Integrated Metabolomics and Transcriptomics Analyses of the Biosynthesis of Arbutin and 6'-O-Caffeoylarbutin in Vaccinium dunalianum Cell Suspension Cultures Fed with Hydroquinone.

Arbutin and 6'-O-caffeoylarbutin (CA) from Vaccinium dunalianum Wight are known for their ability to inhibit melanin synthesis. To boost the production of arbutin and CA, precursor feeding with hydroquinone (HQ) was studied in V. dunalianum suspension cells. The effect of HQ on the biosynthesis of arbutin and CA in the suspension cells was investigated using high-performance liquid chromatography (HPLC), and possible molecular mechanisms were analyzed using metabolomics and transcriptomics analyses. HPLC analysis only showed that the addition of HQ significantly enhanced arbutin synthesis in cells, peaking at 15.52 ± 0.28 mg·g-1 after 0.5 mmol·L-1 HQ treatment for 12 h. Subsequently, metabolomics identified 78 differential expression metabolites (DEMs), of which arbutin and CA were significantly up-regulated metabolites. Moreover, transcriptomics found a total of 10,628 differential expression genes (DEGs). The integrated transcriptomics and metabolomics revealed that HQ significantly enhanced the expression of two arbutin synthase (AS) genes (Unigene0063512 and Unigene0063513), boosting arbutin synthesis. Additionally, it is speculated that CA was generated from arbutin and 3,4,5-tricaffeoylquinic acid catalyzed by caffeoyl transferase, with Unigene0044545, Unigene0043539, and Unigene0017356 as potentially associated genes with CA synthesis. These findings indicate that the precursor feeding strategy offers a promising approach for the mass production of arbutin and CA in V. dunalianum suspension cells and provides new insights for CA biosynthesis in V. dunalianum.

Protective Effect of Que Zui Tea on d-Galactose-Induced Oxidative Stress Damage in Mice via Regulating SIRT1/Nrf2 Signaling Pathway.

Que Zui tea (QT) is an important herbal tea in the diet of the 'Yi' people, an ethnic group in China, and it has shown significant antioxidant, anti-inflammatory, and hepatoprotective effects in vitro. This study aims to explore the protective effects of the aqueous-ethanol extract (QE) taken from QT against ᴅ-galactose (ᴅ-gal)-induced oxidative stress damage in mice and its potential mechanisms. QE was identified as UHPLC-HRMS/MS for its chemical composition and possible bioactive substances. Thus, QE is rich in phenolic and flavonoid compounds. Twelve compounds were identified, the main components of which were chlorogenic acid, quinic acid, and 6'-O-caffeoylarbutin. Histopathological and biochemical analysis revealed that QE significantly alleviated brain, liver, and kidney damage in ᴅ-gal-treated mice. Moreover, QE remarkably attenuated oxidative stress by activating the Nrf2/HO-1 pathway to increase the expression of antioxidant indexes, including GSH, GSH-Px, CAT, SOD, and T-AOC. In addition, QE administration could inhibit the IL-1ß and IL-6 levels, which suppress the inflammatory response. QE could noticeably alleviate apoptosis by inhibiting the expressions of Caspase-3 and Bax proteins in the brains, livers, and kidneys of mice. The anti-apoptosis mechanism may be related to the upregulation of the SIRT1 protein and the downregulation of the p53 protein induced by QE in the brain, liver, and kidney tissues of mice. Molecular docking analysis demonstrated that the main components of QE, 6'-O-caffeoylarbutin, chlorogenic acid, quinic acid, and robustaside A, had good binding ability with Nrf2 and SIRT1 proteins. The present study indicated that QE could alleviate ᴅ-gal-induced brain, liver and kidney damage in mice by inhibiting the oxidative stress and cell apoptosis; additionally, the potential mechanism may be associated with the SIRT1/Nrf2 signaling pathway.

Hypolipidemic and Antithrombotic Effect of 6'-O-Caffeoylarbutin from Vaccinium dunalianum Based on Zebrafish Model, Network Pharmacology, and Molecular Docking.

Vaccinium dunalianum leaf buds make one of the most commonly used herbal teas of the Yi people in China, which is used to treat articular rheumatism, relax tendons, and stimulates blood circulation in the body. In addition, 6'-O-caffeoylarbutin (CA) is a standardized extract of V. dunalianum, which has been found in dried leaf buds, reaching levels of up to 31.76%. Because of the uncommon phenomenon, it is suggested that CA may have a potential therapeutic role in hyperlipidemia and thrombosis. This study was designed to study the efficacy of CA on treating hyperlipidemia and thrombosis and the possible mechanisms behind these effects. Hyperlipidemia and thrombosis zebrafish models were treated with CA to observe variations of the integrated optical density within the vessels and the intensity of erythrocyte staining within the hearts. The possible mechanisms were explored using network pharmacology and molecular docking. The results demonstrate that CA exhibits an excellent hypolipidemic effect on zebrafish at concentrations ranging from 3.0 to 30.0 µg/mL and shows thrombosis inhibitory activity in zebrafish at a concentration of 30.0 µg/mL, with an inhibition rate of 44%. Moreover, network pharmacological research shows that MMP9, RELA, MMP2, PRKCA, HSP90AA1, and APP are major targets of CA for therapy of hyperlipidemia and thrombosis, and may relate to pathways in cancer, chemical carcinogenesis-receptor activation, estrogen signaling pathway, and the AGE-RAGE signaling pathway in diabetic complications.

6'-O-Caffeoylarbutin from Quezui Tea: A Highly Effective and Safe Tyrosinase Inhibitor.

Tyrosinase is vital in fruit and vegetable browning and melanin synthesis, crucial for food preservation and pharmaceuticals. We investigated 6'-O-caffeoylarbutin's inhibition, safety, and preservation on tyrosinase. Using HPLC, we analyzed its effect on mushroom tyrosinase and confirmed reversible competitive inhibition. UV_vis and fluorescence spectroscopy revealed a stable complex formation with specific binding, causing enzyme conformational changes. Molecular docking and simulations highlighted strong binding, enabled by hydrogen bonds and hydrophobic interactions. Cellular tests showed growth reduction of A375 cells with mild HaCaT cell toxicity, indicating favorable safety. Animal experiments demonstrated slight toxicity within safe doses. Preservation trials on apple juice showcased 6'-O-caffeoylarbutin's potential in reducing browning. In essence, this study reveals intricate mechanisms and applications of 6'-O-caffeoylarbutin as an effective tyrosinase inhibitor, emphasizing its importance in food preservation and pharmaceuticals. Our research enhances understanding in this field, laying a solid foundation for future exploration.

6'-O-Caffeoylarbutin from Que Zui tea ameliorates acetaminophen-induced liver injury via enhancing antioxidant ability and regulating the PI3K signaling pathway.

Que Zui tea (QT), a traditional herbal tea in China, has a significant hepatoprotective effect. 6'-O-Caffeoylarbutin (CA) is the most abundant chemical compound in the QT. However, the hepatoprotective effect of CA has not been investigated. This study is aimed to evaluate the protective effect of CA on acetaminophen (APAP) induced hepatotoxicity in vivo and in vitro and its possible underlying mechanism. In APAP-induced HepG-2 cells, CA inhibited intracellular ROS accumulation and cell apoptosis, and improved the expression of antioxidants including SOD, CAT and GSH. In APAP-administrated mice, CA pretreatment remarkably ameliorated the histopathological damage and inflammatory response, and antioxidant enzyme activity in the serum and liver tissues. Moreover, the immunohistochemistry and immunofluorescence assay results revealed that the CA markedly reduced ROS production and apoptosis, and activated antioxidant transcription factor Nrf2 in the liver. Meanwhile, molecular docking results showed that the strong binding force of CA and PI3K was due to the higher number of hydrogen- and π-bonds with active site residues. Notably, CA pretreatment significantly regulated the expression of PI3K, Akt, Nrf2, NQO1, HO-1, Bcl-2, Bax, caspase-3, and caspase-9 proteins in APAP-treated liver tissues. These data demonstrated that CA had a protective effect against APAP-induced hepatotoxicity via regulating the PI3K/Akt and Nrf2 signaling pathway.

Using a Cellular System to Directly Assess the Effects of Cosmetic Microemulsion Encapsulated DeoxyArbutin.

DeoxyArbutin (dA) is a tyrosinase inhibitor that has effective skin-lightening activity and has no obvious cytotoxicity toward melanocytes. With the aim of directly evaluating the effects of microemulsions containing dA on cells, we developed oil-in-water (O/W) microemulsions with relatively lower cytotoxicities by using polysorbate-series surfactants. Measurement of the transparent properties and particle size analysis at different storage time periods revealed that the developed microemulsions were stable. Moreover, the developed microemulsions had direct effects on B16-F10 mouse melanoma cells. The anti-melanogenesis activities of dA-containing microemulsions were evidently better than that of the free dA group. The results demonstrated that the developed microemulsion encapsulating dA may allow the use of deoxyArbutin instead of hydroquinone to treat dermal hyperpigmentation disorders in the future.

Bioactivity-Guided Isolation of Phytochemicals from Vaccinium dunalianum Wight and Their Antioxidant and Enzyme Inhibitory Activities.

Vaccinium dunalianum Wight, usually processed as a traditional folk tea beverage, is widely distributed in the southwest of China. The present study aimed to investigate the antioxidant, α-glucosidase and pancreatic lipase inhibitory activities of V.dunalianum extract and isolate the bioactive components. In this study, the crude extract (CE) from the buds of V. dunalianum was prepared by the ultrasound-assisted extraction method in 70% methanol and then purified with macroporous resin D101 to obtain the purified extract (PM). Five fractions (Fr. A-E) were further obtained by MPLC column (RP-C18). Bioactivity assays revealed that Fr. B with 40% methanol and Fr. D with 80% methanol had better antioxidant with 0.48 ± 0.03 and 0.62 ± 0.01 nM Trolox equivalent (TE)/mg extract for DPPH, 0.87 ± 0.02 and 1.58 ± 0.02 nM TE/mg extract for FRAP, 14.42 ± 0.41 and 19.25 ± 0.23 nM TE/mg extract for ABTS, and enzyme inhibitory effects with IC50 values of 95.21 ± 2.21 and 74.55 ± 3.85 for α-glucosidase, and 142.53 ± 11.45 and 128.76 ± 13.85 µg/mL for pancreatic lipase. Multivariate analysis indicated that the TPC and TFC were positively related to the antioxidant activities. Further phytochemical purification led to the isolation of ten compounds (1-10). 6-O-Caffeoylarbutin (7) showed significant inhibitory effects on α-glucosidase and pancreatic lipase enzymes with values of 38.38 ± 1.84 and 97.56 ± 7.53 µg/mL, and had the highest antioxidant capacity compared to the other compounds.

Comparison of 2% deoxyarbutin and 4% hydroquinone as a depigmenting agent in healthy individuals: A double-blind randomized controlled clinical trial.

BACKGROUND: Hydroquinone, which is considered the gold standard skin depigmenting agent, has been associated with multiple side effects. Lately, deoxyarbutin has been suggested to be an alternative of hydroquinone with better safety profile. OBJECTIVE: To compare the depigmenting effect of 2% deoxyarbutin and 4% hydroquinone sera. METHODS: This double-blind randomized controlled study was done on the right and left arms of healthy participants. Subjects were instructed to apply either 2% deoxyarbutin or 4% hydroquinone serum on each arm, which were randomly labeled as group A and B, every day for 12 weeks. Chromameter and mexameter analysis were done every 2 weeks to assess the color change. Paired and independent t-tests were used to assess the color change within and between both groups, respectively. RESULTS: A total of 59 females participated in this study. Both groups showed significant improvement in skin depigmentation as shown by the chromameter (increase in L* value) and mexameter (decrease in melanin index) analysis at the end of the study (p < 0.05). No significant difference in both parameters was observed between both groups (p > 0.05). No side effects were reported in either groups. CONCLUSION: 2% deoxyarbutin and 4% hydroquinone sera showed comparable depigmenting efficacy.

Molecular modeling and phenoloxidase inhibitory activity of arbutin and arbutin undecylenic acid ester.

Excessive melanin formation has been linked to various skin disorders such as hyperpigmentation and skin cancer. Tyrosinase is the most prominent target for inhibitors of melanin production. In this study, we investigated whether arbutin and its prodrug, arbutin undecylenic acid ester, might inhibit phenoloxidase (PO), a tyrosinase-like enzyme. Molecular docking simulation results suggested that arbutin and arbutin undecylenic acid ester can bind to the substrate-binding pocket of PO. Arbutin undecylenic acid ester with an IC50 6.34 mM was effective to inhibit PO compared to arbutin (IC50 29.42 mM). In addition, arbutin undecylenic acid ester showed low cytotoxicity in Drosophila S2 cells and the compound inhibited the melanization reaction. Therefore, the results of this study have demonstrated that arbutin undecylenic acid ester as a potential inhibitor of PO. We successfully designed a new platform utilizing Drosophila melanogaster and Bombyx mori as animal models propounding fast, cheap, and high effectiveness in method to screen tyrosinase inhibitors.

Caffeic acid derivatives (CAFDs) as inhibitors of SARS-CoV-2: CAFDs-based functional foods as a potential alternative approach to combat COVID-19.

BACKGROUND: SARS-CoV-2, an emerging strain of coronavirus, has affected millions of people from all the continents of world and received worldwide attention. This emerging health crisis calls for the urgent development of specific therapeutics against COVID-19 to potentially reduce the burden of this emerging pandemic. PURPOSE: This study aims to evaluate the anti-viral efficacy of natural bioactive entities against COVID-19 via molecular docking and molecular dynamics simulation. METHODS: A library of 27 caffeic-acid derivatives was screened against 5 proteins of SARS-CoV-2 by using Molegro Virtual Docker 7 to obtain the binding energies and interactions between compounds and SARS-CoV-2 proteins. ADME properties and toxicity profiles were investigated via www.swissadme.ch web tools and Toxtree respectively. Molecular dynamics simulation was performed to determine the stability of the lead-protein interactions. RESULTS: Our obtained results has uncovered khainaoside C, 6-O-Caffeoylarbutin, khainaoside B, khainaoside C and vitexfolin A as potent modulators of COVID-19 possessing more binding energies than nelfinavir against COVID-19 Mpro, Nsp15, SARS-CoV-2 spike S2 subunit, spike open state and closed state structure respectively. While Calceolarioside B was identified as pan inhibitor, showing strong molecular interactions with all proteins except SARS-CoV-2 spike glycoprotein closed state. The results are supported by 20 ns molecular dynamics simulations of the best complexes. CONCLUSION: This study will hopefully pave a way for development of phytonutrients-based antiviral therapeutic for treatment or prevention of COVID-19 and further studies are recommended to evaluate the antiviral effects of these phytochemicals against SARS-CoV-2 in in vitro and in vivo models.

Investigation of the pro-apoptotic effects of arbutin and its acetylated derivative on murine melanoma cells.

Arbutin, a natural polyphenol isolated from the bearberry plant Arctostaphylos uvaursi, possesses whitening and anticancer properties. The effects of arbutin on melanogenesis and its pro-apoptotic effect on B16 murine melanoma cells have not yet been reported. In the present study, acetylated arbutin was prepared in order to improve the biological effects of arbutin, and it was found to significantly inhibit the biosynthesis of melanin and tyrosinase activity compared with parent arbutin in B16 murine melanoma cells. Interestingly, only acetylated arbutin strongly inhibited B16 murine melanoma cell migration in a dose-dependent manner. Both arbutin and acetylated arbutin significantly reduced cell viability, promoted cell apoptosis, caused G1 cell cycle arrest and induced mitochondrial disruption in B16 murine melanoma cells. Furthermore, reduced expression of B-cell lymphoma­extra large (Bcl-xL) and Bcl-2 were observed in arbutin- and acetylated arbutin-treated cells. Therefore, arbutin and acetylated arbutin were found to exert pro-apoptotic effects on B16 murine melanoma cells, mediated through the mitochondrial pathway. The findings of the present study also support the use of acetylated arbutin as a new potential candidate agent for skin whitening and melanoma treatment.

A new arbutin derivative from the leaves of Vaccinium dunalianum wight.

A new arbutin derivative, namely dunalianosides J (1), along with six known compounds, arbutin (2), robustaside A (3), 6'-O-caffeoylarbutin (4), dunalianoside D (5), kaempferol 3-O-ß-D-glucopyranoside (6) and kaempferol 3-O-ß-D-sambubioside (7) were isolated from the leaves of Vaccinium dunalianum Wight (Ericaceae). The structure of 1 was elucidated by extensive 1D and 2D NMR, HR-MS and CD spectroscopic analyses. In which, kaempferol 3-O-ß-D-sambubioside (7) was isolated from the genus Vaccinium for the first time.

Structural and kinetic considerations on the catalysis of deoxyarbutin by tyrosinase.

Deoxyarbutin, a potent inhibitor of tyrosinase, could act as substrate of the enzyme. Oxytyrosinase is able to hydroxylate deoxyarbutin and finishes the catalytic cycle by oxidizing the formed o-diphenol to quinone, while the enzyme becomes deoxytyrosinase, which evolves to oxytyrosinase in the presence of oxygen. This compound is the only one described that does not release o-diphenol after the hydroxylation step. Oxytyrosinase hydroxylates the deoxyarbutin in ortho position of the phenolic hydroxyl group by means of an aromatic electrophilic substitution. As the oxygen orbitals and the copper atoms are not coplanar, but in axial/equatorial position, the concerted oxidation/reduction cannot occur and the release of a copper atom to bind again in coplanar position, enabling the oxidation/reduction or release of the o-diphenol from the active site to the medium. In the case of deoxyarbutin, the o-diphenol formed is repulsed by the water due to its hydrophobicity, and so can bind correctly and be oxidized to a quinone before being released. Deoxyarbutin has been characterized with: [Formula: see text] = 1.95 ± 0.06 s-1 and [Formula: see text] = 33 ± 4 µM. Computational simulations of the interaction of ß-arbutin, deoxyarbutin and their o-diphenol products with tyrosinase show how these ligands bind at the copper centre of tyrosinase. The presence of an energy barrier in the release of the o-diphenol product of deoxyarbutin, which is not present in the case of ß-arbutin, together with the differences in polarity and, consequently differences in their interaction with water help understand the differences in the kinetic behaviour of both compounds. Therefore, it is proposed that the release of the o-diphenol product of deoxyarbutin from the active site might be slower than in the case of ß-arbutin, contributing to its oxidation to a quinone before being released from the protein into the water phase.

Deoxyarbutin displays antitumour activity against melanoma in vitro and in vivo through a p38-mediated mitochondria associated apoptotic pathway.

Deoxyarbutin (DeoxyArbutin, dA), a natural compound widely used in skin lighting, displayed selectively cytotoxicity in vitro. In the study, we found that dA significantly inhibited viability/proliferation of B16F10 melanoma cells, induced tumour cell arrest and apoptosis. Furthermore, dA triggered its pro-apoptosis through damaging the mitochondrial function (membrane potential loss, ATP depletion and ROS overload generation etc.) and activating caspase-9, PARP, caspase-3 and the phosphorylation of p38. Treatment with p38 agonist confirmed the involvement of p38 pathway triggered by dA in B16F10 cells. The in vivo finding also revealed that administration of dA significantly decreased the tumour volume and tumour metastasis in B16F10 xenograft model by inhibiting tumour proliferation and inducing tumour apoptosis. Importantly, the results indicated that dA was specific against tumour cell lines and had no observed systemic toxicity in vivo. Taken together, our study demonstrated that dA could combate tumour in vitro and in vivo by inhibiting the proliferation and metastasis of tumour via a p38-mediated mitochondria associated apoptotic pathway.

Study of Hydroquinone Mediated Cytotoxicity and Hypopigmentation Effects from UVB-Irradiated Arbutin and DeoxyArbutin.

Arbutin (Arb) and deoxyArbutin (dA) are both effective hypopigmentation agents. However, they are glucoside derivatives of hydroquinone (HQ), which may be decayed into HQ under higher energy environments. Therefore, safety and toxicity are very important issues when considering the usage of these compounds. However, no study has verified the properties of Ultra-Violet B (UVB)-irradiated Arb and dA. In this work, we investigated the cytotoxicity and hypopigmentation effects of UVB-irradiated Arb and dA in Detroit 551 human fibroblast cells and B16-F10 mouse melanoma cells. The results showed that UVB-irradiated Arb and dA have strong cytotoxicity for the fibroblast cells, especially for dA, the caspase-3 is also activated by the treatment of UVB-irradiated dA in Detroit 551 cells. The results correlated with the produced HQ. In addition, UVB-irradiated Arb and dA suppressed the production of melanin in melanoma cells; this is due to the release of HQ that compensates for the UVB triggered Arb and dA decomposition.

Deoxyarbutin Possesses a Potent Skin-Lightening Capacity with No Discernible Cytotoxicity against Melanosomes.

Safe and effective ingredients capable of removing undesired hyperpigmentation from facial skin are urgently needed for both pharmaceutical and cosmetic purposes. Deoxyarbutin (4-[(tetrahydro-2H-pyran-2-yl) oxy] phenol, D-Arb) is a glucoside derivative of hydroquinone. Here, we investigated the toxicity and efficacy of D-Arb at the sub-cellular level (directly on melanosomes) and skin pigmentation using in vivo and in vitro models to compare with its parent compound hydroquinone (1,4-benzenediol, HQ). At first, we examined the ultrastructural changes of melanosomes in hyperpigmented guinea pig skin induced by 308-nm monochromatic excimer lightand/or treated with HQ and D-Arb using transmission electron microscopy. The results showed that prominent changes in the melanosomal membrane, such as bulb-like structure and even complete rupture of the outer membranes, were found in the skin after topical application of 5% HQ for 10 days. These changes were barely observed in the skin treated with D-Arb. To further clarify whether membrane toxicity of HQ was a direct result of the compound treatment, we also examinedultrastructural changes of individual melanosomes purified from MNT1 human melanoma cells. Similar observations were obtained from the naked melanosome model in vitro. Finally, we determined the effects of melanosomal fractions exposed to HQ or D-Arb on hydroxyl radical generation in the Fenton reaction utilizing an electron spin resonance assay. D-Arb-treated melanosomesexhibit a moderate hydroxyl radical-scavenging activity, whereas HQ-treated melanosomessignificantly generate more hydroxyl free radicals. This study suggests that D-Arb possesses a potent ability in skin lightening and antioxidation with less melanosome cytotoxicity.

Opinion of the Scientific Committee on Consumer safety (SCCS) - Opinion on the safety of the use of deoxyarbutin in cosmetic products.

CONCLUSION OF THE OPINION: Although on the basis of the provided scientific data the use of deoxyarbutin as such can be considered safe for consumers in cosmetic products in a concentration up to 3% in face creams, hydroquinone will be formed at levels which raise concerns with regard to the safety of such products during life-cycle of the product (e.g. storage conditions and stability under in-use conditions). Therefore, the overall conclusion of the SCCS is that the use of deoxyarbutin up to 3% in face creams is not safe.

HPLC simultaneous determination of arbutin, chlorogenic acid and 6'-O-caffeoylarbutin in different parts of Vaccinium dunalianum Wight.

Arbutin (1), chlorogenic acid (2) and 6'-O-caffeoylarbutin (3) are three major components in Vaccinium dunalianum Wight with various promising bioactivities. A reliable, reproducible and accurate method for simultaneous and quantitative determination of 1-3 is developed by RP-HPLC analysis. This method should be appropriate for the quality assurance of unprocessed and processed materials of V. dunalianum. The contents of 1-3 in different parts of V. dunalianum from different origins were analysed. The content of 3 was much higher than those of 1 and 2, accounting for up to 31.76% in the dried leaf buds. Moreover, the leaf buds, flower buds and leaves showed a tendency towards higher contents of 1-3 than the other plant parts.

Grevillosides J-Q, arbutin derivatives from the leaves of Grevillea robusta and their melanogenesis inhibitory activity.

From the 1-BuOH-soluble fraction of a MeOH extract of the leaves of Grevillea robusta, new arbutin derivatives and related compounds, named grevillosides J-Q (1-8), together with eight known compounds (9-18) were isolated. Various kind of acyl groups were attached to ß-D-glucose at the 6-position through an ester linkage. Their structures were mainly elucidated from one- and two-dimensional NMR spectroscopic data. For exploitation as skin-lightening and anti-chloasma agents, the inhibitory activities of the isolated compounds as well as ones isolated in previous experiments (19-31) toward tyrosinase and melanin-producing B16 cells were assayed. Several compounds showed promising activity.

6'-O-Caffeoylarbutin inhibits melanogenesis in zebrafish.

6'-O-Caffeoylarbutin, an arbutin derivative, is a naturally occurring glucoside of hydroquinone from Vaccinium dunalianum. On anti-melanogenic effect assay, 6'-O-caffeoylarbutin expressed a stronger anti-melanin activity in a dose-dependent manner with about a two-fold more than that of arbutin, but with less toxicity about a two-fold lower than that of arbutin. In addition, melanin synthesis could be fully recovered after the removal of 6'-O-caffeoylarbutin. The result suggested that 6'-O-caffeoylarbutin could be a candidate natural product to serve as a skin-whitening ingredient with the merits of potent melanin inhibition, less toxicity and reversible melanin synthesis after stopping use.