Fuente: WIPO "tobacco agriculture" The present invention relates to a method for obtaining a powder composition for oral use comprising alginate, fucoidan and laminaran of a brown alga, said method comprising submitting a brown alga to parboiling; soaking in an aqueous sodium chloride solution; and soaking in an aqueous sodium carbonate solution. The present invention also relates to compositions obtainable by such methods, and to compositions comprising alginate, fucoidan and laminaran of a brown alga, as well as medicinal use of such compositions, in particular in a method for prevention, treatment, or reducing risk, of a viral infection.