The amino-de-alkoxylation of the esterified polysaccharides with primary alkylamines led to the formation of secondary amide. Amides are highly stable organic compounds, which can be exploited for various other applications. The main advantage of this reaction is the easy isolation of the product from the reaction medium by precipitation or filtration; however, the purification of the product involves thorough washing by the organic solvent and acidified ethanol to remove excess reagent (free and in the form of amine salts) and degradation products. An interesting group of amidated polysaccharides are secondary amides with long alkyl chains. Hydrophobic amidated derivatives containing n-alkyl chains (C4 to C18) are able to absorb non-polar compounds and thereby decrease the in vivo level of neutral sterols and triglycerides. The newly prepared derivatives with long alkyl chains could be used hydrophobic sorbents capable of reducing the level of neutral sterols and lipids action in the digestive tract. Alginic acid is a very active substance for these issues. N-Alkylamides of alginic acid are also interesting derivatives that can be applied during the sorption of neutral sterol, with the assumption of lowering cholesterol in the body. This is especially important in medicine. The N-octadecylamide of alginic acid especially has been successfully tested in-vitro and in-vivo experiments. The advantage of alginic acid is the presence of carboxyl groups in the molecule (no oxidation, carboxymethylation or other modification of the polysaccharide necessary). Alginic acid can be directly used for amidation, with the advantage of the presence of a high content of carboxyl groups with the aim of preparation of highly amidated products.