Extraction of starch by dimethyl sulfoxide and quantitation by enzymatic assay.

A method for the rapid, sensitive, and specific determination of starch in plant tissues is described. Starch from a variety of plant tissues is solubilized by stirring for 24 h or by sonication for 40 min in dimethyl sulfoxide. Dilution of this extract to less than 20% dimethyl sulfoxide permits a nearly complete hydrolysis of the starch in less than 3 h with glucoamylase from Rhizopus niveus. Quantitation of liberated glucose by a coupled hexokinase and glucose-6-phosphate dehydrogenase method provides an additional degree of specificity.