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

Special Part
Carbohydrates
Monosaccharides

CARBOHYDRATES (glycides) are primary products of Photosynthesis composed of carbon, hydrogen, and oxygen. They include aldehydes or ketones of polyhydric alcohols, their derivatives, and Condensation products. The term "carbohydrates"—meaning carbon combined with Water—originates from their general formula C_n(Н₂O)_n. Depending on molecular size and their ability to hydrolyze into varying numbers of monomer units, carbohydrates are classified into monosaccharides, Oligosaccharides, and Polysaccharides (higher polyols).

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Monosaccharides (monoses, sugars) are polyhydroxy aldehydes or polyhydroxy ketones with the general formula C_nН_2nО_n (n = 3–9). Based on the presence of aldehyde or ketone groups, monosaccharides are divided into aldoses and ketoses. They include trioses—aldoses (aldotrioses) or ketoses (ketotrioses); tetroses—aldoses (aldotetroses) or ketoses (ketotetroses); pentoses—aldoses (aldopentoses) or ketoses (ketopentoses, pentuloses); and hexoses—aldoses (aldohexoses) or ketoses (ketohexoses).

Most monosaccharides contain a straight carbon chain, though "branched" sugars are also known—for instance, in apiin (a glycoside found in the roots and leaves of parsley, Petroselinum sativum, Apiaceae); apiose, discovered in seaweeds; and streptose, which is a component of the antibiotic streptomycin.

Monosaccharides occur in a free state or as components of oligosaccharides, polysaccharides, and mixed carbohydrate-containing compounds such as Glycosides and Glycoproteins. They participate in the secondary Biosynthesis of glycosides, Amino Acids, polyphenols, etc. These transformations typically involve nucleoside diphosphate sugars.

In plants, monosaccharides occur both freely and as high-molecular-weight polysaccharides—pentosans and hexosans. The most important pentoses are D-xylose, L-arabinose, D-arabinose, and D-ribose, while notable methylpentoses include L-rhamnose and L-fucose.

D-Xylose (wood sugar) is a structural component of the widespread disaccharide primverose and takes part in the synthesis of polysaccharides (xylans), Gums, Pectins, and hemicelluloses. L-Arabinose is a constituent of natural gums, glycosides (arabinosides), and polysaccharides (arabans, mucilages). D-Arabinose is rarely found in nature. D-Ribose is involved in the synthesis of Nucleic Acids and vitamin B₁₂.

Methylpentoses can be viewed as 6-deoxyhexoses. L-Rhamnose is a component of glycosides and polysaccharides. L-Fucose forms milk oligosaccharides as well as PLANT AND ANIMAL polysaccharides.

Hexoses—specifically glucose and fructose—find medical Applications as excipients or as standalone pharmaceutical agents.

D-Glucose (dextrose, grape sugar), C₆Н₁₂O₆, is a monosaccharide carbohydrate belonging to the aldose group. In its free state, it is found in the Cytoplasm of PLANT Cells AND animal Blood; in bound form, it is a structural component of sucrose, starch, Cellulose, Glycogen, dextrins, and numerous glycosides. It serves as the primary energy source for most organisms.

Isotonic (4.5–5%) and hypertonic (10–40%) glucose solutions are used in cases of hypoglycemia, infections, intoxications, hemorrhagic diathesis, decompensated Heart Failure, Kidney diseases, and pulmonary edema. Glucose also serves as a nutrient and an essential component of blood substitutes.

D-Fructose (levulose, fruit sugar) is a monosaccharide carbohydrate belonging to the ketohexoses. Fructose is the sweetest of all sugars: it is 2.5–3 times sweeter than glucose and 1.5 times sweeter than sucrose. Found alongside glucose in fruits, floral nectar, and green plant Tissues, it is a major constituent of honey.

In the form of D-fructofuranose, fructose is a building block of the Disaccharides sucrose and raffinose, as well as many polysaccharides known as Fructans. The best-known fructan is inulin.

Fructose is involved in Carbohydrate METABOLISM and can be converted into glucose. Because it is metabolized better than glucose by patients with Diabetes Mellitus, it is widely used as a sugar substitute in therapeutic diets. Fructose accounts for over a third of the composition of honey.

Honey (Mel depuratum) is a sweet substance produced in the Salivary Glands of honeybees (Apis mellifera, family Apidae) from floral nectar or honeydew. Honeydew is a sweetish liquid secreted by insects after Processing plant sap. Bees collect honeydew when nectar is scarce, meaning honey may be floral, honeydew-based, or mixed. In the honey Stomach of the bee, nectar mixes with salivary acids and Enzymes, and is then deposited into wax cells. Gradually, the nectar loses moisture, thickens, and ripens into mature honey.

Honey consists of 15–18% water, 0.4–0.8% Proteins, 70–80% invert sugars (including 38.19% fructose, 31.28% glucose, 5% sucrose, 6.83% maltose, and other oligosaccharides), 3.2% Vitamins, enzymes (invertase, diastase, catalase, oxidase, etc.), amines (Choline, acetylcholine, etc.), mineral salts (salts of sodium, potassium, calcium, iron, manganese, and phosphorus), organic acids, Flavonoids, Coumarins, terpenoid compounds, and more. Honey contains substances characteristic of the flowers from which the bee foraged. For instance, linden honey contains farnesol, a sesquiterpene alcohol with sedative and antiseptic properties.

Fresh honey is a thick, transparent, semi-fluid aromatic mass with a specific gravity of 1.420–1.440. Over time, it crystallizes, which is a sign of high quality. Granulated honey can be liquefied in a water bath at 50 °C. The color of honey depends on the pigments present in the nectar, while its aroma is determined by volatile Organic compounds from the nectar. Depending on its chemical composition, its taste may range from sweet to slightly tart or bittersweet.

Honey is a high-calorie, easily digestible food product. It is particularly beneficial for children, convalescent patients, and the elderly. The constituents of honey dilate Blood Vessels, improve myocardial Nutrition and metabolism, increase diuresis, reduce Gastric Acidity, stimulate hematopoiesis, boost the body's immune defenses, and exhibit sedative, laxative, antimicrobial, detoxifying, and antiprotozoal properties. Honey acts as a natural preservative by preventing mold growth.

Apitherapy (Treatment with honey) is used for Disorders of the gastrointestinal tract, Kidneys, Liver, nervous and cardiovascular systems, as well as for diabetes mellitus, anemia, Bronchial Asthma, colds, Skin and eye conditions, and gynecological diseases. The daily dosage of honey is 100 g for adults and 30–50 g for children. Honey is contraindicated in individuals with individual idiosyncrasy to it.