In vitro and in vivo prolonged biological activities of novel vitamin C derivative, 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G), in cosmetic fields

Antioxidants in Sunscreens: Which and What For?

Ultraviolet (UV) radiation promotes the generation of reactive oxygen species (ROS) and nitrogen species (RNS), resulting in skin damage. Cosmetic industries have adopted a strategy to incorporate antioxidants in sunscreen formulations to prevent or minimize UV-induced oxidative damage, boost photoprotection effectiveness, and mitigate skin photoaging. Many antioxidants are naturally derived, mainly from terrestrial plants; however, marine organisms have been increasingly explored as a source of new potent antioxidant molecules. This work aims to characterize the frequency of the use of antioxidants in commercial sunscreens. Photoprotective formulations currently marketed in parapharmacies and pharmacies were analyzed with respect to the composition described on the label. As a result, pure compounds with antioxidant activity were found. The majority of sunscreen formulations contained antioxidants, with vitamin E and its derivatives the most frequent. A more thorough analysis of these antioxidants is also provided, unveiling the top antioxidant ingredients found in sunscreens. A critical appraisal of the scientific evidence regarding their effectiveness is also performed. In conclusion, this work provides an up-to-date overview of the use of antioxidants in commercial sunscreens for a better understanding of the advantages associated with their use in photoprotective formulations.

Timeline of the Development of Skin-Lightening Active Ingredients in Japan

Japanese pharmaceutical cosmetics, often referred to as quasi-drugs, contain skin-lightening active ingredients formulated to prevent sun-induced pigment spots and freckles. Their mechanisms of action include suppressing melanin production in melanocytes and promoting epidermal growth to eliminate melanin more rapidly. For example, arbutin and rucinol are representative skin-lightening active ingredients that inhibit melanin production, and disodium adenosine monophosphate and dexpanthenol are skin-lightening active ingredients that inhibit melanin accumulation in the epidermis. In contrast, oral administration of vitamin C and tranexamic acid in pharmaceutical products can lighten freckles and melasma, and these products are more effective than quasi-drugs. On the basis of their clinical effectiveness, skin-lightening active ingredients can be divided into four categories according to their effectiveness and adverse effects. This review discusses academic research and development regarding skin-lightening ingredients in Japan.

Efficient dermal delivery of ascorbic acid 2-glucoside with photoacoustic waves

OBJECTIVE

Ascorbic acid (i.e., vitamin C) is an important antioxidant present in skin. The protective role of vitamin C against photoaging motivated numerous attempts to promote its topical delivery, with a success limited by its chemical instability and poor skin permeability. Vitamin C precursors, such as ascorbic acid 2-glucoside (AA2G), that are metabolized to vitamin C by enzymes present in the skin, solve the problem of stability but are limited by low skin permeability. We developed a 2% (w/v) gel formulation of AA2G application (viscosity 4.30 × 10⁴ Pa.s, pH 5.94) and compared its passive dermal delivery with the delivery promoted by photoacoustic waves that transiently perturb the skin barrier.

METHODS

Photoacoustic (PA) waves were generated by laser pulses absorbed by piezophotonic (light-to-pressure) transducers. Pig skin samples were exposed to the 2% AA2G formulation alone or combined with 5 minutes of PA waves. One hour later, AA2G was extracted from the skin and quantified by reverse-phase HPLC. AA2G transdermal fluxes using Franz cells with 760 μm thick pig skin samples were also measured.

RESULTS

PA waves transiently enhanced skin permeability and increased dermal delivery of AA2G. AA2G was released from the formulation nearly quantitatively (92.6 ± 6.2%) in 24 hours, showing a non-Fickian behaviour controlled by diffusion and swelling. AA2G dermal delivery with exposure for 5 minutes to PA waves was compared with passive delivery to pig skin. PA waves increased the delivery of AA2G to the skin by a factor of 15 fold with respect to passive delivery, as measured from skin extracts after 1 hour of contact of the formulation with the skin.

CONCLUSION

5 minutes of exposure to PA waves is a safe and effective method to deliver large quantities of AA2G to the skin.

Identification of Process-Related Impurities and Corresponding Control Strategy in Biocatalytic Production of 2-O-α-d-Glucopyranosyl-l-ascorbic Acid Using Sucrose Phosphorylase

2-O-α-d-Glucopyranosyl-l-ascorbic acid (AA-2G) is an ideal substitute for l-ascorbic acid because of its remarkable stability and improved biological activity, which can be easily applied in cosmetic, food, and medicine fields. However, impurity identification and control are significant procedures during the manufacturing of AA-2G. This study assessed a manufacturing routine of AA-2G synthesized by sucrose phosphorylase (SPase). First, three unknown process-related impurities were observed, which were further identified as 3-O-α-d-glucopyranosyl- l-ascorbic acid (impurity I), 2-O-α-d-glucopyranosyl-l-dehydroascorbic acid (impurity II), and 13-O-α-d-glucopyranosyl-2-O-α-d-glucopyranosyl-l-ascorbic acid (impurity III), respectively. Second, a comprehensive formation pathway of impurities was elucidated, and specific strategies corresponding to controlling each impurity were also proposed. Specifically, the content of impurity I can be reduced by 50% by fine tuning reaction conditions. The impurity II-free purification process was also achieved by applying a low concentration of alkali. Finally, a semi-rational design was introduced, and a single mutant L343F was obtained by site-directed mutagenesis, which reduced impurities I and III by 63.9 and 100%, respectively, without affecting the transglycosylation activity. It is expected that the reported impurity identification and control strategies during the AA-2G production will facilitate its industrial production.

Effect of Grass Carp Scale Collagen Peptide FTGML on cAMP-PI3K/Akt and MAPK Signaling Pathways in B16F10 Melanoma Cells and Correlation between Anti-Melanin and Antioxidant Properties

Peptide Phe-Thr-Gly-Met-Leu (FTGML) is a bioactive oligopeptide with tyrosinase inhibitory activity derived from gelatin hydrolysate of grass carp scales. Previous studies have shown that FTGML addition can effectively inhibit mushroom tyrosinase activity in vitro, and also has some effect on the inhibition of melanogenesis in zebrafish in vivo, but the underlying mechanism is not fully understood. In this study, we used FTGML to treat B16F10 melanoma cells, and found a significant inhibition of tyrosinase activity and melanin synthesis. Interestingly, the treatment showed a strong correlation between antioxidant activity and anti-melanin, which was associated with FTGML reducing the involvement of reactive oxygen species in melanin synthesis. Furthermore, FTGML reduced melanogenesis in B16F10 cells by downregulating the cAMP-PI3K/Akt and MAPK pathways (p38 and JNK). These results suggested that FTGML can reduce melanin production in mouse B16F10 melanoma cells through multiple pathways.

Ascorbic acid 2-glucoside: An ascorbic acid pro-drug with longer-term antioxidant efficacy in skin

OBJECTIVE

Deleterious effects of pollutants and ultraviolet radiation on the skin can be attenuated using formulations containing antioxidants. However, these have disadvantages, including chemical instability, photodegradation, poor bioavailability or biological activity. Here, two commercial formulations were evaluated: one optimized to stabilize and deliver ascorbic acid (AA) at 15% and the other containing a glucoside form of AA, namely ascorbic acid 2-glucoside (AA2G), at 1.8% and at a physiological pH. We compared the skin delivery, antioxidative effects and chemical stability of AA2G with AA in their respective formulations.

METHODS

Skin delivery was measured using fresh viable human skin explants, and oxidative stress was measured using a human reconstructed epidermal (RHE) model according to levels of malondialdehyde (MDA), superoxide dismutase (SOD) and catalase.

RESULTS

Ascorbic acid 2-glucoside was completely metabolized to AA by the skin before entering the receptor compartment. The skin contained parent and AA, indicating a reserve of AA2G was present for further metabolism. For AA2G and AA, maximum flux of AA-equivalents was at 12 h, with continued absorption over 24 h. The absolute amount in µg was higher in the skin after application of AA than after application of AA2G. This may suggest a greater antioxidative effect; however, according to all three measurements of oxidative stress, the protective effect of AA and AA2G was similar. Unlike AA, AA2G was chemically stable under storage conditions.

CONCLUSION

A lower concentration of AA2G is as effective as the active metabolite, AA, in terms of antioxidant effects. AA2G was chemically stable and can be applied at a lower concentration than AA, thus avoiding the need for an acidic formulation with a pH below 3.5.

A review of topical vitamin C derivatives and their efficacy

Vitamin C is a popular ingredient in over-the-counter cosmeceuticals due to its many biological functions in maintaining and improving skin health by treating UV damage, improving discoloration, and boosting collagen production. Several chemically modified derivatives of vitamin C have been developed in an attempt to increase the stability, percutaneous absorption, and overall activity of this ingredient in topical formulations. The goal of this review is to evaluate the differences between vitamin C derivatives that have been designed for cosmeceutical use and their efficacy.

Determination of the Chemical Composition, Antioxidant, and Enzyme Inhibitory Activity of Onosma mollis DC

Onosma species have long been used traditionally for respiratory tract infections, abdominal pain, wound treatment, burns, and constipation. This study aims to investigate the chemical composition and in vitro antioxidant and enzyme inhibitory activities of ethyl acetate (EtOAc), methanol (MeOH), and water extracts of Onosma mollis DC. MeOH extract was richer in both phenolics and flavonoids than other extracts (44.06 mg GAEs/g and 41.57 mg QEs/g, respectively). The findings obtained from the results of the chromatographic analysis also supported the results of the spectrophotometric analysis. The MeOH extract was the richest in terms of most of the phytochemicals screened. Apigenin 7-glucoside, luteolin 7-glucoside, rosmarinic acid, vanillic acid, and pinoresinol were over 1000.0 μg/g in MeOH extract. The extract in question showed the highest activity in phosphomolybdenum, DPPH, and ABTS radical scavenging and CUPRAC and FRAP reducing power activity assays (2.01, 3.33, 2.30, 1.48, and 0.79 mg/ml, respectively). The water extract presented the highest activity in the ferrous ion chelating assay (1.01 mg/ml). While EtOAc extract showed high activity in acetylcholinesterase (AChE), butyrylcholinesterase (BChE), and α-glucosidase inhibitory activity tests (1.11, 1.49, and 1.07 mg/ml, respectively), MeOH extract showed significant efficacy in tyrosinase and α-amylase inhibitory activity assays (2.94 and 2.08 mg/ml, respectively). There was a high correlation between the total phenolics/flavonoids of the extracts and their antioxidant activities (correlation coefficients were over 0.9). In addition, the phytochemicals mentioned above were found to contribute significantly to the antioxidant activity. It was concluded that a more detailed analysis should be done to determine the compounds responsible for the enzyme inhibitory activities of the extracts.

Ascorbic Acid 2-Glucoside Pretreatment Protects Cells from Ionizing Radiation, UVC, and Short Wavelength of UVB

Ascorbic acid 2-glucoside (AA2G), glucosylated ascorbic acid (AA), has superior properties for bioavailability and stability compared to AA. Although AA2G has shown radioprotective properties similar to AA, effects for UV light, especially UVC and UVB, are not studied. AA2G was tested for cytotoxicity and protective effects against ionizing radiation, UVC, and broadband and narrowband UVB in Chinese hamster ovary (CHO) cells and compared to AA and dimethyl sulfoxide (DMSO). Pretreatment with DMSO, AA, and AA2G showed comparative protective effects in CHO wild type and radiosensitive xrs5 cells for cell death against ionizing radiation with reducing the number of radiation-induced DNA damages. Pretreatment with AA and AA2G protected CHO wild type and UV sensitive UV135 cells from UVC and broadband UV, but not from narrowband UVB. DMSO showed no protective effects against tested UV. The UV filtration effects of AA and AA2G were analyzed with a spectrometer and spectroradiometer. AA and AA2G blocked UVC and reduced short wavelengths of UVB, but had no effect on wavelengths above 300nm. These results suggest that AA2G protects cells from radiation by acting as a radical scavenger to reduce initial DNA damage, as well as protecting cells from certain UVB wavelengths by filtration.

Therapeutic Perspective of Vitamin C and Its Derivatives

l-Ascorbic acid (ASA), vitamin C, is a ubiquitous carbohydrate-like compound that has an essential role in a number of cellular processes, such as collagen synthesis, cellular oxidation, and various hydroxylation reactions. ASA is a biomolecule of critical importance for protection of cellular components against oxidative damage caused by toxic free radicals and other reactive oxygen species (ROS) that are involved in the development of various types of chronic diseases. Vitamin C has a switchover role from being an antioxidant in physiological conditions to a prooxidant under pathologic conditions. Moreover, some l-ascorbic acid derivatives exhibit strong and selective antitumor and antiviral activity. This review emphasizes the advances on diverse and potent biological profiles of l-ascorbic acid and its derivatives, and their perspective in the development of new bioactive chemical entities in the future. The work is primarily addressed at antioxidant, anticancer, and antiviral potencies of l-ascorbic acid and compounds containing its butenolide structural motif.

Intramelanocytic Acidification Plays a Role in the Antimelanogenic and Antioxidative Properties of Vitamin C and Its Derivatives

Although vitamin C (VC, L-ascorbic acid) has been widely used as a skin lightening agent for a long time, the mechanism by which it inhibits melanogenesis remains poorly understood. It is well-documented that the intramelanocytic pH is an important factor in regulating tyrosinase function and melanosome maturation. The activity of tyrosinase, the rate-limiting enzyme required for melanin synthesis, is generally minimal in an acidic environment. Given that VC is an acidic compound, we might speculate that the intracellular acidification of melanocytes induced by VC likely reduces melanin content through the suppression of tyrosinase activity. The results of this study reveal that treatment of melanocytes with VC or its derivatives, magnesium ascorbyl phosphate (MAP) and 3-O-ethyl-L-ascorbic acid (AAE), resulted in significant decreases in the tyrosinase activity and melanin content and in the levels of intracellular reactive oxygen species (ROS), indicating that VC and its derivatives possess antimelanogenic and antioxidative activities. Western blotting analysis indicated that VC, MAP, and AAE exert their antimelanogenic activity by inhibiting the tyrosinase activity rather than by downregulating the expression of melanogenic proteins such as tyrosinase, premelanosome protein 17 (Pmel17) and microphthalmia-associated transcription factor (MITF). Further, we found that the reduced tyrosinase activity of melanocytes treated with VC or its derivatives could be reactivated following intracellular neutralization induced by ammonium chloride (NH₄Cl) or concanamycin A (Con A). Finally, we examined the expression of sodium-dependent VC transporter-2 (SVCT-2) using western blotting and qPCR, which revealed that there was a significant increase in the expression of SVCT-2 in melanocytes following treatment with VC. VC-mediated intracellular acidification was neutralized by phloretin (a putative SVCT-2 inhibitor) in a dose-dependent manner. Taken together, these data show that VC and its derivatives suppress tyrosinase activity through cytoplasmic acidification that potentially results from enhanced VC transmembrane transport via the VC transporter SVCT-2.

Structural Requirements of Alkylglyceryl-l-Ascorbic Acid Derivatives for Melanogenesis Inhibitory Activity

l-Ascorbic acid has multifunctional benefits on skin aesthetics, including inhibition of melanin production, and is widely used in cosmetics. It, however, has low stability and poor skin penetration. We hypothesize that alkylglyceryl-l-ascorbic acid derivatives, highly stable vitamin C–alkylglycerol conjugates, would have similar anti-melanogenic activity with better stability and penetration. We test 28 alkylglyceryl-l-ascorbic acid derivatives (1–28) on theophylline-stimulated B16 melanoma 4A5 cells to determine if they inhibit melanogenesis and establish any structure–function relationships. Although not the most potent inhibitors, 3-O-(2,3-dihydroxypropyl)-2-O-hexyl-l-ascorbic acid (6, IC₅₀ = 81.4 µM) and 2-O-(2,3-dihydroxypropyl)-3-O-hexyl-l-ascorbic acid (20, IC₅₀ = 117 µM) are deemed the best candidate derivatives based on their inhibitory activities and low toxicities. These derivatives are also found to be more stable than l-ascorbic acid and to have favorable characteristics for skin penetration. The following structural requirements for inhibitory activity of alkylglyceryl-l-ascorbic acid derivatives are also determined: (i) alkylation of glyceryl-l-ascorbic acid is essential for inhibitory activity; (ii) the 3-O-alkyl-derivatives (2–14) exhibit stronger inhibitory activity than the corresponding 2-O-alkyl-derivatives (16–28); and (iii) derivatives with longer alkyl chains have stronger inhibitory activities. Mechanistically, our studies suggest that l-ascorbic acid derivatives exert their effects by suppressing the mRNA expression of tyrosinase and tyrosine-related protein-1.

Melaleuca quinquenervia essential oil inhibits α-melanocyte-stimulating hormone-induced melanin production and oxidative stress in B16 melanoma cells

BACKGROUND

Essential oils are odorous, volatile products of plant secondary metabolism, which are found in many leaves and stems. They show important biological activities, which account for the development of aromatherapy used in complementary and alternative medicine. The essential oil extracted from Melaleuca quinquenervia (Cav.) S.T. Blake (paperbark) (MQ-EO) has various functional properties.

PURPOSE

The aim of this study is to investigate the chemical composition of MQ-EO by using gas chromatography-mass spectrometry (GC-MS) and evaluate its tyrosinase inhibitory activity.

METHODS

Gas chromatography-mass spectrometry (GC-MS)-based metabolomics was used to identify 18 components in MQ-EO. The main components identified were 1,8-cineole (21.60%), α-pinene (15.93%), viridiflorol (14.55%), and α-terpineol (13.73%). B16 melanoma cells were treated with α-melanocyte-stimulating hormone (α-MSH) in the presence of various concentrations of MQ-EO or its major compounds. Cell viability was accessed by MTT assay and cellular tyrosinase activity and melanin content were determined by using spectrophotographic methods. The antioxidant mechanism of MQ-EO in α-MSH stimulated B16 cells was also investigated.

RESULTS

In α-melanocyte-stimulating hormone (α-MSH)-stimulated murine B16 melanoma cells, MQ-EO, 1,8-cineole, α-pinene, and α-terpineol significantly reduced melanin content and tyrosinase activity. Moreover, MQ-EO, 1,8-cineole, α-pinene, and α-terpineol decreased malondialdehyde (MDA) levels. In addition, restored glutathione (GSH) levels, glutathione peroxidase (GPx), superoxide dismutase (SOD), and catalase activities were increased in α-MSH-stimulated B16 cells. MQ-EO not only decreased apoptosis but also reduced DNA damage in α-MSH stimulated B16 cells. These results showed that MQ-EO and its main components, 1,8-cineole, α-pinene, and α-terpineol, possessed potent anti-tyrosinase and anti-melanogenic activities besides the antioxidant properties.

CONCLUSIONS

The active functional components of MQ-EO were found to be 1,8-cineole, α-pinene, and α-terpineol. Consequently, the results of present study suggest that MQ-EO is non-cytotoxic and can be used as a skin-whitening agent, both medically and cosmetically.

Walking a Fine Line with Sucrose Phosphorylase: Efficient Single-Step Biocatalytic Production of l-Ascorbic Acid 2-Glucoside from Sucrose

The 2-O-α-d-glucoside of l-ascorbic acid (AA-2G) is a highly stabilized form of vitamin C, with important industrial applications in cosmetics, food, and pharmaceuticals. AA-2G is currently produced through biocatalytic glucosylation of l-ascorbic acid from starch-derived oligosaccharides. Sucrose would be an ideal substrate for AA-2G synthesis, but it lacks a suitable transglycosidase. We show here that in a narrow pH window (pH 4.8-6.0, with sharp optimum at pH 5.2), sucrose phosphorylases catalyzed the 2-O-α-glucosylation of l-ascorbic acid from sucrose with high efficiency and perfect site-selectivity. Optimized synthesis with the enzyme from Bifidobacterium longum at 40 °C gave a concentrated product (155 g L^-1 ; 460 mm), from which pure AA-2G was readily recovered in ∼50 % overall yield, thus providing the basis for advanced production. The peculiar pH dependence is suggested to arise from a "reverse-protonation" mechanism in which the catalytic base Glu232 on the glucosyl-enzyme intermediate must be protonated for attack on the anomeric carbon from the 2-hydroxyl of the ionized l-ascorbate substrate.

Inhibition of melanogenesis by β-caryophyllene from lime mint essential oil in mouse B16 melanoma cells

OBJECTIVE

Volatile essential oils of mint species are used for cosmetics and in skin care products. In this study, we evaluated the main chemical components of the lime mint and the anti-melanogenic properties of its main components.

METHODS

The essential oil was analysed by gas chromatography-mass spectrometry (GC/MS). The anti-melanogenic effects of mint essential oil and β-caryophyllene were investigated in B16F10 murine melanoma cells.

RESULTS

The main components of lime mint essential oil were found to be D-limonene (41.10%), D-carvone (8.58%), δ-selinene (6.73%) and β-caryophyllene (6.24%). The lime mint essential oil reduced melanin production in a dose-dependent manner in murine B16F10 cells. β-Caryophyllene, one of the main compounds in lime mint essential oil, could reduce melanogenesis by down-regulating the expression of MITF, TRP-1, TRP-2 and tyrosinase, resulting in a decrease in melanin content decrease.

CONCLUSION

These results reveal that lime mint essential oil and β-caryophyllene are considered to be valuable as potential skin-whitening agents.

Supercritical fluid extract of Lycium chinense Miller root inhibition of melanin production and its potential mechanisms of action

Background

The mode of action of Lycium chinense Miller root extract in skin care has never been explored. In the present study, Lycium chinense Miller root was extracted by the supercritical fluid CO₂ extraction method.

Methods

In the present study, the components of the root extract were analyzed by HPLC. The effects of the extract on tyrosinase activity and melanin content were determined spectrophotometrically; the expression of melanogenesis-related proteins was determined by Western blotting; the possible signaling pathways involved in the root extract-mediated depigmentation were also investigated using specific inhibitors.

Results

The results revealed that the SFE of Lycium chinense Miller root (2.37-7.11 mg/mL) effectively suppressed intracellular tyrosinase activity and decreased the melanin content in B16F10 cells. The root extract also effectively decreased intracellular reactive oxygen species (ROS) levels. Furthermore, the root extract decreased the expression of melanocortin 1 receptor (MC1R), microphthalmia-associated transcription factor (MITF), tyrosinase and tyrosinase-related protein-1 (TRP-1) and then inhibited melanogenesis in B16F10 cells. The root extract also showed antioxidant capacities and depleted cellular ROS.

Conclusions

Our results indicate that the SFE of Lycium chinense Miller root inhibited melanogenesis in B16F10 cells by down-regulation of both mitogen-activated protein kinases (MAPK) and protein kinase A (PKA) signaling pathways or through its antioxidant properties.

Stability, transdermal penetration, and cutaneous effects of ascorbic acid and its derivatives

Topically applied antioxidants exert their benefits by offering protection from damaging free radicals and over-the-counter cosmeceuticals incorporating antioxidants are among the most popular anti-aging products available. One potent antioxidant of particular note, vitamin C, has been extensively utilized because it possesses a variety of other cutaneous benefits including photoprotection from UV A & B, neocollagenesis, inhibition of melanogenesis and improvement of a variety of inflammatory skin disorders. However, the instability of this water-soluble vitamin, together with difficulties associated with its topical delivery, has presented issues for the formulation chemist. This article reviews the scientific data and clinical studies that underpin the stability, percutaneous absorption, and cutaneous effects of vitamin C together with its commonly utilized, commercially available derivatives.

Biosynthesis of 2-O-D-glucopyranosyl-l-ascorbic acid from maltose by an engineered cyclodextrin glycosyltransferase from Paenibacillus macerans

In this work, the specificity of cyclodextrin glycosyltransferase (CGTase) of Paenibacillus macerans towards maltose was improved by the site-saturation engineering of lysine 47, and the enzymatic synthesis of 2-O-d-glucopyranosyl-l-ascorbic acid (AA-2G) with l-ascorbic acid and maltose as substrates was optimized. Compared to the AA-2G yield of the wild-type CGTase, that of the mutants K47F (lysine→phenylalanine), K47P (lysine→proline), and K47Y (lysine→tyrosine) was increased by 17.1%, 32.9%, and 21.1%, respectively. Under the optimal transformation conditions (pH 6.5, temperature 36°C, the mass ratio of l-ascorbic acid to maltose 1:1), the highest AA-2G titer by the K47P reached 1.12g/L, which was 1.32-fold of that (0.85g/L) obtained by the wild-type CGTase. The reaction kinetics analysis confirmed the enhanced maltose specificity of the mutants K47F, K47P, and K47Y. It was also found that compared to the wild-type CGTase, the three mutants had relatively lower cyclization activities and higher disproportionation activities, which was favorable for AA-2G synthesis. As revealed by the interaction structure model of CGTase with substrate, the enhancement of maltose specificity may be due to the removal of hydrogen bonding interactions between the side chain of residue 47 and the sugar at -3 subsite. The obtained mutant CGTases, especially the K47P, has a great potential in the large-scale production of AA-2G with maltose as a cheap and soluble substrate.

Site-saturation engineering of lysine 47 in cyclodextrin glycosyltransferase from Paenibacillus macerans to enhance substrate specificity towards maltodextrin for enzymatic synthesis of 2-O-D-glucopyranosyl-L-ascorbic acid (AA-2G)

In this work, the site-saturation engineering of lysine 47 in cyclodextrin glycosyltransferase (CGTase) from Paenibacillus macerans was conducted to improve the specificity of CGTase towards maltodextrin, which can be used as a cheap and easily soluble glycosyl donor for the enzymatic synthesis of 2-O-D-glucopyranosyl-L-ascorbic acid (AA-2G) by CGTase. When using maltodextrin as glycosyl donor, four mutants K47F (lysine→ phenylalanine), K47L (lysine→ leucine), K47V (lysine→ valine) and K47W (lysine→ tryptophan) showed higher AA-2G yield as compared with that produced by the wild-type CGTase. The transformation conditions (temperature, pH and the mass ratio of L-ascorbic acid to maltodextrin) were optimized and the highest titer of AA-2G produced by the mutant K47L could reach 1.97 g/l, which was 64.2% higher than that (1.20 g/l) produced by the wild-type CGTase. The reaction kinetics analysis confirmed the enhanced maltodextrin specificity, and it was also found that compared with the wild-type CGTase, the four mutants had relatively lower cyclization activities and higher disproportionation activities, which was favorable for AA-2G synthesis. The mechanism responsible for the enhanced substrate specificity was further explored by structure modeling and it was indicated that the enhancement of maltodextrin specificity may be due to the short residue chain and the removal of hydrogen bonding interactions between the side chain of residue 47 and the sugar at -3 subsite. Here the obtained mutant CGTases, especially the K47L, has a great potential in the production of AA-2G with maltodextrin as a cheap and easily soluble substrate.

Antioxidative properties and inhibitory effect of Bifidobacterium adolescentis on melanogenesis

Melanin is a dark pigment produced by melanocytes. Tyrosinase is a key enzyme which catalyzes the rate-limiting step of melanogenesis. However, accumulation of melanin leads to various skin hyperpigmentation disorders. To find a novel skin-whitening agent, the antioxidant capacity of Bifidobacterium adolescentis culture filtrate and inhibitory effect on melanogenesis were investigated. The antioxidant effects of B. adolescentis culture filtrate include 2,2-diphenyl-1-picryl-hydrazyl (DPPH) radical scavenging capacity, 2,2'-azino-bis (3-ethylbenzthiazoline-6-sulphonic acid)(ABTS) radical cation scavenging activity and reducing power were measured spectrophotometrically. The reducing power is a useful index for the evaluation of potential antioxidants which carry out reduction of ferricyanide to ferrocyanide. Furthermore, the inhibitory effects of the bacterial culture filtrate on mushroom tyrosinase, B16F10 intracellular tyrosinase activity and melanin content were also determined. The results revealed that B. adolescentis culture filtrate (2.5, 5.0 and 7.5 %; v/v) effectively scavenged DPPH and ABTS radicals, and lower concentrations of the bacterial culture filtrates (0.5, 1.0 and 1.5 %; v/v) showed potent reducing power in a dose-dependent pattern. Additionally, the bacterial culture filtrate suppressed murine tyrosinase activity and decreased the amount of melanin in a dose-dependent manner. Our results demonstrated that B. adolescentis culture filtrate decreases the melanogenesis process of melanoma cells by inhibiting tyrosinase activity, which we suggest may be mediated through its antioxidant activity.

Inhibition of melanogenesis and antioxidant properties of Magnolia grandiflora L. flower extract

Background

Magnolia grandiflora L. flower is wildly used in Asian as a traditional herbal medication. The purpose of the study was to investigate the antimelanogenic and antioxidant properties of Magnolia grandiflora L. flower extract. In the study, the inhibitory effects of M. grandiflora L. flower extract on mushroom tyrosinase, B16F10 intracellular tyrosinase activity and melanin content were determined spectrophotometrically. Meanwhile, the antioxidative capacity of the flower extract was also investigated.

Results

Our results revealed that M. grandiflora L. flower extract inhibit mushroom tyrosinase activity (IC₅₀ =11.1%; v/v), the flower extract also effectively suppressed intracellular tyrosinase activity (IC₅₀ = 13.6%; v/v) and decreased the amount of melanin (IC₅₀ = 25.6%; v/v) in a dose-dependent manner in B16F10 cells. Protein expression level of tyrosinase and tyrosinase-related protein 1 (TRP-1) were also decreased by the flower extract. Additionally, antioxidant capacities such as ABTS⁺ free radical scavenging activity, reducing capacity and total phenolic content of the flower extract were increased in a dose-dependent pattern.

Conclusions

Our results concluded that M. grandiflora L. flower extract decreased the expression of tyrosinase and TRP-1, and then inhibited melanogenesis in B16F10 cells. The flower extract also show antioxidant capacities and depleted cellular reactive oxygen species (ROS). Hence, M. grandiflora L. flower extract could be applied as a type of dermatological whitening agent in skin care products.

Antioxidative characteristics of Anisomeles indica extract and inhibitory effect of ovatodiolide on melanogenesis

The purpose of the study was to investigate the antioxidant characteristics of Anisomeles indica methanol extract and the inhibitory effect of ovatodiolide on melanogenesis. In the study, the antioxidant capacities of A. indica methanol extract such as DPPH assay, ABTS radical scavenging assay, reducing capacity and metal ion chelating capacity as well as total phenolic content of the extract were investigated. In addition, the inhibitory effects of ovatodiolide on mushroom tyrosinase, B16F10 intracellular tyrosinase and melanin content were determined spectrophotometrically. Our results revealed that the antioxidant capacities of A. indica methanol extract increased in a dose-dependent pattern. The purified ovatodiolide inhibited mushroom tyrosinase activity (IC₅₀ = 0.253 mM), the compound also effectively suppressed intracellular tyrosinase activity (IC₅₀ = 0.469 mM) and decreased the amount of melanin (IC₅₀ = 0.435 mM) in a dose-dependent manner in B16F10 cells. Our results concluded that A. indica methanol extract displays antioxidant capacities and ovatodiolide purified from the extract inhibited melanogenesis in B16F10 cells. Hence, A. indica methanol extract and ovatodiolide could be applied as a type of dermatological whitening agent in skin care products.

Dose of 3-methylcholanthrene enhances vitamin C accumulation and mRNA expression of its transporter in the liver of ODS rats and in HepG2 cells

Polycyclic aromatic hydrocarbon (PAH) compounds including 3-methylcholanthrene induce harmful reactive intermediates and reactive oxygen species. This study reports the effect of 3-methylcholanthrene on the accumulation of vitamin C and the expression of vitamin C transporters. ODS rats were given l-ascorbic acid daily and intraperitoneal injections of 10 mg 3-methylcholanthrene in total. On day 10, vitamin C concentrations and the expression of vitamin C transporter in the tissues were measured. As a result, the levels of sodium-dependent vitamin C transporter (SVCTs) 1 and the l-ascorbic acid concentration in 3-methylcholanthrene-treated livers and hepatocytes have increased significantly. However, the content of vitamin C in the urine and TBARS in the liver have not changed. These results suggest that the administration of 3-methylcholanthrene elevates the requirement for vitamin C via (SVCTs) 1 due to xenobitics-metabolizing, such as the induction of cytochrome P450 family.

Inhibitory effect of [6]-gingerol on melanogenesis in B16F10 melanoma cells and a possible mechanism of action

[6]-Gingerol is an active component of ginger that shows antipyretic and anti-inflammation activities. To find a novel skin-whitening agent, the melanogeneis inhibitory effects and action mechanisms of [6]-gingerol were investigated. In the present study, the effects of [6]-gingerol on mushroom tyrosinase, tyrosinase activity, and melanin content were determined spectrophotometrically, and the expression of tyrosinase and related proteins in B16F10 murine melanoma cells was evaluated by Western blotting. Furthermore, a possible signaling pathway involved in [6]-gingerolmediated depigmentation was investigated by means of specific inhibitors. The results revealed that [6]-gingerol (25-100 µM) effectively suppresses murine tyrosinase activity and decreases the amount of melanin in a dose-dependent manner. Additionally, it also effectively decreased the intracellular reactive oxygen species (ROS) level in a dose-dependent pattern in the same dose range. Our results indicate that [6]-gingerol inhibits melanogenesis of B16F10 melanoma and can function as a good skinwhitening agent.

Inhibitory effects of 2-amino-3H-phenoxazin-3-one on the melanogenesis of murine B16 melanoma cell line

Hyperpigmentations are a serious concern addressed by both the medical community and the cosmetic industry through the development of agents that block melanin biosynthesis. In this study, we found that 2-amino-3H-phenoxazin-3-one (APO), isolated from extracts of the edible mushroom Agaricus bisporus Imbach, exhibited potent inhibitory effects on melanogenesis in B16 cells, a murine melanoma cell line. APO inhibited melanin biosynthesis at 1,000 times lower concentrations (IC(50)=1.31+/-0.08 microM) than kojic acid (IC(50)=1.31+/-0.13 mM), without causing cellular toxicity. APO did not directly inhibit the enzyme activity of tyrosinase, the rate-limiting melanogenic enzyme. Further study showed that APO inhibited the protein expression of tyrosinase and microphthalmia-associated transcription factor (MITF), a melanogenic transcription factor that regulates the expression of tyrosinase. These results suggest that APO is a promising depigmenting agent with both therapeutic and cosmetic value in preventing melanogenesis.

Permeation enhancement of ascorbic acid by self-dissolving micropile array tip through rat skin

Ascorbic acid (AA) loaded self-dissolving micropiles (SDMP) were prepared using chondroitin sulfate as the base for the percutaneous administration of AA. AA solution was added to dense solution of chondroitin solution, glue, and array tip, 1.0 cm(2), containing 100 SDMPs of which length was 500 microm and basal diameter was 300 microm, were prepared. Two kinds of AA array tips containing 1344.2+/-1.7 microg (high content ones) and 638.7+/-4.3 microg (low content ones) were used. In vitro dissolution study showed that more than 90% of AA were released from both SDMP array tips within 5 min. Stability experiment showed that 99.2-99.4% of AA was detected in SDMP array tips when stored at 23 degrees C for 1 week. When in vitro permeation experiments were performed after AA SDMP array was inserted to the isolated rat abdominal skin, extremely high amounts of AA, 1285.3+/-369.0 microg (95.3%) for high content SDMP tip and 405.6+/-84.3 microg (65.8%) for low content SDMP tip, were permeated for 6 h into the receptor compartment due to the break down of the skin barrier function. When AA SDMP array tip was administered to the rat skin under anesthetized condition with the different contact times, 10, 20 and 30 min, the permeated amount of AA was dependent on both the AA content in SDMP array tips and the contact time. When AA SDMP was contact to the skin for 30 min, permeated amounts of AA were 146.8+/-22.9 microg (10.9%) for high content-SDMP tip and 61.2+/-18.2 microg (9.6%) for low content SDMP tip. These results suggest the usefulness of SDMP array tip for the percutaneous absorption of AA.

Quasi-drugs developed in Japan for the prevention or treatment of hyperpigmentary disorders

Excess production of melanin or its abnormal distribution, or both, can cause irregular hyperpigmentation of the skin, leading to melasma and age spots. To date, various quasi-drugs that prevent or improve hyperpigmentary disorders have been developed and officially approved by the Ministry of Health, Labor and Welfare of Japan. Many of these inhibit the activity of tyrosinase, an enzyme required for melanin synthesis, for example, by competitive or non-competitive inhibition of its catalytic activity, by inhibiting its maturation, or by accelerating its degradation. In this review, we categorize the quasi-drugs developed in Japan to prevent or treat hyperpigmentary disorders, or both, and discuss perspectives for future development.

Evaluation of depigmenting activity by 8-hydroxydaidzein in mouse B16 melanoma cells and human volunteers

In our previous study, 8-hydroxydaidzein (8-OHDe) was demonstrated to be a potent and unique suicide substrate of mushroom tyrosinase. In this study, the compound was evaluated for in vitro cellular tyrosinase and melanogenesis inhibitory activities in mouse B16 melanoma cells and for in vivo skin-whitening activity in human volunteers. Tyrosinase activity and melanogenesis in the cell culture incubated with 10 μM of 8-OHDe were decreased to 20.1% and 51.8% of control, respectively, while no obvious cytotoxicity was observed in this concentration. In contrast, a standard tyrosinase inhibitor, kojic acid, showed 69.9% and 71.3% of control in cellular tyrosinase and melanogenesis activity, respectively, at a concentration as high as 100 μM. Hence, 8-OHDe exhibited more than an inhibitory effects on melanin production in B16 cells 10-fold stronger than kojic acid. In addition, when a cream containing 4% 8-OHDe was applied to human skin in an in vivo study, significant increases in the dL*-values were observed after three weeks. Moreover, the increase in the dL*-values after 8-week treatment with 4% 8-OHDe (from −0.57 to 1.94) is stronger than those of 2% 8-OHDe treatment (from 0.26 to 0.94) and 2% ascorbic acid-2-glucoside treatment (from 0.07 to 1.54). From the results of the study, it was concluded that 8-OHDe, the potent suicide substrate of mushroom tyrosinase, has depigmenting activities in both mouse melanoma cells and in human volunteers. Thus, the compound has significant potential for use in cosmetics as a skin-whitening ingredient.

Antioxidant properties of 2-O-beta-D-glucopyranosyl-L-ascorbic acid

The antioxidant activity of a provitamin C agent, 2-O-beta-D-glucopyranosyl-L-ascorbic acid (AA-2betaG), was compared to that of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) and ascorbic acid (AA) using four in vitro methods, 1,1-diphenyl-picrylhydrazyl (DPPH) radical-scavenging assay, 2,2'-azinobis(3-ethylbenzothiazoline-6-sulfonic acid) radical cation (ABTS(*+))-scavenging assay, oxygen radical absorbance capacity (ORAC) assay, and 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced erythrocyte hemolysis inhibition assay. AA-2betaG slowly and continuously scavenged DPPH radicals and ABTS(*+) in roughly the same reaction profiles as AA-2G, whereas AA quenched these radicals immediately. In the ORAC assay and the hemolysis inhibition assay, AA-2betaG showed similar overall activities to AA-2G and to AA, although the reactivity of AA-2betaG against the peroxyl radical generated in both assays was lower than that of AA-2G and AA. These data indicate that AA-2betaG had roughly the same radical-scavenging properties as AA-2G, and a comprehensive in vitro antioxidant activity of AA-2betaG appeared to be comparable not only to that of AA-2G but also to that of AA.

Inhibition of free radical-induced erythrocyte hemolysis by 2-O-substituted ascorbic acid derivatives

Inhibitory effects of 2-O-substituted ascorbic acid derivatives, ascorbic acid 2-glucoside (AA-2G), ascorbic acid 2-phosphate (AA-2P), and ascorbic acid 2-sulfate (AA-2S), on 2,2'-azobis(2-amidinopropane) dihydrochloride (AAPH)-induced oxidative hemolysis of sheep erythrocytes were studied and were compared with those of ascorbic acid (AA) and other antioxidants. The order of the inhibition efficiency was AA-2S> or =Trolox=uric acid> or =AA-2P> or =AA-2G=AA>glutathione. Although the reactivity of the AA derivatives against AAPH-derived peroxyl radical (ROO(*)) was much lower than that of AA, the derivatives exerted equal or more potent protective effects on AAPH-induced hemolysis and membrane protein oxidation. In addition, the AA derivatives were found to react per se with ROO(*), not via AA as an intermediate. These findings suggest that secondary reactions between the AA derivative radical and ROO(*) play a part in hemolysis inhibition. Delayed addition of the AA derivatives after AAPH-induced oxidation of erythrocytes had already proceeded showed weaker inhibition of hemolysis compared to that of AA. These results suggest that the AA derivatives per se act as biologically effective antioxidants under moderate oxidative stress and that AA-2G and AA-2P may be able to act under severe oxidative stress after enzymatic conversion to AA in vivo.

Approaches to Identify Inhibitors of Melanin Biosynthesis via the Quality Control of Tyrosinase

Tyrosinase, a copper-containing glycoprotein, is the rate-limiting enzyme critical for melanin biosynthesis in specialized organelles termed melanosomes that are produced only by melanocytic cells. Inhibitors of tyrosinase activity have long been sought as therapeutic means to treat cutaneous hyperpigmentary disorders. Multiple potential approaches exist that could control pigmentation via the regulation of tyrosinase activity, for example: the transcription of its messenger RNA, its maturation via glycosylation, its trafficking to melanosomes, as well as modulation of its catalytic activity and/or stability. However, relatively little attention has been paid to regulating pigmentation via the stability of tyrosinase, which depends on its processing and maturation in the endoplasmic reticulum and Golgi, its delivery to melanosomes and its degradation via the ubiquitin-proteasome pathway and/or the endosomal/lysosomal system. Recently, it has been shown that carbohydrate modification, molecular chaperone engagement, and ubiquitylation all play pivotal roles in regulating the degradation/stability of tyrosinase. While such processes affect virtually all proteins, such effects on tyrosinase have immediate and dramatic consequences on pigmentation. In this review, we classify melanogenic inhibitory factors in terms of their modulation of tyrosinase function and we summarize current understanding of how the quality control of tyrosinase processing impacts its stability and melanogenic activity.

2-O-alpha-D-glucopyranosyl-L-ascorbic acid scavenges 1,1-diphenyl-2-picrylhydrazyl radicals via a covalent adduct formation

The 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical-scavenging mechanism of 2-O-alpha-D-glucopyranosyl-L-ascorbic acid (AA-2G) was studied. We found two undefined products, named X and Y, in the reaction mixture of AA-2G and the DPPH radical under acidic conditions by HPLC analysis. The reaction mixture was further subjected to LC-MS analysis. X was found to be a covalent adduct of AA-2G and the DPPH radical. On the other hand, Y could not be identified, probably because it was a mixture. A time-course study of the radical-scavenging reaction revealed that one molecule of AA-2G scavenged one molecule of DPPH radical to generate an AA-2G radical, which readily reacted with another molecule of the DPPH radical to form a covalent adduct (X). Subsequently, this adduct slowly quenched a third molecule of the DPPH radical, resulting in reaction products (Y). Therefore, one molecule of AA-2G has only one oxidizable -OH group, but can scavenge three molecules of the DPPH radical. The radical-scavenging mechanism of AA-2G elucidated in this study should be useful in understanding the biological roles of AA-2G per se in the food and cosmetic fields.

A Novel Melanin Inhibitor: Hydroperoxy Traxastane-Type Triterpene from Flowers of Arnica montana

We isolated a novel inhibitor of melanin biosynthesis from the flowers of Arnica montana L. (Compositae), and identified it as a traxastane-type triterpene (3beta,16beta-dihydroxy-21alpha-hydroperoxy-20(30)-taraxastene) [1] by means of 1D or 2D-NMR and liquid chromatography/high-resolution mass spectrometry (LC-HR-MS). Compound [1] at the concentration of 0.53 muM completely inhibited melanin accumulation in cultured B16 melanoma cells. It is one of the most potent among known plant inhibitors of melanin biosynthesis in cultured cells, being 50 times more potent than 4-methoxyphenol, which is used as an anti-pigmentation agent. Its mechanism of action is considered to involve inhibition of transcriptional factor MITF-M (melanocyte-type isoform of microphthalmia-associated transcription factor), which would lead to a decrease of tyrosinase and related genes. We confirmed that compound [1] decreased the protein levels of tyrosinase and its related proteins in B16 melanoma cells. Further study revealed that a similar hydroperoxy triterpene also suppressed the melanin pigment accumulation of B16 melanoma cells. These results indicate that the hydroperoxy group may play an important role in the suppression of the melanin accumulation by compound [1].

Antimelanogenic and Antioxidant Properties of Gallic Acid

To find novel skin-whitening agents, the melanogenesis inhibitory action of gallic acid (GA) was investigated. In this current study, the effects of GA on mushroom tyrosinase, tyrosinase inhibitory activity, and melanin content were assessed in B16 melanoma cells (B16 cells). Results indicated that GA has a strong antityrosinase activity (IC50=3.59x10(-6) M). Furthermore, data on murine tyrosinase activity and melanin biosynthesis revealed that GA effectively suppressed murine tyrosinase action and the amount of melanin. To investigate the relation between GA's inhibition of melanogenesis and antioxidant activity, the effect of GA on reactive species (RS) generation and the reduced glutathione (GSH)/oxidized glutathione (GSSG) ratio in were determined in B16 cells. Results indicated that GA effectively down-regulated the RS generation and enhanced the GSH/GSSG ratio. Based on these results, I propose that GA exerts antimelanogenic activity coupled with antioxidant properties by suppressing RS generation and maintaining a higher GSH/GSSG ratio.

Combining high-performance liquid chromatography with on-line microdialysis sampling for the simultaneous determination of ascorbyl glucoside, kojic acid, and niacinamide in bleaching cosmetics

We have used on-line microdialysis sampling coupled with high-performance liquid chromatography and UV-vis detection to simultaneously determine the contents of ascorbyl glucoside (AA-2G), kojic acid (KA), and niacinamide (VitB(3)) in commercial bleaching cosmetics. Our results indicate that AA-2G, KA, and VitB(3) separated well within 4.5 min on a reverse-phase Hypersil Fluophase PFP column when eluting with 0.020 M phosphate buffer solution in 40% (v/v) methanol at pH 5.5. The calibration curves were linear over the ranges 0.068-304, 0.071-284, and 0.024-488 microg mL(-1) for AA-2G, KA, and VitB(3), respectively, with correlation coefficients for the linear regression analyses falling within the range 0.9982-0.9999. The detection limits for AA-2G, KA, and VitB(3) were 0.01, 0.01, and 0.007 microg mL(-1), respectively. The detection wavelength was robust when the levels of the analytes in the samples were high (0.1-2%). The analytes were all detected using ultraviolet light (254 nm). The compounds diffuse through the membrane more readily when KA and VitB(3) are in their molecular forms and AA-2G is ionized. The recoveries were in the range 92-106% with good reproducibility (R.S.D.=3.9-8.7%). We used this procedure to assay six commercially available bleaching cosmetics; our results confirmed not only the precision of the method but also the claims made on the labels of the cosmetics. This approach provides a very simple means to determine the contents of AA-2G, KA, and VitB(3) in various dosages in bleaching cosmetics.

Topical Application of .GAMMA.-Tocopherol Derivative Prevents UV-Induced Skin Pigmentation

We previously reported that a novel hydrophilic gamma-tocopherol (gamma-Toc) derivative, gamma-tocopheryl-N,N-dimethylglycinate hydrochloride (gamma-TDMG) gets converted to the antioxidant gamma-Toc in skin. We also found that this derivative displayed greater bioavailability than gamma-Toc itself. In the present study, we determined whether gamma-TDMG could reduce UV-induced skin pigmentation in brownish guinea pigs. gamma-TDMG (0.1 or 0.5%) was topically applied to the skin before and after it was exposed to UVB plus UVA (3 times/week for 1 week), and then 10 times/week for 4 weeks thereafter. Treatment with 0.5% gamma-TDMG resulted in significant skin lightening (70% of the pigmentation of irradiated controls). We also found that melanin synthesis was dose-dependently inhibited by gamma-TDMG in murine B16 melanoma cells. When gamma-TDMG or kojic acid (250 microM) were added to homogenates of B16 melanoma cells, their tyrosinase activity was significantly inhibited by approximately 40% and 75%, respectively. Mushroom tyrosinase activity was significantly inhibited by 200 microM gamma-Toc and kojic acid, but not gamma-TDMG. When B16 cells were incubated with 250 microM gamma-TDMG for 24 or 48 h, their intracellular gamma-Toc concentrations rose over 100 fold to 10.5 and 11.2 nmol/10(6) cells, respectively, suggesting that gamma-TDMG was rapidly converted to gamma-Toc in these cells and that their reduced melanin synthesis may have been due to the activity of gamma-Toc. Our data further suggest that the topical application of gamma-TDMG may be efficacious in preventing photo-induced skin pigmentation in humans.