Dextran is a complex branched glucan (polysaccharide made of many glucose molecules) composed of chains of varying lengths (from 3 to 2000 kilodaltons). It is used medicinally as an antithrombotic (antiplatelet), to reduce blood viscosity, and as a volume expander in hypovolaemia.
The straight chain consists of a-1,6 glycosidic linkages between glucose molecules, while branches begin from a-1,3 linkages. Dextran is synthesized from sucrose by certain lactic acid bacteria, the best-known being Leuconostoc mesenteroides and Streptococcus mutans. Dental plaque is rich in dextrans.