Pharmacognosy with the Basics of Plant Biochemistry - Kovalyov V. M. 2004

Special Part
Carbohydrates
Medicinal plants and raw materials containing fructans

CHICORY ROOTS — RADICES CICHORІІ

Chicory, blue daisy — Cichorium intybus L., fam. Asteraceae

Common chicory; the international, Ukrainian, and Russian names derive from the Arabic kichorion, while intybus is the Latinized name of chicory. Commonly known as "blue sailors" due to its rod-like stems.

Perennial or biennial (cultivated varieties) herbaceous plant. The ROOT is taproot, fleshy, spindle-shaped, with a wrinkled surface; brownish-gray on the outside, white or yellowish on the inside. The stem is branching, 75-120 cm high, with spreading twiggy branches. Basal leaves have winged petioles, pinnatifid or entire, with serrated margins, forming a basal rosette. Upper leaves are lanceolate, clasping the stem at the base. Flower heads are arranged in twos or threes in the axils of the upper and middle leaves, with a multi-layered involucre bordered by ciliated leaflets. All flowers are blue (rarely pale violet), ligulate, bisexual. Achenes are glabrous, three- to pentagonal. Articulated laticifers are present in all plant Organs.

Distribution. Grows throughout Eastern Europe, the Caucasus, Siberia, Central Asia, in waste grounds, along roads, in ditches, meadows, and forest clearings. Natural reserves are unlimited. Cultivated as a biennial plant in Ukraine, Belarus, Russia, the Baltic states, Belgium, Germany, and the USA.

Harvesting. In autumn (September-October), roots are dug up or plowed out, cleaned of soil, the aerial parts are trimmed, and washed in cold Water. Thick short roots are cut lengthwise, and long ones crosswise into pieces. They are dried after wilting in kilns or dryers at a Temperature of 40-50 °C.

Chemical composition of the raw material. Roots contain CARBOHYDRATES (40%), including inulin, free fructose; the milky sap also contains bitter sesquiterpene lactones (lactucin, lactucopicrin), phenolic acids (chicoric), taraxasterol, Choline, methoxycoumarin, cichorin, ascorbic acid, protein and resinous substances.

Biological activity and application. Galenical preparations of chicory are used to stimulate appetite and improve digestive function, particularly in gastritis, enteritis, and colitis; they activate METABOLISM and are used for dermatological conditions. The root decoction exhibits hypoglycemic effects, and preparations derived from it show thyrastatic activity. Chicory is a component of the medicinal product Gastrovitot.

ECHINACEA HERB — HERBА ECHINACEАE PURPUREAE ECHINACEA RHIZOMES AND ROOTS — RHIZOMATA ET RADICES ECHІNACEAE PURPUREAE

Purple coneflower — Echinacea purpurea (L.) Moench., fam. Asteraceae

Purple coneflower; the Latinized name originates from the Greek echinos, meaning hedgehog.

Perennial herbaceous plant. Taproot with numerous lateral fleshy roots. Stem is erect, 50-150 cm high. Leaves are simple, rough, oval- or linear-lanceolate, with crenate-serrate margins; lower leaves are long-petioled, upper ones are nearly sessile. Flowers are gathered in large (up to 10 cm in diameter) heads, located singly at the ends of stems and branches. Ray flowers are small, long-ligulate, sterile, purple, dark red, or yellow; disk flowers are tubular, bisexual. The fruit is a four-sided achene with a pappus-like calyx.

Distribution. Native to the eastern United States. Cultivated as an ornamental and medicinal plant in Ukraine, Russia, the Baltic states, and many Eastern European countries.

Along with Echinacea purpurea, narrow-leafed coneflower — Echinacea angustifolia DC, and pale purple coneflower — Echinacea pallida Nutt. are also utilized. Both species are widely cultivated.

Harvesting. Flowering shoots 25-35 cm long are cut. Rhizomes and roots are harvested in autumn, freed from soil, washed, wilted, and cut into pieces. Dried in well-ventilated areas or dryers at a temperature of 40-45 °C.

Chemical COMPOSITION OF THE raw material. Polysaccharides found in all PARTS OF THE plant structurally belong to heteroxylans, arabinorhamnogalactans, and Fructans (inulin). Phenolic Compounds of the herb are represented by hydroxycinnamic acids (chicoric, ferulic, coumaric, caffeic), the phenolic glycoside echinacoside, which hydrolyzes into pyrocatechol, caffeic acid, ethanol, two glucose molecules, and one rhamnose molecule; in addition, there are Flavonoids, Tannins, saponins, polyamides, echinacin (an amide of a polyunsaturated acid) and echinolon (an unsaturated ketol alcohol), and essential oil (0.04-0.22%). Carbohydrates of the underground organs are represented by low-molecular-weight fructans and inulin, the content of which reaches 6%; glucose (7%) is also present, along with fatty oil, betaine, phenolcarboxylic acids, and resins. The plant is rich in Enzymes and Trace Elements: selenium, cobalt, silver, molybdenum, zinc, manganese, etc.

Biological activity and application. Echinacea preparations such as tincture and Immunal exhibit immunostimulating, antioxidant, and membrane-stabilizing effects; they promote the healing of wounds, Burns, and ulcers, and are used for infectious and viral diseases, particularly those of the Upper Respiratory Tract.

In homeopathy, the fresh flowering herb of three Echinacea species is used to prepare a tincture, which is applied in appropriate dilutions topically, internally, or via injection for boils, slow-healing wounds, suppurative and ulcerative processes, as well as insect and snake bites.

Galactans

Galactans are isolated from various plant raw Materials (fir, white birch, sugar maple, white lupine, etc.). Sulfated galactans have medical Applications, which include polysaccharides of marine Algae belonging to the subkingdom of red algae — Rhodobiota. Based on their composition, Structure, and properties, these polysaccharides are divided into two groups: the Agar group and the carrageenan group.

Agar-agar is a mixture of agarose polysaccharides (up to 50-80%) and "agaropectin". Agarose is built from strictly repeating agarobiose units linked into chains by ß-1 → 3 glycosidic bonds. Monosaccharide residues in agarobiose (3-O-substituted ß-D-galactopyranose and 4-O-substituted 3,6-anhydro-a-L-galactopyranose) are linked by a-1 → 4 bonds.

The agarobiose unit in agarose has the following structure:

Depending on the algae species, The chemical composition of agarose may vary due to The formation of galactose derivatives.

"Agaropectin" is a fraction of acidic polysaccharides in which carbohydrates are linked in a similar manner, but their regularity is masked by the presence of pyruvic acid residues. Due to this, cyclic acetals are formed with OH groups at C-4 and C-6 of certain ß-D-galactose residues. It is also known that its sulfate group content is higher, and a significant amount of 3,6-anhydrogalactose is replaced by 6-sulfo-a-L-galactose residues.

Agar is a polyanion and can therefore act as a barrier to seawater cations, while its hydrophilicity prevents the algae from drying out during low tide. Industrially, agar is obtained from red algae of the genera Gracilaria (about 60% of world agar-agar production) and Gelidium. In Russia, Ahnfeltia plicata from the family Phyllophoraceae is of industrial importance.

Appearance of red algae (Gelidium spp.)

The Cell walls of red algae consist of Cellulose micelles or other polysaccharides embedded in a mucilaginous agar matrix. In algae, this matrix firmly binds the Cells together, ensuring structural integrity of the Organism. To obtain agar-agar, the algae are crushed, treated with an alkali solution to remove some of the impurities, and extracted with hot water. Agar is purified via a freeze-thaw method, during which the mother liquor and gel separate. Impurities are removed along with the mother liquor. After drying, thin flakes are obtained.

Agar-agar is a brownish, transparent film, 1–3 mm thick, with a wrinkled surface, odorless and tasteless. Agarose is insoluble in cold water, but readily soluble in boiling water. Solutions containing 0.5–1.5% agar, upon cooling to 32–39 °C, form firm gels that liquefy at 60 °C and melt at 85 °C. Gel formation is more characteristic of agarose than of agaropectin. The moisture content in agar-agar ranges from 17–22%, and the ash content is about 8%; when burned, it should not produce the odor of scorched horn.

Agar is used to prepare solid nutrient media for the cultivation and Diagnosis of Bacteria, and as a gelling agent in the food industry (especially confectionery). Agarose serves as a carrier in Gel chromatography, Affinity Chromatography, gel Electrophoresis, immunodiffusion, and Immunoelectrophoresis. It is also included in certain medications as an excipient or enterosorbent.

Carrageenan was first obtained by K. Schmidt in 1844 from the red alga Chondrus crispus. It is a group of unbranched sulfated polysaccharides whose molecules are built from D-galactopyranose derivative residues with a strict alternation of a-1 → 3 and ß-1 → 4 bonds between them (i.e., alternating disaccharide units). The difference among individual carrageenans is due to the fact that the 4-O-substituted monosaccharide residue can be not only D-galactose but also 3,6-anhydro-D-galactose. The OH groups can be sulfated and occasionally methylated; the sulfate content is quite high (over 20%). Carrageenans are designated by Greek letters.

The molecules of these polysaccharides have a double-helix conformation. Each helix is a polysaccharide chain with three disaccharide residues per turn. The double-helix form is stabilized by Hydrogen Bonds between the OH groups at C-2 of one carabiose unit and C-6 of another unit.

R₁= R₂= R₄= Н, R₃= SO₃ у - carrageenan

R₁= R₂= Н, R₃= R₄= SO₃ 5 - carrageenan and other sulfation variants of D-galactose

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R₁ = R₂ = R₃ = R₄ = H ß - carrageenan

R₁ = R₂ = R₃ = H, R₄ = SО₃ a - carrageenan and others

In the form of sodium salts, carrageenans are soluble in cold water, forming viscous solutions; their molecular weight ranges from several hundred thousand to millions. Similar to agar, carrageenan forms gels.

For the industrial production of carrageenans, red algae of the genera Chondrus, Gigartina, and Hypnea are used, as well as the Black Sea Phyllophora (Phyllophora nervosa) in Ukraine. The algae are treated with cold water, often in the presence of alkali or soda. Due to the formation of 3,6-anhydrogalactose during extraction, the quality of the polysaccharides and their gelling properties are improved.

Carrageenan is used in the food industry as a stabilizer for protein solutions, as well as in pharmacy and cosmetics. Its global production reaches 13 thousand tons per year.

Heteropolysaccharides

Heteropolysaccharides are composed of various Monosaccharides. They are widely distributed in plants and find applications in medicine, pharmacy, the food industry, and other fields. Heteropolysaccharides include Gums, mucilages, pectic substances, hemicelluloses, and certain polysaccharides found in algae.

Gums

Gums (Gummi) are formed in plants As a result of the mucilaginous degeneration of the cell walls in young or old pith or wood Tissues located near the cambial layer, triggered by injury to the tree or shrub. In arid regions, plants produce significant amounts of gum, which helps retain moisture.

Classification and chemical structure. Gums are polysaccharides containing calcium and magnesium salts of uronic acids, along with partially esterified neutral monosaccharides. Their exact structure remains unknown, which somewhat complicates their systematic classification. Gums are classified based on their Chemical Composition and solubility.

According to their chemical composition, they are divided into:

acidic gums, whose acidity is due to the presence of glucuronic and galacturonic acids (e.g., acacia and apricot gums);

acidic gums, whose acidity is due to the presence of sulfite groups;

neutral gums (glucomannans, galactomannans, etc.).

According to solubility, they are distinguished as:

arabinogums — gums that dissolve in cold water (gum arabic; gums of apricot, plum, sweet cherry, silver wattle, and Siberian larch, or gumilarix);

bassorin — gums that are sparingly soluble yet swell considerably in water (such as tragacanth and Caspian boxthorn gums);

cerasin — gums insoluble in cold water, partially soluble upon boiling, and non-Swelling (such as cherry gum).

The chemical constitution of certain gums has been studied and their structures elucidated.

Physicochemical Properties. Gums are hydrophilic colloids. They are insoluble in fatty oils, alcohol, ether, chloroform, and other organic Solvents, which distinguishes them from resins, rubber, and gutta-percha that also exude from cuts and cracks in tree trunks. Resins and rubber are insoluble in water yet readily soluble in alcohol; when burned, resins emit an aromatic fragrance, whereas gums smell like burning paper. Gums are classified as polysaccharides, whereas resins, rubbers, and gutta-percha belong to terpenoids.

Upon reaction with a solution of lithium chloride and iodine in potassium iodide, gums yield a violet coloration, while Dragendorff's reagent precipitates them in various hues ranging from pale red (gum arabic) to muddy green (tragacanth).

Harvesting. Gum is contained within tree trunks under significant pressure. When the bark is damaged or cracks appear, the gum exudes outward via medullary rays and seals the wounds.

To obtain gum, incisions are made in the trunks. Tapping is conducted in calm weather to prevent the raw material from becoming contaminated with dust and sand. The gum emerges as a viscous mass. It is collected 5–6 days post-tapping and sorted by color. White grades are utilized in the pharmaceutical industry, whereas yellow and brown grades serve technical purposes.

The volume of exuded gum depends on the plant's vegetative stage and age: the greatest yield occurs prior to flowering, and as the plant matures, gum output increases.

Despite the advent of synthetic polymers, gums have lost none of their importance. They are still harvested on a large scale for the food, textile, paint and varnish, leather, and pharmaceutical industries, among others.

Mucilages

Mucilages (Mucilago) are heteropolysaccharides that accumulate within specific, undamaged plant organs such as tubers, roots, and seeds. They are synthesized as normal metabolic products and function as nutritional reserves or water-retaining agents, particularly in the tissues of succulents.

Based on their origin and formation, mucilages are divided into the following groups:

mucilages formed in plants via mucous degeneration of cell walls;

mucilages formed through the mucilagination of living cells;

algal mucilages;

bacterial mucilages.

Structurally, mucilages are less complex than gums. Chemically, they can be categorized into four groups: glucomannans, galactomannans, gum-like mucilages, and cereal mucilages.

Glucomannans are found in various representatives of Araceae, Liliaceae, Iridaceae, and Orchidaceae (specifically in salep tubers). These polysaccharides possess a linear structure wherein glucose and mannose residues alternate via ß-1 → 4 linkages, occasionally bearing acetyl groups.

Galactomannans are Reserve Polysaccharides found in the seeds of leguminous plants. Regardless of their source, they share common structural features: a linear backbone of D-mannopyranose residues linked by ß-1 → 4 bonds. Some of these possess single galactopyranose residues at the C-6 position. These polysaccharides differ in their mannose-to-galactose ratio and degree of branching. Certain Examples, such as guaran from guar seeds (guar gum) or the locust bean gum from Ceratonia siliqua, are produced industrially and employed as thickeners or stabilizers for Suspensions and emulsions. Guarem is a commercially available preparation consisting of microgranules of gelling fibers, used as a hypoglycemic, hypocholesterolemic, and antihypertensive agent.

Gum-like mucilages occur in plants such as flax, plantain, elm, members of the Apiaceae family, and others. The structure of these polysaccharides is more complex, comprising various neutral monosaccharides and specific uronic acids. As a rule, the content of uronic acids does not exceed 40% relative to the other monosaccharides.

Cereal mucilages (often referred to as cereal gums) are extracted from wheat, rye, barley, and other flours via aqueous extraction. The exact structure of these arabinoxylans has not been definitively established. The main polysaccharide chain comprises ß-D-xylopyranose residues linked by 1 → 4 bonds. Side chains feature single L-arabinofuranose residues attached to the main chain at the C-3 carbon atom. The acid hydrolysate of rye flour mucilage predominantly contains xylose alongside arabinose and minor amounts of galactose.

Pectic Substances, Pectin (Pectinum)

Pectic substances are polyuronides that are widely distributed in the aerial parts of plants and various algae. They are particularly abundant in fruits (apples, quinces, plums, etc.), roots and tubers (beets, carrots, radishes), and stems (flax, hemp, etc.). The softening of fruits during ripening and storage is associated with the degradation of pectic substances, as their insoluble forms convert into water-soluble pectin. Insoluble pectic substances are termed protopectins and reside within the primary Cell wall. Treatment with dilute acids yields water-soluble pectic acids bearing methoxyl groups. Salts of these acids are called pectates. Substances formed following the removal of methoxyl groups are referred to as pectic acids (or pectic substances lacking methoxyls), and their salts as pectates.

Pectic substances are vital components of cell walls and intercellular spaces in all higher and lower plants, and they have also been detected in plant sap. Within The cell wall, pectic substances are associated with cellulose, hemicelluloses, and Lignin, while being scarce or entirely absent in the secondary cell wall. Being hydrophilic colloids, pectic substances are responsible for the water-holding capacity and turgor of plant tissues.

Pectic substances fill the intercellular spaces. When stems of flax, jute, or hemp are soaked in water, the pectic substances dissolve, allowing the bast fibers to easily separate from one another.

Pectic substances are primarily composed of a-D-galacturonic acid residues linked by 1 → 4 bonds. The hydrogen atoms of the carboxyl groups are partially or fully substituted by methyl groups or Metal Ions. Side-branched chains consisting of D-galactose, L-arabinose, and less frequently D-xylose, L-rhamnose, and L-fucose residues can be attached to the hydroxyl groups.

In most cases, pectic substances in higher plants consist of three heteropolysaccharides: polygalacturonan, araban, and galactan. Galacturonan can exist in two forms: one devoid of neutral monosaccharides (pectic acid) and another associated with neutral monosaccharides (such as rhamnose and arabinose). Unlike the highly branched araban, the galactan of pectic substances forms a chain of galactose molecules connected by 1 → 4 glycosidic bonds. Araban and galactan are linked to pectic acid via ester bonds. Xylose, rhamnose, and glucose are involved exclusively in the formation of polysaccharide side chains.

Pectin extracted from various fruits and vegetables contains varying amounts of galacturonic acid residues: orange pectin contains 92.1%, lemon pectin 90.4%, apple pectin 88%, sugar beet pectin 82.3%, and carrot pectin 76.7%.

Algal pectic substances differ from the analogous polysaccharides of terrestrial plants by a low degree of uronic acid methoxylation.

In their pure form, Pectins are amorphous powders with a molecular weight ranging from 25,000 to 50,000. They appear white to yellowish, occasionally brownish or greyish, are virtually odorless, poorly soluble in cold water, and form colloidal solutions upon heating. The solubility of pectin depends on its degree of polymerization and Esterification. Water solubility improves with a high degree of methoxylation and a smaller molecular size. Pectin is insoluble in alcohol and other organic solvents; rather than melting at elevated temperatures, it decomposes. Pectin solutions are optically active and exhibit dextrorotation.

Complete or partial Hydrolysis of pectic substances can occur in the presence of a mineral acid or enzymatically. Polyuronides are more difficult to hydrolyze than neutral glycans (requiring significant acid concentration, prolonged heating, and sometimes pressure).

A characteristic property of pectin is its ability to form gels in the presence of sugars and acids in specific ratios. Such gels form most effectively at pH 3.1–3.5 with The addition of sucrose or hexose.

The physical and mechanical parameters that characterize pectic substances and determine their Practical Applications include the average molecular weight, degree of esterification, methoxyl content, and gelling capacity. The most critical quality indicator for pectins is the degree of esterification (DE), which is defined by the number of methoxylated carboxyl groups in the polygalacturonic acid chain. Pectins with a 100% degree of esterification contain 16.32% methoxyl groups. Typically, pectins are classified into low-ester (DE < 50%) and high-ester (DE > 50%) pectins. Low-ester pectins form gels in the presence of divalent cations without the addition of sucrose, whereas high-ester pectins require sucrose to gel.