Green tea extract derived from the leaves of Camellia sinensis L. (CS), is a representative beverage with antioxidant, anti-cancer, and anti-viral properties. CS extract is also used in cosmetics. Colloidal gold is generally a sol or colloidal suspension of gold nanoparticles in water. Colloidal gold green tea (CGCS), cultivated as a fertilizer using this colloidal gold solution, contains gold minerals and possesses anti-inflammatory, analgesic, and anti-tumor properties. However, the skin bioactivity of CGCS has not yet been investigated. In this study, we investigated the effect of the CGCS extract on skin whitening. CGCS extract contained high levels of phenols and flavonoids and displayed 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging activity in a concentration-dependent manner. CGCS extract inhibited melanin synthesis and tyrosinase activity in B16F10 cells more effectively than the CS extract. Moreover, the CGCS extract decreased the expression levels of the melanogenesis-related proteins, tyrosinase, tyrosinase-related proteins (TRPs), and microphthalmia-associated transcription factor (MITF). In conclusion, our study showed that the CGCS extract inhibits the expression of tyrosinase, TRP-1, and TRP-2 via the downregulation of MITF, thereby inhibiting melanin synthesis. Therefore, CGCS can potentially be used as a skin-whitening ingredient in the cosmetic industry.

Although the roots and flowers of P. thunbergiana are known to have various physiologically active effects, studies on the anti-melanin production and anti-photoaging effects of its leaf extracts and cellular mechanisms are still lacking. In this study, we evaluated the possibility of using Pueraria thunbergiana leaves as a natural material for skin whitening and anti-aging-related functional cosmetics. The 30% ethyl alcohol (EtOH) extract from P. thunbergiana leaves was fractionated using n-hexane, ethyl acetate (EtOAc), butanol, and aqueous solution to measure their whitening, and anti-aging effects. The EtOAc fraction contained a high content of phenolic and flavonoids and showed higher 1,1-diphenyl-2-picryhydrazyl (DPPH) and 2,2-azino-bis (3-ethylbenzothiazoline-6-sulfonic acid) diammonium salt (ABTS) radical scavenging activities than the other fractions. It was also confirmed that the EtOAc fraction markedly inhibited α-melanocyte stimulating hormone (α-MSH)-induced melanogenesis in B16F10 melanoma cells. In addition, the EtOAc fraction showed a protective effect against ultraviolet B (UVB) in HaCaT cells and increased the collagen synthesis that was decreased due to UVB exposure. Matrix metalloproteinase-1 (MMP-1) activity and MMP-1 protein expression were reduced in human epidermal keratinocytes (HaCaT) cells. These results indicate that the EtOAc fraction has superior antioxidant activity, anti-melanogenesis, and anti-photoaging effects compared to the other fractions. Therefore, in this study, we confirmed the potential of P. thunbergiana leaf extract as a functional cosmetic ingredient, and it can be used as basic data for the physiological activity of P. thunbergiana leaf extracts.