Berries beat UV-B

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  • Published: May 1, 2009
  • Author: David Bradley
  • Channels: UV/Vis Spectroscopy
thumbnail image: Berries beat UV-B

Using hairless laboratory rodents, researchers in Korea have demonstrated that the antioxidant ellagic acid, which is found in certain fruits and berries, can protect against damage to the skin caused by incident ultraviolet-B radiation. Their work suggests that the compound could help protect people to some extent from the skin-aging effects of the sun.

Ji-Young Bae, Young-Hee Kang, Jung-Suk Choi, Sang-Wook Kang, Dong Shoo Kim, and Jung Lye Kim of Hallym University in the Republic of Korea tested the effects of a topical application of the antioxidant ellagic acid on skin exposed to UV-B from sunlight. UV-B is in the wavelength of 290 to 320 nm and along with the higher energy UV-A (100 to 290 nm) accounts for 90 percent of premature skin aging seen in chronic sun exposure.

Previous research had hinted at a photoprotective effect for ellagic acid and the related compound epigallocatechin gallate, which is found in green tea. Indeed, Kang and colleagues published details of how this compound hampers collagen destruction and collagenase activation in human dermal fibroblasts irradiated with UV-B in 2008 when they hinted at the involvement of a mitogen-activated protein kinase (Food Chem Toxicol, 2008, 46, 1298-307). They have also shown that anthocyanins from the bog blueberry have similar protective effects on the photo-aging of human skin cells (Mol Nutr Food Res, 2009, in press)

The team has now demonstrated that this polyphenolic antioxidant, which is found in raspberries, strawberries, cranberries, walnuts, pecans, pomegranates, and other fruits and vegetables, can cause a marked reduction in collagen damage and inflammatory response. Tests were carried out on human skin cells in vitro and the sensitive skin of hairless mice in vivo. The team reported details of their findings on Tuesday, 21st April 21 at the Experimental Biology 2009 meeting in New Orleans as part of the scientific program of the American Society for Nutrition. They presented data from a two-part study funded by Korea Research Foundation and Brain Korea 21.

The Kang laboratory results explain that ellagic acid protects human skin cells from ultraviolet damage by blocking production of MMP (matrix metalloproteinase enzymes). These enzymes would otherwise break down collagen in damaged skin cells. Ellagic acid also seems to reduce the production of an intercellular adhesion molecule (ICAM), a molecule involved in the inflammatory response.

With the in vitro data in hand, the team then focused on an in vivo model, four-week old male, genetically modified hairless mice commonly used in dermatology studies to simulate human skin.

The team exposed twelve mice for a period of eight weeks to increasing levels of ultraviolet radiation, to mimic exposure to sunlight, three times a week. Initial exposure was established at a level that would cause reddening of the skin in or sunburn in a human and then increased exposure to the point where minor skin damage would be caused to human skin.

Half of the mice were given a daily 10 micromolar topical application of ellagic acid on their skin. The other half received no ellagic acid. Six additional mice that received no ellagic acid but no exposure to ultraviolet acted as experimental controls for the study.

The team observed rapid wrinkling and thickening of the skin in the UV exposed mice not receiving ellagic acid. And, as anticipated those mice receiving topical ellagic acid showed much reduced wrinkle formation. Additional evidence at the microscopic and molecular levels corroborated the findings of the human cell study in that the presence of ellagic acid reduced inflammatory response and MMP secretion. It this was apparently protecting against the degradation of collagen and prevented thickening of the epidermis.

The researchers say that their results demonstrate that ellagic acid works to prevent wrinkle formation and photo-aging that would otherwise be caused by UV destruction of collagen and inflammatory response. You can rest assured that the marketing departments across the cosmetics industry will be developing fruity advertising campaigns for new antiaging products rich in berry extract.




Sunlight by David Bradley

Adapted from CC image: Structure by DB


Could ellagic acid from raspberries protect skin against UV damage?

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