69 NATURAL ACTIVE INGREDIENTS AND SKIN HYDRATION HYALURONIC ACID IN COSMETIC FORMULATIONS AND SKIN HYDRATION Hyaluronic acid (HA) is an anionic, nonsulfated glycosaminoglycan scattered widely throughout epithelial, connective, and neutral tissues (14). HA can be found in plants and animals (15). HA is also a main component of the skin, where it is involved in tissue repair. HA is abundant in the extracellular matrices of skin. Cosmetic formulations containing HA have been found to moisturize the skin (15). HA is the active ingredient for many moisturizing, protecting, and anti-aging products (16). It was reported that Estée Lauder™ (The Estée Lauder Companies Inc., New York) was the first to apply animal HA in cosmetics. The effectiveness of using HA in cosmetics is further supported in the Journal of Drugs in Dermatology, which indicates that formulations containing 0.1% HA resulted in significant improvement of skin hydration and elasticity (17). A study by Olejnik et al. (16) stated that HA acts by forming a film on the surface of the epidermis (the SC), and it prevents TEWL. In cosmetic formulations, HA also works as a potent humectant, or a moisturizing agent. This is a category of skin-care ingredients that attracts water to the skin, increases the water content of the SC, and keeps the cosmetic formulation from becoming dry (11). C asiatica extract also was found to inhibit the enzymatic action of hyaluronidase it demonstrated potent inhibitory effects for elastase and hyaluronidase (12). A study by Milani and Sparavigna (12) showed that the inhibition activity for Table II Animal- and Marine-Based Sources Used in Cosmetics Sources Bioactive ingredients Therapeutic value/s Reference Snail secretion Hyaluronic acid Moisturizing Skin rejuvenating (17) (16) Algae Marine polysaccharides Vitamins Alginates Unsaturated fatty acids Moisturizing Antioxidant Restore damaged skin (3) (63) (49) Microalgae Hyaluronic acid Exopolysachharides Biopolymers (65) (19) (64) (67) Shark fish (oil and cartilage) Fatty acids Squalene Squalene Collagen Peptides Moisturizing Anti-inflammatory Antioxidant (74) (68) (69) (73) (63) Hydras Vitamin C Vitamin E Antioxidant Emollient (63) Fish (scales/bone/ cartilage/muscle) Collagen Peptides Antioxidant Chondroitin Sulphate Skin regeneration Improve skin barriers Antioxidant (75) (102) (106) (76) (77) Sea cucumber Jellyfish Cuttlefish Sea urchin Collagen Moisturizing Rebuild damaged skin Improve skin barriers (107) (58) (103) (104) Starfish Collagen Moisturizing Antioxidant Anti-aging (57)

70 JOURNAL OF COSMETIC SCIENCE hyaluronidase can prolong the hydrating action of HA and increase the long-lasting effects of moisturizing the skin. Several studies have concluded that microalgae have high antioxidant activity and that microalgal extracts or bioactive compounds derived from microalgae have significant potential to be accessional new biobased products like cosmetics, pharmaceuticals, nutraceuticals, bioplastics, and biopolymers (18–20). It has been shown that the level of skin moisturization is related to the frequency of washing with tensioactive supplies or defensive potential from any irritant agent. HA has been used in cosmetic products for moisturizing the skin in accordance with these two mentioned mechanisms. Hydroxy acids can be produced by plants, but there are restrictions of HA production from plants. Therefore, interest in algal polysaccharides has increased. Studies have shown that Pediastrum duplex extract contains significant quantities of polysaccharides and can be evaluated for skin moisturization and protection (20). HA can be classified as alpha-HA, beta-HA, and salicylic acid. Alpha-HA is also known as 2-hydroxy acid because of its hydroxyl group attached to the carbon atom next to the carboxyl group. The most popular 2-hydroxy acids used in cosmetics are glycolic acid and lactic acid. In addition, beta-HA is named 3-hydroxy acid because of its hydroxyl group attached to the carbon atom that is situated in the second place when counted starting from the carboxyl group. The most well-known 3-hydroxy acid used in cosmetic formulations is citric acid (21). Other microalgae species that have been reported to have moisturizing properties include Anabaena variabilis, Anacystis nidulans, Chlorella pyrenoidosa, Chlamydomonas reinhardtii, Cyanidium caldarium, Phormidium foveolarum, and Oscillatoria spp. They produce 2-hydroxy acids and 3-hydroxy acids, and their extracts can serve as promising candidates as cosmetic ingredients (22,23). VITAMINS IN COSMETIC FORMULATIONS AND MOISTURIZING PROPERTIES Palm oil is one of the primary sources of vitamin E that has abundant quantities of tocopherols and tocotrienols. Because of its abundant amounts of tocotrienols and tocopherols, palm oil has shown great capability as a skin penetration enhancer because of intercalation within the lipid bilayer region of the SC (17). This has resulted in modification of the membrane, impacting permeability. Shea butter is known for its high content of vitamin A, which is effective in soothing the skin and promoting healing. Shea butter also contains vitamin F, which has the ability to act as a rejuvenator for soothing and healing rough and chapped skin (24). Shea butter is rich in vitamins A and E, which makes it a good moisturizer for the skin and hair (9). Mango butter and cocoa butter contain high amounts of vitamin E it exhibits the same properties as shea butter in terms of effectiveness in healing and soothing the skin. Vitamin E from mango butter helps with water retention in the skin and can significantly reduce the roughness of skin upon multiple applications. In cosmetics, cucumber has exhibited an excellent ability for skin soothing and cooling, and cucumber extract is sometimes used as an antioxidant. Cucumber extracts are rich in vitamins, especially vitamins A and C, which display several cosmetic benefits for the skin (25). Vitamin C is known to increase collagen fibers in the dermis. Increase in collagen fibers helps improve the hydration state of the skin (25). In studies by Naveed A et al., the studies