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Century-old medicine could be used as coral-friendly sunscreen ingredient

May 28 (UPI) -- According to a study, the century-old medicine called methylene blue, typically used used to treat the blood disorder methemoglobinemia, could serve as a coral-friendly substitute for traditional sunscreen ingredients.

In tests, scientists found methylene blue, also known as methylthioninium chloride, absorbs the full spectrum of ultraviolet rays, as well as repairs DNA damage caused by reactive oxygen species and UV radiation.

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Researchers detailed methylene blue's UV-blocking bonafides in a new paper, published Friday in the journal Scientific Reports.

Some 80 percent of sunscreens continue to deploy oxybenzone as their primary UV-blocker, despite the threat it poses to coral reef health.

Studies show oxybenzone degrades the genetic health of coral, as well as fish embryos.

Meanwhile, skin cancer rates have skyrocketed in recent decades, and public health officials continue to encourage greater sunscreen use.

When it comes to limiting the negative effects of the sun's rays on skin tissue, most people focus on a sunscreen's SPF, or sun protection factor, which measures a sunscreen's ability to block UVB radiation.

However, UVA-triggered oxidative stress and photo-aging can also damage human skin.

The latest research suggests methylene blue is capable of more well-rounded sun protection.

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"Our work suggests that methylene blue is an effective UVB blocker with a number of highly desired characteristics as a promising ingredient to be included in sunscreens," senior study author Kan Cao, a professor of cellular biology and molecular genetics at the University of Maryland, said in a press release.

"It shows a broad spectrum absorption of both UVA and UVB rays, promotes DNA damage repair, combats reactive oxygen species, ROS, induced by UVA, and most importantly, poses no harm to coral reefs," said Cao, founder of Mblue Labs and Bluelene Skincare, which has developed skin products using methylene blue.

In the lab, researchers measured how well the two UV-blocking compounds protected human keratinocytes and skin fibroblasts from radiation.

In addition to absorbing UV rays, methylene blue triggered the repair of DNA damage caused by ultraviolet irradiation, leading to greater cell survival.

"We are extremely excited to see that skin fibroblasts, derived from both young and old individuals, have improved so much in terms of proliferation and cellular stress in a methylene blue-containing cell culture medium," said Cao.

Additionally, on skin tissue from older donors, the combination of methylene blue and vitamin C yielded measurable anti-aging effects.

Researchers also tested the two types of sunscreen -- one with oxybenzone and the other with methylene blue -- on a soft coral species called Xenia umbellate.

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The corals exposed to elevated oxybenzone levels suffered severe bleaching and were dead within a week, while methylene blue had no effect on coral health at high levels.

"Altogether, our study suggests that Methylene Blue has the potential to be a coral reef-friendly sunscreen active ingredient that can provide broad-spectrum protection against UVA and UVB," researchers wrote in the paper.

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