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Complexation of apple pectin with L-phenylalanine and L-histidine in aqueous solutions was studied using spectral methods. Stoichiometric compositions of complexes and stability constants were determined. Standard thermodynamic characteristics (ΔH°, ΔG°, and ΔS°) of complexation were calculated.

The dynamics of changes in the size of polyelectrolyte complex microparticles of chitosan hydrochloride and polyanions—the sodium salt of N-succinylchitosan and hyaluronic acid under the action of enzyme hyaluronidase—is considered. We demonstrate that polyelectrolyte complex microparticles undergo enzymatic degradation, which leads to a decrease in particle size to 16–70 nm within 2 to 10 min depending on the polymer pair. We assume that the enzymatic degradation of polyelectrolyte complex microparticles proceeds due to the enzymatic cleavage of the lyophilizing chain fragments and the release of a hydrophobic core of nanoparticles composed of densely packed ladder sequences of pairs of units of electrostatically complementary polyelectrolytes linked by salt bonds. The subsequent hydrophobic interactions between these particles lead to the rapid formation of precipitates of stoichiometric polyelectrolyte complexes.

Low- and high-methoxylated pectins were synthesized and modified with anthranilic and salicylic acids to obtain effective polymeric ligands. On their basis, new copper(II) metal-polymer complexes were obtained, their composition was determined, stability constants and thermodynamic characteristics of the complex formation process were calculated. The efficiency of the metal binding to the polymer ligand depends mainly on the degree of pectin methoxylation, the acidity of the medium, the temperature of the process, and also on the structure of the pharmacologically active modifier acid. The thermal stability of polymeric copper(II) complexes increases with the introduction of an organic complexone into the polysaccharide and with a decrease in the degree of pectin methoxylation.

Spectral methods have been used to study the complexation of apple pectin modified with organic pharmacophores (nicotinic, salicylic, 5-aminosalicylic, or anthranilic acid) with Cu2+, Co2+, and Mn2+ ions in an aqueous solution. The composition and stability series of the metal complexes, corresponding to the empirical Irving–Williams series, have been established. The standard thermodynamic parameters (ΔH°, ΔG°, and ΔS°) of the complexation process have been calculated. It has been shown by means of 13C NMR and IR spectroscopy that the interaction of pharmacophore-containing pectins with d-metal ions (Cu2+, Co2+, Mn2+) occurs via the carbonyl and hydroxyl groups of the modified polymer matrices. The viscosity and thermal properties of the metal complexes have been determined.

Complexation of cobalt(II) chloride with apple pectin modified with organic pharmacophores (nicotinic, salicylic, 5-aminosalicylic, or anthranilic acid) has been studied by spectral methods. Molar composition, stability constants of the complexes, and pH range of their existence have been determined; standard thermodynamic characteristics (ΔH°, ΔG°, ΔS°) of the complexes formation have been calculated. it has been shown that cobalt(II) ions form complexes of different stability with pharmacophore-containing pectins, which may be due to the unequal affinity of the metal ions to the donor groups of the monomer unit of the polysaccharide matrices.

From the point of view of aggregative stability, aqueous dispersions of particles of polyelectrolyte complexes based on chitosan hydrochloride and sodium salt of N-succinyl-chitosan were obtained and characterized. It is shown that, in the entire range of experimental conditions considered, these polyelectrolytes form an aggregately unstable disperse system. At the same time, the relative aggregative stability of the systems (the time before the formation of a precipitate of the polyelectrolyte complex) increases with an increase in the molecular weights of the polymers, with an increase in the molar ratio of the components, and with an increase in the concentration of polymers in the solution and reaches 30 days. The average particle size in the region of the relative aggregative stability of dispersed systems is 100–380 nm, which is promising for their use as lysed drug carriers for their targeted transport in the body.

Aqueous dispersion of particles of interpolyelectrolyte complexes based on chitosan hydrochloride and sodium salt of chitosan succinamide have been prepared and characterized. The size of the complex particles and the system stability are affected by the concentration of the polymers in the solution and the molar ratio of the components. In the studied disperse systems, steady aggregation of the particles has led to the precipitation of the insoluble complex, and the relative stability of the systems against aggregation has increased with the increase in the fraction of the lower-molecular component and concentration of the polymers in the solution.

The chemical modification of chitosan, pectin, and arabinogalactan with poorly soluble herbicide chlorsulfuron under mechanical effect is studied. It is shown that the mechanical stress on polysaccharides and herbicide provokes conformational and configurational transformations and disordering in biopolymer macromolecules as well as an increase in the concentration of defects in the crystalline phase of the polysaccharides and herbicide. The change in the conformational state of the polysaccharides under shock-shear impacts gives rise to intermolecular complexes stabilized by hydrogen bonds.

We summarize data on the kinetics of the oxidative transformations of natural polysaccharides (arabinogalactan, citrous and apple pectins) under the action of the hydrogen peroxide and ozone-oxygen mixture in water solutions. The oxidation of biopolymers is accompanied by the destruction of their molecules leading to the creation of low-molecular polymer products with additional functional groups. Variation of the conditions for the process (oxidation time, temperature, biopolymer and oxidizer concentration) allows us to control the destruction rate of the polysaccharides as well as the functionalization rate of the created low-molecular products. We show that the oxidation of the polysaccharides goes by a radical mechanism. We propose a possible scheme of the oxidative transformations of the polysaccharides.

Preparation of a polyelectrolyte complex of chitosan with the oxidized form of Siberian larch arabinogalactan at the component ratio from 0.05: 1 to 1: 1 was studied by spectrometry and laser scattering. Water-insoluble films based on this complex were prepared. These films were used as a matrix for drug immobilization. The possibility of controlling the rate and degree of the drug release from the film by variation of the polysaccharide ratio, modification of the polymer film with a sodium dodecyl sulfate solution, or heat treatment was demonstrated with cefazolin antibiotic as example. The films obtained exhibit high bactericidal activity.

The thermodynamics of complexation of arabinogalactan with salicylic and p-aminobenzoic acids in aqueous solutions is studied by means spectroscopy. The standard thermodynamic characteristics (ΔH°; ΔG°; ΔS°) of complexation are calculated.

The modification of arabinogalactan by poorly soluble pesticides (chlorsulfuron, carbendasim, and thiram) is studied via an impact–deformation action method. It is found that the mechanochemical action on arabinogalactan leads to change in its macromolecular structure owing to the polymer chain breakage, splitting of the side fragments, and the appearance of new functional (carboxyl) groups. The impact–shear action on pesticides leads to disordering of the crystalline structure with the breakage of the intermolecular hydrogen bonds. NMR relaxation, UV, IR, and 13C NMR spectroscopic methods are used to demonstrate the formation of the inclusion complexes with the participation of the nitrogen-containing groups of a herbicide and hydroxyl and ester groups of the polymer. The complex formation results in increases in the characteristic viscosities of the composition solutions relative to those of the components activated individually and an increase in the pesticide content going into solution (from 1.5 to 5.0 times). The investigation of the thermal characteristics of the compositions via TGA and DTA methods shows that, first, the sample decomposition is more intense than that of the initial components and, second, the crystalline phase of the herbicide in the modified compositions almost completely disappears. The formation of new properties provides high stability and biological activity to the compositions with a simultaneous possibility to decrease the pesticide consumption norm 10-fold.

A procedure was developed for preparing stable iodine-containing films and powders based on pectin and pectin-nicotinic acid complex; their high bactericidal activity was revealed. The complexation relationships in the pectin-iodine and pectin-nicotinic acid-iodine systems were studied by spectrophotometry. The optimum preparation conditions, compositions, and stability constants of the complexes were determined. The dynamics of iodine release from the films and powders was studied.

Interaction of citrus pectin with Ceftriaxone has been studied by UV, IR, and NMR spectroscopy. Polymer films capable of controlled Ceftriaxone release have been prepared based on the citrus pectin mixture with polyvinyl alcohol. The decisive role of supramolecular structure of the polymeric matrix on the films transport properties has been demonstrated.

The interaction of the natural polysaccharide arabinogalactan and its oxidized fractions with 5-aminosalicylic acid, 4-aminosalicylic acid, and isonicotinic acid hydrazide in aqueous solutions is investigated with the use of physicochemical methods. The compositions and stability constants of the formed complexes are studied, and the optimal conditions of their preparation are found. On the basis of spectral investigations and quantum-chemical calculations, the scheme of interaction between system components that leads to formation of cyclic structures is developed.

Arabinogalactan poly- and oligosaccharides from Siberian larch (Larix sibirica L.) were modified with 5-aminosalicylic acid. The chemical composition and certain physicochemical properties were studied. The optimal conditions for preparing the modified compounds were found. These compounds were demonstrated to possess anti-ulcer and anti-inflammatory activity in tests on experimental animals.

The oxidation of an arabinogalactan in an aqueous medium under the action of hydrogen peroxide and dioxygen is accompanied by accumulation of carbonyl and carboxy groups in the oxidized polysaccharide macromolecules and derived oligomers. The addition of iron sulfate accelerates the radical oxidation of the biopolymer, while the addition of phenol inhibits the oxidation. The influence of the temperature and the initial H2O2 and arabinogalactan concentrations on the kinetics of the initial oxidation stage of the natural polysaccharide was studied.

The reaction of an arabinogalactan and its oxidized forms with the antituberculosis preparation isonicotinic acid hydrazide was investigated. The chemical composition and certain physicochemical properties of the modified compounds were studied. A correlation was found between the concentration of carboxylic acids in the polysaccharides and the drug content in the modified compounds.