ANTI-POLLUTION DAY 0 DAY 28
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Figure 4: Oxygenating activity of green tea leaves extract after 28 days of treatment at 0.5%
At the cell, tissue and mitochondrial level, oxygenation is altered. At the surface, skin appears older: the complexion is dull, pores are clogged, the natural balance of the skin is upset.6
The skin suffocates. Green tea extract is derived from leaves,
issued from a controlled sourcing, harvested in the Nilgiris mountains in India. This powerful extract, rich in polyphenols, has shown great activity as an antioxidant, providing protection against free radicals.
Skin oxygenation improvement The main effects of pollutants on the skin are the production of reactive oxygen species and the reduction of tissue oxygenation. This hypoxic stress condition induces the
activation of HIF-1α factor (Hypoxia inducible factor-1), which is degraded by proteasome in its normal state (normoxia). HIF-1α is accumulated in contact to pollutants and is then translocated to the nucleus. There, this factor will activate stress genes (belonging to HRE domain=hypoxia-response element). In response, cell produces more oxygen to revert to normoxia. HIF-1α reductions mean a reversion to the basal oxygenation state (normal state) under stress condition, and so, the protection of cell against pollutants. Therefore, it is interesting to provide the skin with compound helping to reduce HIF-1α. The active’s efficacy was evaluated on skin
explants, obtained from an abdominal plastic surgery, on a 37-year-old woman donor. Green tea extract is applied topically on skin explants at 0.50% for three days, once a day, and is compared to an untreated control. After three days of treatment, explants are exposed to pollutants of cigarette smoke in a Pollubox. Image analysis quantification shows a significant decrease of 23% (Student test (p<0.05)) of HIF-1α factor compared to an untreated control. Green tea leaves extract at 0.5% protects
explants from hypoxic stress induced by cigarette smoke. It allows a returns to normoxia and avoids cell overactivity,
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which would produce more HIF-1α. The skin is better oxygenised and protected from pollutants. In vivo, the effectiveness of the green
tea leaves extract was evaluated on the skin oxygenation. A 28-day study was conducted on a panel of 18 female smoking volunteers with slack skin, aged from 30 to 50, with a twice daily application of the product, in a polluted urban environment. The results from the evaluation, at 0.5% active ingredient, were compared to a placebo. The oxygenating effect was measured
thanks to an innovative system called SpectraCam®. This consists of a hyperspectral measurement tool, which facilitates the acquisition of a series of pictures at different wavelength on skin. The stack of pictures obtained (or hypercube) is then treated to establish an oxygen cartography of the study zone: the more oxygenation rate is important, the clearer the picture is. At the end of the 28-day period, the
green tea leaves extract induces a significant improvement of 4% (Student test (p<0.05)) of skin’s oxygenation (Figure 4). The placebo had no significant effect. In addition, 79% of the volunteers had declared they felt their skin protected from pollution, fresher and unified. Fighting against pollutants and free
radicals, green tea leaves extract makes it possible to oxygenate the skin and avoids premature ageing.
Effect on oxidative stress & skin ageing Induced by pollution and (also by UV rays and stress), free radicals cause oxidative damages in DNA, proteins and lipids, which undergo changes and can no longer fulfil their function. The accumulation of oxidised compounds leads to cellular dysfunction and accelerates the cutaneous ageing process. The lipid membrane oxidation level is
decreased by 45% in the presence of the green tea leaves extract compared to the untreated control after UV irradiation. This anti-radical activity is four times higher than the one
obtained with vitamin E, a leading antioxidant substance in cosmetics. This extract has therefore a powerful antioxidant effect in presence of pollutants. As pollution induces premature ageing, it
is helpful to provide the skin with anti-ageing actives. Therefore, the effectiveness of the green tea leaves extract on the synthesis of collagen IV and fibrilline-1 was tested on skin explants (46-year-old donor), after six days of treatment. Green tea leaves extract was used at concentrations of 0.25% for collagen IV and 0.5% for fibrilline-1. Activity was assessed by morphology observations with optical microscope, and by image analysis after specific immunolabelling of collagen IV and fibrilline-1. The results showed that the plant extract stimulates the synthesis of collagen IV by 40% at 0.25%, and the synthesis of fibrilline-1 by 21% at 0.5%, compared to untreated explants. The skin is protected from the signs of ageing.
References 1. Fussell JC, Kelly FJ. Oxidative contribution of air pollution to extrinsic skin ageing. Free Radic Biol Med, 2019
2. Galliano A, Ye C, Su F, et al. Particulate matter adheres to human hair exposed to severe aerial pollution: consequences for certain hair surface properties. International journal of cosmetic science 2017; 39(6): 610-616
3. Evans. Testing Tactics in Hair Tress Stress. Cosmetics & Toiletries 2019; 134(3): 32-42
4. Evans A, Marsh J, Wickett R. The structural implications of water hardness metal uptake by human hair. International Journal of Cosmetic Science 2011; 33(5): 477-482
5. Qu X, Niu L, Kroon B, Foltis L. Pollution Damage and Protection of Asian Hair, Cosmetics 2018; 5(1): 17
6. Boisnic S, Branchet MC. Vieillissement cutané chronologique. EMC - Dermatologie- Cosmétologie 2005; 2(4): 232-241
7. WHO (2016). Ambient air pollution: A global assessment of exposure and burden of disease
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