Precarthamin is known as a precursor of carthamin, a red pigment from Carthamus tinctorius L. (Safflower) and its existance in the petals have been proved since 1953. However, the structure determination has not been accomplished because of the difficulty of purification and the high sensitivity to autooxidation. Now we succeeded in the isolation of precarthamin by combination of several separation methods including HPLC (ODS column). The aqueous solution of the isolated precarthamin was quantitatively converted into carthamin by exposure to the air or treatment with dilute permanganate solution in the nutral condition. The ^1H and ^<13>C NMR (^1H, ^<13>C, DEPT, HH-COSY, CH-COSY, HMBC), UV, IR, and positive FAB-MS (m/z=979 as sodium salt) spectra were measured.The NMR spectra were analysed mainly by comparing with those of carthamin. As a result, the presence of a disubstituted acetic acid moiety instead of a methenyl moiety in carthamin was disclosed. Consequantly, the structure of precarthamin was determined to be the formula 1.
