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Stable Vitamin C for skin lightening
A fair, flawless complexion is without doubt a desirable attribute across many cultures. Especially in Asia, the obsession with white skin has greatly evolved, shifting from beauty to a symbol of social status
Vitamin C serves many functions as a cosmetic ingredient, including skin lightening, promoting collagen synthesis and inhibiting lipid peroxidation. In addition, Vitamin C is reported to protect skin from ultraviolet B damage and also enhance collagen synthesis. Therefore, Vitamin C is widely used in cosmetics as a whitening ingredient, especially in Asia. Due to the instability of Vitamin C, some derivatives are developed as a new whitening ingredient of cosmetics. As a derivative of Vitamin C, ethyl ascorbic acid (trade name Corum 9515), is metabolised the same way as ascorbic acid in the body. It exhibits excellent percutaneous absorption and effectively converts into free vitamin C in the skin, leading to various physiological functions. Corum 9515 is a new type of vitamin C derivative, which is more stable for cosmetic products.
Melanogenesis mechanism After exposure to sunlight, melanin is produced through a process called melanogensis. Melanogenesis is a biological process which is meant to protect human DNA from ultraviolet rays of the sun. Melanin is produced by melanocytes embedded in the skin. The amount of melanin in human skin defines its colour. People in all different countries and climate conditions usually have the same number of melanocytes.
The melanin synthesis pathway is shown in Fig 1. In this pathway, tyrosine is oxidised to dopa which is then converted to dopaquinone, due to the action of tyrosinase. The reaction progress by autoxidation is thought to be accelerated by the enzymes (1). Tyrosinase also accelerates the reaction of monomer aggregation which leads to the production of eumelanin.
Tyrosinase activity inhibition test Corum used mushroom tyrosinase (sigma T3824) and two different substrates, L-DOPA and tyrosine. This test method is convenient and widely used to evaluate the effects of skin whitening. The result from this experiment showed that Corum 9515 was able to inhibit the tyrosinase activity. It also worked on all three steps of tyrosinase activity in melanogenesis.
Radical scavenging activity The scavenging effect on α,α-diphenyl-β- picrylhydrazyl (DPPH) free radical was measured after 1mL Corum 9515 solution (1mg/ml THF) was added to 2mL of 0.4 mM
DPPH in methanol. The mixture was left for 30 minutes at room temperature and the absorbance was measured at 517nm. The result (Table 1) shows that Corum 9515 has a similar effect as Vitamin C in radical scavenging activity.
Table 2.
Promotion of collagen synthesis An activity study on collagen synthesis from human fibroblast culture was carried out by IDEA France. The test subject Corum 9515 presents a substantial effect on collagen synthesis: a 27% stimulation in comparison to the control TGF β1 (as shown in Table 3).
Table 1. Melanin reduction
A whitening activity study with theophylline, a molecule that increases the production of melanin, was carried out by IDEA France. After 12 hours of contact with the product and stimulation with theophylline at 0.5mM, an effective whitening effect was observed at both 15mg/ml and 20mg/ml (as shown in Table 2).
Table 3. Figure 1. Continued over page
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