PLANT-BASED SQUALENE IN COSMETOLOGY 63 quencher of singlet oxygen and prevents the corresponding lipid peroxidation at the hu- man skin surface (19,20). Other studies have shown the effect of squalene on reducing superoxide anion. These results suggest the possible role in alleviating skin irritation (6,21). Topical application of antioxidants has been recently suggested as preventive ther- apy for skin photoaging and UV-induced cancer (20). It has been known that treating the skin with oils offers considerable protection from sunburn because of a strong absorption band in the erythemogenic region (21). Topical application of the cream containing anti- oxidants (vitamin E, CoQ10, squalene) led to a signifi cant increase in the sebum level (22). This could be a signifi cant proof of the unique composition of amaranth oil. Emollient. Amaranth oil has been reported to contain relatively large amount of squalene, which is used as an important ingredient in skin cosmetics and penetrants (13). Squalene as a natural emollient is quickly and effi ciently absorbed deep into the skin, restoring healthy suppleness and fl exibility without leaving an oily residue (6,23). When applied to washed or sun exposed skin and hair, squalene helps to restore the lost oils. It readily forms emulsions with fi xed oils and lipophilic substances and does not oxidize nor turn rancid. Squalene has also been found to accelerate dye-dispersion in lipsticks, producing a high gloss and acts as a long-lasting fi xative for perfumes. (21). Skin hydration. Since squalene is a part of our skin’s natural lubrication, it has a moistur- izing effect on the skin. The ingredient not only provides hydration but also helps reduce the appearance of wrinkles and fi ne lines by fi lling the skin with water. On the basis of amaranth oil, characterized by a unique content of squalene, forms such as emulsion of “oleogel” can be used (17). The vernix caseosa (VC) substitute based on squalene, which is composed of different lipid fractions mixed with squalene, triglycerides, cholesterol, ceramides, and fatty acids, mimic the lipid composition of VC. This substitute can be used as an innovative barrier cream for barrier-defi cient skin (i.e., psoriasis) (6,24). There are no confi rmed clinical studies for atopic dermatitis by using VC substitute. Treating skin diseases. Seborrheic dermatitis and acne (following seborrheic dermatitis) are the most common skin disorders. It is important to keep the same level ingredients of sebum. The correct amount of free, unsaturated fatty acids (linoleic acid) ensures the proper density, fl uidity, and viscosity of sebum. If the sebum is suffi ciently liquid and not very viscous, it freely fl ows on the skin surface causing hyperkeratosis. Decisive is the percentage of triglycerides and squalene: the more the squalene, the less the acne changes. Squalene is often used in acne-against cosmetics that changes the composition of the lipid layer of the skin—when the content of squalene increases, fats are reduced appropriately (25). The protective action of squalene and alkylglycerols from bacterial and fungal infection indicates that they could be recommended for patients suffering from atopic dermatitis. Patients with xerosis and disturbances of skin barrier are easily susceptible to atopic der- matitis (25). These studies were based on shark liver oil. Analysis on the effects of cosmetics containing squalene have made several proposals. First, by improving the composition of sebum (i.e., by the enrichment of essential fatty acids and squalene), keratosis disorders are eliminated. Second, these cosmetics could prevent the skin irritations caused by product oxidation. Third, these act as bacteriostatic and antifungal agents to limit the number of microorganisms settled in the follicles (26).

JOURNAL OF COSMETIC SCIENCE 64 Topically applied vehicles. Squalene is also used as a material or additive in topically applied vehicles such as lipid emulsions and nanostructured lipid carriers (NLCs). NLC is a novel type of lipid nanoparticle with a solid particle matrix possessing structural specialties and improvements, such as increased loading capacity, long-term physical and chemical sta- bility, triggered release, and potentially supersaturated topical formulations (6). In many instances, it would be advantageous if the rate of penetration of medicaments through the epidermis could be increased. This would help in bringing about a more rapid and pro- found action of the locally applied compounds. If penetration (transfollicular, transepi- dermal, and into the horny layer) could be increased, many new compounds could be introduced into different therapies (27). CONCLUSIONS Because of the biological activity of squalene, which is widely used in cosmetics and phar- maceuticals, further tests are necessary for the verifi cation of its use in preparations for skin. Since squalene is a part of our skin’s natural ingredient, it has a moisturizing effect on the skin. The ingredient not only provides hydration but also helps reduce the appear- ance of wrinkles and fi ne lines by fi lling the skin with water. The VC substitute based on squalene brings the novel role in psoriasis and atopic dermatitis. The results of the studies on psoriasis are promising and possibly further clinical studies enable a wide application of squalene. There are no confi rmed clinical studies for atopic dermatitis by using VC substitute, which seems to be taken. Bacterial and fungal protection was improved by squalene in atopic dermatitis, seborrhea, and acne. Also a combined role of squalene as an antioxidant, natural emollient, and skin hydration agent can be used to improve skin physiology problems. Squalene is also used as a material or additive in topically applied vehicles that may improve rapid and profound action of the locally applied compounds. Further studies on alternative sources are needed to explore the utility of squalene for treating skin, the high-quality amaranth oil seems to be the key of it. Several implica- tions can be drawn from this review. Squalene shows several advantages for skin tissues. The present success of squalene shows the promise of further clinical trials for skin uses. REFERENCES (1) B. Das and S. Baruchel, The Science Behind Squalene: The Human Antioxidant, 2nd Ed. (Toronto Medical Publishing, Canada, 2005), pp. 11–12. (2) P. Jame, H. Casabianca, M. Batteau, P. Goetinck, and V. Salomon, Differentiation of the origin of squalene and squalane using stable isotopes ratio analysis, SOFW J., 136(1/2), 2–8 (2010). (3) H. P. He and H. Corke, Oil and squalene in Amaranthus grain and leaf, J. Agric. Food Chem., 51, 7913–7920 (2003). (4) L. L. Gershbein and E. J. Singh, Hydrocarbons of dogfi sh and cod liver and herring oil, J. Am. Oil Chem. Soc., 46, 554–557 (1969). (5) K. Januszewska-Józ ´wiak and J. Synowiecki, Characteristic and suitability of the amaranth components in food biotechnology, Biotechnologia, 3(82), 89–102 (2008) (in Polish). (6) Z.-R. Huang, Y.-K. Lin, J.-Y. Fang, Biological and pharmacological activities of squalene and related compounds: Potential uses in cosmetic dermatology, Molecules, 14, 540–554 (2009). (7) H. Du Preez, Squalene—Antioxidant of the future? Nat. Med., 33, 106–112 (2007/2008). (8) The International Union for Conservation of Nature (IUCN) Red List of Threatened Species, Version 2012.2, accessed December 29, 2011, http://www.iucnredlist.org