MAAs occupy a unique niche in biology. To date, only cyanobacteria, phytoplankton, and algae are known to synthesize them, and more than 570 species of marine macroalgae are thought to harbor the compounds. Their chemical structures are diverse, their light and thermal stability is excellent, and they are considered non-toxic, qualities that have long made them attractive candidates for cosmetics and pharmaceuticals. Yet their antioxidant behavior has remained surprisingly understudied, particularly in comparison with the polysaccharides, phenols, and pigments that dominate the seaweed antioxidant literature. The Jiangsu team, led by Yingying Sun, set out to close that gap by focusing on six species that are common in Chinese waters and cuisine: Bangia fuscopurpurea, Gelidium amansii, Sargassum fusiforme, Palmaria palmata, Sargassum sp., and Undaria pinnatifida.

The first hurdle was cosmetic in the most literal sense. In the researchers’ earlier work, MAA extracts from several of these algae came out stained black-red or black-green by co-extracted pigments, which muddied subsequent activity assays and complicated any practical application. Their solution was elegantly simple: wash the dried, powdered algae with anhydrous ethanol before the real extraction begins, discarding the pigment-laden supernatant. Spectrophotometric scans confirmed the wash was pulling out chlorophyll, phycobiliproteins, and beta-carotene, the compounds responsible for the unwanted color. Only then did the team extract the MAAs themselves using 25 percent methanol at 45 degrees Celsius, followed by repeated rounds of cold ethanol precipitation to strip away remaining non-target material.

The results of this pretreatment were striking. The purified extracts emerged a transparent reddish hue rather than an opaque dark sludge, and for two species the yield actually improved rather than suffered. Bangia fuscopurpurea delivered 1.5 times its previous MAA output, reaching a yield of 23.62 percent of the dried algal powder, while Gelidium amansii improved by a factor of 1.1. For the brown algae, the trade-off was less favorable: yields of Sargassum fusiforme, Sargassum sp., and Undaria pinnatifida declined significantly, suggesting that some MAAs were lost during the extra purification steps and that the protocol will need species-specific refinement. High-performance liquid chromatography coupled with mass spectrometry showed that the cleanup did not alter the underlying chemistry. The extracts were dominated by four familiar MAAs: palythine, palythenic acid, shinorine, and porphyra-334. Notably, the team reports the first detection of palythenic acid in Palmaria palmata, a compound previously known mainly from phytoplankton and a handful of other macroalgal species.

With clean extracts in hand, the antioxidant testing began. Using a Trolox-based assay, the researchers found that the total antioxidant capacity of the extracts from Bangia fuscopurpurea and Sargassum fusiforme towered over the rest, running 1.8 to 5.1 times higher than the other four species. The superoxide anion scavenging assay told a similar story. At a concentration of 50 milligrams per milliliter, the extracts from Sargassum fusiforme, Bangia fuscopurpurea, and Sargassum sp. neutralized more than 93 percent of the superoxide radicals in solution, while the remaining three species still managed above 64 percent. The half-maximal effective concentrations for the two standouts hovered around 30 milligrams per milliliter. Vitamin C, it should be said, remains the benchmark, achieving over 96 percent scavenging at a mere 0.035 milligrams per milliliter, so the MAAs are not about to displace ascorbic acid on potency alone.

But potency is not the whole story, and the authors point to a mechanistic nuance that could change the calculus. Earlier studies have shown that although porphyra-334 and shinorine score modestly in DPPH radical assays, they are remarkably effective at quenching free radicals through hydrogen atom transfer, a different chemical pathway. The relatively low concentration of active MAAs within the crude extracts may also be masking their true capability, and the researchers anticipate that further purification could substantially boost performance. There is even suggestive evidence that MAA antioxidant activity contributes to inhibiting cancer cell activity, though that frontier remains exploratory.

Perhaps the most immediately practical finding concerns browning, the enzymatic discoloration that turns a sliced apple or yam an unappetizing brown within hours and drives consumer rejection of fresh-cut produce. When the team soaked yam slices and red Fuji apple slices in dilute MAA solutions and tracked them over three days, the untreated controls browned dramatically while the treated slices stayed visibly fresh. The extracts from Bangia fuscopurpurea and Sargassum fusiforme performed best, and a component isolated from the Bangia extract via silica gel chromatography outdid them all, suppressing browning in more than 52 percent of yam and apple slices after 48 hours. That performance exceeded what has been reported for green tea extract, a standard natural anti-browning agent. The researchers speculate the effect may be linked to the impressive moisture-absorption and retention properties previously documented for Bangia MAAs, though the precise mechanism awaits further study.

Safety and formulation matter just as much as activity for any food additive, and here the mineral analysis delivered reassuring news. Inductively coupled plasma optical emission spectrometry revealed that the extracts are rich in essential macro-elements such as calcium, potassium, magnesium, sodium, and phosphorus, along with beneficial trace elements including iron, zinc, copper, and molybdenum. Critically, no harmful heavy metals, lead, cadmium, arsenic, or mercury, were detected, and copper levels sat far below the limits set by the Chinese Pharmacopoeia. The team then stress-tested the two star extracts against five common food additives over 40 days at both 25 and 48 degrees Celsius. Citric acid proved destructive, cutting absorbance by more than 23 percent for the Bangia extract and over 40 percent for the Sargassum extract by the experiment’s end, while sodium glutamate also destabilized the Bangia extract. Agar and carrageenan, by contrast, actually enhanced stability, making them natural formulation partners.

The convergence of these findings, cleaner and higher-yielding extraction, demonstrated antioxidant and anti-browning activity, a benign mineral profile, and compatibility with common food hydrocolloids, sketches a credible path from laboratory bench to grocery shelf. The authors are careful to note the limitations: yields for the brown algae need improvement, antioxidant potency trails vitamin C, and the anti-browning mechanism remains unexplained. Future work will expand the evaluation to weight loss, texture, color, and visual quality of treated produce, and will probe the health-food applications of the Sargassum fusiforme and Bangia fuscopurpurea extracts in greater depth. Still, the study marks a first on several fronts, from the mineral content analysis to the food-additive stability data, and it strengthens the case that the ocean’s humble seaweeds, already hailed as biorefineries and super plants of sustainable development, hold molecules capable of keeping our food fresher and perhaps our bodies healthier.

Subject of Research: Optimized extraction and antioxidant application of mycosporine-like amino acids from marine macroalgae

Article Title: Research on the optimization of preparation and the application analysis of antioxidant activity of mycosporine-like amino acids derived from marine macroalgae

Article References: Li, Y., Wang, J., Wang, S., Jiang, X., Shi, S., & Sun, Y. (2025). Research on the optimization of preparation and the application analysis of antioxidant activity of mycosporine-like amino acids derived from marine macroalgae. Blue Biotechnology, 2(1), Article 2. https://doi.org/10.1186/s44315-025-00023-z

Image Credits: AI Generated

DOI: 10.1186/s44315-025-00023-z

Keywords: mycosporine-like amino acids, marine macroalgae, antioxidant activity, seaweed, food preservation, anti-browning, palythine, shinorine, porphyra-334, extraction optimization, food additives, blue biotechnology