## 4 Natural Antioxidants and Their Role in Cosmetics
### Vitamins
#### 4.1.2 Vitamin E (\(\alpha\)-Tocopherol)  
Vitamin E (Figure 2), primarily in the form of \(\alpha\)-tocopherol, refers to a group of fat-soluble organic compounds, including tocopherols (T) and tocotrienols (T3). These compounds share a common structural feature: a bicyclic 6-hydroxychromane ring system attached to a side chain composed of three isoprene units. The parent compound of the vitamin E family is tool. \(\alpha\)-Tocopherol functions as an effective antioxidant by neutralizing superoxide free radicals (O\({}_{2}\bullet^{-}\)), converting them into hydroperoxides (ROOH). In this reaction, the tocopherol molecule is oxidized, forming a tocopheryl radical (T\(\bullet\)). This radical can be regenerated back to its active form through reduction by other antioxidants, such as ascorbate or glutathione (GSH) [33].  
Vitamin E is a potent antioxidant that plays a crucial role in mitigating oxidative damage, thereby contributing to the prevention of age-related processes. Its primary mechanism of action involves neutralizing free radicals within the body. Despite its significant biological activity, vitamin E is only partially absorbed from dietary sources and is either poorly absorbed or rapidly excreted. Malabsorption, inadequate dietary intake, or the consumption of substances such as caffeine or nicotine may impair its absorption, leading to hypovitaminosis or deficiency. A vitamin E deficiency can manifest as a range of symptoms, including reduced immune function, fatigue, muscle and joint pain, and vascular fragility [34].  
Additionally, vitamin E has a protective role in cellular mitochondrial function, specifically by reducing mitochondrial superoxide levels and preventing \"electron leakage\" during oxidative phosphorylation. \(\alpha\)-Tocopherol is particularly important for the maintenance of brain health [35].  
Vitamin E, often referred to as the \"elixir of youth\", plays a significant role in dermatological care due to its potent antioxidant properties. Tocopherols, particularly \(\alpha\)-tocopherol, are commonly incorporated into cosmetic formulations that contain UV filters. These compounds protect epidermal lipids, collagen, and elastin fibers from oxidative damage, thereby preserving skin elasticity and structural integrity. Tocopherols prevent lipid peroxidation, which is crucial for maintaining the function and resilience of the skin barrier. Additionally, derivatives such as linoleic and tocopherol acetate are effectively integrated into the epidermal lipid matrix, providing sustained moisturizing effects and contributing to enhanced photoproduction, thereby supporting the skin's defense against UV-induced oxidative stress [31].  
Tocopherols absorb light in the mid-wavelength ultraviolet (UVB) range. Most tocopherols function in cosmetics as antioxidants or skin-conditioning agents. In contrast, tocotrienols do not function as antioxidants in cosmetics but instead serve as light stabilizers, oral care agents, or skin-conditioning agents [32].  
The concentration of tocopherol in leave-on products has increased from 2% to 5.4%, while tocotrienols have a maximum reported leave-on concentration of 0.12% [32].  
Tocopherols are commercially produced from vegetable oils, while locotrienols can be isolated from various plant sources, including Vitis vinifera and Avena sativa. The most efficient extraction method is Soxhlet extraction using hexane as a solvent. Alternatively, locotrienols can be synthesized through various synthetic pathways, predominantly involving multistep processes that introduce an alkenyl group to the chromatal core [32].