Two studies conducted at the University of Colorado Denver suggest that an extract from milk thistle called silibinin protects agains UVB damage and also kills skin cells damaged by UVB.
The team of researchers believe that the studies indicated that the extract may be used to protect against UV-induced skin cancer as well as photo-ageing, giving it both medical and cosmetic applications, specifically sunscreens.
"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," said Rajesh Agarwal, PhD, co-program leader of Cancer Prevention and Control at the CU Cancer Center and professor at the Skaggs School of Pharmacy and Pharmaceutical Sciences.
The first study, which has been published in the journal of Photochemistry and Photobiology, looked a the effect the extract has on human skin cells exposed to UVA radiation, showing that cells treated with silibinin demonstrated a marked decreased in damaged skin cells.
Removing mutated skin cells that cause cancer and photo-aging
"When you take human skin cells – keratinocytes – and treat them with silibinin, nothing happens. It's not toxic. But when you damage these cells with UVA radiation, treatment with silibinin kills the cells," Agarwal says, which removes the mutated cells that can cause skin cancer and photo-aging.
The second study, which was published in the journal Molecular Carcinongenesis, showed that, instead of the benefit of killing cells damaged by UVA radiation, silibinin protected human skin cells from damage by UVB radiation.
According to a report that outlines the two studies, Agarwal's suggestion that the prevention of UV-induced skin cancer can happen in two ways: by protecting against DNA damage or by killing cells with damaged DNA.
Study is the result of 20 years of research
"It has been 20 years of work with this compound, silibinin," Agarwal says. "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."
The study teams say they will now continue to test the effectiveness of silibinin and are working toward human trials for therapeutics that will incorporate the compound.