Milk thistle constituent shows promising skin protection properties

By Helen Albert, Senior medwireNews Reporter

Silibinin, a key component of milk thistle seeds, can help protect against skin damage caused by ultraviolet B radiation (UVB), show study findings published in Molecular Carcinogenesis.

These results support previous findings by the same researchers that show that silibinin promotes destruction of cells damaged by ultraviolet A radiation (UVA), but not healthy cells.

"When you have a cell affected by UV radiation, you either want to repair it or kill it so that it cannot go on to cause cancer. We show that silibinin does both," commented senior author of both studies Rajesh Agarwal (University of Colorado, Aurora, USA) in a press statement.

The previous study, published in Photochemistry and Photobiology, showed that human skin cells that were treated with silibinin before being exposed to UVA were more likely to self-destruct after being damaged than those that were not, potentially acting as an early anti-cancer mechanism. The researchers believe that this was due to an increase in the release of reactive oxygen species.

The second, more recent study shows that silibinin protects human skin cells from being damaged by UVB exposure by increasing the amount of interleukin (IL)-12 that they produce, thus allowing them to repair damage more easily. IL-12 is able to induce immune responses and has potent anti-angiogenic activity, which has led to suggestions that it may be a useful anti-cancer agent.

These findings were validated in vivo in a mouse study. The team found that topically applied silibinin increased the amount of IL-12 in skin with UVB damage, but not in healthy unexposed skin.

"Considering the fact that millions of people get constantly exposed to solar UVB... the post-damage use of silibinin as an inducer of endogenous IL-12 in UVB-damaged human skin for the repair of DNA damage could be a practical and translational approach in reducing sunlight-caused damages in human skin which eventually lead to skin cancer," suggest the authors of the Molecular Carcinogenesis study.

"It has been 20 years of work with this compound, silibinin," Agarwal told the press. "We first noticed its effectiveness in treating both skin and solid cancers, and we now have a much more complete picture of the mechanisms that allow this compound to work."

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