The molecule is a digalacturonic acid in which an alpha-D-galactopyranuronic acid unit is joined to a D-galactopyranuronic acid unit via an alpha-(1->4)-linkage. It is a conjugate acid of an alpha-D-galacturonosyl-(1->4)-D-galacturonate(2-).
(2S,3R,4S,5R,6S)-6-[(2S,3R,4R,5R)-2-carboxy-4,5,6-trihydroxyoxan-3-yl]oxy-3,4,5-trihydroxyoxane-2-carboxylic acid