Announcement of the thesis defense of the Doctor of Philosophy (PhD) Siddikova Azizakhon Abdug‘afforovna

Announcement of the thesis defense of the Doctor of Philosophy (PhD) Siddikova Azizakhon Abdug‘afforovna

 

I. General information

The topic of the dissertation, the cipher of the specialty (the name of the branch of science in which the academic degree is awarded): “Polysaccharides of two plant species Scutellaria and Stachys hissarica”, 02.00.10 – Bioorganic chemistry (technical sciences).

The registration number of the thesis topic: V2019.2.PhD/K206.

Scientific supervisor: Doctor of Technical Sciences, senior scientific researcher Khalilov Ravshanjon Muratdjanovich.

The name of the institution where the dissertation was performed: S. Yu. Yunusov Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan.

The name of the institution where the Scientific council works, the number of the scientific council: S. Yu. Yunusov Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, DSс.02/30.01.2020. К/Т. 104.01.

Official opponents: Doctor of Chemical Sciences, Normaxamatov Nodirali Saxobataliyevich, Doctor of Chemical Sciences, Shomurotov Shavkat Abduganiyevich

Leading organization: National University of Uzbekistan

II. The purpose of the study.  

Study of polysaccharides from the plants Scutellaria adenostegia, S. comosa, and Stachys hissarica. Determination of the structure and properties of glucoarabinogalactans and identification of their specific biological activity.

III. Scientific novelty of the research:

New data have been obtained on the properties, structure, and biological activity of polysaccharides from Stachys hissarica, Scutellaria adenostegia, and S. comosa.

For the first time, a water-soluble polysaccharide (WSP) with molecular masses of 43.8 and 29.5 kDa, rich in arabinose monosaccharide residues (50.54–60.41%), was isolated from the aerial parts of Stachys hissarica. Chemical and NMR spectroscopic analyses showed that the WSP contains fragments of α-(1→3)-Araf, β-(1→4)-Xylp, α-(1→3)-Glcp, β-(1→3,6)-Galp, as well as terminal α-Araf and α-Glcp residues at the non-reducing ends.

The obtained results suggest that the WSP of St. hissarica represents a heterogeneous polysaccharide, consisting of two types of polysaccharides – gluco- and/or galactoxylarabans.

The prebiotic activity of the WSP-s from Stachys hissarica and S. comosa was revealed based on their influence on the growth of the probiotic strain Lactobacillus casei K7. The analysis showed that the addition of WSP from St. hissarica to MRS broth led to a more pronounced stimulation of L. casei K7 growth and resulted in a higher viable cell count (2×10¹⁰ CFU/mL) compared to the WSP of Scutellaria comosa and the control (9×10⁹ CFU/mL).

For the first time, glucoarabinogalactans (GAG-Sa and GAG-Sco) were isolated from the WSPs of Scutellaria adenostegia and S. comosa. Chemical and spectral analyses showed that GAG-Sa and GAG-Sco are branched polysaccharides with a main chain composed of β-(1→6)-linked galactopyranose residues, differing in their side chains.

The side chain of GAG-Sa includes single residues of β-D-galactopyranose, α-D-glucopyranose, α-L-arabinofuranose, and its (1→3)-linked disaccharide fragments, as well as the presence of 6-O-methyl-α-glucuronic acid attached at position C-3 of the main chain.

In GAG-Sco, the side chains at C-2 include terminal arabinofuranose and glucose, as well as α-Araf-(1→5)-α-Araf oligosaccharide fragments.

The immunological activity (phagocytic activity and phagocytic index) of water-soluble polysaccharides from Scutellaria adenostegia and S. comosa was studied for the first time. It was shown that administration of the WSP from Scutellaria comosa increased the number of killed Staphylococcus particles captured by neutrophils by 35%, and the WSP from Scutellaria adenostegia by 30% relative to the baseline level with prednisolone. This suggests their potential use in the diagnosis of primary and secondary immunodeficiency conditions.

The gastroprotective properties of pectic substances from S. comosa were identified. It was established that the anti-ulcer activity of these pectic substances is related to such physicochemical parameters as molecular weight, viscosity, degree of esterification, and especially their gel-forming ability.

The relationship between the biological activity of polysaccharides and their chemical structure was studied. It was shown that an important contribution to biological activity is made primarily by the branching of the main chain, including differences in oligosaccharide fragments, types of monosaccharides, and glycosidic linkages in the side chains of the macromolecule.

IV. Implementation of the research results.

For the first time, an antimicrobial herbal preparation was developed based on polysaccharides from Scutellaria comosa and a dry aqueous extract of onion husks (Allium cepa L.) (DAEOH). This preparation demonstrated the ability to inhibit the growth of Pseudomonas aeruginosa 003841/114, Proteus mirabilis 9, Staphylococcus aureus, and Bacillus subtilis VKM.

The developed phytopreparation expands the range of agents with prebiotic and antibacterial activity, including against antibiotic-resistant strains of microorganisms.

Based on the results of scientific research, a patent of the Republic of Uzbekistan No. IAP 7778 (registered in the state registry on July 30, 2024) was obtained for the method of obtaining the antimicrobial agent.

Expert conclusions were received from: the Institute of Immunology and Human Genomics, Academy of Sciences of the Republic of Uzbekistan (dated July 25, 2025) — on the phagocytic activity of polysaccharides from two Scutellaria species;

 the LLC AllWellLab of the Institute of Microbiology (dated August 14, 2023) — on the prebiotic activity of polysaccharides from Stachys hissarica and Scutellaria;

 the Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan (dated May 12, 2022) — on the anti-inflammatory and gastroprotective activity of pectic substances from Scutellaria comosa.

The obtained data make it possible to create agents with antimicrobial, phagocytic, and anti-ulcer activity.

The scientific results on the chemical structure and biological activity of the polysaccharides were used in the implementation of the basic research project (2021–2025) carried out at the Laboratory of Chemistry of High-Molecular Plant Substances, Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan (reference No. 4/1255-497, February 27, 2025, and No. 4/1255-2476, October 17, 2025).

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