The present invention provides a new class of compounds presenting a high compatibility with tissues and organic fluids. Such new compounds are polysaccharides essentially formed of units of uronic acid and/or hexosamine, containing nitro groups —ONO₂ covalently bonded to the saccharide structure. Preferably, the polysaccharides according to the invention are prevalently formed of disaccharide repeating units formed of uronic acid and hexosamine. These compounds, in psychological conditions, selectively release NO, allowing a reduction in the amount of NO needed to achieve a determined therapeutical effect. This result has been achieved by functionalizing polysaccharides essentially formed of units of uronic acid and/or hexosamine, with subsituents containing a ONO

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2 ? group.