Vitamins C and E are considered essential vitamins for the skin. Vitamin C, also called L-ascorbic acid, is an antioxidant, which means it can reverse oxidation in liquids, and thereby help with the condition known as oxidative stress.
Vitamin E is also an antioxidant, however, because vitamin C is water soluble and vitamin E is oil soluble, it has been impossible to prepare a cream or a lotion that contains both vitamins C and E together. EPC (Senju) (Fig. 1) which contains vitamins C and E linked with phosphoric acid, was developed to utilise both vitamins for skin care. Its INCI name is: Potassium Ascorbyl Tocopheryl Phosphate. EPC is water-soluble and stable in water. It is an excellent raw material for skin care products having multiple functions derived from the combination of vitamins C and E, including scavenging of oxygen radicals generated by exposure to ultraviolet rays, moisturising effects, normalisation of roughened skin turnover and inhibition of the growth of Propionibacterium acnes (the bacteria that causes acne). Furthermore, this material reduces the incidence of dandruff and can be used as an active ingredient for hair tonics (quasipharmaceutical products in Japan). This article aims to illustrate the efficacy of this ingredient in a range of areas that will be of interest to formulators of both hair and skin products.
Strong ROS scavenging efficacy1
For this test, the following materials were used: EPC (Potassium Ascorbyl Tocopheryl Phosphate), Asc-2-P.Na (Sodium Ascorbyl 2-Phosphate), Asc-2-P.Mg (Magnesium Ascorbyl 2-Phosphate), Asc-2-G (Ascorbic Acid 2-Glucoside), CME (Ascorbyl Tocopheryl Maleate). Results were obtained using Chemiluminescent method (NightOWL Molecular Light Imager, LB 981, EG&G, Berthold, Germany) or ESR Strapping method, which detected ROS scavenging activity. When human skin is exposed to ultraviolet rays, oxygen radicals are always generated, causing spot and wrinkle formation on the skin. EPC (now referred to as ‘the active hybrid’)is capable of powerfully scavenging oxygen radicals such as singlet oxygen (1O2), superoxide anion (•O2–) and lipid peroxide (t-BuOO•, a cause of acne). The active hybrid shows potent scavenging activity against all oxygen radicals as compared to other vitamin C derivatives (Table 1).
Inhibitory effects on acne2
Test samples were dissolved in agar medium, placed as suspensions (cell count 106 P. acnes) over agar medium and tested for MIC. The samples for this test were: the active hybrid, ascorbic acid, and tocopherol. The active hybrid inhibited growth of P. acnes (cell count 106 mL) at the concentration of 0.3125 mg/mL. In contrast, vitamin E and vitamin C did not inhibit growth even at concentrations of 5 mg/mL (Table 2). The mechanism of acne formation is acceleration of sebaceous secretion and skin lipase activation, etc. P. acnes needs sebaceous secretion in order to grow and secretes lipase. The active hybrid appears to inhibit the acceleration of sebaceous secretion and lipase activity.
Normalisation of skin turnover time3
Prepared human roughened abdominal region (n=3). 0.2% the active hybrid was applied and turnover time was measured. The turnover time of roughened defatted skin treated with acetone/ether was decreased. When 0.2% the active hybrid was applied to roughened skin, the turnover time tended to exhibit normalisation significantly (Fig. 2).
Effect on UV-induced damage4
Normal human epidermis keratinocytes were cultured. After UV irradiation of 310 nm, 660 m/Jcm2, 100 mM EPC was added. Cell viability was determined after 48 hours of irradiation. The cell viability decreased to 30%, the active hybrid recovered the viability to control level (Fig. 3).
Studied double blind clinical study of hair tonic containing 0.2% EPC (n=72) and noactive agent containing placebo (n=69). Hair tonic was applied 2 times a day for 4 months and the amount of dandruff was measured every month. After 2, 3 and 4 months, the amount of dandruff of the active hybrid hair tonic was significantly decreased compared to placebo (Fig. 4). Mechanism of action on dandruff: when the scalp is dry, dandruff increases. Free fatty acid and peroxide lipids accelerate the turnover time of scalp. The active hybrid has mechanisms of moisturising, and also an inhibitory effect against the formation of fatty acid, and improvement of turnover of roughened scalp. So, the active hybrid has efficacy to decrease dandruff.
Stability in solution5
0.2% the active hybrid was formulated in a water-based lotion and adjusted to pH 6.0. Surface active agent EDTA-2Na (0.05%, 0.1%, 0.15%, 0.2%, 0.3%) was added to this formulation as a chelate agent. The active hybrid solution is stable usually at pH 5.5-6.5, so the lotion (pH 6.0) was stable. And at the lowest level of 0.05% EDTA-2Na (Table 3, Formulation 1), EPC lotion was the most stable. So, we can formulate the active hybrid with a minimum amount of EDTA-2Na for hair lotions and skin care products.
To conclude, EPC has shown different profiles among vitamin C derivatives. EPC has efficacy for not only powerful scavenging oxygen radicals to reduce the effect of UV exposure in skin, but also has for inhibiting the growth of the bacteria that causes acne and reducing dandruff. This ingredient is also stable in water, enabling easy inclusion into a variety of products. In addition to this, EPC has no irritation and sensitisation, so it is very useful for skin care and hair care products.
1 Presented at 23rd Annual Meeting of Aesthetic Dermatology (2005). 2 Matsuura S et al. JSCCJ 1997; 31 (4): 439-46. 3 Sakamoto et al. JSCCJ 1993; 27 (3): 394-408. 4 Aoki et al. The Japanese Pharmacological Society (2010). 5 Internal document of Iwase Cosfa Co. Ltd. (2011).