The invention relates to substituted anionic compounds consisting of a backbone made up of a discrete number u of between 1 and 8 (1≦u≦8) of identical or different saccharide units, linked via identical or different glycosidic bonds, said saccharide units being chosen from the group consisting of pentoses, hexoses, uronic acids, N-acetylhexosamines in cyclic form or in open reduced form, which are randomly substituted. It also relates to the process for the preparation thereof and to the pharmaceutical compositions comprising same.