Rich in active ingredients such as polysaccharides, terpenoids and proteins, Ganoderma extracts, including Ganoderma lucidum (G. lucidum or Lingzhi), are listed as cosmetic ingredients in China.
Among them, functional proteins are popular for its stable composition and well-defined structure. Fungal immunomodulatory proteins (FIP-glu) are a subclass of active ingredients isolated from Ganoderma, although its content in natural mushrooms is low.
Nevertheless, the advancement of biotechnology has improved production of FIP-glu, which is said to have “great potential for application”.
To evaluate the application potential of a G. lucidum-derived recombinant fungal immunomodulatory protein (rFIP-glu), researchers from Shanghai Jiao Tong University in China conducted a study to assess its antioxidant efficacy, melanogenesis-inhibitory effect, and safe usage as an ingredient in whitening cosmetics.
Human epidermal keratinocytes (HaCaT) cells were employed in a cytotoxicity assay to determine the safety of rFIP-glu in a cosmetic formulation.
Results showed that rFIP-glu had a significant elevating effect on the cell viability of HaCaT cells within the range of 6 to 48μg/mL in a dose-dependent manner.
“The cell viability of HaCaT cells reached 124.3% at 48μg/mL. This suggests that rFIP-glu at 6 to 48μg/mL has no cytotoxicity to human HaCaT cells. Although rFIP-glu exhibited a certain inhibitory effect on the growth of B16 cells, cell viability maintained at about 80% under 48 μg/mL, which met the basic requirement for cosmetic safety evaluation,” the authors wrote.
DPPH free radical scavenging is a recognised mechanism for measuring antioxidant activity of plant extracts.
It was found that DPPH radical scavenging capacity reached 68.6% at 4mg/mL and 84.5% at 6mg/mL of rFIP-glu application, which indicated that rFIP-glu had strong antioxidant activity.
Significant whitening efficacy
Tyrosinase (TYR) is a key enzyme in the process of melanogenesis and TYR activity strongly affects pigmentation — the higher TYR activity is, the bigger amount of melanogenesis it will cause.
Currently, the most commercially available skin whitening agents are TYR inhibitors.
For example, arbutin is a polyphenolic compound derived from plant metabolites that is commonly applied in products for whitening because of its ability to prevent the accumulation of melanin in the skin.
“Arbutin, kojic acid and vitamin C are known for de-pigmentation, but the demand for alternative active ingredients from natural sources with high efficacy and less toxicity is still strong. G. lucidum has been widely documented and used in traditional Chinese medicine for its various pharmaceutical functions,” said the authors.
To investigate the effect of rFIP-glu on melanin synthesis, B16 cells were treated with rFIP-glu (0, 100, 500, 1000 μg/mL). Arbutin at 1000μg/mL served as a control.
Results showed that rFIP-glu had inhibitory effect on melanogenesis at 500μg/mL and 1000μg/mL, which was almost equal to that of arbutin. Notably, rFIP-glu at 500μg/mL reduced melanin-synthesis by 16.8%.
In addition, regulation of melanogenesis-associated gene expression, such as microphthalmia-associated transcription factor (MITF), is essential in treating skin hyperpigmentation.
Previous studies have indicated that MITF plays an important role in modulating the gene expression of melanogenic enzymes, including TYR, tyrosinase-related protein 1 (TYRP-1) and tyrosinase-related protein 2 (TYRP-2).
In this study, a mechanism analysis found that rFIP-glu inhibited TYR activity by down-regulating the mRNA expression of TYR and TYRP-1, and up-regulating the mRNA expression of MITF, which further impacted melanin synthesis in B16 cells.
“Our study provides valuable insights into the suitability of rFIP-glu as a bioactive ingredient to repair skin damage and promote skin whitening,” the authors concluded.
“Evaluating the Application Potential of a Recombinant Ganoderma Protein as Bioactive Ingredients in Cosmetics”
Authors: Zhi-Jian Guo, et al