Regioselective sulfation of polysaccharides from sustainable sources

Sulfated glycosaminoglycans (GAGs) are highly complex, anionic, linear polysaccharides extracted from extracellular matrix of animals cells. Some of them are exploited in already approved therapeutic treatments, and a significant number of novel drugs are currently under development. Nonetheless, naturally occurring GAGs exhibit variable chemical compositions and biological activities, which could cause unpredictable results during applications (e.g. heparin crisis in 2007). However, sulfated polysaccharides can also be obtained in a semi-synthetic way: the introduction of sulfate groups into the backbones of natural unsulfated polysaccharides allows to endow them with bioactivities similar to sulfated GAGs but without risks derived from their typical animal sources. In this frame, a special interest is focused on the sulfation of polysaccharides from eco-sustainable natural and/or biotech sources (algae, fungi, bacteria) already used in the biomedical and/or food fields, in order to improve their properties or to introduce new ones. Regioselective sulfation reactions can be conducted through multi-step strategies consisting in protection-sulfation-deprotection sequences. In particular, the polysaccharides selected to this aim are M-rich alginic acid extracted from brown algae, curdlan from Agrobacterium strains, and finally an exopolysaccharide (EPS) from Vibrio diabolicus HE800 with a GAG-like structure composed only of aminosugars and uronic acids. Their regioselective sulfation has been performed to obtain new derivatives acting as GAG mimics.