72 JOURNAL OF COSMETIC SCIENCE as humectants they attract water from the deeper parts of skin and help keep the water bound in the SC. The humectant mechanism of aloe vera improves skin hydration. These factors make aloe vera an ideal ingredient in cosmetic and dermatological products. A study by Vaughn et al. (36) stated that argan oil was found to have good emollient properties and was effective in reducing dryness of skin thus, it helped to enhance the skin condition. Almond oil contains highly active natural humectants and emollients, which possess excellent moisturizing abilities, to prevent the skin from drying out, thus avoiding peeling or chapping. Almond oil has properties that nourish, sooth, protect, and calm the skin by helping the epidermis maintain optimum moisture levels (37–39). Jin et al. (40) evaluated the nutritional composition of Actinidia arguta (kiwi berry), reporting the presence of palmitic acid (a saturated fatty acid) and α-linoleic acid (an unsaturated fatty acid). Fatty acids—such as lauric acid, linoleic acid, palmitic acid, stearic acid, linolenic acid, myristic acid, oleic acid, and isostearic acid—are known as skin penetration enhancers in topical and transdermal formulations (41). Linoleic and α-linoleic acids have influence on the skin physiology and can be oxidized to eicosanoids, which are extremely important compounds in cell signaling (42). Similarly, linoleic acid is described as a topical treatment for skin inflammation (43). Fluhr et al. (44) applied free fatty acids—such as palmitic acid, stearic acid, and linoleic acid in murine skin surfaces—concluding that they play an important role in acidification, integrity, and cohesion of the SC. In addition, topical application of polyunsaturated fatty acid was shown to induce the hyperproliferation in guinea pig skin (45). Furthermore, fatty acids are easily incorporated in cell membrane lipids, improving the epidermis lipid barrier and softening the SC (26). Barcelos et al. (46) administered daily omega-3 fish oils (FOs) to rats and observed the changes in dermal responses to skin irritation after 30, 60, and 90 days of supplementation. After 60 days of supplementation, both irritation and TEWL were significantly reduced in response to acetone exposure. After 90 days, TEWL had gone down by 50% compared with the control group without FO. Cutaneous hydration significantly increased by 30% after 60 days of FO treatment, which was maintained after 90 days compared with the control group. This supports previous claims that dietary fatty acids are transported to the SC (47,48) and are able to improve cutaneous health through oral administration. MARINE SOURCES IN COSMETIC FORMULATIONS AND SKIN HYDRATION The expanding market and increasing demand for skin-care products and continual studies on new ingredients in cosmetic formulations have led to a revolution in cosmetic products based on marine constituents (49). According to a study by Silvipriya et al., marine sources were found to be the safest sources of collagen. Collagen is the major structural protein constituting the extracellular matrix of connective tissues and is widely used in various industries such as medical tissue regeneration (50), pharmaceuticals, food, and cosmetics. Collagen is biocompatible and biodegradable, which enables superior cell accommodation with a relatively low immunogenicity compared with other biomaterials (51). Hydrolyzed collagens, or small-molecular-weight peptides, have been found to penetrate deep layers of the skin easily compared with high-molecular weight native collagens. They play an important role in fibroblast growth (52), collagen expression (53), and strong collagen fiber formation in the epidermis (54). In addition, they are important molecular components in improving the functionality of the skin layer by increasing the water content of the SC (55).

73 NATURAL ACTIVE INGREDIENTS AND SKIN HYDRATION Therefore, they are widely used in cosmetic applications to maintain skin homeostasis and to restore disrupted skin layers (56). Seong-Beom Han et al. studied Asterina pectinifera, a marine species of starfish found mainly in Korea, eastern Russia, Japan, and China. Collagen peptides were isolated from A pectinifera starfish with a lower molecular weight. These were then encapsulated into elastic liposomes with high efficiency to overcome the low absorption rate of collagen peptides into the skin. In conclusion, they demonstrated this combination to be superior as a cosmetic ingredient by measuring the reduction of matrix metalloproteinase expression in photoaged cells (57). Collagens are found in cosmetic applications acting as moisturizers and natural humectants with anti-aging properties (58). Most marine organisms contain active ingredients such as polysaccharides, fatty acids, and collagens that possess excellent moisturizing properties for the skin (59). In a study by Li et al. (60), collagen extracted from sea cucumber contained a significant composition of moisture content. Sea cucumber collagen shows strong moisture absorption and high moisture retention ability, which determined the moisturizing properties for the skin. The author compared this collagen with those from the skins of tilapia and pigs. The three collagens that were extracted exhibited better moisture- retention and moisture-absorption capacity than glycerol. This showed that the collagen molecules were rich in hydrophilic groups, which have potential applications in cosmetic formulations. Another study suggested that the moisture absorption and retention potential of collagen in sea cucumber extract was excellent compared with glycerol. Therefore, the extracted collagen could be utilized as a moisturizer in the cosmetic industry (15). Studies by Wang et al. (3) concluded that extracts from algae or other marine organisms can be used for skin moisturization, as they are promising substances that can boost collagen synthesis, helping to promoting skin tissue, which eventually helps in reducing wrinkles. Another study by Brunt and Burgess (61) found that collagen extracted from jellyfish had a notable moisturizing effect on skin. Swatschek et al. (62) reported the successful extraction of collagen from the marine sponge Chondrosia reniformis. A total of a 30% yield of freeze- dried collagen was obtained, and two cosmetic formulae were trialed on human skin. They found no significant difference in skin hydration between the sponge collagen treatments and the existing collagen product control however, there was a significant increase in skin lipid content of 140–180 lg cm−2 1 hour after treatment. A review by Uppala (63) stated that hydras can be used as a moisturizer, as it contains vitamin C, which helps to increase collagen production in the dermis, and vitamin E, which helps in enhancing the skin’s barrier properties. Hydras are also rich in olive oil, which has emollient properties. Shark fish liver oil is highly rich in fatty acids and squalene, which have moisturizing properties. The application of seaweed as a cosmetic ingredient was also found to be effective as a moisturizing agent. This was supported by a study from Wang et al. (3), which showed that polysaccharides extracted from brown algae absorbed and retained more moisture than those from four other species of algae. The abundance of polysaccharides in red algae species also have hydrating, therapeutic, and moisturizing effects (15). An extract from green algae was also found to be efficient in regulating water distribution in the skin, thus protecting the skin from becoming dry, particularly in arid environments (15). In addition to producing HA, exopolysaccharides (EPS) are also produced by microalgae and can be considered significant moisturizing products. EPS involve several significant high molecular weight biopolymers. Microalgae produce these biopolymers and secrete them to a medium size during their cultivation (64,65). Glucuronic acid is one of the