Alpha‐tocopherol (AT) is the vitamin E homologue with the highest in vivo biological activity. AT protects against the carcinogenic and mutagenic activity of ionizing radiation and chemical agents, and possibly against UV‐induced cutaneous damage. For stability consideration, alpha‐tocopherol is usually used as its prodrug ester, alpha‐tocopherol acetate (ATA), which once absorbed into the skin is hydrolyzed to alpha‐tocopherol, the active form. The objective of this research was to characterize in vitro the permeation properties of ATA from various solutions and gel formulations. Permeation studies were conducted using modified Franz diffusion cells and human cadaver skin as the membrane. Specifically, 5% (w/w) alpha‐tocopherol acetate was formulated in the following vehicles: ethanol, isopropyl myristate, light mineral oil, 1% Klucel_gel in ethanol, and 3% Klucel_gel in ethanol (w/w). The receiver temperature was 37°C. Samples from the receiver were collected at 2, 4, 6, 8, 12, 24, 30, 36, and 48 h and analyzed by HPLC for concentrations of alpha‐tocopherol acetate and alpha‐tocopherol. The permeabilities of ATA through human cadaver skin were 1.0 × 10–4, 1.1 × 10–2, 1.4 × 10–4, 2.1 × 10–4, and 4.7 × 10–4 cm/h for the ethanol solution, isopropyl myristate solution, light mineral oil solution, 1% Klucel_gel, and 3% Klucel gel, respectively. The results show that the formulation had relatively minor effects on the permeability coefficients of ATA through cadaver skin in all cases except for the isopropyl myristate solution.
Introduction The exposure of unprotected skin to solar ultraviolet UV radiation, especially UVA and UVB rays, causes skin inflammation, photoaging 1 , and erythema 2. In addition, it may cause DNA abnormality in human skin cells, which directly leads to skin cancer 3. The scientific evidence of the harmful effects of UV radiation provides a compelling reason for applying sun protection products to protect the skin from both UVA and UVB radiation. Consequently, broad-spectrum sun protection products refer to products that have a critical wavelength value of at least 370 nm, which leads to a breadth of protection from both UVB and UVA radiation. The UV absorbers are properly combined to achieve broad protection activity for commercial products. Titanium dioxide and zinc oxide are preferable UVA absorbers because of their efficiency and low irritation. They primarily absorb UV radiation and to a lesser extent act by reflection and scattering the radiation 4. However, these inorganic mineral UV absorbers, which function well at reflecting light, tend to be opaque and white colored on the skin, which is unfavorable for cosmetics unless nanosized
Alpha‐tocopherol (AT) is the vitamin E homologue with the highest in vivo biological activity. Alpha‐tocopherol protects against the carcinogenic and mutagenic activity of ionizing radiation and chemical agents, and possibly against a UV‐induced cutaneous damage. For stability consideration, AT is usually used as its prodrug ester, alpha‐tocopherol acetate (ATA), which once absorbed into the skin is hydrolyzed to AT, the active form. The objective of this research was to characterize in vitro the permeation properties of ATA from various solutions and gel formulations. Permeation studies were conducted using modified Franz diffusion cells and human cadaver skin as the membrane. Specifically, 5% (w/w) ATA was formulated in the following vehicles: ethanol, isopropyl myristate, light mineral oil, 1% Klucel_ gel in ethanol, and 3% Klucel_ gel in ethanol (w/w). The receiver temperature was 37 °C. Samples from the receiver were collected at 2, 4, 6, 8, 12, 24, 30, 36, and 48 h and analysed by HPLC for concentrations of ATA and AT. The permeabilities of ATA through human cadaver skin were 1.0 × 10 – 4, 1.1 × 10 – 2, 1.4 × 10 – 4, 2.1 × 10 – 4, and 4.7 × 10 – 4 cm h–1 for the ethanol solution, isopropyl myristate solution, light mineral oil solution, 1% Klucel_ gel, and 3% Klucel_ gel, respectively. The results show that the formulation had relatively minor effects on the permeability coefficients of ATA through cadaver skin in all cases except for the isopropyl myristate solution.
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