Scientists Unlock an Edible Alga's Natural Sunscreen Secret

Researchers in Japan have pinpointed the enzyme that unlocks a natural sunscreen. According to a report from Phys.org on findings published in the Journal of Natural Products in October 2026, a team led by Hakuto Kageyama of Meijo University identified a lipoxygenase they named AsLOX2 as the gateway step that builds saclipins — the edible alga's natural sunscreen secret. The work is the first to assemble these molecules outside the organism, using an enzymatic step followed by chemical conversion.

Saclipins A and B are members of the oxylipin family, oxidized derivatives of fatty acids. What sets them apart is function: they soak up both UV-A and UV-B, and they remain stable under light and heat. Earlier work also credited them with antioxidative and antiglycative activity — the latter meaning they slow the sugar-driven stiffening of proteins such as collagen, a process tied to skin aging, a theme we follow in our Science coverage. The source organism, Aphanothece sacrum, is a freshwater microbe traditionally harvested as food, which makes the chemistry especially intriguing for cosmetics.

Finding the gateway step

The researchers went hunting in the microbe's genome for lipoxygenases, enzymes known for inserting oxygen into polyunsaturated fatty acids with precision. They found two candidates and built recombinant versions of each, then tested them against three fatty acids. Only one worked: AsLOX2, which showed its strongest activity toward alpha-linolenic acid, a common plant-derived fatty acid. Instead of adding oxygen at a single site, the enzyme oxygenated the fatty acid at two positions, producing a doubly oxygenated hydroperoxide known as 9,16-diHPOTE. The team confirmed the molecule with chromatography and mass spectrometry, and reported that under tuned conditions the enzyme converted more than 80 percent of the starting material within a few minutes.

With the intermediate in hand, the researchers reduced it chemically to a more stable dihydroxy form, then oxidized it again — and obtained compounds matching saclipins A and B, with the A form produced in much greater amounts than the B form. The overall yield was modest, but the demonstration mattered: nobody had built these UV-absorbing molecules outside the living microbe before. "Identifying AsLOX2 as the gateway enzyme gives us an important biochemical entry point for understanding how this unusual UV-absorbing compound is produced," Kageyama said. He added that chaining an enzymatic gateway step to chemical conversion offers a practical route toward production, while the natural downstream reactions still remain to be found.

The result caps a short but fast-moving research trail. In October 2023, the same group first described saclipins in the journal paper, showing the two compounds absorb most strongly near 316 and 319 nanometers and accumulate twenty- and ten-fold, respectively, when the microbe is dried out. That study, reported by Phys.org at the time, also found the purified compounds inhibited the glycation of collagen more strongly than a well-known laboratory inhibitor. A 2024 follow-up reported further anti-aging effects, including support for collagen. The new paper supplies the missing biochemical origin story.

Why a natural UV filter matters

The discovery lands as conventional sunscreens face growing scrutiny. According to reporting by Science Norway, chemical UV filters have been detected even in remote marine sanctuaries and Arctic waters, and laboratory work has linked filters such as oxybenzone to coral bleaching and reproductive disruption in reef organisms. Hawaii, Palau, the US Virgin Islands and Bonaire have banned over-the-counter sales of sunscreens containing oxybenzone, and California is preparing rules that will bar "reef safe" marketing claims on products that still contain certain chemical filters. A naturally derived UV absorber that is stable and sourced from an edible organism could sidestep several of those concerns at once — though "natural" alone never guarantees safety.

What could this mean for readers? A reef-friendly sunscreen built around a lab-made natural compound is an attractive picture, but the researchers stress it is years away. The enzymes that carry out the final steps in the living microbe are still unknown, and productivity, safety and long-term stability all need testing before any cosmetic use. Still, the pathway now has its front door. With the gateway enzyme characterized and a semi-synthetic route demonstrated, engineered microbes fed the plant fatty acid could one day brew saclipins at scale — turning a traditional Japanese food alga into the starting point for a new generation of sun protection and skin-health innovation, and finally putting that natural sunscreen secret to work.

Sources: a report from Phys.org on the enzyme discovery; the study in the Journal of Natural Products; Phys.org's coverage of the 2024 anti-aging study; Science Norway on sunscreen chemicals and coral reefs.