What is "rhamnose"

n. (context carbohydrate English) A methyl-pentose, ''6-deoxy-L-mannose'', which occurs in the leaves and flowers of poison ivy and is a constituent of many plant glycosides.

Rhamnose (Rha, Rham) is a naturally occurring deoxy sugar. It can be classified as either a methyl- pentose or a 6-deoxy- hexose. Rhamnose occurs in nature in its L-form as L-rhamnose (6-deoxy-L- mannose). This is unusual, since most of the naturally occurring sugars are in D-form. Exceptions are the methyl pentoses L- fucose and L-rhamnose and the pentose L- arabinose.

Rhamnose can be isolated from Buckthorn (Rhamnus), poison sumac, and plants in the genus Uncaria. Rhamnose is also produced by microalgae belonging to class Bacillariophyceae (diatoms).

Rhamnose is commonly bound to other sugars in nature. It is a common glycone component of glycosides from many plants. Rhamnose is also a component of the outer cell membrane of acid-fast bacteria in the Mycobacterium genus, which includes the organism that causes tuberculosis.