PECTIN SUBSTANCES OF THE FRUIT OF TWO TYPES OF HAWTHORN GROWING IN UZBEKISTAN

The article is devoted to the isolation and study of the physicochemical properties of pectin substances (PS) of the fruits of two species of hawthorn – Crataegus songarica and Crataegus turkestanica, growing in Uzbekistan. The yield of PS from the fruits of C. songarica and C. turkestanica is 9.58, 11.25%, respectively. In the hydrolysis products of the obtained PS, monosaccharides galactose, glucose, arabinose, xylose, uronic acids and traces of rhamnose were found. The data of titrimetric analysis show that there is no strong difference in the values of namber of free hydroxyl groups, estereied carboxyl groups, common carboxyl groups and degree of esterification between the two studied hawthorn species. The PSs of the studied hawthorn species are highly esterified (61.9–62.4%). Solutions of pectin substances with iodine solution give a characteristic blue color, which indicates the presence of starch-type glucans. The indicators of relative viscosity (ηrel) of aqueous solutions of pectin substances according to viscometry data are 2.03 (C. songarica) and 6.56 (C. turkestanica). Analysis of the IR spectra of pectin substances from the fruits of C. songarica and C. turkestanica shows that the studied biopolymers are carboxypolysaccharides with the main α-1→4 glycosidic bond between D-galacturonic acid residues in the main chain, where carboxyl groups are methylated. The molecular weights of the samples were determined by the universal calibration gel chromatography method. It has been established that C. songarica fruit pectin consists of three components, while C. turcistanica fruit pectin consists of two components. The total molecular weight of pectin from the fruits of C. songarica and C. turkestanica is 110630 Da and 110000 Da, respectively.

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