Coral Yields Antisunburn Secret

With the southern sun beating down through clear waters, tropical corals need something to protect their delicate tissues from damaging doses of ultraviolet (UV) radiation. Soon their secret shield may show up on drugstore shelves: Researchers at the Australian Institute of Marine Science (AIMS) in Townsville have developed a new sunscreen for humans based on that used by many corals.

In the early 1970s, researchers in Japan and Hawaii noticed that the algae that live symbiotically within coral produce a UV-absorbing substance. A decade later, photochemist Walt Dunlap at AIMS identified it as a member of a family of compounds found in fungi--the mycosporine-like amino acids (MAA). Test tube studies showed that MAA is a highly efficient sunscreen, absorbing and dissipating UV energy. But MAA is a tricky molecule to work with because it's highly unstable in water. "Stabilizing the molecule and making it insoluble has taken us the best part of 10 years," says Dunlap. Scientists, in collaboration with ICI Australia, experimented with hundreds of versions of the MAA molecule, knocking off water-soluble groups and adding others to enhance the ruggedness of the light-absorbing part of the molecule.

Now researchers have a financial backer, Sunscreen Technologies Pty. Ltd., which plans to run clinical trials. Dunlap says the coral byproduct is chemically simpler than the aromatic ring molecules at the basis of commercial sunscreens and thus is less likely to trigger allergic responses. A coral sunscreen should appeal to people looking for "natural" products, adds Gavin Greenoak of the Australian Photobiology Testing Facility in Sydney: "After all, coral has been using it for millennia."

Posted in Chemistry