Evaluation of Depigmenting Activity by 8-Hydroxydaidzein in Mouse B16 Melanoma Cells and Human Volunteers

Te-Sheng Chang,Ching-Gong Lin,Mon-Han Wu,Sorgan Tai

doi:10.3390/ijms10104257

Abstract

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.

Highlights

Mammalian skin color is mainly determined by the content of the pigment melanin, which is produced in unique organelles of the neurocrest-derived melanocyte in skin [1]
Before the in vivo skin-whitening assay was conducted, mouse B16 melanoma cells were utilized as a cellular assay system to evaluate the depigmenting activity of 8-OHDe in the cell cultures
8-OHDe, which exhibited more than a 10-fold stronger inhibitory effects on melanin production in B16 cells than the standard tyrosinase inhibitor, kojic acid, in view of the

Summary

Introduction

Mammalian skin color is mainly determined by the content of the pigment melanin, which is produced in unique organelles of the neurocrest-derived melanocyte in skin [1]. Because the inhibitory mechanism of the suicide substrates is completely different from those of reversible inhibitors and displays irreversible and partition ratio-dependent inhibition, it has been proposed that the suicide substrates have superior performance in skin-whitening activity than those of usual tyrosinase inhibitors [2]. Potent suicide substrates have rarely been discovered, and no suicide substrate has been confirmed in depigmenting activity either in cell cultures or in human skin. 8-OHDe 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, and the depigmenting activities of the compound in both assay systems were confirmed

Results and Discussion

In Vivo Evaluation of Skin-Whitening Activity of 8-OHDe in Human Volunteers

Experimental Section

Cell Cultures

Determination of Melanin Content

Measurements of Tyrosinase Activity

Instruments for in Vivo Measurements

In Vivo Measurements

Conclusions