rhamnose

A methylated pentose sugar, rarely occurring free, but common as a constituent of many glycosides, e.g. the flavonol glycoside quercitrin, isolated from the bark of the oak Quercus tinctoria. Rhamnose is also found in certain gums (e.g. gum arabic and the gum of flax seeds), mucilages, and in bacterial polysaccharides. It has been identified in the free state in poison ivy (Rhus toxicodendron).