## 4 Natural Antioxidants and Their Role in Cosmetics
### Vitamins
#### 4.1.4 Vitamin B5 (Pantothenic Acid)  
Pantothenic acid (Figure 2), also known as vitamin B5, is a water-soluble vitamin and a critical component of coenzyme A (CoA), which plays an essential role in the metabolic pathways of proteins, carbohydrates, and lipids. It is considered the most thermolabile of the B vitamins, exhibiting high sensitivity to heat and degrading at elevated temperatures. Approximately 85% of dietary pantothenic acid exists as CoA or phosphopantetheine, which are subsequently converted to pantothenic acid in the intestines by digestive enzymes [48]. This vitamin plays a pivotal role in maintaining optimal skin function and health. It is involved in the synthesis of acetylcholinesterase, a neurotransmitter crucial for cellular communication, and supports wound healing by enhancing cellular regeneration. Pantothenic acid, the alcohol derivative of pantothenic acid, also exerts anti-inflammatory effects on mucosal membranes, facilitates proper growth and development, and possesses antioxidant properties that help mitigate oxidative stress. These attributes make it essential for maintaining overall skin integrity and promoting the repair of damaged tissues [48; 49]. Vitamin B5 plays a critical role in regulating sebum production, contributing to its softening, reparative, moisturizing, and anti-inflammatory properties. These characteristics make it a key ingredient in dermatological and cosmetic formulations, including sun care, after-sun care, intimate hygiene products, and treatments for post-epilation and post-shaving irritation. Additionally, it is frequently incorporated into products for sensitive or atopic skin, including baby skincare formulations [31]. In hair care, pantothenic acid is indispensable due to its active involvement in protein and lipid synthesis, which are essential for healthy hair growth and maintenance. It has been shown to stimulate hair growth, influence pigmentation, and enhance hair strength and resilience. Furthermore, it is commonly used in hair care products designed to prevent split ends, improve elasticity, and impart shine and vitality. Pantothenic acid also enhances hair manageability, facilitating detangling and giving the appearance of thicker, fuller hair. These effects are primarily attributed to its ability to penetrate the hair shaft and replenish essential nutrients needed for hair structure and function [50]. Panthenol has long been utilized in hair care formulations due to its humectant properties. By enhancing water retention, it increases hydration levels within the hair shaft,thereby improving elasticity and overall hair resilience. In cosmetic applications, panthenol serves as a highly effective moisturizing agent, capable of drawing water into the stratum corneum. This action not only enhances skin hydration but also promotes a smoother and softer texture [51]. Notably, five derivatives of pantothenic acid are commonly used in cosmetic formulations: panthenol, pantothenic acid, panthenyl ethyl ether, panthenyl ethyl ether acetate, panthenyl triacetate, calcium pantothenate, and sodium pantothenate. The highest maximum use concentrations in leave-on products are reported for panthenol (5.3% in body and hand products), panthenyl ethyl ether (2% in foundation), and panthenyl triacetate (2% in lipstick and other makeup products) [32]. In recent years, there has been growing interest in biotechnological methods for producing pantothenic acid and its derivatives. Microbial fermentation using specific bacterial strains has been explored as a sustainable alternative, offering advantages such as renewable resources and reduced environmental impact compared to traditional chemical synthesis [52]. Pantothenic acid can be synthesized via the saponification of sodium \(\beta\)-alanine with sodium hydroxide, followed by reaction with L-pantolactone [32]. Natural sources of pantothenic acid include eggs, meat, vegetables, and whole grains.