Applicability of Nanoemulsions for the Incorporation of Bioactive Compounds in Cosmetics: A Review.

Plants are important sources of metabolites used in the cosmetics, food, and pharmaceutical industries, especially in cosmetics, where bioactive compounds offer benefits for the skin, such as protection against environmental stresses. The term "cosmeceutical" has emerged to describe products that combine aesthetic effects and dermatological treatments. With the growth of the cosmetics industry, the demand for ingredients that combat the signs of aging and oxidative stress - the main cause of skin aging - has increased. Bioactive compounds, such as phenols, flavonoids, and carotenoids, have antioxidant properties that are widely used to control the skin's aging process, triggered by environmental factors or the body's own metabolism, leading to excessive production of free radicals and, consequently, oxidative stress. However, incorporating these lipophilic compounds into water-based cosmetic formulas presents major challenges, including poor solubility, low stability, limited skin penetration, and rapid degradation. Nanoemulsions overcome these limitations by enabling droplet sizes of 20-200 nm through high-energy (e.g., high-pressure homogenization, ultrasonication) or low-energy (e.g., phase inversion temperature, spontaneous emulsification) methods. Their significance in cosmeceuticals lies in enhanced skin penetration, improved bioavailability of lipophilic actives, and prolonged product stability, making them ideal for antiaging creams, sunscreens, and moisturizers. This review article aims to address antioxidant compounds, their cosmetic applications, and the techniques used to obtain them, including characterization methods, validation of nanoemulsions, the main difficulties, and future prospects.