Puerarin, C₂₁H₂₀O₉ m.p. 187°(decomp.), and the substance f, which were isolated from Pueraria root were studied to establish their structure. puerarin was proved to be 8-D-glucopyranosyl-4', 7-dihydroxyisoflavone (=8-D-glucopyranosyldaidzein) by oxidation of its dimethyl ether with sodium iodate to 8-formyl-4', 7-dimethoxyisoflavone and by ozonolysis of puerarin to D-glucose and D-arabinose. On hydrolysis with sulfuric acid, the substance f yielded puerarin and D-xylose.