Quinochalcones and flavonoids from fresh florets in different cultivars of Carthamus tinctorius L.

The flavonoid constituents in fresh florets of the three distinctive cultivars of Carthamus tinctorius L. were purified and identified to investigate flavonoid biosynthesis in the petals. From the orange flower of cv. Kenba (K.), four new compounds, anhydrosafflor yellow B (1), two kaempferols, 9 and 13, and a quercetin, 17, were isolated, as well as the twelve known compounds, and their structures were determined by spectral data, chemical reactions, and molecular mechanics calculations. From the yellow flower of cv. Ogon-hanagasa (O.), two flavonols and two quinochalcones, and from the white flower of cv. Shiro-bana (S.), three flavonois were isolated. These compounds were the same as those contained in cv. K. To compare the flavonoid constituents among the three cultivars, crude extracts were analyzed by a LC/PDA/MS system. In cv. K., six quinochalcones and eleven flavonols were identified. In cv. O., three quinochalcones and nine flavonols were identified, but the red pigment, carthamin (4), and its precursor, precarthamin (3), were not detected. In cv. S., four flavonols without a 6-hydroxyl group were identified. On the basis of a comparative study on the constituents among these three cultivars, a possible biosynthetic pathway to form quinochalcones via the intermediate, pentahydroxychalcone (19), is proposed.