Intermolecular Interactions between Iodine and Low-Methoxylated Apple Pectin Modified with Pharmacophores

The interaction of iodine with low-methoxylated apple pectin (esterification degree 10%) modified with pharmacophores (salicylic, 5-aminosalicylic, and anthranilic acids) in aqueous solution has been investigated by spectral methods. Composition and stability constants of the iodine-containing complexes have been determined, and standard thermodynamic parameters of the complex formation have been calculated. Formation of the molecular 1 : 1 complexes in the considered systems has been governed by the enthalpy term (∆Н° < 0, ∆S° < 0). It has been found that hydroxyl as well as amino groups of the modified polysaccharide matrix can act as the main active sites involved in the interaction with iodine. The influence of the degree of methoxylation of the polysaccharide matrix and the structure of the modifying pharmacophore on the content of iodine, duration of the iodine release from the sample, and the antimicrobial activity has been demonstrated.