A plant compound containing one or more alcohols or sugars and a biologically active compound. The sugar part is called a glycone, the other stuff is called an aglycone. The important things to remember about some glycosides is that they may pass through much of the intestinal tract, with the hydrolysis of the molecule only occurring in the brush borders of the small intestine. The result is that the bioactive part, the aglycone, is absorbed directly into the bloodstream, and is often not floating around the intestinal tract contents at all. Quinones are irritating and even toxic when ingested, but when taken as glycosides, they are absorbed directly into the bloodstream, where they are not dangerous (in moderation), and get excreted in the urine, where they inhibit infections. Plants like Madrone, Uva Ursi, and Manzanita work in this fashion. Some plant-derived heart medicines are only safe in proper doses because they, too, are glycosides, and they can be carried safely bound to proteins in the bloodstream, whereas if the aglycone were in the free form in the gut it might be either toxic or be digested directly into an inactive form.
A compound of a sugar and a non-sugar unit. Glycosides are widespread throughout nature and include many important drugs such as DIGOXIN.
n. a compound formed by replacing the hydroxyl (–OH) group of a sugar by another group. (If the sugar is glucose the compound is known as a glucoside.) Glycosides found in plants include some pharmacologically important products, such as the cardiac glycoside *digoxin, derived from the foxglove (Digitalis). Other plant glycosides are natural food toxins, present in cassava, almonds, and other plant products, and may yield hydrogen cyanide if the plant is not prepared properly before eating.
Drugs whose main actions are to increase the force of myocardial contraction and reduce the conductivity of the nerve ?bres in the atrioventricular node of the heart. They are useful in treating supraventricular tachycardias (rapid heart rhythm) and some forms of heart failure. Glycosides are a traditional group of cardiac drugs, originally derived from the leaves of foxglove plants and used as digitalis. The active principle has long been synthesised and used as DIGOXIN. They are potentaially toxic and their use, especially during initial treatment, should be monitored. Side-effects include ANOREXIA, nausea, vomiting, diarrhoea and abdominal pain; drowsiness, confusion and DEPRESSION may occur. An abnormally slow heart rate may develop. The glycosides should be used with special care in the elderly who are sometimes particularly susceptible to their toxic effects.... cardiac glycosides
Including cardiac glycosides. Discovered by Dr Withering (1785) who was the first physician to prescribe Foxglove for heart disorders. Glycosides are water-soluble constituents of a plant which when heated with dilute acid, or in the presence of an enzyme, are resolved into two or more substances, one of which is sugar. Thus, the root of Horseradish contains the glycoside sinigrin which is decomposed in the presence of water by the ferment myrosin. Cardiac glycosides occur in Lily of the Valley (used as an alternative to Foxglove), Bitter root and Strophantus. An important group of glycosides (flavonoid glycosides) are found in the labiatae family – a family well-represented among medicinal plants. ... glycosides
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