In Vivo Anti-Inflammatory Activity of Lipids Extracted from the Most Abundant Cyanobacterial Strains of the Therapeutic Euganean Thermal Muds

: Cyanobacteria are a natural source of bioactive compounds increasingly recognized for their anti-inflammatory properties. In the Euganean Thermal District (Italy), thermal muds, used to cure arthro-rheumatic diseases, are prepared using natural clay and thermal water, resulting in a mature mud characterized by a complex microbial biofilm dominated by Cyanobacteria. Among these, Phormidium sp. ETS-05 has been shown to contribute to the therapeutic properties of the mud, mainly through the production of bioactive compounds such as exopolysaccharides (EPSs) and glycoglycerolipids (GLs). In contrast, the role of biomolecules from Thermospirulina andreolii ETS-09 and Kovacikia euganea ETS-13, also abundant in mature muds but at higher maturation temperatures, has not been investigated. This study focuses on the lipid profiles of these cyanobacteria, cultivated under temperature conditions that mimic their natural environment and that are different for the three species. Lipid extracts were analyzed for GLs classes and fatty acid composition, and their anti-inflammatory potential was assessed in vivo using a zebrafish inflammation model. All extracts showed anti-inflammatory activity with Phormidium sp. ETS-05 displaying the highest lipid content and the most rapid and potent beneficial effect, likely due to the specific composition of its GLs, presenting the greatest abundance of polyunsaturated fatty acids. These findings provide new insights into the biological basis of the therapeutic effects of Euganean muds and emphasize the importance of maturation conditions for cyanobacterial growth and bioactive lipid production.