respectively, the difference between the control and 2% KA groups being statistically significant. The mean values for multiplicity of hepatocellular adenomas in the control and 0.5, 1 and 2% KA groups were 0.05, 0.2, 0.2 and 0.2, respectively, and those for hepatocellular foci were 0.2, 0.6, 0.8 and 0.6, respectively. The results of the present study suggest that KA has a hepatocarcinogenic potential in CBA mice. 2005
Kojic acid (KA) has been used as a food additive for preventing enzymatic browning of crustaceans and as a cosmetic agent for skin whitening. To date, it has been reported that female B6C3F1 mice receiving 3% KA in the diet were found to develop hepatocellular tumors, but the underlying mechanism of liver tumorigenicity is still not clear. In the present experiments, in order to investigate possible liver initiation activity, partially hepatectomized male F344 rats received a single oral dose of 0, 1000 and 2000 mg/kg body weight of KA followed by dietary administration of 0.015% of N-2-acetylaminofluorene (2-AAF) for 2 weeks and a single 0.8 mL/kg body weight dose of CCl4. Furthermore, male F344 rats were fed a diet containing 0 or 2% KA for 3, 7 and 28 days, and the 8-oxodeoxyguanosine (8-OxodG) levels in nuclear DNA were measured to examine the formation of oxidative DNA adduct and cell proliferating activities of hepatocytes in the liver. In the liver initiation assay, there were no significant differences in the number or area of glutathione S-transferase placental form (GST-P) positive foci, putative preneoplastic lesions, between the KA-treated and control groups. Cell proliferation of hepatocytes in rats given KA for 3 and 7 days was significantly increased as compared with the relevant control values, but no significant elevation in 8-OxodG levels was apparent. The results of the present study suggest that KA has neither liver initiation activity nor capability of 8-OxodG formation, but some evidences suggestive of liver tumor promoting effects in rats. 2005
Three lots of kojic acid (KA) which were produced for use as a reagent, food additive and in cosmetics were shown to be mutagenic in S. typhimurium TA100 with or without S9 mix, with a specific activity of around 100 revertants per mg of KA. Since there are contradictory reports on genotoxicity of KA, we examined, using HPLC, whether the mutagenicity to S. typhimurium is due to KA itself, or due to contaminants present in the KA samples. Although two UV absorbing fractions were separated by HPLC, mutagenicity was detected only in the major fraction and the specific mutagenic activity of KA did not change before and after HPLC separation. The material in the major peak fractions on HPLC was confirmed to be KA by NMR. Thus it was demonstrated that KA itself is mutagenic and no mutagenic contaminants were detected in the three lots of samples. Since KA is known to produce liver tumors in mice, we further examined the genotoxicity of KA in the liver of rodents. KA induced micronuclei (MN) in the regenerating liver of adult mice by its gastric intubation at 1 g per kg body weight. However, no MN were induced in young mice (3 weeks old) without partial hepatectomy. Since it was recently found that KA had no tumor-initiating activity in the liver of mice in a two-step carcinogenicity study, there is no evidence that the genotoxicity detected in the mouse liver is involved in liver carcinogenesis.
A chronic toxicity study of kojic acid (KA) was performed using male F344 rats by dietary administration at concentrations of 0 (control), 0.5 and 2.0% for 55 weeks. Body weight gain was suppressed in the 2.0% group. The major hematological findings were decreased red blood cell (RBC) count and hematocrit (Ht) values at both 0.5 and 2.0%. In serum biochemistry, increased aspartate transaminase (AsT), alanine transaminase (AlT), alkaline phosphatase (ALP) and gamma-glutamyl transpeptidase (gamma-GTP) levels were detected in the 0.5 and 2.0% groups. Histopathologically, single cell necrosis of hepatocytes and proliferation of bile ductules in both treatment groups, and hypertrophy of hepatocytes, granulomas and proliferation of bile ducts in the 2.0% group were increased in incidence, and numbers and areas of glutathione-S-transferase placental-form (GST-P) positive foci were increased in the liver of the 2.0% group. In the thyroids, diffuse follicular cell hyperplasia at 0.5 and 2.0% and focal follicular cell hyperplasia and follicular adenoma at 2.0% were increased. A thyroid follicular carcinoma was also observed at 2.0%. Additionally, increased incidences of hyaline casts and basophilic tubules in the kidneys at 2.0% and microgranulomas containing crystals in the lung in both treatment groups were noted. At 2.0%, hypertrophy of cortical cells in zona fasciculata was also increased in the adrenals. In conclusion, no observed adverse effect level of KA was below 0.5%, which is equivalent to 227 mg/kg body weight/day in male rats.
Our continued interest in naturally occurring mutagens has led us to examine the mutagenic activity of a series of 1,2-dicarbonyl compounds in the Salmonella/microsome assay. Several compounds in this class are of particular toxicological interest because they occur in various foods. Maltol, a product of carbohydrate dehydration, is found in coffee, chicory, soybeans, baked cereals, bread crusts and other products [4,5]. This compound and ethyl maltol, a synthetic homolog of maltol, are also used extensively as flavor-enhancing agents, particularly in carbohydrate-rich foods [10]. Kojic acid was originally isolated from mold-fermented rice. It is a metabolite of many microorganisms including several fungi used in food production [10]. Diacetyl is an aroma component of butter, beer, coffee and other foods [3,12,16,18]. In addition, glyoxal and some related 1,2-dicarbonyl compounds exhibit antiviral and carcinostatic properties [2,19]. We wish to report on the mutagenic activities of these and several other related compounds.
Kojic acid, a fungal metabolite produced by some species of Aspergillus and Penicillium, was found to induce sister chromatid exchanges and chromosomal aberrations in Chinese hamster ovary cells in the presence or absence of the rat liver S9 mix. Furthermore, this compound was demonstrated to induce mutations in Salmonella typhimurium strains TA98 and TA100 using both plate-incorporation and preincubation methods.
An analytical procedure based on gas chromatography of silyl derivatives is described for separation and quantitation of the mycotoxins kojic acid, terreic acid, and terrein. The method can be used for as little as 0.1 μg of the compounds and appears to be suitable for separating these substances from each other and from other mold metabolites in crude extracts. A cleanup procedure, based on silica gel column chromatography, is also described for separation of kojic acid from other metabolites of Aspergillus flavus and for purification and crystallization of kojic acid.
It was found that kojic acid, which is used in cosmetics for its excellent whitening effect, inhibits catecholase activity of tyrosinase in a non-classical manner. A decrease in the initial velocity to a steady-state inhibited velocity can be observed over a few minutes. This time-dependence, which is unaltered by prior incubation of the enzyme with the inhibitor, is consistent with a first-order transition. The kinetic data obtained correspond to those for a postulated mechanism that involves the rapid formation of an enzyme inhibitor complex that subsequently undergoes a relatively slow reversible reaction. Kinetic parameters characterizing this type of inhibition were evaluated by means of nonlinear regression of product accumulation curves.
Kojic acid (5-hydroxy-2-(hydroxymethyl)-4-pyrone), a fungal metabolic product, has increasingly been used as a skin-depigmenting agent in skin care products marketed in Japan since 1988. In order to determine its frequency of sensitization, during 1 year from October 1992 to September 1993, we performed patch testing with it in 220 female patients with suspected cosmetic-related contact dermatitis. Of the 220 patients, 8 used at least 1 skin care product containing kojic acid, 5 of whom reacted to kojic acid as well as to 1 or more their own products containing 1% kojic acid, but not to their other products not containing it, and 3 of whom were negative to kojic acid and all their own products. Patch testing with kojic acid in the remaining group of 212 patients, who had not previously used skin care products containing it, was negative without exception. The 5 kojic-acid-sensitive patients, aged 34 to 58 years, developed facial dermatitis 1-12 months after starting application of kojic-acid-containing products. Kojic acid is considered to have high sensitizing potential, as a comparatively high frequency of contact sensitivity was observed in patients using products containing it (5 out of 8).
Melasma continues to be a difficult problem. Although the cause is genetic, the condition is aggravated with sunlight, birth control pills, and pregnancy. Although hydroquinone is effective and has been available for years, a new product, kojic acid, has the advantage of being pharmaceutically more stable and, also, a tyrosinase inhibitor.
To evaluate on melasma and related conditions two similar formulations of glycolic acid/hydroquinone and glycolic acid/kojic acid. The therapeutic index of the two formulations is examined.
Thirty-nine patients were treated with kojic acid on one side of the face and hydroquinone in a similar vehicle on the other side of the face. The results were documented by a clinical investigator and with Wood's light examination combined with ultraviolet light photography.
Fifty-one percent of the patients responded equally to hydroquinone and kojic acid. Twenty-eight percent had a more dramatic reduction in pigment on the kojic acid side; whereas 21% had a more dramatic improvement with the hydroquinone formulation. These results were not statistically different. The kojic acid preparation was more irritating.
Both glycolic acid/kojic acid and glycolic acid/hydroquinone topical skin care products are highly effective in reducing the pigment in melasma patients. Both formulations should be available to the dermatologist to satisfy the patient's preferences.
Many goitrogenic xenobiotics that increase the incidence of thyroid tumors in rodents exert a direct effect on the thyroid gland to disrupt one of several possible steps in the biosynthesis, secretion, and metabolism of thyroid hormones. This includes (a) inhibition of the iodine trapping mechanism, (b) blockage of organic binding of iodine and coupling of iodothyronines to form thyroxine (T4) and triiodothyronine (T3), and (c) inhibition of thyroid hormone secretion by an effect on proteolysis of active hormone from the colloid. Another large group of goitrogenic chemicals disrupts thyroid hormone economy by increasing the peripheral metabolism of thyroid hormones through an induction of hepatic microsomal enzymes. This group includes central nervous system-acting drugs, calcium channel blockers, steroids, retinoids, chlorinated hydrocarbons, polyhalogenated biphenyls, and enzyme inducers. Thyroid hormone economy also can be disrupted by xenobiotics that inhibit the 5'-monodeiodinase that converts T4 in peripheral sites to biologically active T3. Inhibition of this enzyme by FD&C Red No. 3 lowers circulating T3 levels, which results in a compensatory increased secretion of thyroid-stimulating hormone (TSH), follicular cell hypertrophy and hyperplasia, and an increased incidence of follicular cell tumors in 2-yr or lifetime studies in rats. Physiologic perturbations alone, such as the feeding of an iodine-deficient diet, partial thyroidectomy, natural goitrogens in certain foods, and transplantation of TSH-secreting pituitary tumors in rodents also can disrupt thyroid hormone economy and, if sustained, increase the development of thyroid tumors in rats. A consistent finding with all of these goitrogens, be they either physiologic perturbations or xenobiotics, is the chronic hypersecretion of TSH, which places the rodent thyroid gland at greater risk to develop tumors through a secondary (indirect) mechanism of thyroid oncogenesis associated with hormonal imbalances.
Thyroid follicular cell tumors arise in rodents from mutations, perturbations of thyroid and pituitary hormone status with increased stimulation of thyroid cell growth by thyroid-stimulating hormone (TSH), or a combination of the two. The only known human thyroid carcinogen is ionizing radiation. It is not known for certain whether chemicals that affect thyroid cell growth lead to human thyroid cancer. The U.S. Environmental Protection Agency applies the following science policy positions: 1) chemically induced rodent thyroid tumors are presumed to be relevant to humans; 2) when interspecies information is lacking, the default is to assume comparable carcinogenic sensitivity in rodents and humans; 3) adverse rodent noncancer thyroid effects due to chemically induced thyroid-pituitary disruption are presumed to be relevant to humans; 4) linear dose-response considerations are applied to thyroid cancer induced by chemical substances that either do not disrupt thyroid functioning or lack mode of action information; 5) nonlinear thyroid cancer dose-response considerations are applied to chemicals that reduce thyroid hormone levels, increase TSH and thyroid cell division, and are judged to lack mutagenic activity; and 6) nonlinear considerations may be applied in thyroid cancer dose-response assessments on a case-by-case basis for chemicals that disrupt thyroid-pituitary functioning and demonstrate some mutagenic activity. Required data for risk assessment purposes is mode of action information on mutagenicity, increases in follicular cell growth (cell size and number) and thyroid gland weight, thyroid-pituitary hormones, site of action, correlations between doses producing thyroid effects and cancer, and reversibility of effects when dosing ceases.
Images
Figure 1
Figure 2
Figure 3
The tumorigenicity of kojic acid (KA), which is widely used for food and cosmetics in Japan, was examined in B6C3F1 mice. Female and male animals were divided into three groups and given 0, 1.5 and 3.0% KA containing food from the age of 6 weeks. At sacrifice after 20 months, thyroid weights were significantly increased in both sexes of mice receiving KA, especially in the male groups. The enlarged thyroid glands histologically featured diffuse hyperplasia and follicular adenomas, the incidences of the latter being 65% and 87%, respectively in 1.5% and 3.0% KA-treated males, significantly higher than the control value of 2%. In the females, the figures were 2%, 8% and 80% in the 0%, 1.5% and 3.0% KA groups, respectively. The serum free T3 levels in the 3.0% KA animals of both sexes at month 6 were significantly lower than in the controls. On the other hand, their serum TSH levels were higher, although the differences disappeared at later time points. In conclusion, continuous administration of high dose of KA induces thyroid adenomas in male and female B6C3F, mice, presumably by a mechanism involving decrease in serum free T3 levels and increased TSH.
In order to examine whether kojic acid (KA) exerts a promoting effect on thyroid carcinogenesis, male F344 rats were initiated with N-bis(2-hydroxypropyl)nitrosamine (BHP; 2800 mg/kg body wt, single s.c. injection) and, starting 1 week later, received pulverized basal diet containing 2 or 0% KA for 12 weeks. Untreated control rats were given basal diet for 13 weeks. As an additional experiment, two groups without BHP initiation received basal diet or diet containing 2% KA for 20 weeks. The serum triiodothyronine (T3) and thyroxine (T4) levels were significantly decreased (half to one-third of values of the BHP alone group) and serum thyroid-stimulating hormone (TSH) was markedly increased (13-19 times higher than the values of the BHP-alone group) in the BHP + KA group at weeks 4 and 12. Similar changes in serum thyroid-related hormones were observed in the group with 2% KA alone at week 4, but not at week 20. Thyroid weights were significantly increased in the BHP + KA and KA-alone groups. Focal thyroid follicular hyperplasias and adenomas were observed in 4/5 and 3/ 5 rats in the BHP + KA group at week 4, respectively. At weeks 12, these lesions were observed in all rats in the BHP + KA group. Animals of the KA alone group showed marked diffuse hypertrophy of follicular epithelial cells at weeks 4 and 20. No changes in thyroid-related hormone levels or thyroid histopathological lesions were observed in either the BHP alone or the untreated control groups. Measurement of liver T4-uridine diphosphate glucuronosyltransferase (UDP-GT) activity at week 4 revealed no significant intergroup differences. These results suggest that thyroid proliferative lesions were induced by KA administration due to continuous serum TSH stimulation through the negative feedback mechanism of the pituitary-thyroid axis, with decreases of T3 and T4 caused by a mechanism independent of T4-UDP-GT activity.
To discover safe and effective topical skin-lightening agents, we have evaluated alkyl esters of the natural product gentisic acid (GA), which is related to our lead compound methyl gentisate (MG), and four putative tyrosinase inhibitors, utilizing mammalian melanocyte cell cultures and cell-free extracts. Desirable characteristics include the ability to inhibit melanogenesis in cells (IC50 < 100 microg/mL) without cytotoxicity, preferably due to tyrosinase inhibition. Of the six esters synthesized, the smaller esters (e.g. methyl and ethyl) were more effective enzyme inhibitors (IC50 approximately 11 and 20 microg/mL, respectively). For comparison, hydroquinone (HQ), a commercial skin "bleaching" agent, was a less effective enzyme inhibitor (IC50 approximately 72 microg/mL), and was highly cytotoxic to melanocytes in vitro at concentrations substantially lower than the IC50 for enzymatic inhibition. Kojic acid was a potent inhibitor of the mammalian enzyme (IC50 approximately 6 microg/mL), but did not reduce pigmentation in cells. Both arbutin and magnesium ascorbyl phosphate were ineffective in the cell-free and cell-based assays. MG at 100 microg/mL exhibited a minimal inhibitory effect on DHICA oxidase (TRP 1) and no effect on DOPAchrome tautomerase (TRP-2), suggesting that MG inhibits melanogenesis primarily via tyrosinase inhibition. MG and GA were non-mutagenic at the hprt locus in V79 Chinese hamster cells, whereas HQ was highly mutagenic and cytotoxic. The properties of MG in vitro, including (1) pigmentation inhibition in melanocytes, (2) tyrosinase inhibition and selectivity, (3) reduced cytotoxicity relative to HQ, and (4) lack of mutagenic potential in mammalian cells, establish MG as a superior candidate skin-lightening agent.
In order to elucidate the mechanisms of reduction of serum thyroid hormones caused by continuous administration of kojic acid (KA) and its thyroid tumor-promotion effects, male F344 rats were given pulverized basal diet containing 0.008%, 0.03%, 0.125%, 0.5%, or 2% KA for 4 weeks. As an untreated control group, additional rats were given basal diet alone for the same period. The thyroid 125I uptake was significantly decreased in the groups receiving 0.03% or more. In addition, significant reduction of organic formation of iodine and serum T3 and T4 levels were observed in the 2% KA group along with pronounced elevation of serum (TSH). Both absolute and relative thyroid weights were significantly increased in the groups receiving 0.5% of KA or more. Histopathologically, decreased colloid in the thyroid follicles and follicular cell hypertrophy in the thyroid were apparent at high incidences in the groups given 0.03% or more. In addition, thyroid capsular fibrosis was evident in all rats of the 2% KA group. In quantitative morphometrical analysis, the ratio of the area of follicular epithelial cells to the area of colloids was significantly increased in the groups given 0.03% KA or more. The results suggest that KA alteration of thyroid-related hormone levels in the 2% KA group are due to inhibition of iodide uptake and iodine organification in the thyroid, with tumor-promoting effects on development of thyroid proliferative lesions, probably secondary to prolonged serum TSH stimulation resulting from negative feedback through the pituitary-thyroid axis.
To clarify the mechanism of tumorigenesis by kojic acid (KA), dose and time dependence of iodine uptake in the thyroid gland and serum thyroid stimulating hormone (TSH) and thyroid hormone levels were investigated in F344 rats fed a diet containing 2% KA. After 4 weeks, thyroid hyperplasia was apparent in males, associated with a decrease in (125)I uptake into the thyroid gland to only 3% of that in controls. The serum triiodothyronine (T(3)) and thyroxine (T(4)) levels dropped to 0.36 ng/ml, 1.7 micrograms/dl from the initial values of 0.61 ng/ml, 4.0 micrograms/dl and TSH increased seven times to 15 ng/ml. In females, the effects on thyroid weight and (125)I uptake were less prominent, although the changes in serum T(3), T(4) and TSH levels were similar to those in males. Time-dependent changes in serum T(3), T(4) and TSH levels correlated with the inhibition of iodine uptake in the thyroid. Inhibition of organic iodine formation was only observed after 3 weeks treatment. On return to the control diet, normal serum T(3), T(4) and TSH levels became evident within 48 h in both sexes. These data suggest that KA interrupts thyroid function, primarily by inhibiting iodine intake, consequently causing a decrease in serum T(3) and T(4). Increased TSH from the pituitary gland in turn stimulates thyroid hyperplasia, which is reversible on withdrawal of KA.
Time course changes in thyroid proliferative lesions as well as related hormone levels in the blood of male F344 rats given N-bis(2-hydroxypropyl)nitrosamine (DHPN: 2800 mg/kg body weight, single s.c. injection) as an initiation treatment followed by pulverized basal diet containing 0% (Group 2), 2% (Group 3) or 4% (Group 4) kojic acid (KA) were examined at Weeks 1, 2, 4, 8 and 12. As an untreated control group (Group 1), rats were given basal diet for 13 weeks and examined in the same manner. Serum T3/T4 levels in the DHPN + 2% KA and DHPN + 4% KA groups were significantly reduced as compared with the DHPN-alone group at each time point. Serum TSH levels in both DHPN + KA groups were significantly increased at each time point in a treatment period-dependent manner from Weeks 1 to 12, and the extent of elevation was more remarkable in the DHPN + 4% KA group. At Week 2, there were no statistically significant intergroup differences in liver T4-UDP-GT activities on a milligram microsomal protein basis. Histopathologically, no thyroid proliferative lesions were observed in the untreated control group or the DHPN-alone group. However, diffuse follicular cell hypertrophy and decreased colloid in the thyroid were apparent in all rats of the DHPN + KA groups at each time point. In addition, focal follicular cell hyperplasias and adenomas of the thyroid were observed at high incidence in the DHPN + 2% KA group from Week 4 and in the DHPN + 4% KA group from Week 8. Multiplicities of focal follicular cell hyperplasias and adenomas of the thyroid in the DHPN + 2% KA group were significantly greater than those in the DHPN + 4% KA group at Week 8. In the pituitary, an increase in the number of TSH producing cells with expanded cytoplasm was apparent from Weeks 4 to 12 in both DHPN + KA groups. These results strongly suggest that thyroid proliferative lesions were induced by KA administration due to continuous serum TSH stimulation through the negative feedback mechanism of the pituitary-thyroid axis, resulting from depression of serum T3 and T4.
To elucidate the effects of kojic acid on thyroid function, the compound was given orally to male rats for 4 weeks at 0, 4, 15, 62.5, 250 and 1,000 mg/kg. In 1,000 mg/kg treatment of kojic acid, the rats showed a slight decrease in motility, inhibition of body weight gain, and a decrease in food consumption. An increase in thyroid weight and a morphological change, i.e., hypertrophy of epithelial cells of the thyroid gland follicles, were observed after 1 week of administration. In addition, the uptake of radioactive iodine from blood into the thyroid gland was enhanced and the TCA-precipitable radioactive iodine in the thyroid gland increased in those rats. However, the rates of the iodination in the thyroid gland did not change during the experiment period. Although serum T4 concentration was low in the rats treated with 1,000 mg/kg kojic acid, it was not observed in any changes in TSH concentration. None of these changes were found in the other groups. These observations suggest that massive administration of kojic acid may decrease blood T4 concentration and that thyroid function may be enhanced compensatorily. On the other hand, the absorption of kojic acid was rapid as manifested by the Tmax of blood concentrations of radioactivity, which was as short as 1.0 +/- 0.0 hr, and the t1/2 was 4.8 +/- 0.3 hr. Blood concentrations of radioactivity disappeared nearly completely at 24 hr after administration. This result indicates that the toxic effect observed on the thyroid gland treated with only the largest dosage of kojic acid may depend on a fast decrease following a transient increase of concentration of the compound in the blood.
Kojic acid is a fungal metabolite commonly produced by many species of Aspergillus, Acetobacter, and Penicillium. The Aspergillus flavus group has traditionally been used in the production of a number of foods, including miso (soybean paste), shoyu (soy sauce), and sake. Kojic acid is widely used as a food additive for preventing enzymatic browning, and in cosmetic preparations as a skin-lightening or bleaching agent. Because kojic acid is often produced during the fermentation of historically used dietary staples, it has a long history of consumption. Various types of compounds, such as glucose, sucrose, acetate, ethanol, arabinose, and xylose, have been used as carbon sources for kojic acid production. Different Aspergillus species are known to produce variable amounts of kojic acid. The mechanism of action of kojic acid is well defined and it has been shown to act as a competitive and reversible inhibitor of animal and plant polyphenol oxidases, xanthine oxidase, and D- and some L-amino acid oxidases. The structure of kojic acid indicates a relatively simple route of metabolism much like dietary hexoses. Acute or subchronic toxicity resulting from an oral dose has not been reported, but convulsions may occur if kojic acid is injected. Results of mutagenicity studies are mixed, but in the in vivo mammalian dominant lethal assay, kojic acid was proven negative. Continuous administration of high doses of kojic acid in mice resulted in induction of thyroid adenomas in both sexes. Kojic acid reversibly affects thyroid function primarily by inhibiting iodine uptake, leading to decreases in T3 and T4 and increase in TSH. Increased TSH from pituitary gland in turn stimulates thyroid hyperplasia. Several lines of evidence indicate that the proliferative effects of kojic acid on thyroid are not related to a genotoxic pathway. The risk of functional inhibition of iodine uptake and its metabolism (organification) and thyroid tumor induction by kojic acid in humans appears to be extremely low. Based on the literature reviewed and discussed here, consumption of kojic acid at levels normally found in food does not present a concern for safety.