Plant polysaccharides: the magical effects and potential of cosmetic applications

The main dosage form of Chinese medicine used in clinical practice is decoction, also known as "drinking soup medicine", and the main ingredient is polysaccharide. Polysaccharide is a natural high molecular polymer composed of more than 10 monosaccharides such as glucose, rhamnose, arabinose, fucose, etc. It is a polyhydroxy polymer and its derivatives formed by linear or branched glycosidic bond polymerization.

Traditional Chinese medicine is rich in various polysaccharides and has been used as a Chinese medicine supplement and medicine to improve human health and treat diseases. Most of the Chinese medicines with tonic effects, especially those that benefit qi, yin, and blood, are rich in polysaccharides, such as ginseng, rhubarb, angelica, ganoderma, dendrobium, etc. The content of dendrobium polysaccharide can even reach more than 50% of the total dry mass. Modern pharmacological studies have shown that Chinese medicine polysaccharides have strong pharmacological activity, can regulate cell division and differentiation, and also have biological activities such as moisturizing, antibacterial, anti-inflammatory, immunomodulatory, anti-tumor, antioxidant, anti-depressant, and antiviral.

Polysaccharides are important bioactive macromolecules and are important components of the dermis of human skin. Many polysaccharides have outstanding regulatory effects in the process of skin metabolism. The application of bioactive polysaccharides as functional cosmetic additives in cosmetics is an important direction of biological beauty. They can produce multiple functions such as moisturizing, delaying aging, promoting epithelial fibroblast proliferation and beautifying skin color, injecting new vitality into the development of functional cosmetics.

1 Structural characterization of polysaccharides

The structure of polysaccharides is diverse and complex. They are polymers composed of monosaccharides with different glycosidic bonds, such as 1→3, 1→2, 1→4 and 1→6 connections, with α and β configurations. In addition, the chain conformation of polysaccharides is a unique structural feature of polysaccharides, including spherical, helical, flexible and rod-like structures. Structural characteristics are the basis of polysaccharide bioactivity. For example, relative molecular mass, monosaccharide composition and ratio, glycosidic bond type and connection mode, location and length of branch chains and spatial structure have significant effects on the bioactivity of polysaccharides. The chemical structure of plant polysaccharides is the material basis for their biological activity. Polysaccharides with different chemical structures have great differences in their biological activities. Therefore, the key to successfully applying Chinese medicine polysaccharides in the field of biochemistry is to clarify their necessary structural characteristics.

2 Skin care effects of polysaccharides

2.1 Moisturizing

The moisturizing effect of plant polysaccharides is mainly attributed to the good film-forming properties of polysaccharides, which can form a uniform film on the skin surface and reduce the evaporation of water on the skin surface. Its main mechanism is that the molecular chains of plant polysaccharides can interweave to form a dense three-dimensional network structure, which shows good film-forming properties. At the same time, functional groups such as hydroxyl and carboxyl in plant polysaccharide molecules can bind to water molecules through hydrogen bonds, reducing the loss of water molecules from the skin surface, thereby playing a moisturizing role. In summary, the good film-forming properties and water-binding abilities of plant polysaccharides are perfectly combined to provide a good moisturizing effect for the skin.

2.2 Antioxidant

Plant polysaccharides have been found to have good antioxidant effects and are natural ingredients that delay skin aging. All their mechanisms of action can be divided into the following two categories:

1) Polysaccharides act indirectly on free radicals. It can be divided into two types: ① Polysaccharides indirectly act on antioxidant enzymes. Polysaccharides indirectly play an antioxidant role by increasing the activity of existing antioxidant enzymes in the body, such as SOD, CAT, GSH-Px, etc. The Keap1-Nrf2-ARE signaling pathway is one of the most important mechanisms for cells to defend against oxidative stress damage. Nuclear factor E2-related factor 2 (Nrf2) usually binds to Kelch-like epichlorohydrin-related protein 1 (Keapl), then rapidly degrades and maintains a low level in the cytoplasm. Under the action of polysaccharides, Nrf2 enters the cell nucleus and interacts with antioxidant elements (ARE) to increase the expression of antioxidant enzymes. Therefore, polysaccharides can upregulate the expression of antioxidant enzymes through the Nrf2-ARE pathway, thereby removing excess free radicals and achieving the purpose of anti-aging. ② Polysaccharides can complex the metal ions required to produce R0s. The hydroxyl groups of polysaccharides can form complexes with metal ions, inhibiting the production of hydroxyl radicals that can initiate lipid peroxidation or making it unable to decompose lipid peroxides produced by lipid peroxidation, thereby inhibiting the production of ROS.

2) Polysaccharides directly act on free radicals. For lipid peroxidation, polysaccharides can directly capture ROS produced in the lipid peroxidation chain reaction, blocking or slowing lipid peroxidation. For hydroxyl radicals, the hydrogen atoms on the polysaccharide chain can combine with them to generate water. Therefore, it can achieve the purpose of removing hydroxyl radicals. The carbon atoms of polysaccharides become carbon radicals, which are further oxidized to form peroxide radicals, and finally decompose into harmless products. In addition, polysaccharides are easily oxidized by superoxide anion radicals, thereby achieving the effect of removing superoxide anion radicals.

Antioxidant mechanism of plant polysaccharides

2.3 Anti-inflammatory

Inflammatory response is related to immunity and is a normal physiological response of the human body. However, when the inflammatory response exceeds the normal immune response, a large amount of pro-inflammatory mediators such as interleukin-6 (IL-6), tumor necrosis factor-α (TNF-α), and cyclooxygenase-2 (COX2) will be released, resulting in inflammatory damage to the skin and gradually developing into aging damage to the skin. Inflammatory response and oxidative stress are closely related and interdependent. The inflammatory process can induce oxidative stress, and oxidative stress can also induce inflammation by activating multiple pathways. At the site of inflammation, activated inflammatory cells release many enzymes, active substances and chemical mediators, thereby inducing tissue damage and oxidative stress. Excessive reactive oxygen can initiate intracellular signal cascades, activate transcription factors such as AP-1 and NF-KB, and regulate the expression of other inflammatory networks, immunoglobulins, interleukins and other signaling molecules in leukocytes, thereby enhancing the inflammatory response. Plant polysaccharides can promote the reduction of nitric oxide levels in the pathogenesis of inflammation, inhibit pro-inflammatory cytokines (TNF-α, IL-1 B and IL-6) in keratinocytes stimulated by lipopolysaccharide, block NF-kB/P65 and MAPK signaling pathways, reduce the secretion of pro-inflammatory factors, and exert anti-inflammatory effects.

2.4 Antibacterial

Plant polysaccharides have been developed as antibacterial agents to combat microorganisms associated with skin infections, thereby helping to prevent and treat them. The antibacterial mechanism of plant polysaccharides is divided into two stages:

1) Plant polysaccharides interact with bacterial cell membranes through hydrophilic and hydrophobic effects, electrostatic adsorption or glycoprotein receptors.

2) After plant polysaccharides are adsorbed on the surface of the cell membrane, they inhibit the adsorption of pathogens to host cells by increasing the permeability of the cell membrane, or block the transmembrane transport of nutrients or energy substances to exert antibacterial effects.

2.5 Anti-blue light and ultraviolet

By reducing the inflammatory response caused by ultraviolet and blue light irradiation, reducing the effect of ultraviolet rays on collagen synthesis, better maintaining the normal morphology of the skin, and ultimately protecting the skin.

2.6 Whitening

Polysaccharides extracted from plants can inhibit UVB-activated protein kinase A (PKA), mitogen-activated protein kinase (MAPK) and cyclic adenosine monophosphate (cAMP) signaling pathways, and downregulate the expression of ultraviolet-induced melanin production-related genes (MITF, TYR, TYRPl, TYRP2) to block melanin synthesis. The inhibition of tyrosinase activity depends on the hydroxyl group of polysaccharides, which can form hydrogen bonds with the enzyme site, resulting in lower enzyme activity.

2.7 Repairing skin tissue

The elasticity and smoothness of the skin are determined to a certain extent by the proliferation and division functions of the cells that constitute the different components of the skin. This process is regulated by the comprehensive regulation of various cytokines in the skin. For example, epidermal growth factor (EGF) can promote the metabolism of epidermal cells in the skin, and basic fibroblast growth factor (bFGF) can promote the metabolism, proliferation, growth and differentiation of fibroblasts and epidermal cells, promote the development of elastic fiber cells and enhance their functions. Studies have confirmed that fucoidan helps to produce various cell growth factors. It shows that polysaccharides can repair skin tissue by activating cell growth factors.

The application of bioactive polysaccharides as functional cosmetic additives in cosmetics is an important direction of biological beauty. It can produce a variety of functions such as delaying aging, vascular beauty, anti-acne, repairing skin tissue, whitening and moisturizing, promoting the proliferation of epithelial fibroblasts and beautifying skin color, injecting new vitality into the development of functional cosmetics. The polysaccharides currently used in cosmetics mainly include: fucoidan, β-glucan, Tremella polysaccharide, Dendrobium polysaccharide, Bletilla striata polysaccharide, etc.

[1] Zhao Ning, Han Zhu, et al. Research progress on structural characterization and quality evaluation of Chinese medicine polysaccharides [J]. Chinese Herbal Medicine, 2024, 55(21): 7491-7506.

[2] Liu Hui, Yang Sijia, et al. Research progress on extraction and separation of natural plant polysaccharides and their application in the field of skin.