glycoside, any of a wide variety of naturally occurring substances in which acarbohydrate portion, consisting of one or more sugars or a uronicacid (i.e., asugar acid), is combined with a hydroxycompound. The hydroxy compound, usually a non-sugar entity (aglycon), such as a derivative of phenol or analcohol, may also be another carbohydrate, as in cellulose, glycogen, or starch, which consist of manyglucose units.

Many glycosides occur in plants, often as flower and fruit pigments; for example, anthocyanins.

Various medicines, condiments, and dyes from plants occur as glycosides; of great value are the heart-stimulating glycosides ofDigitalis andStrophanthus, members of a group known ascardiac glycosides. Several antibiotics are glycosides (e.g., streptomycin).Saponins, widely distributed in plants, are glycosides that lower thesurface tension of water;saponin solutions have been used as cleansing agents.

Glycosides derived from glucuronic acid (the uronic acid of glucose) and steroids areconstituents of normal animal urine.Compounds (nucleosides) derived from the partial breakdown of nucleic acids are also glycosides.