Rhamnose-also known as mannose-is a methyl five-carbon sugar with two isomers, L-type and D-type. In water, the [α]D16.5 of D-rhamnose-type is -8.25°, and the [α]D15 of L-rhamnose-type is +9.1°. L-rhamnose is a type of deoxyhexaldose, or 6-deoxyL-mannose, which is a component of plant cell walls and a variety of glycosides. Alpha type: colorless crystal. Crystallized from aqueous solution is a crystal containing crystalline water. Melting point 105℃. Soluble in water and methanol. It has optical activity and rotatory phenomenon. The abundance in Marine plankton is generally greater than that of arabinose. It is also found in seawater, particulate matter and sediment. Can exist in free or combined form (refer to related literature)