Skin aging is often marked by the emergence of wrinkles. This natural process is primarily caused by the passage of time and exposure to the sun. Several active ingredients present in cosmetic care targeting skin aging help to slow it down. What about green tea extract? Can this natural ingredient act on the signs of time?
How are wrinkles formed?
Reaching a certain age, it is entirely normal and natural to have wrinkles. These form in various areas of the face, particularly on the forehead, around the eyes, and around the lips. It's important to note that we refer to them as wrinkles when the depth of the grooves exceeds 1 millimeter. If the grooves have a depth between 0.2 and 1 millimeter, they are considered as fine lines.
It is important to know that the causes of skin aging are multifactorial. Among them, we can mention the gradual decrease of collagen, elastin and hyaluronic acid in the dermis over the years. Collagen and elastin are support proteins of the skin's extracellular matrix that provide it with flexibility and firmness. Hyaluronic acid, on the other hand, is a macromolecule with a strong moisturizing power and is capable of retaining up to 1000 times its weight in water.
The appearance of wrinkles is also promoted by certain external factors to the body, such as pollution, UV rays and tobacco, elements that generate oxidative stress in the skin cells. This particularly damages DNA, and collagen and elastin fibers. It should be noted that UV rays alone are responsible for about 80% of premature skin aging.
The effects of green tea on wrinkles?
The green tea (INCI: Camellia Sinensis Leaf Extract) is extracted from the leaves of Camellia sinensis, a shrub species belonging to the Theaceae family and native to East Asia. In addition to being a beverage appreciated for its flavor and digestive virtues, green tea is a natural ingredient abundantly present in the cosmetics market. Antioxidant, anti-inflammatory... Its properties are numerous. Green tea is often incorporated into treatments targeting signs of aging.
Green tea prevents the onset of fine dehydration lines.
Originating from a lack of hydration and a thinning of the hydrolipidic film, dehydration fine lines can be prevented by sufficient facial hydration. However, a study conducted on 24 volunteers showed that the daily application on the forearm of a moisturizing cream containing 6% green tea extract for a month significantly increased the overall skin hydration and its suppleness. Thus, green tea extract would help to reduce dehydration fine lines.
Green tea protects the skin from oxidative stress.
The antioxidant properties of green tea extract are derived from its richness in polyphenols. These compounds act at various levels within the skin cells to prevent and inhibit damage caused by free radicals. They are particularly capable of chelating, or binding to, certain metals involved in the generation of these reactive species (copper, iron...). In doing so, the polyphenols prevent them from producing free radicals. Studies have also shown that these compounds have a protective effect on certain antioxidant compounds such as vitamins C and E.
Finally, polyphenols can stimulate the production of certain endogenous antioxidant enzymes, such as superoxide dismutase (SOD) and glutathione peroxidase (GPx), both playing a crucial role in combating oxidative stress. Specifically, SOD catalyzes the dismutation of superoxide anions O2.- into oxygen O2 and hydrogen peroxide H2O2. GPx, on the other hand, facilitates the transformation of organic hydroperoxides before they can damage cells.
Green tea prevents the degradation of collagen, elastin, and hyaluronic acid.
It has been demonstrated that green tea extract is capable ofinhibiting certain enzymes, playing a role in skin aging. These include metalloproteinases, involved in the proteolytic degradation of extracellular matrix proteins, hyaluronidase, catalyzing the hydrolysis of hyaluronic acids, and collagenase, responsible for breaking down the peptide bonds of collagen. By inhibiting these processes, green tea extract helps to delay skin aging. However, the precise mechanisms through which it operates are still unknown to date.
KUKULA-KOCH W. & al. Applications of Tea ( Camellia sinensis) and its Active Constituents in Cosmetics. Molecules (2019).
TENCOMNAO T. & al. A Review of the Role of Green Tea ( Camellia sinensis) in Antiphotoaging, Stress Resistance, Neuroprotection, and Autophagy. Nutrients (2019).