In recent years, interest in the health effects of natural antioxidants has increased due to their safety and applicability in cosmetic formulation. Nevertheless, efficacy of natural antioxidants in vivo is less documented than their prooxidant properties in vivo. Plant extracts rich in vitamins, flavonoids, and phenolic compounds can induce oxidative damage by reacting with various biomolecules while also providing antioxidant properties. Because the biological activities of natural antioxidants differ, their effectiveness for slowing the aging process remains unclear. This review article focuses on the use of natural antioxidants in skincare and the possible mechanisms underlying their desired effect, along with recent applications in skincare formulation and their limitations.
The skin is the body’ s largest living organ, and it protects the body from the outside environment by maintaining homeostasis, keeping harmful microbes and chemicals out, and blocking sunlight. The stratum corneum, the outermost layer of the skin, is a selectively permeable, heterogeneous epidermal layer that provides protection against dryness and environmental damage while retaining sufficient moisture to function. Impairment in skin barrier function frequently manifests as altered stratum corneum integrity, which leads to an increase in transepidermal water loss and a decrease in skin hydration. The term “cosmeceutical” refers to cosmetics that contain active chemicals having drug-like properties. Cosmeceuticals with medicinal properties have beneficial local effects and prevent degenerative skin diseases. They enhance appearance by supplying nutrients required for healthy skin. They can improve skin tone, texture, and radiance while reducing wrinkles. Cosmeceuticals are a rapidly expanding subset of the natural personal care industry. Although natural ingredients have been used for centuries in skincare, they are becoming increasingly prevalent in modern formulations. The phrase “natural” refers to a substance that is derived directly from plants or animal products and is generated or found in nature. Herbs, fruits, flowers, leaves, minerals, water, and land can be sources of natural ingredients. Natural ingredients’ efficacy in skincare products is determined by their in vitro and in vivo efficacy as well as the type of dermatological base into which they are incorporated. Plants have long been used for medicinal purposes, and it is likely that new products containing natural oils and herbs will continue to emerge on the market in the coming years. Before the use of synthetic substances with similar properties, plants were the primary sources of all cosmetics. Natural plant molecules continue to pique the interest of researchers. However, using extracts necessitates paying close attention to extraction methods, plant-to-solvent ratios, and active-ingredient content. The use of plant extracts in skincare products is demanded by consumers, who are becoming increasingly concerned with purchasing ecofriendly products. However, consumers, are frequently unaware that natural products are complex mixtures of many chemical compounds that can cause adverse reactions. To avoid this issue, researchers should chemically characterize their extracts with regard to composition. Furthermore, the in vitro cytotoxic potential of extracts should be tested in several human cell lines prior to human use, and the irritant potential of cosmetic formulations can be screened. These procedures can help to ensure the safety of natural products and thus their acceptability on the market. Bioactive extracts and phytochemicals from various botanicals are used for two purposes: (1) body care and (2) as ingredients to influence the biological functions of the skin, providing nutrients for healthy skin. Vitamins, antioxidants, essential oils and oils, hydrocolloids, proteins, terpenoids, and other bioactive substances are all abundant in botanical products. These extracts can have a variety of properties depending on their compositions. Modern skincare cosmetics are distinguished by their multiactivity, which enables multidirectional complex effects even in relatively simple formulations. The biologic impacts of the most widely used cosmetic surgery, which involves coating the epidermis with a hydrolipid occlusion layer or various forms of antiradical protection, are a good example. The meaning of cosmetic multi-activity is encoded in a legal definition of cosmetic product use: “keeping (the skin) in good condition”. A comprehensive search was performed to find reports of the use of natural antioxidants in skincare in PubMed, Science Direct, and Scopus, and the articles satisfying the search criteria were screened and filtered. In this review article, we summarize the use of natural antioxidants and their possible mechanisms in skincare applications.
Antioxidants are molecules that can oxidize themselves before or instead of other molecules. They are compounds or systems that can interact with free radicals and stop a chain reaction before vital molecules are harmed. Antioxidants are used in food, cosmetics, beverages, pharmaceuticals, and even the feed industry. They can be used as health supplements and active ingredients as well as stabilizers. Antioxidants can be synthetic or natural, and both are used in cosmetic products. Synthetic antioxidants (e.g., butylated hydroxyanisole (BHA), butylated hydroxytoluene (BHT), and propyl gallate) are widely used because they are inexpensive to produce. However, research suggests that excessive consumption of synthetic antioxidants may pose health risks. Despite the fact that synthetic antioxidants dominate the market, demand for natural antioxidants has increased in recent years and is expected to continue. This pattern can be explained by a growing consumer preference for organic and natural products that contain fewer additives and may have fewer side effects than synthetic ingredients.
Natural antioxidants used in the cosmetic industry include various substances and extracts derived from a wide range of plants, grains, and fruits, and are capable of reducing oxidative stress on the skin or protecting products from oxidative degradation. One of the major causes of oxidative stress that accelerates skin aging is reactive oxygen species (ROS). Intrinsic aging is associated with the natural process of aging, whereas extrinsic aging is associated with external factors that affect the aging process (e.g., air pollution, UV radiation, and pathogenic microorganisms). Photoaging is most likely the primary cause of ROS production. Factors that drive the process of skin aging are presented. Several potential skin targets have been discovered to interact with ROS (e.g., lipids, DNA, and proteins). Antioxidant molecules can be enzymes or low-molecular-weight antioxidants that donate an electron to reactive species, preventing the radical chain reaction, which prevents the formation of reactive oxidants, or behave as metal chelators, oxidative enzyme inhibitors, or enzyme cofactors. Antioxidants can also be used as stabilizers, preventing lipid rancidity. Lipid oxidation occurs not only in cosmetics but also in the human body. Thus, when antioxidants are present in a product, they may serve multiple functions. The number of radicals increases during the initiation phase of lipid oxidation. Molecular oxygen and fatty acid radicals react during the propagation phase, resulting in the formation of hydroperoxide products. Hydroperoxides are unstable and can degrade to produce radicals, which can accelerate the propagation reaction. The termination phase is dominated by radical reactions. Antioxidants can inhibit lipid oxidation by reacting with lipid and peroxy radicals and converting them to more stable, non-radical products. Additionally, antioxidants can deplete molecular oxygen, inactivate singlet oxygen, eliminate peroxidative metal ions, covert hydrogen into other antioxidants, and dissipate UV light. Antioxidants can be used in cancer treatments, because the production of ROS is altered during tumorigenesis, with anti-inflammatory and antimicrobial effects. Plants are well known for producing natural antioxidant compounds that can reduce the amount of oxidative stress caused by sunlight and oxygen. Plant extracts are used in a variety of patents and commercial cosmetic products. Green tea, rosemary, grape seed, basil grape, blueberry, tomato, acerola seed, pine bark, and milk thistle are some of the plant extracts commonly found in cosmetic formulations. Polyphenols, flavonoids, flavanols, stilbenes, and terpenes are natural antioxidants found in plant extracts (including carotenoids and essential oils). Antioxidants are classified as primary or natural antioxidants and as secondary or synthetic antioxidants according to their function. Mineral antioxidants (such as selenium, copper, iron, zinc, and manganese), vitamins (C and E), and phyto-antioxidants are examples of primary antioxidants. Generally, a mineral antioxidant is a cofactor of enzymatic antioxidants. Secondary or synthetic antioxidants capture free radicals and stop the chain reaction. BHA, BHT, propyl gallate, metal chelating agents, tertiary butylhydroquinone, and nordihydroguaiaretic acid are examples of secondary antioxidants. The use of plant antioxidants is increasing and may eventually replace the use of synthetic antioxidants. A natural antioxidant can be a single pure compound/isolate, a combination of compounds, or plant extracts; these antioxidants are widely used in cosmetic products. A summary of natural antioxidants commonly used in cosmetic preparations is presented. Innate antioxidants act as oxygen free radical scavengers (singlet and triplet), ROS, peroxide decomposers, and enzyme inhibitors. Polyphenols and terpenes are key natural antioxidants.
