Glycosides are formed by elimination of water between the anomeric hydroxyl of a cyclic monosaccharide and the hydroxyl group of another compound (see here). Glycosides do not undergo mutarotation (see here) in the absence of an acid catalyst, so they remain locked in the or configuration. (Remember that the hydroxyl group on the anomeric carbon can undergo a change in orientation from the to position, or vice versa. This change is called mutarotation). Glycosidic bonds are very common in plant and animal tissues. Many glycosides are known. Some, such as ouabain or amygdalin (Figure 9.15) are very poisonous. Others, such as the common oligosaccarides and polysaccharides found in our cells, are not.