Chemical characterization of different macroalgae species for biostimulant formulation

At present, macroalgal biomass is utilized in the formulation of agricultural biostimulants, products that enhance plant growth and tolerance to abiotic stress. Their action is attributed to bioactive metabolites that modulate physiological and biochemical processes in plants. Selecting algal biomass is the first step in the formulation of these products, as it significantly influences their properties and effectiveness. This study analyzed four representative brown algae species ( Fucus spp., Ascophyllum nodosum , Undaria pinnatifida and Laminaria digitata ), four red algae species ( Gigartina skottsbergii , Chondrus crispus , Mastocarpus stellatus and Palmaria palmata ), and three green algae species ( Codium spp., Ulva spp. and Ulva rigida ). The dry biomass from these species was analyzed to determine the content of total phenolics, proteins, vitamins A and C, reducing sugars, antioxidant activity, macro and micronutrients, anions, ammonium, total nitrogen, phytohormones, amino acids, organic acids, sugars, and other metabolites. The results indicated that 98% of the analyzed compounds were present in the algal biomass, although their presence and concentrations varied according to species. A. nodosum and U. pinnatifida were distinguished by the highest diversity and concentration of metabolites. L. digitata featured a high mannitol content, P. palmata had the highest concentrations of nitrates and betaines, and U. rigida was notable for its total nitrogen and asparagine contents. Green algae stood out for their high content of magnesium, ammonium, and total nitrogen. These findings provide relevant and important information for the formulation of agricultural biostimulants based on macroalgae, which will allow optimizing extraction techniques, product formulation, and application to crops. • Chemical profiling of 11 macroalgae species was performed. • 98% of analyzed metabolites were detected in algal biomass. • nodosum and U. pinnatifida showed highest metabolite diversity. • L. digitata showed high mannitol concentrations. • Green algae had high Mg, ammonium and total nitrogen contents.