The physicochemical properties and results of spectroscopy have enabled the empirical formula of drupacin, isolated previously from the seeds of Psoralea drupaceae, to be corrected and its structure to be established. It is 2',2'-dimethyl-3',4'-dihydropyrano(5',6':3,4)-trans-cinnamic acid. In addition to drupacin, a new component with the composition C14H13O3, mp 147-148°C has been isolated; this has been named drupanin and has the structure of 4-hydroxy-3-(3'-methylbut-2'-enyl) trans-cinnamic acid.