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

71 NATURAL ACTIVE INGREDIENTS AND SKIN HYDRATION found that TEWL values increased after the use of formulation with cucumber extracts. They caused disruption of the skin, thus increasing the rate of water evaporation from the SC and leading to reduction of skin moisture. However, these effects were statistically insignificant (p 0.05) (25). In addition, studies of C asiatica have shown effectiveness in skin hydration that has resulted from improvement in elasticity and firmness of the skin (14). A total of 20 healthy women, with a mean age of 40 years old, were enrolled in an intrasubject (right versus left), randomized, assessor-blinded, controlled, 1-day trial. The primary end points were the skin hydration and TEWL, evaluated at the volar surface of the forearm and in standardized conditions (temperature- and humidity-controlled room: 23°C and 30% of humidity). The author found that a single application of the fluid containing C asiatica extract, HA, and glycerin, significantly improved skin hydration for up to 24 hours while improving skin barrier function. In addition, a study by Vaughn et al. (15) stated that almond oil is rich in vitamin E and has been shown to have occlusive properties, thus improving skin hydration. The author conducted a multicenter randomized, clinical study of the effects of natural oils on xerosis and skin barrier properties. The study outcome showed that almond oil, jojoba oil, and coconut oil significantly increased hydration after 2 weeks and are as effective as white petrolatum as daily moisturizers for xerosis. The participants also preferred natural oils over white petrolatum, which indicates that these moisturizer options may improve patient compliance. EMOLLIENTS AND HUMECTANTS IN COSMETIC FORMULATIONS ON SKIN CONDITION The emollient action of some ingredients is a consequence of skin softening, smoothing, and moisturizing capacity (26). These compounds have the ability to maintain almost 25% of the water in corneocytes and protect the skin barrier (27,28). The main functions of emollients are to protect and help maintain skin sebum and lipid levels (28). The topical application of these compounds improves skin hydration and prevents the appearance of dry skin (29). In physiological terms, emollients create a thin layer on the skin’s surface that is able to prevent water evaporation (28). Compounds such as ceramide, cholesterol, and free fatty acid may be included in cosmetic and medical skin-care formulations to improve barrier homeostasis and, consequently, hydration and sebum levels (30). Palm oil is a natural oil that has emollient properties and does not create any irritation effects on the skin (31). In addition, palm oil has moisturizing properties by reducing the level of dryness and roughness of skin. It works by strengthening the water-binding capacity of the SC (11). According to Fluhr et al., palm oil works by forming an occlusive film that inhibits water evaporation from beneath the skin. Palm oil contains tocotrienols, with the highest levels among all vegetable oils, and tocopherols (32,33) Shea butter also exhibits emollient properties, protecting the skin by stimulating the production of structural proteins by specialized skin cells (10). A study by Nandal et al. (34) found that aloe vera is useful for maintaining skin moisture and helping to sooth the skin to prevent dryness due to harsh weather. Aloe vera can also be used as a moisturizer for oily skin. It acts by improving the skin’s ability to hydrate itself, helps in removal of dead keratin cells, and has an effective penetrating ability that aids in transporting healthy materials through the skin barrier (34). Development of aloe sugar with a combination of selected essential oils makes it an excellent moisturizing agent that helps to smoothen the skin. A study by Sajjad et al. (35) stated that aloe vera extracts act