Review on the Use of Kojic Acid—A Skin-Lightening Ingredient

Abstract

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.

Full text

Citation: Phasha, V.; Senabe, J.;
Ndzotoyi, P.; Okole, B.; Fouche, G.;
Chuturgoon, A. Review on the Use of
Kojic Acid—A Skin-Lightening
Ingredient. Cosmetics 2022,9, 64.
https://doi.org/10.3390/
cosmetics9030064
Academic Editor: Enzo Berardesca
Received: 15 April 2022
Accepted: 10 May 2022
Published: 15 June 2022
Publisher’s Note: MDPI stays neutral
with regard to jurisdictional claims in
published maps and institutional affil-
iations.
Copyright: © 2022 by the authors.
Licensee MDPI, Basel, Switzerland.
This article is an open access article
distributed under the terms and
conditions of the Creative Commons
Attribution (CC BY) license (https://
creativecommons.org/licenses/by/
4.0/).
cosmetics
Review
Review on the Use of Kojic Acid—A Skin-Lightening Ingredient
Vivey Phasha 1, Jeremiah Senabe 1, Phatheka Ndzotoyi 1, Blessed Okole 1, Gerda Fouche 2
and Anil Chuturgoon 3, *
1Council for Scientific and Industrial Research, Pretoria 0001, South Africa; vphasha@csir.co.za (V.P.);
jsenabe@csir.co.za (J.S.); bokole@csir.co.za (B.O.); pndzotoyi@csir.co.za (P.N.)
2
Department of Chemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria 0028,
South Africa; foucheg51@gmail.com
3School of Laboratory Medicine and Medical Sciences, Durban 4319, South Africa
*Correspondence: CHUTUR@ukzn.ac.za
Abstract:
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.
Keywords: Kojic acid; hyper-pigmentation; tyrosinase; melasma; cytotoxicity; sensitization
1. Introduction
Global researchers are exploring the development of various groups of tyrosinase
inhibitors, as they have a huge impact on the cosmetic and pharmaceutical industries and
the global economy [
1
]. One of the main considerations for tyrosinase inhibitors is safety,
particularly when applied regularly and not considering the recommended dosages. Some
challenges experienced with the use of these agents include high cytotoxicity and insta-
bility, thus necessitating additional research to improve their applications as ingredients
in cosmetics [1,2].
KA inhibits tyrosinase and has been commonly researched in the cosmetic
industry [1–6]
.
KA and its derivatives have radioprotective, skin-lightening, anti-inflammatory, anti-oxidant,
and anti-proliferative properties [
1
,
7
]. Due to its tyrosinase inhibitory activity, KA can
protect the skin from ultraviolet (UV) rays, reduce hyperpigmentation, and prevent melanin
formation [
1
,
8
]. It is produced by several types of fungi, and it is also a by-product of the
fermentation process of certain foods, such as soy sauce and sake [1].
KA is incorporated in many kinds of cosmetic products [
9
]. The CIR approved KA as
safe at a concentration of 1% in cosmeceutical products [
9
]. The existing dermatological
safety data also support the safety of KA at a concentration of 2% in cosmeceuticals,
indicating that a limit of 2% might be applicable [9].
2. Fungi-Producing Kojic Acid
KA was discovered in 1907 by Saito in cultures of Aspergillus oryzae [
10
,
11
]. This
organic acid is formed when various types of fungi ferment. KA is mostly secreted by
more than 58 fungal strains of the Aspergillus genus [
10
]. Some of the species that form
Cosmetics 2022,9, 64. https://doi.org/10.3390/cosmetics9030064 https://www.mdpi.com/journal/cosmetics

Cosmetics 2022,9, 64 2 of 11
this acid include Aspergillus,Penicillium,Acetobacter, and others [
2
,
10
,
12
–
14
]. Amongst
the Aspergillus species, its main producers are Aspergillus oryzae, Aspergillus flavus, and
Aspergillus parasiticus (Table 1) [
15
–
18
]. It is used in the food and cosmeceutical industries
for preserving or changing the color of substances. In the cosmetic industry, it is well
known for its tyrosinase inhibition activity [19,20].
Table 1. Production of KA. Adapted from Chaudhary, 2014 [10].
Fungus Toxins Characteristics Production Yield
Aspergillus. flavus
Aflatoxins, Aflatrem,
Aspergilic acid, Cydoplazonic
acid, β-nitropionic acid, and
Serigmatocyctin
Pathogenicity: Generally, a contaminant but
also known to cause disease; commonly
associated with aflatoxins
Macroscopic morphology:
Velvety, yellow to green or brown, Reverse
goldish to red-brown
Macroscopic morphology of conidiophores:
Variable length, rough, pitted, spiny
Macroscopic morphology of conidiophores:
Uni-seriate and bi-seriate, covers entire vesicle,
points out in all directions
High
Aspergillus orizae
Aspergillus acid,
Cycopiazonic acid,
Maltoryzine β-nitropropionic
acid, Ochtratoxins
Medium to High
Aspergillus parasiticus
Aflatoxins, Aspergillic acid,
and Sterigmatocyctin High
Aspergillus Tamarii Aflatoxins Low
3. Physical and Chemical Properties
KA chemical structure is defined as 5-hydroxy-2-hydroxymethyl-
γ
-pyrone [
14
]. It is also
known as 5-hydroxy-2-hydroxymethyl-4H-pyran-4-one and 5-hydroxy-2-hydroxymethyl-4-
pyrone [14,21]. KA is a heterocyclic compound with a structure as shown in Figure 1below.
Figure 1. Kojic acid chemical structure, Adapted with permission from Ref. [6], 2020, Hasil et al.
The crystals of KA are acicular and colorless, and they sublime in a vacuum with no
variations. KA is soluble in some organic solvents, such as ethyl acetate, water, and ethanol.
It is unlikely to dissolve in ether, alcohol ether mixture, chloroform, and pyridine [10,14].
The melting point of KA lies between 151–154 degrees Celsius (
◦
C) [
10
,
14
]. According
to Cryoscopy Technique, the molecular weight of KA is 142.1, and its maximum peak of
UV Absorption Spectra is at 260–284 nanometers (nm).
KA is a weak acid with multidimensional uses. It reacts at every position on the
ring, thus forming several products, such as ethers, pyridines, metal chelates, azodyes,
mannich base, pyridines, and cyanoethylation products [
10
,
14
]. Several chemical reactions
of KA have been studied over the years since its isolation. At the carbon 5 position of this

Cosmetics 2022,9, 64 3 of 11
compound, the hydroxy becomes a weak acid, therefore forming salts when reacted with
metals such as cadmium, nickel, copper, zinc, and sodium due to its weakly acidic proper-
ties [
14
]. Introducing new functional groups on the KA skeleton via the hydroxy ketone or
hydroxyalkyl allows for the improvement in the solubility of subsequent complexes [22].
4. Safety Assessment of Kojic Acid
Several studies have been conducted to evaluate the safety and efficiency of tyrosi-
nase inhibitors in the cosmeceutical and medicinal industries [
2
,
23
]. These inhibitors are
important due to their ability to prevent pigmentation disorders.
The safety studies performed recommend the use of KA in topical preparations at a
concentration of 1% or less because, in these ranges, it shows efficient and safe properties [
2
].
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].
KA produced from bearberry leaves is safe and efficient for topical use, although it is
not satisfactorily effective and not stable for use in cosmeceuticals [1,7,18].
A survey conducted by the cosmetics industry also indicated that it is safe for use at a
concentration ranging from (0.1 to 2.0)% [23,24]
A determination by the European Commission’s Scientific Committee on Consumer
Products (SCCP) indicated that KA is safe for use at a concentration limit of 1% (
Burnett et al.
,
2010; Mann et al., 2018).
Available data to date indicate that KA is safe for application as a skin lightening agent
at a concentration of 1% in leave-on creams [2,9].
Various investigations have shown that when used at 1 and 2%, KA does not show
any ocular or allergenic sensitivity. It was also declared a group 3 carcinogen by the
International Agency For Research On Cancer (IARC) [
2
]. In addition, the Food and Drug
Administration (FDA) does not permit the use of KA in pharmaceutical products without a
prescription; however, the SCCP reported that the dose of KA should be 1.0% in skincare
products and that it is not a toxicant in generative, chronic, acute, and genotoxicity form [
2
].
Despite the extensive benefits of using KA in topical products, there are some disad-
vantages, including contact dermatitis and possible photo-damaging of the skin [
2
]. These
are outlined in Table 2below.
Table 2. Positive and negative effects of using KA for skin lightening.
Benefits Disadvantages
- Lightening effect on visible sun damage and age spots
- Anti-aging
- Antimicrobial
- Antifungal
- Anti-acne
-
Treatment of yeast infections, candidiasis, and ringworm
- Contact eczema (especially in sensitive skins)
-
Long-term use of KA may make skin more prone to sunburn
- Carcinogenic when used on damaged or broken skin
5. Kojic Acid Derivatives
KA causes skin irritation, has inadequate inhibitory activity, and is not stable during
storage, thus reducing its use in cosmetic products [
1
,
13
,
26
–
28
]. To overcome these dis-

Cosmetics 2022,9, 64 4 of 11
advantages, many derivatives of KA have been produced [
29
]. These derivatives were
produced to improve stability and solubility.
By modifying the alcoholic hydroxyl group of KA, it can be converted into an ester,
glycoside, amino acid derivatives, hydroxyphenyl ether, or tripeptide derivatives [1].
The KA derivatized through an ethylene linkage of the phosphonate with aldehyde
using intermediates derived from KA is about eight times more effective in tyrosinase
inhibitory activity than KA [1,14].
Recently, methods for the synthesis of a variety of KA derivatives, such as KA di-
palmitate, KA ester, and KA laureate, have been reported [
14
,
30
]. KA peptides have also
been investigated as potent tyrosinase inhibitors [31].
6. Cosmetic Applications of Kojic Acid
KA is a popular ingredient and is used by various industries globally [
15
,
19
]. In
the cosmetic industry, it is used as a topical treatment for skin conditions such as spots,
melasma, and patches of light brown color resulting from post-inflammatory hyperpigmen-
tation [15,32–35].
KA has skin-lightening properties and can act as a UV protector, whereby it prevents
the development of hyperpigmentation in human skin by inhibiting the formation of
melanin through the prevention of tyrosinase formation [14,19,33].
KA also enhances the shelf life of cosmetic products through its preservative prop-
erties [
36
]. It is normally combined with alpha-hydroxy acid in the formulation of skin-
lightening products to manage age spots and lightened freckles. Due to its manganese and
zinc complexes, it can be used as a radioprotective agent against
γ
-ray [
14
]. Figure 2below
summarizes the above-discussed applications of KA.
Figure 2. Cosmetic applications of kojic acid [2].
7. Biological Activities of Kojic Acid
The available literature indicates that this ingredient has various biological activities,
and they are listed below.

Cosmetics 2022,9, 64 5 of 11
7.1. Antibacterial and Antimicrobial Activity
KA has antifungal and antibacterial properties [
37
]. Preceding antimicrobial activity
assays showed that KA was more active against Gram-negative bacteria than against
Gram-positive bacteria [
1
]. However, some of its derivatives have shown conflicting effects
distinct from KA’s antibacterial activity [1].
When used in cosmetic products, KA can prevent the growth of microorganisms and
can be used as a preservative [38].
The antimicrobial activity of the ethyl acetate (EtOAc) extract of Colletotrichum gloeospo-
rioides and its major compound KA were evaluated, and the results showed considerable
antimicrobial activity against all tested strains [
34
]. When tested against various microor-
ganisms, KA was most active against Micrococcus luteus and least active against Pseudomonas
aeruginosa [34].
Due to its antifungal properties, KA is incorporated into some antifungal products
to improve their effectiveness [
34
]. Furthermore, it could be useful in treating various
fungal infections of the skin as well as yeast infections, ringworm, athlete’s foot, and
candidiasis [34].
KA and its derivatives have potent activity against bacteria such as Staphylococcus
aureus [
14
]. The KA derivatives were also validated for antifungal activities against Fusarium
oxysporum, Rhizoctonia solani, and Pythium graminicola, which cause fungal infections such
as fusarium wilt, sheath blight, and seedling blight. Besides its antibiotic properties, KA also
shows some insecticidal activity against Spodoptera frugiperda and Heliothis zea insects [14].
7.2. Antioxidant Activity
KA has anti-oxidant properties [
7
] and is used as a substitute for hydroquinone (HQ)
for skin lightening by the cosmeceutical industry [1,39].
Studies by Zhang et al., (2017) showed that KA improved oxidative stress response
in fungi, thus showing the anti-oxidant ability of this metabolite [
39
]. Other preceding
bioactivity studies on KA revealed that it has anti-oxidant properties [34].
The correlation between anti-melanogenic activity with oxidative effects of KA and
KA esters was investigated by Lajis et al.,2012. The results of the study showed that both
KA and its esters had mild free radical scavenging activities at concentrations ranging from
1.95 to 1000 µg/mL [40].
7.3. Anti-Inflammatory Activity
KA may exert slight anti-inflammatory effects that may favorably improve by sub-
sequent derivation of chosen KA derivatives [
41
]. In a recent study to develop a safe
anti-inflammatory compound, a derivative of KA and p-coumaric acid were synthesized,
as they are known to have anti-inflammatory properties. The study suggested that the
anti-inflammatory action of KA was enhanced by the addition of cinnamate moiety in
p-coumaric acid as an hydrophobic part [
42
]. A study assessed the anti-inflammatory
activity of KA and p-coumaric acid and revealed that both possessed anti-inflammatory
properties [39].
In another study, KA and its two novel derivatives were isolated from the fungus
Aspergillus versicolor and evaluated for their anti-inflammatory effects [
43
], showing that
KA has a moderate anti-inflammatory effect, while the derivatives 1 and 2 were found to
have improved effects [43].
7.4. Tyrosinase Inhibition Activity
KA is regarded as one of the best skin-lightening agents in the beauty industry [
1
].
It exerts a slow and effective reversible inhibition of tyrosinase, thus preventing melanin
formation, and also plays an important role in cellular melanin formation [
1
]. According to
available data from various studies, it can be used as a monotherapy or combined with other
agents [
32
]. In Japan, this ingredient is known as a quasi-drug [
23
,
44
]. Due to its ability to
inhibit tyrosinase activity, KA has been used in several studies as a standard [
1
,
31
,
45
–
50
].

Cosmetics 2022,9, 64 6 of 11
Another study revealed that KA inhibits melanosis by interfering with the uptake of oxygen
required for enzymatic browning [1].
8. Kojic Acid Mechanism of Action
KA is a kind of secondary metabolite, whose biosynthesis pathway continues to
be uncertain to date [
11
]. However, it is stated that it chelates divalent ions and acts
as a tyrosinase inhibitor and a free radical scavenger [
19
,
51
]. It works by chelating the
copper (Cu
+
) at the active site of the tyrosinase enzyme [
8
,
52
]. The tyrosinase enzyme, also
known as polyphenol oxidase, limits the rate of melanin synthesis, and it is responsible
for converting L-tyrosine to L-3–4 dihydroxyphenylalanine [
8
,
19
,
27
]. It belongs to the type
3 copper-containing protein family, with two copper ions (CuA and CuB) in the active
site [
53
]. CuA and CUB catalyze the conversion of monophenols (e.g., tyrosine) into o-
diphenols (monophenolase activity) followed by the oxidation of the o-diphenols to the
resultant o-quinone derivatives (diphenolase activity) (Figure 3) [54].
Figure 3. The reaction catalyzed by tyrosinase. Adapted with permission from Ref. [55]., 2018, Lai et al.
Low-pigmenting agents can be generally classified according to which step of melanin
production is disrupted [
55
]. This depends on whether the agents can act before, during,
or after melanin production. KA acts during the actual synthesis of melanin, exhibiting a
sufficient inhibitory effect on monophenolase activity and a varied inhibitory effect on the
diphenolase activity of mushroom tyrosinase [55].
8.1. Assays for Evaluating the Efficacy of Kojic Acid
The efficacy of KA may be assessed by several methodologies, varying from
in vitro
experiments to
in vivo
and clinical studies. All these methods have their advantages and
disadvantages and may, from time to time, lead to false positives and false negatives [56].
The following sections describe some of the findings from previous studies conducted
on the efficacy of KA in treating or managing skin disorders such as hyperpigmentation.
8.2. Melanin Depigmentation Assays
There is substantial evidence indicating that KA is effective in inhibiting melanin
production and reducing the pigment in melasma patients [
57
]. To investigate the effect of
melanin reduction by KA and KA esters, various studies have been conducted, and they
reveal the efficacy of these agents.
An
in vitro
study to evaluate the capacity of KA to inhibit melanogenesis on living
pigment cells showed that it is effective. In addition, hyper-pigmented B16 cells, and
their essential precursor monomer, 5,6 DHI 2C, influence a different eumelanin content
reduction [14].
A study to investigate the depigmentation effect of KA esters (KA mono-oleate,
KA mono-laurate, and KA mono-palmitate) on B16F1 melanoma cells was conducted
(
Lajis et al.
, 2012), which revealed that these esters at a concentration range of (31.3 to 62.5)
µg/mL efficiently depigment melanoma cells [40].
KA and KA esters showed comparable melanin inhibitory properties at the minimum
and maximum doses assessed in this study (1.95
µ
g/mL). However, KA mono-palmitate
showed a somewhat greater inhibitory effect than the other derivatives assessed at doses of
(15.63 to 62.5) µg/mL [40].

Cosmetics 2022,9, 64 7 of 11
Lee et al. evaluated the anti-melanogenic effects of the synthesized derivatives KA
and hydroxycinnamic acid individually and in combination and found that both had anti-
melanogenic properties [
58
]. The results suggest that the chelating portion of KA had more
effect on tyrosinase inhibition than the phenol moiety of hydroxycinnamic acid [
58
]. The
anti-melanogenic activity from these studies also showed that all the compounds evaluated
reduced tyrosinase activity in a dose-dependent manner [58].
8.3. Tyrosinase Inhibition Assays
Tyrosinase inhibition is the safest and most effective approach to minimizing hyper-
pigmentation [
59
]. However, there is a limitation in the clinical efficacy of the currently
used tyrosinase inhibitors, as these inhibitors were specifically chosen based on their ability
to inhibit mushroom tyrosinase [
59
]. This is also a widely reported screening method in
the literature for skin-lightening ingredients [60]. Tyrosinase is an enzyme responsible for
synthesizing melanin through melanogenesis [61].
Lajis et al. (2012) further investigated the inhibitory effect of KA and its esters at
safe dosages of (1.95 to 62.5)
µ
g/mL [
40
]. When pigmented melanoma B16F1 cells were
incubated with KA and its derivatives, a major reduction in tyrosinase activity was revealed
at (31.25 to 62.5) µg/mL [40].
At minimal doses of (1.95 to 15.25)
µ
g/mL, KA and its derivatives showed a minor
reduction in tyrosinase activity [40].
The available IC
50
values for KA tyrosinase inhibitory effect ranges from (6 to more
than 100) mmol/L [
24
]. An
in vivo
study to compare KA with several phenolic-derived com-
pounds on the catalysis of human tyrosinase and synthesis of melanin was conducted [
24
].
It was revealed that KA is less effective in tyrosinase inhibition, with an IC
50
of about
0.5 mmol/mL [24]
. KA also shows a non-competitive inhibition, with an inhibitory con-
stant value of 0.145 mmol/mL, indicating selective binding to the deoxy form [24].
Amongst the KA esters, KA monooleate inhibited mushroom tyrosinase more than KA
monolaurate and KA mono-palmitate. The KA monooleate inhibitory effect on mushroom
tyrosinase was more or less similar to that of KA at doses of (62.5 to 250) µg/mL [40].
Another study to assess the tyrosinase inhibition of KA derivatives was conducted
by Rho et al., (2010), where a series of KA derivatives comprising sulfoxide, sulfone,
and thioether bonds were produced. In the tyrosinase assay, KA thioether derivatives
comprising suitable lipophilic alkyl chains exhibited effective inhibitory activity [62].
8.4. Mushroom Tyrosinase
Mushroom tyrosinase is the most commonly used method to screen for tyrosinase
inhibitors [
61
]. In most of these studies, the tyrosinase activity is expressed as the half-
maximal inhibitory concentration (IC
50
), which is the concentration of the samples produc-
ing 50% inhibition [5].
KA demonstrates a great inhibitory outcome on monophenolase activity and a non-
competitive inhibitory outcome on the diphenolase activity of mushroom
tyrosinase [1,19,55]
.
In a study by Aytemir et al., KA (10
µ
M) showed the best inhibitory properties
against mushroom tyrosinase activity, cellular tyrosinase activity, and cellular melanin
formation [1].
Khezri et al., 2021, evaluated the tyrosinase inhibitory activity of a KA derivative (KA-
nano structured lipid carrier (NLC
3)
) against mushroom tyrosinase. The results obtained
revealed that the prepared NLC
3
and KA solutions inhibited the activity of tyrosinase
mushroom in a concentration-dependent manner; however, KA-NLC
3
showed greater
potency in tyrosinase inhibitory activity than pure KA [51].
KA was previously found to be attached at the entrance to the active site of Bacillus
megaterium tyrosinase, recommending one considerable intermediate binding site. However,
the full mechanism of KA inhibition continues to be unclear [53].
An et al., 2010, conducted a study to compare the inhibitory effects of p coumaric
acid (pCA), arbutin, and KA on the catalytic activities of mushroom, murine, and human

Cosmetics 2022,9, 64 8 of 11
tyrosinases
in vitro
, using tyrosine and 3,4 dihydroxyphenylalanine as substrates. The
results revealed that pCA is a greater inhibitor of human or murine than mushroom
tyrosinase, in comparison with KA and arbutin as a positive control. Furthermore, pCA
showed inhibition of human tyrosinase at much lower concentrations than those required
for the inhibition of murine or mushroom tyrosinase [5].
8.5. In Vivo Clinical Studies
Studies have shown that hyperpigmentation, particularly melasma, greatly affects
quality of life, causing psychosocial distress. Treatments for melasma include topical
depigmenting agents such as KA [
3
]. The efficacy of a given ingredient may be evaluated
by clinical trials. Depigmentation of the affected skin areas may be evaluated visually,
which may be done using color charts such as Munsell or by measuring with cutaneous
colorimeters [
56
,
63
]. The results in both cases depend on the nature and size of the studied
skin area; furthermore, after the observation, it can only be recommended that both methods
are concurrently used [56].
In a clinical trial, a formulation containing 1.0% KA was shown to be effective in the
treatment of hyper pigmentary conditions, such as freckles, age spots, post-inflammatory
hyperpigmentation, and melasma [44].
Another study to determine the effects of adding KA to a formulation comprising
two other lightening agents in 40 females with epidermal melasma was conducted. It was
stated that more than half of the melasma was cleared in 60% of the patients treated with
KA compared to 47.5% of patients treated with a formulation without KA [32].
A 12-week trial to test the efficacy of KA as a skin lightener in patients with dyschro-
mia revealed that patients treated with Vitamin C/KA had greater improvement in the
appearance of dyschromia, skin tone, and radiance when compared to patients treated with
HQ. In this study, KA was better tolerated with less stinging and tightness to the skin [
35
].
KA has been combined with other therapies to treat facial hyperpigmentation. In a
randomized, split-face study of 39 patients with facial hyperpigmentation, it was revealed
that 51% of patients had an equal decrease of melasma on both the KA 2% plus glycolic
acid (GA) 5% side and the HQ 2% plus GA 5% sides of their faces [
64
]. Additionally, 28%
and 21% of patients saw benefits with KA and HQ, respectively, indicating that KA and
2% HQ are equally effective in the treatment and management of melasma [64].
The efficacy of KA and other agents in treating melasma was evaluated by Desai et al.,
2019, in a randomized clinical study of 55 healthy subjects [
3
]. A hydro glycolic topical face
serum containing tranexamic acid, KA, niacinamide, and hydroxyethylpiperazineethane
sulfonic acid was used as a treatment [
3
]. Significant reduction in hyperpigmentation
increased skin texture, and skin tone homogeneity was observed in the patients. A major
reduction in melasma was also observed at all time points afterwards [
3
]. Table 3shows a
summary of the above-mentioned clinical trials conducted on KA.
Table 3. Some of the findings of the clinical trials conducted on kojic acid.
Study Design and Setting Concentration Dosing Regimen (Weeks) Result Reference
Treatment of freckles, age spots,
post-inflammatory hyperpigmentation,
and melasma
1% - Effective [44]
KA was combined with two other
lightening agents in 40 females to treat
epidermal melasma. Treatment on half of
the face with KA. The other half was
treated with the same application with no
KA.
5% - Effective [32]

Cosmetics 2022,9, 64 9 of 11
Table 3. Cont.
Study Design and Setting Concentration Dosing Regimen (Weeks) Result Reference
Skin lightening in patients with
dyschromia Not stated 12 Effective [35]
KA was combined with other therapies to
treat facial hyperpigmentation and
melasma in 39 patients
KA 2% plus
glycolic acid (GA)
5% side and HQ 2%
plus GA 5%
Effective [64]
The efficacy of KA and other agents in
treating melasma in a randomized clinical
study of 55 healthy subjects
1% KA, 5%
niacinamide, and
3% Traxenamic acid
Significant
reduction [3]
9. Conclusions
Kojic acid is a well-known and intensively studied ingredient for tyrosinase inhibition.
However, KA is not stable, is less sufficient in inhibiting tyrosinase activity, and has undesir-
able side effects. To overcome these adverse effects, researchers have attempted to produce
new analogs of KA with higher efficiency in treating hyperpigmentation, acceptable sta-
bility, and safety. Various methods have evaluated the efficacy of KA and its derivatives.
The findings from these studies revealed that these new agents are effective in treating
various skin conditions such as hyperpigmentation and melasma. It was also established
that KA derivatives were more efficient in tyrosinase inhibition than KA. Skin lightening
agents such as KA have proven to have improved safety profiles for prolonged treatment of
skin conditions like melasma, which may be treated using mono or combination therapies.
More research on this topic will be supportive in producing safer and efficient agents for
tyrosinase inhibition.
Author Contributions:
V.P.: writing—original draft preparation and editing, funding acquisition;
J.S.: writing—review and editing; G.F.: writing—review editing and supervision; P.N.: review and
supervision; B.O.: review, editing, and supervision; A.C.: writing, review, editing, and supervision.
All authors have read and agreed to the published version of the manuscript.
Funding:
This research was funded by the CSIR, Young Researchers Fund, Funding number: A2BAP28
and the APC was funded by the CSIR and The University of Kwa-Zulu Natal, South Africa.
Institutional Review Board Statement: Not applicable.
Informed Consent Statement: Not applicable.
Acknowledgments:
We would like to thank the CSIR-Young Researchers Fund for funding this study.
Conflicts of Interest: The authors declare no conflict of interest.
References
1. Aytemir, D.M.; Karakay, G. Kojic Acid Derivatives. Med. Chem. Drug Des. 2012, 1–27.
2.
Saeedi, M.; Eslamifar, M.; Khezri, K. Kojic acid applications in cosmetic and pharmaceutical preparations. Biomed. Pharmacother.
2019,110, 582–593. [CrossRef] [PubMed]
3.
Desai, S. Effect of a Tranexamic Acid, Kojic Acid, and Niacinamide Containing Serum on Facial Dyschromia: A Clinical Evaluation.
J. Drugs Dermatol. 2019,18, 454–459. [PubMed]
4.
Lourith, N.; Kanlayavattanakul, M.; Ruktanonchai, U. Formulation and stability of Moringa oleifera Oil Microemulsion. Soft
Mater. 2016,14, 64–71. [CrossRef]
5.
Masum, M.N.; Yamauchi, K.; Mitsunaga, T. Tyrosinase inhibitors from natural and synthetic sources as skin-lightening agents.
Rev. Agric. Sci. 2019,7, 41–58. [CrossRef]
6.
Hasil, A.; Mehmood, A.; Noureen, S.; Ahmed, M. Experimental and theoretical charge density analysis of skin whitening agent
kojic acid. J. Mol. Struct. 2020,1216, 128295. [CrossRef]
7.
Van Tran, V.; Loi Nguyen, T.; Moon, J.Y.; Lee, Y.C. Core-shell materials, lipid particles and nanoemulsions, for delivery of active
anti-oxidants in cosmetics applications: Challenges and development strategies. Chem. Eng. J. 2018,368, 88–114. [CrossRef]
8.
Bashir, F.; Sultana, K.; Khalid, M.; Rabia, H.; Khan, H. Kojic Acid: A Comprehensive Review Abstract: Keywords: The Applications
of Kojic Acid Kojic acid. AJAHAS 2021,6, 13–17.

Cosmetics 2022,9, 64 10 of 11
9. Chambers, C. Opinion on kojic acid. Sci. Committees Consum. Prod. 2008, 1–79.
10. Chaudhary, J. Production Technology and Applications of Kojic Acid. Annu. Res. Rev. Biol. 2014,4, 3165–3196. [CrossRef]
11.
Feng, W.; Liang, J.; Wang, B.; Chen, J. Improvement of kojic acid production in Aspergillus oryzae AR-47 mutant strain by
combined mutagenesis. Bioprocess Biosyst. Eng. 2019,42, 753–761. [CrossRef] [PubMed]
12.
Chib, S.; Dogra, A.; Nandi, U.; Saran, S. Consistent production of kojic acid from Aspergillus sojae SSC-3 isolated from rice husk.
Mol. Biol. Rep. 2019,46, 5995–6002. [CrossRef] [PubMed]
13.
Masse, M.O.; Duvallet, V.; Borremans, M.; Goeyens, L. Identification and quantitative analysis of kojic acid and arbutine in
skin-whitening cosmetics. Int. J. Cosmet. Sci. 2001,23, 219–232. [CrossRef] [PubMed]
14.
Rosfarizan, M.; Mohamed, M.S.; Suhaili, N.; Salleh, M.M.; Ariff, A.B. Kojic acid: Applications and development of fermentation
process for production. Biotechnol. Mol. Biol. Rev. 2010,5, 24–37.
15.
Gomes, C.; Silva, A.C.; Marques, A.C.; Lobo, S.; Amaral, M.H. Biotechnology Applied to Cosmetics and Aesthetic Medicines.
Cosmetics 2020,7, 33. [CrossRef]
16. Kim, J.H. Enhancement of commercial antifungal agents by Kojic acid. Int. J. Mol. Sci. 2012,13, 13867–13880. [CrossRef]
17.
Ola, A.R.B. Single production of Kojic acid by Aspergillus flavus and the revision of flufuran. Molecules
2019
,24, 4200. [CrossRef]
18. Velliou, E.G. In vitro Studies. Model. Optim. Control Biomed. Syst. 2017, 233–264. [CrossRef]
19. Couteau, C.; Coiffard, L. Overview of Skin Whitening Agents: Drugs and Cosmetic Products. Cosmetics 2016,3, 27. [CrossRef]
20.
Siddiquee, S. Advancements on the Role of Biologically Active Secondary Metabolites from Aspergillus Microbial Production of Organic
Acids for Use in Food; Elsevier: Amsterdam, The Netherlands, 2018.
21.
Zborowski, K.; Grybo´s, R.; Proniewicz, L.M. Determination of the most stable structures of selected hydroxypyrones and their
cations and anions. J. Mol. Struct. THEOCHEM 2003,639, 87–100. [CrossRef]
22.
Annan, N.A.; Butler, I.S.; Titi, H.M.; El-Lazeik, Y.; Jean-Claude, B.J.; Mostafa, S.I. DNA interaction and anticancer evaluation of
new zinc(II), ruthenium(II), rhodium(III), palladium(II), silver(I) and platinum(II) complexes based on kojic acid; X-ray crystal
structure of [Ag(ka)(PPh3)]·H2O. Inorganica Chim. Acta 2019,487, 433–447. [CrossRef]
23.
Burnett, C.L. Final report of the safety assessment of kojic acid as used in cosmetics. Int. J. Toxicol.
2010
,29. [CrossRef] [PubMed]
24.
Mann, T. Inhibition of Human Tyrosinase Requires Molecular Motifs Distinctively Different from Mushroom Tyrosinase. J. Invest.
Dermatol. 2018,138, 1601–1608. [CrossRef] [PubMed]
25.
Bergfeld, W.F. Final Report of the Cosmetic Ingredient Review Expert Panel Safety Assessment of Simmondsia Chinensis (Jojoba)
Seed Oil , Simmondsia Chinensis (Jojoba) Seed Wax, Hydrogenated Jojoba Oil , Hydrolyzed Jojoba Esters , Isomerized Jojoba Oil,
Jojoba Este. Cosmet. Ingred. Rev.
2008
, 1–32. Available online: https://online.personalcarecouncil.org/ctfa-static/online/lists/cir-
pdfs/FR525.pdf (accessed on 10 May 2022).
26.
Buschmann, H.J.; Schollmeyer, E. Applications of cyclodextrins in cosmetic products: A review. J. Cosmet. Sci.
2002
,53, 185–191.
[PubMed]
27. Hashemi, H. Climate change and the future of water management in Iran. Middle East Critique 2015,24, 307–323. [CrossRef]
28.
Kwak, S.Y.; Choi, H.R.; Park, K.C.; Lee, Y.S. Kojic acid-amino acid amide metal complexes and their melanogenesis inhibitory
activities. J. Pept. Sci. 2011,17, 791–797. [CrossRef]
29.
Seyedeh Mahdieh Hashemi, S.E. Kojic acid-derived tyrosinase inhibitors: Synthesis and bioactivity. Pharm. Biomed. Res.
2015
,1,
1–17. Available online: http://pbr.mazums.ac.ir (accessed on 10 May 2022).
30.
Hariri, R.; Saeedi, M.; Akbarzadeh, T. Naturally occurring and synthetic peptides: Efficient tyrosinase inhibitors. J. Pept. Sci.
2021
,
27, 1–10. [CrossRef]
31.
Pillaiyar, T.; Namasivayam, V.; Manickam, M.; Jung, S. H Inhibitors of Melanogenesis: An Updated Review. J. Med. Chem.
2018
,
61, 7395–7418. [CrossRef]
32.
De, A. Hyperpigmentation Case Kojic Acid in the Management of Melasma : An Effective Therapeutic Weapon. Indian J. Dermatol.
2019, 1–4.
33.
Davis, E.C.; Calender, V.D. A Review of the Epidemiology, Clinical Features, and Treatment Options in Skin of Color Year study
population prevalence rank. J. Clin. Aesthet. Dermatol. 2010,3, 20–31. [PubMed]
34.
Nurunnabi, T. Antimicrobial activity of kojic acid from endophytic fungus Colletotrichum gloeosporioides isolated from
Sonneratia apetala, a mangrove plant of the Sundarbans. Asian Pac. J. Trop. Med. 2018,11, 350–354. [CrossRef]
35.
Tetali, B.; Fahs, F.M.; Mehregan, D. Popular over-the-counter cosmeceutical ingredients and their clinical efficacy. Int. J. Dermatol.
2020,59, 393–405. [CrossRef]
36.
El-Kady, I.A.; Zohri, A.N.A.; Hamed, S.R. Kojic Acid Production from Agro-Industrial By-Products Using Fungi. Biotechnol. Res.
Int. 2014,2014, 642385. [CrossRef]
37.
Owolabi, J.O.; Fabiyi, O.S.; Adelakin, L.A.; Ekwerike, M.C. Effects of skin lightening cream agents - hydroquinone and kojic acid,
on the skin of adult female experimental rats. Clin. Cosmet. Investig. Dermatol. 2020,13, 283–289. [CrossRef]
38.
Wang, X.R. Intercalation assembly of kojic acid into Zn-Ti layered double hydroxide with antibacterial and whitening perfor-
mances. Chinese Chem. Lett. 2019,30, 919–923. [CrossRef]
39.
Zhang, J. Kojic acid-mediated damage responses induce mycelial regeneration in the basidiomycete Hypsizygus marmoreus.
PLoS ONE 2017,12, e0187351. [CrossRef]
40.
Lajis, A.F.B.; Hamid, M.; Ariff, A.B. Depigmenting effect of kojic acid esters in hyperpigmented B16F1 melanoma cells. J. Biomed.
Biotechnol. 2012,2012, 952452. [CrossRef]

Cosmetics 2022,9, 64 11 of 11
41.
Brtko, J.; Rondahl, L.; Ficková, M.; Hudecová, D.; Eybl, V.; Uher, M. Kojic acid and its derivatives: History and present state of art.
Cent. Eur. J. Public Health 2004,12, S16–S17. [CrossRef]
42.
Lee, M.; Rho, H.S.; Choi, K. Anti-inflammatory Effects of a P-coumaric Acid and Kojic Acid Derivative in LPS-stimulated
RAW264.7 Macrophage Cells. Biotechnol. Bioprocess Eng. 2019,24, 653–657. [CrossRef]
43.
Li, T.; Liang, J.; Liu, L.; Shi, F.; Jia, X.; Li, M. Fitoterapia Novel kojic acid derivatives with anti-inflammatory effects from
Aspergillus versicolor. Fitoterapia 2021,154, 105027. [CrossRef] [PubMed]
44.
Ando, H.; Matsui, M.S.; Ichihashi, M. Quasi-drugs developed in Japan for the prevention or treatment of hyperpigmentary
disorders. Int. J. Mol. Sci. 2010,11, 2566–2575. [CrossRef] [PubMed]
45.
Li, J. Recent advances in the design and discovery of synthetic tyrosinase inhibitors. Eur. J. Med. Chem.
2021
,224, 113744.
[CrossRef]
46.
Aygun, R.B.; Zengin, G.; Yıldıztugay, E.; Jugreet, S.; Yılmaz, M.A.; Mahomoodally, F.M. Chemical characterization, anti-oxidant
and anti-enzymatic properties of extracts from two Silene species: A focus on different plant parts and extraction methods. Process
Biochem. 2022,116, 206–213. [CrossRef]
47.
Bang, E.J.
In vitro
and
in vivo
evidence of tyrosinase inhibitory activity of a synthesized (Z)-5-(3-hydroxy-4-methoxybenzylidene)-
2-thioxothiazolidin-4-one (5-HMT). Exp. Dermatol. 2019,28, 734–737. [CrossRef]
48.
Pavic, A.; Ilic-Tomic, T.; Glamoˇclija, J. Unravelling anti-melanogenic potency of edible mushrooms laetiporus sulphureus and
agaricus silvaticus in vivo using the zebrafish model. J. Fungi 2021,7, 834. [CrossRef]
49.
Meziant, L.; Bachir-bey, M.; Bensouici, C.; Saci, F.; Boutiche, M.; Louaileche, H. Assessment of inhibitory properties of flavonoid-
rich fig (Ficus carica L.) peel extracts against tyrosinase,
α
-glucosidase, urease and cholinesterases enzymes, and relationship with
antioxidant activity. Eur. J. Integr. Med. 2021,43, 101272. [CrossRef]
50.
Duli´c, M.; Ciganovi´c, P.; Vuji´c, L.; Konˇci´c, M.Z. Antidiabetic and Cosmeceutical Potential of Common Barbery (Berberis vulgaris L.)
Root Bark Extracts Obtained by Optimization of ‘Green’ Ultrasound-Assisted Extraction. Molecules 2019,24, 3613. [CrossRef]
51.
Khezri, K.; Saeedi, M.; Morteza-Semnani, K.; Akbari, J.; Hedayatizadeh-Omran, A. A promising and effective platform for
delivering hydrophilic depigmenting agents in the treatment of cutaneous hyperpigmentation: Kojic acid nanostructured lipid
carrier. Artif. Cells Nanomed. Biotechnol. 2021,49, 38–47. [CrossRef]
52. Mohiuddin, A.K. Skin Lighteners & Hyperpigmentation Management. ASIO J. Pharm. Herbal Med. Res. 2019,5, 1–42.
53. Deri, B. The unravelling of the complex pattern of tyrosinase inhibition. Sci. Rep. 2016,6, 34993. [CrossRef] [PubMed]
54.
Lai, X.; Wichers, H.J.; Dijkstra, B.W. Structure and Function of Human Tyrosinase and Tyrosinase- Related Proteins.
Chem. A Eur. J.
2018,24, 47–55. [CrossRef] [PubMed]
55. Chang, T.S. An updated review of tyrosinase inhibitors. Int. J. Mol. Sci. 2009,10, 2440–2475. [CrossRef]
56.
Burger, P.; Landreau, A.; Azoulay, S.; Michel, T.; Fernandez, X. Skin whitening cosmetics: Feedback and challenges in the
development of natural skin lighteners. Cosmetics 2016,3, 36. [CrossRef]
57.
Gao, X.H.; Zhang, L.; Wei, H.; Chen, H.D. Efficacy and safety of innovative cosmeceuticals. Clin. Dermatol.
2008
,26, 367–374.
[CrossRef] [PubMed]
58.
Lee, M.; Park, H.Y.; Jung, K.H.; Kim, D.H.; Rho, H.S.; Choi, K. Anti-melanogenic Effects of Kojic Acid and Hydroxycinnamic Acid
Derivatives. Biotechnol. Bioprocess Eng. 2020,25, 190–196. [CrossRef]
59.
Arrowitz, C.; Schoelermann, A.M.; Mann, T.; Jiang, L.I.; Weber, T.; Kolbe, L. Effective Tyrosinase Inhibition by Thiamidol Results
in Significant Improvement of Mild to Moderate Melasma. J. Investig. Dermatol. 2019,139, 1691–1698.e6. [CrossRef]
60. Kamakshi, R. Fairness via formulations: A review of cosmetic skin-lightening ingredients. J. Cosmet. Sci. 2012,63, 43–54.
61.
Pillaiyar, T.; Manickam, M.; Namasivayam, V. Skin whitening agents: Medicinal chemistry perspective of tyrosinase inhibitors. J.
Enzyme Inhib. Med. Chem. 2017,32, 403–425. [CrossRef]
62.
Rho, H.S.; Ahn, S.M.; Yoo, D.S.; Kim, M.K.; Cho, D.H.; Cho, J.Y. Kojyl thioether derivatives having both tyrosinase inhibitory and
anti-inflammatory properties. Bioorg. Med. Chem. Lett. 2010,20, 6569–6571. [CrossRef] [PubMed]
63.
Mavon, A.; Bacqueville, D.; De Wever, B. Skin care products. In Handbook of Cosmetic Science and Technology, 3rd ed.; Barel, A.O.,
Paye, M., Maibach, H.I., Eds.; Informa Healthcare: London, UK, 2009; pp. 347–353.
64.
Gupta, A.K.; Gover, M.D.; Nouri, K.; Taylor, S. The treatment of melasma: A review of clinical trials. J. Am. Acad. Dermatol.
2006
,
55, 1048–1065. [CrossRef] [PubMed]