Tanacetan TVF was found to have a branched structure with a backbone of linear alpha-1,4-D-galacturonan. The ramified regions consist of linear alpha-1,2-L-rhamno-alpha-1,4-D-galacturonan as the core. The side chains appear to attach to the 4-position of the L-rhamnopyranose residues. They are present as single beta-galactopyranose residues or a branching beta-1,4-galactopyranan bearing 4,6-substituted beta-D-galactopyranose residues as branched points. In addition, the ramified regions contain side chains of a branched alpha-1,5-arabinofuranan possessing 2,5- and 3,5-substituted alpha-L-arabinofuranose residues as branching points. Some side chains of rhamnogalacturonan appear to be arabinogalactan which contains branched sugar chains of alpha-1,5-arabinofuranan attached to the linear chains of beta-1,4-galactopyranan by 1,3- and 1,6-linkages. The residues of alpha-L-arabinofuranose seem to occupy the terminal positions of the arabinogalactan side chains.