The invention relates to a complex consisted of a polysaccharide and an HBP, said polysaccharide being consisted from glycoside bonds of (1,6) and/or (1,4) and/or (1,3) and/or (1,2) type and functionalized with at least one salifiable or salified tryptophan derivative. The invention also relates to a pharmaceutical composition comprising a complex according to the invention and to the use of a polysaccharide consisted of glycoside bonds of (1,6) and/or (1,4) and/or (1,3) and/or (1,2) type and functionalized with at least one salifiable or salified tryptophan derivative, for the preparation of a pharmaceutical formulation of stable HBPs.