Natural and synthetic substances are becoming increasingly utilized as tyrosinase inhibitors of depigmentation and developed cosmetics industry. However, few have been employed as skin-whitening agents, primarily because of numerous safety concerns.
A novel compound was found, and then its safe concentrations and inhibition effect of hyperpigmentation by the regulation of the tyrosinase family of proteins were examined.
A novel phenolic glucoside, origanoside (1), was isolated from Origanum vulgare. The structure of the origanoside (1) was established on the basis of spectral evidence and the safe concentrations were determined by MTT assay. Skin-whitening capacity in skin fibroblast Hs68 and melanoma B16 cells and in vivo animal test for origanoside (1) were investigated.
Origanoside (1) is non-toxic in concentrations of 0–100 μg/ml in both cells. The ability of origanoside (1) to inhibit cellular tyrosinase and DOPA oxidase in B16 cells was investigated. Origanoside (1) significantly reduced expressions of microphthalmia-associated transcription factor (MITF), tyrosinase and tyrosinase-related proteins 2 (TRP-2) in vitro and in vivo, suggesting that origanoside (1) is responsible for the antimelanogenic effect. Smearing origanoside (1)-gel samples on 12 mice for 10 days increased L*, reduced a* and erythema-melanin (E/M), and b* was almost unchanged compared with those of samples and untreated groups, indicating that the skin lightened.
Experimental data demonstrate that origanoside (1) causes depigmentation and may be useful for novel food additives and skin-whitening cosmetics.
Traditional herbs and plants are widely used for their medicinal properties [1]. The search for, and characterization of, new pharmaceutical and healthcare products from natural sources have increased over the last few years. Such products may provide benefits to humans as antioxidants, and anti-inflammatory- and antihypertensive-drugs [2]. Plant-derived products are becoming increasingly accepted and adopted by the cosmetics industry. Consequently, research interest in the use of natural products, such as chemical extracts from medicinal plants, herbs, and spices, for the development of alternative food additives and cosmetic products is considerable [3], [4].
Origanum species are used in various commercial preparations mainly as antimicrobial agents and antioxidants [5]. Origanum vulgare an aromatic plant found throughout southern Portugal – is commonly called oregano and is used throughout the Mediterranean as a spice. O. vulgare is morphologically distinguished by its small green bracts and white flowers [6]. Previous studies demonstrated that the composition of O. vulgare essential oil is extremely variable due to several factors, including environmental and climatic conditions [7], [8]. However, few studies have examined the whitening effect of O. vulgare and its whitening mechanism. This study determined that origanoside (1), a newly identified compound in O. vulgare, is particularly effective in whitening skin.
In mammals, α-melanocyte-stimulating hormone (α-MSH) is required for development of pigmentation. Notably, α-MSH binds to its specific melanocortin-1 receptor (MC1R) and increases cyclic AMP (cAMP), which induces melanogenesis by activating the microphthalmia-associated transcription factor (MITF) [9]. Furthermore, the MITF strongly up-regulates the expression of melanogenic enzymes such as tyrosinase. Tyrosinase is responsible for the undesirable browning of fruits and vegetables, and skin, hair and eyes in mammals [10]. Tyrosinase has a role in the oxidation of l-tyrosine to l-3-(3,4-dihydroxyphenyl)-alanine (l-DOPA) and of DOPA to dopaquinone, which is the initial step in melanin synthesis. Dopaquinone spontaneously converts to dopachrome. Tyrosinase-related proteins 2 (TRP-2)/dopachrome tautomerase (TRP2/DCT) catalyzes the conversion of dopachrome to 5,6-dihydroxyindole-2-carboxylic acid (DHICA). Tyrosinase-related proteins 1 (TRP1/DHICA oxidase) catalyzes the oxidation of DHICA to indole-5,6-quinone-2-carboxylic acid. These two closely related structures, TRP2/DCT and TRP1, produce unstable quinines that undergo further polymerization, finally yielding melanin [11], [12]. The tyrosinase-related skin-whitening mechanism must be identified to elucidate the whitening effect of origanoside (1).
Natural and synthetic substances have recently been utilized as tyrosinase inhibitors of depigmentation, and for cosmetic and skin-lightening purposes; however, few have been employed as skin-whitening agents, primarily because of numerous safety concerns [13], [14]. Although several tyrosinase inhibitors, including arbutin, kojic acid and linoleic acid, have been employed extensively to whiten skin, they have many side effects [15]. Therefore, the safe in vitro concentration must be determined before skin-whitening tests are conducted. This work determines the safe concentrations, tyrosinase-inhibition activities and inhibition of melanin production by origanoside (1) by comparing the results with those of two well-known skin-whitening agents, arbutin and l-ascorbic acid, in human skin fibroblast Hs68 cells, mouse melanoma B16 cells. Finally, in vivo animal test is also carried out in order to further verify the safety of this new ingredient, origanoside (1).
Check access to the full text by signing in through your organization.
The aerial parts of O. vulgare were purchased from a local Chinese drug store. A specimen of the plant was verified by prof. H.C. Lin and deposited at the herbarium of the Chia Nan University of Pharmacy and Science, Tainan, Taiwan. Mushroom tyrosinase, l-DOPA, 4-hydroxyphenyl β-d-glucopyranoside (arbutin) and l-ascorbic acid were purchased form Sigma Chemical Co. (St. Louis, USA).
Melting points were determined using a Mel-Temp 50/60 cycles, 110–120 V–200 W apparatus and are uncorrected. Optical
Epidermal and dermal hyperpigmentation are the result of either an increased number of melanocytes or melanogenic enzyme activity. UV light, chronic inflammation and rubbing of the skin as well as abnormal α-MSH expression, trigger these disorders [20]. Owing its ability to localize photo-exposed areas, acquired hyperpigmentation is psychosocially and cosmetically important [21]. In the development of skin care drugs, substantial effort has been expended to find natural substances.
This study demonstrated that a new phenolic glucoside, origanoside (1) was isolated from O. vulgare, is much safer and less toxic than both arbutin and l-ascorbic acid at concentrations of 0–100 μg/ml in B16 and Hs68 cells. The cellular tyrosinase and MBTH assay results indicate that the mechanism by which origanoside (1) inhibits melanin synthesis involves the decline in cellular DOPA oxidase activity, rather than direct inhibition of tyrosinase activity. This phenomenon is associated with the
The authors would like to thank the National Science Council of the Republic of China, Taiwan, for financially supporting this research under Contract Nos. NSC 95-2622-B-041-004-CC3 and 97-2320-B-041-002-MY3.
2012, Biochimica Et Biophysica Acta General Subjects
The solubility of apigenin was 100 mM in DMSO. Cells (1 × 104 cells/well) were seeded in 100 μl of 96-well plates and treated with serial concentrations of apigenin, 5-Fu, cisplatin, 5-Fu plus apigenin, and cisplatin plus apigenin for 72 h. Cell viability was determined by using the 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide MTT assay as reported [20]. Absorbance values were expressed as a percentage of vehicle controls (0.1% DMSO), and agents' concentrations resulting in cell growth inhibition of 20% (IC20), 50% (IC50), and 80% (IC80) were calculated.
Crown copyright © 2010 Published by Elsevier Ireland Ltd. All rights reserved.
