Oligosaccharides

These are complex carbohydrates, composed of 2-10 monosaccharide molecules. The simplest complex carbohydrates are disaccharides. They are composed of two identical or different monosaccharide molecules. There are not many disaccharides that exist independently in nature. The most common disaccharides are: maltose (4-O-α-D-glucopyranosyl-D-glucose), cellobiose (D-glucosyl-β-(1→4)-D-glucose), lactose (β-D-galactopyranosyl-(1↔4)α-D-glucopyranose), sucrose (β-D-fructofuranosyl-(2→1)-α-D-glucopyranosidase), trehalose (α-D-glucopyranosyl-(1→1)-α-D-glucopyranosidase). Much more commonly in nature, disaccharide fragments are found, which are part of many plant and bacterial glycosides. Disaccharides are hemiacetals, i.e. O-glycosides, in which the residue of the second monosaccharide molecule is an aglycone. Depending on the nature of glycosidic bond formation, disaccharides are divided into reducing and non-reducing disaccharides. Reducing disaccharides (glycosylglycoses) are formed by the reaction of one monosaccharide hemiacetal hydroxyl with the alcoholic hydroxyl of another monosaccharide. Such a disaccharide molecule has a free hemiacetal hydroxyl, so they exhibit oxocyclization tautomerism and reducing properties. Non-reducing disaccharides (glycosylglycosides) are formed by the reaction of monosaccharide hemiacetal hydroxyls. These disaccharides do not have a free hemiacetal hydroxyl, so they do not exhibit reducing properties, only their cyclic form exists.

Source | Glossary of Most Commonly Used Biomedical Terms and Concepts | Lithuanian University of Health Sciences | Academician Professor Antanas Praškevičius, Professor Laima Ivanovienė