How Arbutin Regulates Melanin Production: α/β Anomeric Configuration and Tyrosinase Action

1 What Is Arbutin?

1.1 Chemical Structure of Arbutin

Hydroquinone, also known as 1,4-dihydroxybenzene, contains two phenolic hydroxyl groups at the para positions of the benzene ring. During the formation of arbutin, one phenolic hydroxyl group forms an O-glycosidic bond with the anomeric carbon of D-glucose, while the other phenolic hydroxyl group remains free.

The structure of arbutin can be summarized as:

4-hydroxyphenoxy moiety + D-glucosyl moiety

1.2 Structural Differences Between α-Arbutin and β-Arbutin

α-Arbutin and β-arbutin are anomers. They have the same molecular composition and atom connectivity, and their essential difference lies solely in the spatial configuration at the anomeric carbon of glucose, namely the C1 position.

In the standard Haworth projection of D-glucopyranose, the hydroxymethyl group at C5 (—CH₂OH) points upward:

① α-Arbutin: The glycosidic bond connecting the 4-hydroxyphenoxy group at C1 points downward and lies on the opposite side of the sugar ring from the —CH₂OH group. In the common ⁴C₁ chair conformation, this substituent occupies an axial position.

② β-Arbutin: The glycosidic bond at C1 points upward and lies on the same side of the sugar ring as the —CH₂OH group. In the ⁴C₁ chair conformation, this substituent occupies an equatorial position.

This difference changes the three-dimensional orientation of the hydroxyphenyl group relative to the glucose ring, thereby affecting the spatial complementarity and recognition of the molecule by tyrosinase and glycosidases. Although the two compounds have the same molecular formula and relative molecular mass, they are distinct chemical substances.[1]

1.3 Where Does Arbutin Come From?

Arbutin commonly found in nature is predominantly β-arbutin, which occurs in bearberry leaves, pear leaves, and the leaves or bark of various other plants. Plant extracts generally also contain phenolic acids, flavonoids, tannins, and other glycosides. Therefore, “bearberry leaf extract” is not equivalent to a β-arbutin raw material with a clearly defined chemical identity and purity specification.[1]

Commercial α-arbutin is mainly produced through selective glycosylation. A representative enzymatic method uses hydroquinone as the glycosyl acceptor and maltose as the glycosyl donor. Microbial cells with transglycosylation activity selectively catalyze the formation of an α-D-glucosidic bond. The principal role of the enzymatic process is to control the configuration and attachment position of the glycosidic bond while reducing the formation of the β-anomer, diglucosylated products, and other by-products.[3]

2 What Changes After Glucosylation?

Glucosylation does not simply add a hydrophilic group. It simultaneously changes enzyme recognition, dissolution behavior, skin partitioning, chemical reactivity, and the approach used for safety assessment.

Structural Change	Effect on Molecular Properties	Effect on Skincare Applications
Retention of one free phenolic hydroxyl group	Preserves some recognition features of phenolic substrates	Arbutin can still interact with the active region of tyrosinase
Formation of a glycosidic bond at one phenolic hydroxyl group	Changes the electronic environment and spatial orientation of the aromatic ring	Produces enzyme-binding and oxidation behavior different from that of free hydroquinone
Introduction of polyhydroxylated glucose	Increases water solubility and hydration capacity	Facilitates dissolution in the aqueous phase of formulations but limits entry into stratum corneum lipids
Increased molecular size	Increases steric hindrance	Changes the conformations adopted by the α- and β-anomers when entering the enzyme-binding region
Formation of an O-glycosidic bond	Provides a relatively stable covalent linkage	Hydrolysis may still occur under acidic conditions, heating, or glycosidase activity
Formation of a hydroquinone mono-O-glucoside structure	Produces a distinct compound different from free hydroquinone	Residual hydroquinone in the raw material and hydroquinone generated through hydrolysis during storage must still be monitored

α-Arbutin has relatively high solubility in water. β-Arbutin also dissolves readily in water and propylene glycol but has low solubility in oil phases such as squalane and olive oil. This pronounced preference for the aqueous phase indicates that arbutin can be readily dissolved in formulations, but its driving force for partitioning from the aqueous phase into the intercellular lipids of the stratum corneum is relatively limited.[1]

3 Differences Between α-Arbutin and β-Arbutin

3.1 Anomeric Configuration Changes Three-Dimensional Shape

α-Arbutin and β-arbutin are anomers. When represented in the cyclic form of D-glucose, the α-glycosidic bond and the C5 hydroxymethyl group of glucose lie on opposite sides of the ring plane, whereas the β-glycosidic bond and the C5 hydroxymethyl group lie on the same side.

This difference changes the spatial orientation of glucose relative to the hydroxyphenyl group, as well as molecular hydration and hydrogen-bonding patterns. Tyrosinase has distinct spatial selectivity and can therefore distinguish between the two anomeric configurations.

Comparison Item	α-Arbutin	β-Arbutin
Position of the key structural difference	C1 of glucose	C1 of glucose
Direction of the glycosidic bond in the Haworth projection	Downward	Upward
Relationship to the C5 —CH₂OH group	Located on opposite sides of the sugar ring	Located on the same side of the sugar ring
⁴C₁ chair conformation	4-Hydroxyphenoxy group in the axial position	4-Hydroxyphenoxy group in the equatorial position
Practical consequence	Produces one enzyme-binding orientation	Produces another enzyme-binding orientation
Molecular formula and relative molecular mass	C₁₂H₁₆O₇; 272.25	C₁₂H₁₆O₇; 272.25

3.2 The Two Configurations Show Different Enzymatic Behavior

A comparative study published in 1995 used mushroom tyrosinase and tyrosinase derived from mouse melanoma. β-Arbutin inhibited both enzymes, whereas α-arbutin in that study mainly inhibited mouse melanoma tyrosinase. Its half-maximal inhibitory concentration was 0.48 mmol/L, and its inhibitory potency was approximately ten times that of β-arbutin in the same model. Kinetic analysis suggested mixed-type inhibition for the α-anomer and noncompetitive inhibition for the β-anomer.[4]

These findings show that anomeric configuration can substantially affect enzyme recognition. However, the “approximately tenfold” difference was obtained with a specific mouse enzyme, substrate, and assay conditions and does not represent a constant difference in efficacy in human skin.

In human melanocyte studies, β-arbutin acted as a reversible competitive inhibitor of tyrosinase. α-Arbutin reduced cellular tyrosinase activity and melanin production in human melanoma cells and a three-dimensional human skin model, although the relevant studies did not determine its complete kinetic inhibition type in a human-derived system.[5,6]

3.3 The Two Configurations Have Similar Stability

Parallel stability studies showed that both α-arbutin and β-arbutin remained relatively stable under mild storage conditions and could generate hydroquinone under strongly hydrolytic conditions. No interconversion between the α- and β-anomers was observed. Their overall stability was influenced primarily by pH, temperature, formulation composition, and storage duration.[8]

Comparison Item	α-Arbutin	β-Arbutin
Natural occurrence	Reported in nature; commercial raw materials are mainly produced through selective biomanufacturing	Widely present in various plants
Commercial production	Represented by enzymatic α-selective glycosylation	Can be obtained through plant extraction, chemical synthesis, or biomanufacturing
Evidence from human-derived cells	Reduces tyrosinase activity and melanin production	Supported by evidence of reversible competitive inhibition
Specific animal enzyme models	Strong activity against mouse melanoma tyrosinase	Inhibits both mushroom and mouse-derived tyrosinase
Chemical stability	Influenced by pH, temperature, and formulation composition	Influenced by pH, temperature, and formulation composition
Main formulation considerations	Activity retention, skin deposition, and hydroquinone control	Activity retention, skin deposition, and hydroquinone control

4 How Does Arbutin Affect Melanin Production?

4.1 Tyrosinase Controls the Early Reactions of Melanin Formation

Melanin is synthesized in melanosomes within melanocytes. Tyrosinase is an oxidase containing a dinuclear copper catalytic center and participates in the first two reactions of melanin synthesis:

L-Tyrosine

↓ Tyrosinase monophenolase activity

L-3,4-Dihydroxyphenylalanine (L-DOPA)

↓ Tyrosinase diphenolase activity

Dopaquinone

↓ Subsequent oxidation, cyclization, and polymerization

Eumelanin or pheomelanin

Arbutin reduces the catalytic flux at the early stage of melanin synthesis. When the conversion of L-tyrosine and L-DOPA into dopaquinone is restricted, the amount of downstream intermediates available for melanin formation is correspondingly reduced.

Melanin that has already formed does not disappear immediately when tyrosinase activity decreases. Visible changes in skin tone also depend on the migration and shedding of melanin-containing keratinocytes toward the skin surface. The effect of arbutin therefore manifests as a gradual reduction in newly formed pigment rather than direct dissolution of existing melanin.

4.2 Competitive Inhibition by β-Arbutin

β-Arbutin retains a phenolic aromatic ring resembling those of tyrosine and L-DOPA and can compete with normal substrates for the substrate-binding region of tyrosinase.

In a cultured human melanocyte study, β-arbutin reduced cellular tyrosinase activity and melanin production at concentrations that did not produce evident cytotoxicity, but it did not significantly reduce the expression of tyrosinase messenger ribonucleic acid (mRNA). Kinetic results supported its classification as a reversible competitive inhibitor.[5]

Competitive inhibition can be represented as follows:

Tyrosinase + normal substrate ⇌ enzyme–substrate complex → dopaquinone

Tyrosinase + β-arbutin ⇌ enzyme–arbutin complex

When β-arbutin occupies or interferes with the substrate-binding region, the probability that a normal substrate will form an effective catalytic complex with the enzyme decreases. After arbutin dissociates, the enzyme can bind a normal substrate again, making the effect reversible.

4.3 α-Arbutin Mainly Reduces Cellular Enzyme Activity

In human HMV-II melanoma cells, 0.5 mmol/L α-arbutin reduced melanin production to approximately 76% of the untreated control level and simultaneously decreased cellular tyrosinase activity, while tyrosinase mRNA expression showed no significant change. In a three-dimensional human skin model, the dose used in the study reduced melanin content to approximately 40% of the control level.[6]

These findings indicate that the principal cellular effect of α-arbutin is likewise concentrated on reducing the catalytic activity of tyrosinase rather than substantially decreasing transcription of the tyrosinase gene.

4.4 Different Enzyme States Correspond to Different Reaction Roles

During its catalytic cycle, tyrosinase can exist in the deoxy, oxy, and met states. Cellular studies observe changes in overall enzyme activity within the complete cellular environment, whereas purified-enzyme studies can resolve chemical reactions occurring in a particular enzyme state.

A 2017 kinetic study using purified mushroom tyrosinase showed that oxy-tyrosinase could hydroxylate the position ortho to the free phenolic hydroxyl group of both α-arbutin and β-arbutin, forming catechol intermediates that subsequently produced unstable ortho-quinones. Under those experimental conditions, both forms of arbutin acted as transformable substrates of tyrosinase, and β-arbutin showed a higher apparent affinity for the enzyme than α-arbutin.[7]

The interaction between arbutin and tyrosinase includes two interrelated processes:

① In biological systems such as human melanocytes, arbutin reduces the catalytic conversion of normal substrates and decreases melanin production.

② Under specific purified-enzyme states and reaction conditions, arbutin can itself undergo further hydroxylation and oxidation by tyrosinase.

Differences in enzyme source, enzyme oxidation state, substrate type, and analytical method can lead to different kinetic behaviors being observed experimentally.

5 Can Arbutin Improve Hyperpigmentation?

5.1 Arbutin Has a Clear In Vitro Basis for Pigmentation Regulation

Available cellular and tissue-model studies support the ability of both α-arbutin and β-arbutin to reduce tyrosinase activity and melanin production. Their principal target is the production of new melanin, making them more suitable for improving uneven skin tone and hyperpigmentation associated with excessive melanin synthesis.[5,6]

The efficacy pathway of arbutin includes:

Remaining stable in the formulation → release from the dosage form → entry into the stratum corneum and partitioning toward the viable epidermis → establishment of a locally effective concentration around melanocytes → reduction of tyrosinase catalytic activity → reduction of newly formed melanin

Enzymatic activity is only one component of this pathway. Insufficient release from the formulation, inadequate skin partitioning, or poor chemical stability can all reduce the final effect.

5.2 Human Studies Mainly Use Combination Formulations

A randomized controlled study evaluated a combination serum containing α-arbutin, tranexamic acid, niacinamide, fermentation filtrate, and other ingredients. After 44 healthy participants applied the product to the skin of the forearm for four weeks, both the combination-serum group and the hydroquinone control group showed improvements in skin brightness and pigmentation intensity.[11]

The study supports short-term improvements in brightness and pigmentation intensity in healthy skin from a combination formulation containing arbutin, but it cannot separately quantify the contribution of arbutin to the overall effect. Human studies involving arbutin alone, carrier controls, and long-term follow-up remain less numerous than enzymatic, cellular, and three-dimensional skin-model studies.

6 How Does the Skin Barrier Limit Arbutin Delivery?

6.1 Water Solubility and Skin Permeability Are Not the Same Property

The glucose moiety of arbutin contains multiple hydroxyl groups, allowing the molecule to form hydrogen bonds readily with water. This property facilitates dissolution in the aqueous phase of serums, gels, and emulsions but reduces the tendency of the molecule to enter the intercellular lipids of the stratum corneum.

Topically applied arbutin must undergo two sequential partitioning steps:

① Release from the aqueous phase of the formulation.

② Entry from the skin surface into the stratum corneum and viable epidermis.

If the formulation has insufficient capacity to dissolve arbutin, the raw material may crystallize. If dissolution and hydration are excessively strong, arbutin may instead remain predominantly in the aqueous phase. Effective delivery requires a balance between dissolution stability and the driving force for skin partitioning.

6.2 Ex Vivo Human Skin Studies Show Low Overall Absorption

The Scientific Committee on Consumer Safety (SCCS) summarized radiolabeled ex vivo human skin studies showing that the 24-hour percutaneous absorption of α-arbutin—defined as the total amount of radioactivity-related substances detected in the epidermis, dermis, and receptor fluid—was approximately 0.27% ± 0.13% of the applied dose. For safety assessment, a value of 0.53%, calculated as the mean plus two standard deviations, was used.

The 24-hour percutaneous absorption of β-arbutin from different creams and gels was approximately 0.126%–0.214% of the applied dose. Because the β-arbutin studies did not include the stratum corneum samples obtained by tape stripping, the measured absorption may have been underestimated. Although these studies had certain limitations in sample size and experimental design, they generally indicate that, under the corresponding ex vivo conditions, only low proportions of either form of arbutin entered the epidermis, dermis, and receptor fluid.[1]

6.3 Carriers Can Modulate Arbutin Release and Skin Deposition

A study of functionalized chitosan nanoparticles loaded with α-arbutin showed that the nanoparticles could prolong α-arbutin release and increase its deposition in ex vivo rat skin, with no transdermal passage into the receptor fluid observed. In a small split-face study involving 20 women with epidermal melasma, the nanoparticle gel produced greater improvements in melasma-related evaluation parameters than a gel containing an equivalent amount of free α-arbutin.[10]

7 How Do pH, Temperature, and Microorganisms Affect Stability?

7.1 Hydrolysis of Arbutin

The O-glycosidic bond in arbutin can be cleaved under chemical or enzymatic conditions:

α-Arbutin or β-arbutin + H₂O

→ Hydroquinone + D-glucose

Hydroquinone formed through hydrolysis may subsequently undergo further oxidation to produce semiquinones, benzoquinone, or other reaction products. A decrease in arbutin content, an increase in hydroquinone, and changes in formulation color may therefore represent different stages of a continuous degradation process.

7.2 pH Is a Key Variable Affecting Glycosidic-Bond Stability

Stability data summarized by the SCCS showed that 2% or 3% α-arbutin maintained a high recovery rate after storage for 28 days at 50 °C in buffers at pH 4.5, 5.0, and 6.0. Hydroquinone was not detected by the analytical method; however, the detection limit for hydroquinone in this test was 50 μg/mL, indicating limited analytical sensitivity.[1] In another aqueous-solution study, 22.7 ppm hydroquinone was detected after samples with an initial pH of 3.5 were stored at 40 °C for three months, whereas hydroquinone remained below 3 ppm in samples with pH values of 4.5–7.5.[1]

β-Arbutin showed relatively good storage stability at pH 5–7 in submitted formulation data. In heated tests at pH ≤3, β-arbutin content decreased and hydroquinone increased rapidly. Published studies and SCCS data also indicate an increased risk of β-arbutin degradation below pH 4.[1]

Based on the available evidence, approximately pH 4.5–6.5 may be used as a preferred screening range for arbutin formulations. The final pH must still be determined according to the specific dosage form, buffer system, combined ingredients, and long-term storage data.

7.3 Temperature Accelerates Hydrolysis and Subsequent Oxidation

Increasing temperature accelerates glycosidic-bond hydrolysis, hydroquinone oxidation, and side reactions among formulation components. Some α-arbutin preparations retained a high proportion of the main component during storage at 40–50 °C but developed yellow or yellow-brown discoloration, indicating that measuring only the remaining arbutin content is insufficient for a complete evaluation of formulation stability.[1]

During manufacturing, arbutin may be added after preparation of the primary emulsion and sufficient cooling to reduce prolonged heat exposure. The addition temperature should be validated according to raw-material solubility, equipment shear, and dosage-form manufacturing processes.

7.4 Light, Oxygen, and Metal Ions Affect Degradation Products

α-Arbutin and β-arbutin raw materials showed relative stability in certain photostability tests. However, light exposure, oxygen, and transition-metal ions in actual formulations may promote further oxidation of hydroquinone that has already formed. Formulation discoloration may arise from hydroquinone and its oxidation products or from reactions between other formulation ingredients.[1,8]

7.5 Skin Microorganisms May Participate in Glycoside Hydrolysis

In vitro studies showed that the tested strains of Staphylococcus epidermidis and Staphylococcus aureus could hydrolyze β-arbutin and form hydroquinone. Hydrolytic activity differed substantially among strains.[9]

SCCS data also showed that hydroquinone and other degradation products could be detected in ex vivo pig skin that had not been treated with antibiotics, whereas the corresponding degradation decreased after antibiotic treatment, suggesting that skin microorganisms may participate in the conversion of α-arbutin. The extent of actual conversion on human skin may also be influenced by microbial composition, skin site, contact time, local pH, and other factors.[1]

8 How Can Formulation Design Balance Stability and Delivery?

Formulation Issue	Underlying Cause	Formulation Design Direction	Parameters Requiring Verification
Increased hydrolysis under strongly acidic conditions	Acid-catalyzed cleavage of the glycosidic bond	Screen pH values from mildly acidic to near neutral and control pH drift during storage	Arbutin, hydroquinone, and pH
Discoloration or degradation at high temperature	Accelerated hydrolysis and oxidation	Shorten high-temperature holding time and add arbutin during an appropriate cooling stage	Content, color difference, and degradation peaks
Transition metals promote oxidation	Iron, copper, and other metals catalyze phenolic oxidation	Control metal impurities in raw materials and evaluate chelating agents	Metal content, color difference, and oxidation products
Exposure to light and oxygen	Promotes oxidation of hydroquinone and intermediate products	Use packaging with low light and oxygen permeability and reduce air ingress caused by repeated opening	Photostability and oxidative stability
Sufficient aqueous solubility but inadequate epidermal deposition	High molecular hydrophilicity limits partitioning into stratum corneum lipids	Adjust humectants, cosolvents, emulsion structure, or use a suitable carrier	Content in the stratum corneum and viable epidermis
Carrier increases transdermal penetration	Penetration enhancement exceeds the need for localized delivery	Adjust particle size, surface properties, and release rate with epidermal retention as the target	Distribution in the epidermis, dermis, and receptor fluid
Combination with strongly acidic active ingredients	Different ingredients have different suitable pH ranges	Determine whether ingredients should be combined in the same product or used separately based on finished-product stability	Content, pH, color, and irritation
Microorganism-related hydrolysis	Microbial glycosidases participate in degradation	Establish a preservative system appropriate for the dosage form	Challenge testing, arbutin, and hydroquinone
Hydroquinone introduced with the raw material	Synthetic residues or raw-material degradation	Establish dual quality specifications for raw materials and finished products	Hydroquinone and related impurities

9 Safety and Regulatory Requirements

Under the provisions of the current European Commission Regulation (EU) 2024/996 for the corresponding product categories:

① The maximum concentration of Alpha-Arbutin in face creams is 2%.

② The maximum concentration of Alpha-Arbutin in body lotions is 0.5%.

③ The maximum concentration of Arbutin, namely β-arbutin, in face creams is 7%.

④ In formulations containing Alpha-Arbutin or Arbutin, hydroquinone levels must remain as low as possible and must not exceed unavoidable trace levels.[2]

In its safety opinion, the SCCS concluded that α-arbutin is safe when used at the concentrations specified above in face creams and body lotions and that β-arbutin is safe when used at 7% in face creams. The SCCS also considered combined exposure to the two substances at their corresponding concentrations to be acceptable.[1]

Raw-material inventories, product categories, and conditions of use vary among regions. Product development must therefore be conducted in accordance with the current regulations of the target market.

10 Classification and Research Applications of Representative Products Related to Arbutin Structure and Degradation, Tyrosinase and Pigmentation Regulation, Formulation Stability, and Skin Delivery

Note: The products listed below cover α/β-arbutin and structural controls, glycoside hydrolysis and oxidation products, tyrosinase and melanin synthesis studies, controls for pigmentation-regulation mechanisms, formulation stability, and skin-delivery materials. Enzymes, cellular model inducers, and certain inhibitors are intended primarily for scientific research and analytical evaluation and are not necessarily suitable for direct use in cosmetic formulations.

Table 1. Products Related to Core Arbutin Compounds, Structural Controls, and Glycoside Hydrolysis and Oxidation Studies

Category	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Applications
α-Arbutin analytical reference	84380-01-8	A140113	α-Arbutin	Analytical standard	Used for qualitative and quantitative analysis of α-arbutin, anomeric configuration identification, analytical method development, and formulation stability studies.
β-Arbutin analytical reference	497-76-7	A106857	Arbutin	Analytical standard, ≥99%	Used for β-arbutin content determination, raw-material purity verification, degradation monitoring, and comparative studies with the α-anomer.
β-Arbutin active research material	497-76-7	A106856	Arbutin	Moligand™, ≥98%	Used for studies of β-arbutin-mediated tyrosinase inhibition, melanocyte responses, formulation delivery, and stability.
Arbutin structural derivative	53936-56-4	D129494	Deoxyarbutin	≥98%	Used for comparative studies of the structure, lipophilicity, stability, and tyrosinase-related activity of deoxyarbutin and α/β-arbutin, as well as for research and analytical controls.
Arbutin aglycone and degradation reference	123-31-9	H108947	Hydroquinone	≥99% (HPLC)	Used as a reference for the arbutin aglycone, hydrolysis products, degradation impurities, formulation stability, and analytical method studies.
Arbutin glycosyl component and hydrolysis product	50-99-7	D755713	D-(+)-Glucose	Anhydrous grade, UltraBio™, ≥99.5% (HPLC), sum of enantiomers	Used for studies of the glycosyl component of arbutin, confirmation of hydrolysis products, glycosylation reactions, and metabolic controls.
Hydroquinone oxidation-product reference	106-51-4	B108671	p-Benzoquinone	Moligand™, ≥99%	Used for studies of hydroquinone oxidation pathways, discoloration of arbutin formulations, oxidative degradation, and analysis of related impurities.
β-Glycosidic-bond hydrolase	9001-22-3	G1522971	β-Glucosidase	Bioactive, recombinant, ActiBioPure™, high performance, EnzymoPure™, ≥90% (SDS-PAGE), ≥5 U/mg enzyme powder; ≥25 U/mg protein	Used to evaluate β-arbutin glycosidic-bond hydrolysis, hydroquinone formation, enzymatic stability, and substrate specificity.
α-Glycosidic-bond hydrolase	9001-42-7	R1505810	Recombinant α-Glucosidase (AGH)	Bioactive, recombinant, ActiBioPure™, high performance, EnzymoPure™, ≥15 U/mg enzyme powder; ≥100 U/mg protein	Used to evaluate enzymatic hydrolysis of α-arbutin, anomeric configuration recognition, glycoside stability, and hydrolysis products.

Table 2. Products Related to Tyrosinase, Melanin-Synthesis Substrates, and Cellular Melanogenesis Models

Category	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Applications
Core enzyme for tyrosinase studies	9002-10-2	T128536	Tyrosinase, from mushroom	EnzymoPure™, ≥500 units/mg dry weight	Used for studies of α/β-arbutin-mediated tyrosinase inhibition, substrate conversion, enzyme kinetics, and activity comparisons.
Tyrosinase monophenolase substrate	60-18-4	T656685	L-Tyrosine	Animal-origin free, low endotoxin, Moligand™, for cell culture, ≥99%	Used for studies of tyrosinase monophenolase activity, substrate competition, and arbutin inhibition kinetics.
Tyrosinase diphenolase substrate	59-92-7	D111049	Levodopa	Analytical standard, Moligand™, ≥99%	Used for evaluating tyrosinase diphenolase activity, reaction rates, kinetic parameters, and arbutin-mediated inhibition.
Pheomelanin-pathway reaction substrate	52-90-4	C108238	L-Cysteine	Animal-origin free, Moligand™, for cell culture, ≥98%	Used for studies of dopaquinone trapping, the pheomelanin pathway, redox conditions, and regulation of pigment type.
Eumelanin-formation intermediate	3131-52-0	D183610	5,6-Dihydroxyindole	≥95%	Used for studies of subsequent eumelanin oxidation and polymerization, indole-intermediate conversion, and pigment-formation pathways.
Cyclic adenosine monophosphate pathway inducer	28822-58-4	I755748	3-Isobutyl-1-methylxanthine	UltraBio™, ≥99%	Used to increase intracellular cyclic adenosine monophosphate levels, establish enhanced melanogenesis models, and evaluate the inhibitory effects of arbutin.
Adenylate cyclase activator	66575-29-9	F127328	Forskolin	Moligand™, ≥98%	Used to activate adenylate cyclase, induce melanogenic signaling, and establish cellular pigmentation models.
Tyrosinase-inhibition experimental control	103-85-5	P110661	N-Phenylthiourea	Moligand™, ≥98%	Used as a positive control for tyrosinase inhibition, intervention at the copper-containing active center, and comparative studies of melanin production.
Copper-center-binding inhibitor control	533-75-5	T112998	Tropolone	Moligand™, ≥98%	Used for studies of binding to the tyrosinase copper center, enzyme-inhibition controls, and comparisons of arbutin mechanisms of action.
Positive control for tyrosinase inhibition	501-30-4	K105452	Kojic Acid	≥99%	Used as a positive control for tyrosinase inhibition, copper-ion coordination, and comparative evaluation of pigmentation-regulating activity.
Component for studying copper-ion effects	7758-99-8	C112411	Copper(II) Sulfate Pentahydrate	For cell culture, ≥98%	Used to study the effects of copper ions on tyrosinase activity, phenolic oxidation, and the stability of arbutin formulations.

Table 3. Products Related to Multi-Pathway Pigmentation Regulation and Mechanistic Studies of Arbutin Combinations

Category	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Applications
Ingredient for melanosome transfer and barrier studies	98-92-0	N108087	Niacinamide	For cell culture, suitable for insect cell culture, ≥99.5% (HPLC)	Used for studies of melanosome transfer, keratinocyte responses, skin-barrier function, and combinations with arbutin.
Amino sugar-type pigmentation-regulating ingredient	7512-17-6	A118965	N-Acetyl-D-glucosamine	For cell culture, ≥98%	Used for studies of amino sugar-related pigmentation regulation, epidermal metabolism, barrier function, and combination with niacinamide.
Dicarboxylic acid-type pigmentation-regulating ingredient	123-99-9	A108439	Azelaic Acid	Moligand™, ≥99%	Used for studies of tyrosinase-related pigmentation regulation, abnormal melanocyte responses, and comparative combinations with arbutin.
Plasmin-related pigmentation-regulating ingredient	1197-18-8	A111900	Tranexamic Acid (AMCA)	Moligand™, ≥98%	Used for studies of plasmin-related pigmentation signaling, post-inflammatory hyperpigmentation, and multi-pathway combinations with arbutin.
Redox-active pigmentation-regulating ingredient	50-81-7	L432793	L-Ascorbic Acid	Anhydrous grade, Moligand™, ACS, ≥99%	Used for studies of dopaquinone reduction, oxidative stress, pigment-intermediate conversion, and antioxidant combinations with arbutin.

Table 4. Products Related to Arbutin Formulation Stability, Buffer Systems, and Skin Delivery

Category	CAS No.	Aladdin Catalog No.	Name	Specification or Purity	Product Features and Applications
Cationic polymer delivery carrier	9012-76-4	C105802	Chitosan	Medium viscosity, 200–400 mPa·s	Used for studies of arbutin nanoparticles, ionically crosslinked carriers, sustained release, and localized deposition in the viable epidermis.
Aqueous-phase humectant and release medium	56-81-5	G116209	Glycerol	For cell culture, suitable for insect cell culture, ≥99% (GC)	Used for studies of arbutin dissolution in the aqueous phase, humectant systems, release behavior, and skin partitioning.
Lipid-carrier membrane-stabilizing component	57-88-5	C104036	Cholesterol	For cell culture, ≥99% (GC)	Used for phospholipid-membrane stabilization, liposome structure, carrier-membrane fluidity, and arbutin delivery studies.
Reducing component for stability studies	7681-57-4	S433809	Sodium Metabisulfite	Anhydrous grade, reagent grade, extra pure, ≥99%	Used for studies of reducing environments, control of hydroquinone oxidation, formulation discoloration, and comparative arbutin stability.
Acidic component of citrate buffer systems	77-92-9	C755557	Anhydrous Citric Acid Powder	Anhydrous grade, UltraBio™, ≥99.5% (T)	Used for pH adjustment of arbutin formulations, citrate buffer systems, acid-catalyzed hydrolysis, and storage stability studies.
Aqueous-phase cosolvent and humectant medium	107-88-0	B119672	1,3-Butanediol	Anhydrous grade, ≥99%	Used for arbutin cosolvency, moisturization, regulation of aqueous-phase activity, and formulation-release studies.
Phospholipid bilayer delivery material	8002-43-5	P1456010	Phospholipids from Sunflower (Non-GMO)	Natural, with ≥60% phosphatidylcholine	Used for arbutin liposomes, phospholipid-bilayer encapsulation, interfacial stabilization, and epidermal delivery studies.
Basic component of citrate buffer systems	6132-04-3	T433112	Trisodium Citrate Dihydrate	European Pharmacopoeia (Ph. Eur.), suitable for analysis, ACS, premium grade	Used with citric acid to prepare buffer systems for pH maintenance, storage stability, and studies of glycoside hydrolysis rates.
Aqueous-phase cosolvent and delivery medium	57-55-6	P103433	1,2-Propanediol	ACS, ≥99.5%	Used for arbutin cosolvency, moisturization, skin partitioning, and formulation-release studies.
Chitosan ionic crosslinking agent	7758-29-4	S100099	Sodium Tripolyphosphate	AR, ≥98%	Used for ionic crosslinking of chitosan, formation of arbutin nanoparticles, particle-size adjustment, and release studies.
Metal-ion-chelating stability component	139-33-3	D684233	Disodium Ethylenediaminetetraacetate	≥99%	Used for metal-ion chelation, control of phenolic oxidation, formulation discoloration, and arbutin stability studies.

Note: The products listed above are representative Aladdin products related to scientific research. Their specific uses should be determined according to the product specifications, batch-specific certificate of analysis (COA), and the intended reaction or evaluation system. Additional product specifications, grades, and COA information can be searched on the Aladdin website using the product name, CAS number, or catalog number.

References

[1] SCCS (Scientific Committee on Consumer Safety). Opinion on the Safety of Alpha- (CAS No. 84380-01-8, EC No. 617-561-8) and Beta-Arbutin (CAS No. 497-76-7, EC No. 207-850-3) in Cosmetic Products. Preliminary version, 15–16 March 2022; final version, 31 January 2023. SCCS/1642/22.

[2] European Commission. Commission Regulation (EU) 2024/996 of 3 April 2024 Amending Regulation (EC) No 1223/2009 of the European Parliament and of the Council as Regards the Use of Vitamin A, Alpha-Arbutin and Arbutin and Certain Substances with Potential Endocrine Disrupting Properties in Cosmetic Products. Official Journal of the European Union. 2024;L 2024/996, 4 April 2024.

[3] Kurosu J, Sato T, Yoshida K, Tsugane T, Shimura S, Kirimura K, Kino K, Usami S. Enzymatic Synthesis of Alpha-Arbutin by Alpha-Anomer-Selective Glucosylation of Hydroquinone Using Lyophilized Cells of Xanthomonas campestris WU-9701. Journal of Bioscience and Bioengineering. 2002;93(3):328–330. doi:10.1263/jbb.93.328.

[4] Funayama M, Arakawa H, Yamamoto R, Nishino T, Shin T, Murao S. Effects of α- and β-Arbutin on Activity of Tyrosinases from Mushroom and Mouse Melanoma. Bioscience, Biotechnology, and Biochemistry. 1995;59(1):143–144. doi:10.1271/bbb.59.143.

[5] Maeda K, Fukuda M. Arbutin: Mechanism of Its Depigmenting Action in Human Melanocyte Culture. Journal of Pharmacology and Experimental Therapeutics. 1996;276(2):765–769.

[6] Sugimoto K, Nishimura T, Nomura K, Sugimoto K, Kuriki T. Inhibitory Effects of α-Arbutin on Melanin Synthesis in Cultured Human Melanoma Cells and a Three-Dimensional Human Skin Model. Biological and Pharmaceutical Bulletin. 2004;27(4):510–514. doi:10.1248/bpb.27.510.

[7] Garcia-Jimenez A, Teruel-Puche JA, Berna J, Rodriguez-Lopez JN, Tudela J, Garcia-Canovas F. Action of Tyrosinase on Alpha and Beta-Arbutin: A Kinetic Study. PLOS ONE. 2017;12(5):e0177330. doi:10.1371/journal.pone.0177330.

[8] Avonto C, Wang YH, Avula B, Wang M, Rua D, Khan IA. Comparative Studies on the Chemical and Enzymatic Stability of Alpha- and Beta-Arbutin. International Journal of Cosmetic Science. 2016;38(2):187–193. doi:10.1111/ics.12275.

[9] Bang SH, Han SJ, Kim DH. Hydrolysis of Arbutin to Hydroquinone by Human Skin Bacteria and Its Effect on Antioxidant Activity. Journal of Cosmetic Dermatology. 2008;7(3):189–193. doi:10.1111/j.1473-2165.2008.00387.x.

[10] Hatem S, Elkheshen SA, Kamel AO, Nasr M, Moftah NH, Ragai MH, Elezaby RS, El Hoffy NM. Functionalized Chitosan Nanoparticles for Cutaneous Delivery of a Skin Whitening Agent: An Approach to Clinically Augment the Therapeutic Efficacy for Melasma Treatment. Drug Delivery. 2022;29(1):1212–1231. doi:10.1080/10717544.2022.2058652.

[11] Anwar AI, Wahab S, Widita W, Nurdin AR, Budhiani S, Seweng A. Randomized Control Trial Outcomes of Tranexamic Acid Combination Serum as a Depigmenting Agent for the Use in Healthy Individuals. Dermatologic Therapy. 2019;32(6):e13146. doi:10.1111/dth.13146.

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