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Quercetin has been increasingly used in cosmetic products in recent years, as a sunscreen, to enhance the stability of tretinoin, as a hair dye and as a skin care ingredient in combination with metal ions, and as a hair growth agent and shine remover.
I. Plant origin of quercetin
Quercetin comes from the Sophora tree, whose flowers are often called Sophora flowers and whose buds are called "Sophora rice", which is oval or ovate in shape (Flos Sophorae).
The use of quercetin in cosmetics
Quercetin is mainly used in sunscreen cosmetics, but can also be added to creams, lotions, serums, toners and other skin care products; it is also used as a hair dye due to its yellow powder appearance.
Safety of quercetin
The Cosmetic Council of America (CTFA) uses quercetin as a cosmetic ingredient.
Quercetin is a natural inhibitor of CD38, which depletes NAD+, and quercetin can slow down the ageing process by increasing NAD+ levels. In addition, quercetin is a photoprotective substance that effectively delays the ageing of skin fibroblasts and has a rejuvenating effect on the skin.
Dihydro quercetin, a reduced form of quercetin, has similar effects to quercetin, scavenging cellular free radicals and acting as an antioxidant, as well as an antiviral, antibacterial and anti-inflammatory agent.
Catechins should be known to everyone, the most famous of which is EGCG, which is very high in green tea, reaching over 15%, and is an important substance for the benefits of green tea. Its antioxidant power is no less than that of the first two, being 40 to 100 times that of vitamin C. In addition to antioxidant, it is also anti-tumour, anti-inflammatory and protects the heart and brain organs.
Flavonoids
Flavonoids usually have multiple phenolic hydroxyl structures, and in many plants the flavonoids combine with sugar groups to form flavonoid glycosides. The flavonoid components of plants are not only hygroscopic, but also have a wide range of biological activities. The addition of flavonoids to cosmetics helps to restore elasticity and radiance to dry, sagging skin. The flavonoid quercetin is widely found in plants. Chamomile extracts containing quercetin enhance the skin's moisturising effect, repair dry, cracked and dehydrated skin and balance oil secretion, and are more effective in soothing sensitive skin.
Quercetin promotes the expression of tight junction proteins in a dose-dependent manner, thereby enhancing the tightness of cell junctions, maintaining the integrity of the skin barrier and regulating the dynamic balance of water, preventing skin dehydration and reducing skin sensitivity; the combination of quercetin and essential oils creates a synergistic effect and promotes the moisturising effect on the skin. Quercetin also has antioxidant, anti-inflammatory, anti-allergic and anti-ageing properties. The combined antioxidant/anti-inflammatory effect of quercetin also facilitates wound healing. Many flavonoid-rich plant extracts such as mother chrysanthemum, pear-fruit cactus and mullein extracts have biological activities such as antioxidant, anti-ageing and anti-inflammatory in addition to their moisturising effects.
